- SCIENTIFIC COMMUNITY
Johns Hopkins Biodefense Pioneers Depart en Masse
- Martin Enserink
In a recruiting coup that puts major league sports in the shade, the University of Pittsburgh Medical Center (UPMC) has snatched away the starring team of a rival biodefense outfit in Baltimore. The entire 20-person staff of the Center for Civilian Biodefense Strategies, including veteran smallpox warrior and top Bush Administration adviser Donald A. Henderson, is resigning from Johns Hopkins University to join UPMC, leaving colleagues in the biodefense field perplexed and officials miffed. The transfer, which was announced in Pittsburgh last week after months of secret negotiations, is the latest move in the high-stakes battle over talent and resources in the biodefense arena.
“I'll be darned. That's a coup for UPMC,” said biodefense expert Kenneth Bloem—a senior fellow affiliated with the Hopkins center—when told about the move last week. “My reaction is: Wow,” adds C. J. Peters, director of the Center for Biodefense at the University of Texas Medical Branch in Galveston. “They're a pretty formidable team. I'm surprised Johns Hopkins is letting them get away.” At UPMC, the group will form a new Center for Biosecurity, led by Tara O'Toole, who currently directs the Hopkins center.
Co-founded in 1998 by Henderson, who led the World Health Organization's successful smallpox eradication campaign, Hopkins's Center for Civilian Biodefense Strategies was one of the first to call attention to the dangers of microbial terrorism. “Dark Winter,” a 2001 smallpox attack exercise organized by the center, helped alert politicians to the need for better preparation. The Hopkins group also co-authored papers on how to prevent and treat diseases terrorists might unleash.
Colleagues say the center's staff had occasionally been frustrated by what members felt was a lack of support from Johns Hopkins. Earlier this year, says O'Toole, UPMC made the group an “unsolicited proposal” that includes a new $12 million endowment for the next 5 years. Still, “it's not about the money,” O'Toole says. UPMC administers a well-integrated system of 20 hospitals with 37,000 staff, she notes—an ideal testing ground for bioterrorism preparedness strategies. O'Toole says she hopes the center's grants, worth several million dollars, can be transferred to UPMC.
The bombshell announcement ruffled some feathers at Hopkins. Alfred Sommer, dean of Hopkins's Bloomberg School of Public Health, says he wishes his colleagues well but is “unhappy” about a press release posted on the university's Web site, which made it seem as if the whole center was moving. “That's inaccurate,” says Sommer. “The center is not moving. The center … is property of Johns Hopkins.” (A later version of the release mentioned only that its leaders were leaving.) Sommer also says an e-mail from the center's leadership to its staff about the move contained “inappropriate” information about their legal status that the university will clarify.
In what appeared to be a preemptive strike the day before the scheduled UPMC briefing, Sommer announced the formation of a new Institute for Global Health and Security, which will bring together a range of biodefense and public health activities at Hopkins. That announcement, which mentioned the departure of Henderson and O'Toole, came as a surprise to many as well.
Sommer and O'Toole both say they want the parting to be amicable. Hopkins has agreed to house the group until UPMC has found a new space, and collaboration between the two centers will continue. They will at least remain close physically: Although it will have an office in Pittsburgh, the new UPMC center plans to have its headquarters in Baltimore, where most of its employees live.
- INFECTIOUS DISEASES
Singapore Lab Faulted in SARS Case
- Martin Enserink
Sloppy lab procedures caused a puzzling case of SARS in Singapore this month, according to a panel headed by Australian biosafety expert Anthony Della-Porta. The Singapore Ministry of Health released the panel's critical report* on Tuesday.
The patient, a 27-year-old virologist, worked on the West Nile virus in a biosafety level 3 lab at the Environmental Health Institute, where the SARS coronavirus was also studied (Science, 19 September, p. 1642). Because record-keeping was poor, it's difficult to tell whether live SARS virus was used in the lab on the days he worked there, the panel says, but contamination seems likely because a frozen sample he studied tested positive for the virus. Moreover, the genome of the SARS virus that sickened him and the lab's strain matched closely.
The panel identified many gaps in procedures at the year-old lab—from missing biohazard stickers to spotty training practices—and recommended structural changes in the building. The group also recommended that two of three other local microbial labs beef up biosafety and suggested that Singapore adopt legal standards for handling infectious agents—especially as it aspires to become a biomedical boomtown.
Good and Bad News From Iraq
- Andrew Lawler
Near East archaeologists are celebrating the recovery of a priceless antiquity even as the situation in Iraq remains perilous. Last week the famed Warka mask, lost during the looting of the Iraq Museum in April, was found buried deep in a field north of the capital. An investigation by Iraqi police led them to a 2-meter-deep hole in a field north of Baghdad, where they recovered the 5000-year-old marble mask.
Elizabeth Stone, an archaeologist at the State University of New York, Stony Brook, says, “The sense is that it has been bouncing around Baghdad all summer, being basically too hot to handle.” The mask, which some researchers believe represents the powerful Sumerian goddess Inanna, is one of the museum's most valuable pieces and illustrates “the ultimate femme fatale,” Stone adds. John Russell, an archaeologist at Boston's Massachusetts College of Art, adds that “the Warka lady exemplifies the classical ideal in sculpture 2500 years before the Greeks thought of it.” It was made in ancient Uruk (modern-day Warka).
Russell, who excavated at Nineveh near Mosul in the 1980s, is on his way to Baghdad to serve as deputy senior adviser to the Ministry of Culture. An outspoken critic of antiquities looting, Russell strongly criticized the failure of U.S. troops to protect the museum in April. His move is welcomed by U.S. and foreign researchers, who are becoming increasingly concerned about the widespread looting and smuggling of antiquities at remote sites. The country's dicey security and economic and political woes pose “a daunting challenge to make a difference,” Russell admits. UNESCO has withdrawn all its staff from Iraq, for example, including those handling archaeology matters.
In an incident last week that graphically illustrated the danger, Russell's boss, Pietro Cordone, escaped serious injury after U.S. troops fired on his car when it tried to pass an American convoy. One of his aides was killed. Cordone, a senior adviser to newly named Culture Minister Mufid al-Jazaeri, has been involved in efforts to revamp the trashed Iraq Museum. He was already slated to be replaced at the end of the month by a colleague, Mario Bondioli Osio, who has served as Italy's minister for the recovery of art and negotiated an antiquities trading agreement between the United States and Italy.
Science Minister Resigns, Faces Rioting Charges
- Pallava Bagla
NEW DELHI—India's high-profile science minister has resigned after being accused of helping foment a deadly religious riot in 1992.
Murli Manohar Joshi submitted his resignation after an Indian court last week implicated him and other leaders of the ruling Bhartiya Janata Party in connection with the 6 December 1992 attack on the Babri Mosque in Ayodhya. The Hindu party leaders acknowledge that they were present on the day Hindu mobs tore down the mosque, triggering a nationwide melee that killed about 1000 people. But they say that they did not direct or in any way influence events. On 10 October Joshi and six others will face formal charges, including rioting, spreading communal frenzy, and creating ill will, that carry lengthy prison terms and hefty fines.
Joshi called the court's decision “unfortunate” and dismissed allegations about his role in the 1992 incident as “baseless.” But he left himself little room to maneuver after pledging one day before the court's announcement that he would step down if the court implicated him.
The 69-year-old Joshi, a former physics professor, is the first scientist to have held the rank of cabinet minister. An acknowledged Hindu scholar and ardent supporter of the Hindu cause, he has been minister for human resource development and science since the party took office in 1998. Joshi has won steady funding increases for research and presided over the adoption of a new Indian science and technology policy (Science, 15 March 2002, p. 1993 and 10 January 2003, p. 187).
- MATERIALS SCIENCE
Tiny Particles Flag Scarce Proteins
- Robert F. Service
Biochemists have long envied their molecular biology colleagues' ability to detect minute quantities of genetic material in a molecular sea. The polymerase chain reaction (PCR), the technology responsible for such exquisite sensitivity, has provided much of the fuel for the molecular biology revolution. Now, biochemists may be on the verge of an equally revolutionary technique of developing their own: one that will enable them to spot minuscule amounts of particular proteins in a biochemical soup.
On page 1884, a team led by Chad Mirkin, a chemist at Northwestern University in Evanston, Illinois, reports a new scheme that can turn specks of iron and gold into biochemical bloodhounds that detect target proteins with up to 1 million times the sensitivity of the conventional approach. “The sensitivity is spectacular,” says Charles Martin, a chemist at the University of Florida in Gainesville. As a result, Martin says, the technique may help proteomics researchers spot proteins present in only minute amounts and link their ebb and flow to a variety of diseases. Eventually, this may help doctors diagnose ailments before they overwhelm the body.
For years, Mirkin's group has used tiny metal particles to detect DNA sequences that can signal the presence of anything from cancer cells to the anthrax bacteria. But the approach couldn't unseat PCR. So Mirkin and graduate students Jwa-Min Nam and C. Shad Thaxton switched to a quarry PCR cannot detect: proteins.
Their target was prostate-specific antigen (PSA), a protein that can indicate prostate cancer in men and that is also being investigated as a possible marker for breast cancer in women. To detect PSA, Mirkin and his students started with two types of particles: 1-micrometer plastic spheres with magnetic iron cores, and much smaller nonmagnetic gold nanoparticles. The researchers linked the iron particles to genetically engineered proteins called monoclonal antibodies, designed to bind to PSA using the same molecular handle. They linked the gold nanoparticles to “polyclonal” antibodies designed to bind to PSA at different sites, and they also tagged them with thousands of snippets of single-stranded DNA bound to even shorter complementary strands. These short strands served as “bio-bar codes” for identifying the protein—in this case PSA—to which the nanoparticles bound.
For their experiments, Mirkin and his students added both sets of nanoparticles to solutions containing PSA proteins. Both the monoclonal and polyclonal antibodies bound to the PSA, sandwiching the target proteins between the particles. The Northwestern researchers then turned on a magnetic field to attract the magnetic particles to the side of the test tube. If PSA was present, both it and any attached DNA-toting nanoparticles were dragged along as well. The researchers then used another standard solution to make the DNA snippets release the “bar code” strands and tested for the bar codes using standard DNA detection schemes.
The approach worked beautifully. The thousands of bar codes on each gold nanoparticle amplified the signal, making it possible to detect vanishingly small quantities of their target protein. Mirkin says his team can detect proteins at concentrations of just 3 attomolar, or about 18 to 20 copies of a protein in 10 microliters of a solution. “You're getting the sensitivity similar to PCR but with proteins,” Mirkin says. By contrast, the conventional antibody-based PSA detection scheme can spot only PSA present at 3 picomolar, a millionfold higher concentration.
Nor is the technique limited to tracking down proteins one by one. By setting loose swarms of particles linked to assorted antibodies and corresponding bar codes, researchers could even detect hundreds of different targets at a time. Martin says this “very clever idea” might revolutionize the task of spotting the myriad proteins that the body harbors at ultralow concentrations.
- ECOLOGICAL NETWORKS
Panel Suggests a Different Shade of NEON
- Jocelyn Kaiser
The National Science Foundation (NSF) received a welcome endorsement last week for its ambitious plan to create a network of ecological observatories around the United States. But the endorsement, from a panel of the National Research Council (NRC), came with important qualifications: The long-delayed, $391 million project, known as NEON (National Ecological Observatory Network), should consist of fewer observatories exploring specific environmental problems, such as invasive species and climate change, rather than research questions proposed by scientists. Supporters say they like NRC's suggestions.
“It's probably even better than the original configuration,” says Kent Holsinger of the University of Connecticut, Storrs, who leads an American Institute of Biological Sciences (AIBS) working group on the project. A congressional aide calls the report “incredibly constructive,” adding that the report's advice for “a major rethink” of the project could win over a reluctant Congress.
NEON first appeared in NSF's budget request 3 years ago as a project to study ecological problems on a regional and continental scale. The network was to consist of 17 core sites, each located in a different biome. But NSF's decision to let scientists choose the research focus of each site puzzled congressional appropriators, who twice rejected the foundation's request for start-up funding after complaining that they didn't understand the project. This summer the House finally agreed to spend $12 million to start building the first two observatories. But the Senate has allotted no money, and NEON's fate lies with an upcoming conference committee that will iron out differences in the two spending bills (Science, 12 September, p. 1450).
Realizing that NEON needed a boost, NSF asked NRC this spring to review the concept. In a report issued last week,* the panel “strongly supports the creation of a NEON-like program and commends NSF's overall vision for NEON.” But “we thought there had to be a more efficient way,” says chair David Tilman, an ecologist at the University of Minnesota, Twin Cities.
Instead of 17 observatories, the panel recommends six that focus on specific “critical environmental challenges”: biodiversity and ecosystem functioning; biogeochemical cycles; ecological implications of climate change; the ecology and evolution of infectious diseases; invasive species; and land use and habitat change. The total costs could be the same as the original plan, it says, which included $20 million to build and $3 million a year to run each of 17 observatories.
Making each observatory national in scale is “more efficient” than adding observatories one by one, as NSF was intending to do, says Tilman. It will also make it easier for each observatory to draw on existing projects, such as a network of towers measuring CO2 fluxes. AIBS's Holsinger says the idea “has come up several times” and is a better way to ensure that the program “addresses national needs.”
“We're very pleased with the report,” says NSF's Joanne Roskoski, who oversees the project. Choosing which themes to start with will be “up to the scientific community,” she adds. Even if Congress fails to approve the $12 million construction request, NEON supporters say, NSF could get the ball rolling with $6 million from its biological research account. Tilman agrees: “I think NEON could be implemented this year with some hustling on NSF's side and some faith on Congress's side.”
- INFECTIOUS DISEASES
Gates Pledges $168 Million for Malaria Research
- Martin Enserink
The chronically underfunded field of malaria research has just received a big booster shot. Traveling in Mozambique, software tycoon and philanthropist Bill Gates announced on 21 September that the Bill & Melinda Gates Foundation will spend $168 million on new research to battle the scourge, which is estimated to sicken more than 300 million people every year and kill more than a million.
The money will be spent on three projects:
· The Malaria Vaccine Initiative (MVI), which aims to bring together governments, industry, and academia to develop vaccines, will receive $100 million. Despite decades of research, there still are no vaccines against malaria. Created in 1999 as a part of the Program for Appropriate Technology in Health in Seattle, Washington, MVI has previously received $50 million from the Gates Foundation.
· The Geneva-based Medicines for Malaria Venture (MMV) will receive $40 million for efforts to develop four new, cheap drugs against the malaria parasite, Plasmodium falciparum, which has evolved resistance to many of the drugs now available. The nonprofit already received $25 million from Gates in 2000.
· A further $28 million will go to the study of an innovative prevention tool, called Intermittent Preventive Treatment in Infants, that relies on existing drugs. Children, the group most vulnerable to malaria, receive an antimalarial drug three times during the first year of life, along with routine vaccinations. A study among 701 children in southern Tanzania, published in 2001, showed that the treatment could reduce the number of cases of malaria and severe anemia; Gates's contribution will pay for bigger, multicountry trials that are needed to decide whether to implement the strategy widely.
“Given the needs in malaria, this is a tremendous boost,” says Michael Gottlieb, chief of Parasitology and International Programs at the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland. Chris Hentschel, CEO of MMV, says he's “delighted” with the new money, adding that Gates's donations put many a rich country to shame. But given the enormous burden of malaria, he cautions, “this doesn't mean we've gone from famine to feast.”
- EARTH OBSERVATION
Satellite Start-Up Offers Cut-Price Window on the World
- Daniel Clery
GUILDFORD, U.K.—If all goes well this week, three satellites the size of washing machines will join a fourth already in orbit to form a novel fleet of spacecraft. The array aims to be the first in the world to provide daily images of any point on Earth; the data would guide relief organizations in the event of hurricanes, floods, or volcanic eruptions. But there's something else unusual about the Disaster Monitoring Constellation (DMC): No major space agency had a hand in its creation. The spacecraft were built by Surrey Satellite Technology Ltd. (SSTL), a university start-up in this commuter town south of London, and the satellites are owned by the United Kingdom, Turkey, Algeria, and Nigeria. For the latter two nations, the DMC marks their first foray into space.
That's no mean feat for a company that has grown in 2 decades from a handful of academics with a zest for ham radio. SSTL, which is located on the University of Surrey campus and shares a building with the Surrey Space Centre, has carved a niche with its small satellites, which weigh in at anything from several hundred kilograms to just a few kilograms. Unlike other satellite-makers that rely on a steady stream of contracts from their own government, SSTL makes almost all its satellites for export, often to developing nations that need a low-cost entry into space. “Our raison d'être is to make space accessible to all,” says Craig Underwood, a spacecraft engineer at Surrey University.
The DMC is an uncommon expression of that philosophy. Like all SSTL output, the spacecraft are made from off-the-shelf components to keep costs down. The whole constellation—including launch onboard a Russian Kosmos from Plesetsk in northern Russia—costs $85 million, a fraction of the cost the major space agencies would spend on a single craft. Despite the low price tag, to a novice spacefaring nation they open a world of opportunities. Their multispectral cameras have a resolution of 32 meters—the same as the U.S. Landsat satellites—and can be used, for example, for mapping and studying everything from deforestation to erosion. But teaming up these budget craft is what gives them an unprecedented ability: daily imaging. A single satellite in low Earth orbit can take weeks to image the planet, but the four DMC craft, each snapping shots 600 kilometers across, should do it in a day. “A constellation solves problems that can't be solved” by a single satellite, says Surrey University's Stephen Mackin.
A group of electrical engineers at Surrey University built their first satellite, the 50-kilogram UoSAT-1, in 1981 for just $400,000 and got a free launch from NASA. Its payload bounced signals from amateur radio enthusiasts around the world, but it also contained environmental sensors and an early charge-coupled device camera. Several increasingly sophisticated research satellites followed, and in 1985 the university spun off SSTL.
The company's first sale went to the South Korean government. As part of the deal, Korean engineers came to Guildford, studied at the university and SSTL, and after the launch of KITSat-1 in 1992 went home to establish their own space program. (South Korea has since built three of its own satellites.) Soon the likes of Chile, Portugal, and China were inking similar deals. Governments closer to home also became interested; SSTL has built craft for the French government and the U.S. Air Force that carry classified payloads.
By the late 1990s, SSTL's engineers felt they had mastered microsatellites—those with masses in the 50-kg range—and bagged bigger game: the 315-kg UoSAT-12, launched in 1999. With help from students at the Surrey Space Centre, “we stuffed it full of things,” says Underwood, including beefed-up communications and a camera with 10-meter resolution. At about the same time, Underwood set out a challenge: to go in the opposite direction and build a “nanosatellite” the size of a soccer ball. His students came up with SNAP-1, a 7-kg spacecraft lofted in 2000 that's controlled by a chip used for palmtop computers and carries cheap and light cameras akin to those in webcams.
It's SSTL's latest achievement, though, that has thrust the company into the spotlight. Disaster monitoring from space was much discussed in the late 1990s following a 1998 United Nations conference that called for better use of satellites to help developing countries mitigate disasters. With input from its customers, SSTL hatched the DMC idea. Four spacecraft are enough to produce daily imaging, but adding more satellites increases the frequency of overflights. A fifth DMC craft, from China, is due to fly in early 2005, and Thailand and Vietnam are negotiating to join too. “Hopefully it will turn into a continuing service,” says SSTL's head of R&D, Alex da Silva Curiel, who adds that as older craft drop out, new ones can be dropped in.
With the DMC about to come on line, SSTL engineers wax evangelical about satellite constellations. “It's not the high technology, it's the concept,” says Mackin. Students at Surrey Space Centre are looking into the feasibility of swarms of tiny satellites with infrared sensors to warn of forest fires less than 15 minutes after they start. SSTL is negotiating with a German company to provide daily imaging of crops across Europe so that farmers can be warned if a field needs water, nutrients, or insecticide. It has also won a contract to build one of two test-bed satellites for Galileo, Europe's planned constellation for navigation.
Steve Schwartz, an astronomer at London's Queen Mary and Westfield College, has been working with SSTL on a proposal for a constellation of 30 microsatellites to study the magnetosphere and ionosphere. SSTL, he says, is “the obvious player in town. They get things done on an affordable budget.” Schwartz is a convert to the constellation cause: In his field, he says, “the days of enormous, heavily instrumented spacecraft are over.”
Despite its commercial success, SSTL hews close to its roots, with university academics and students mixing with SSTL staff in the Surrey facilities. With most of their satellites designed, built, and launched in about a year, students have a rare chance to help midwife the birth of a spacecraft and stick around to analyze the data it produces. The next challenge for Underwood's students is to design a spacecraft the size of a coffee cup that will remotely inspect other spacecraft. Watch out for the upcoming launch of PalmSat.
- PLANETARY SCIENCE
Finally, An End for Galileo
- Richard A. Kerr
It was the spacecraft—and the team of engineers and scientists—that wouldn't quit. Delayed, rerouted, nearly silenced, and shot through with radiation, the Galileo spacecraft performed its final act as directed on 21 September. It was an act of self-destruction. “Galileo is gone,” intoned the flight controller once it dove into Jupiter at 48 kilometers per second, transmitting data until the end. One of the last of the great planetary explorers, Galileo had pushed back frontiers, exploring everything from the solar system's most massive planet to motes of dust from other stars while overcoming a raft of obstacles along the way.
Galileo and crew almost missed the chance to go anywhere. Intended for launch from the cargo bay of the space shuttle, the mission nearly succumbed to the Challenger disaster in 1986. It got off the ground at last with a safer but less powerful booster for a shuttle launch in 1989, almost 4 years behind schedule. Then it had to take a roundabout route—by Venus, Earth, and Earth again—to get the gravity boosts to make up for the weak rocket booster. Irksome problems cropped up with radiation-induced glitches and a balky tape recorder (Galileo's technology was primitive by today's standards), but “the problem with the main antenna really threatened the mission,” says Torrence Johnson of the Jet Propulsion Laboratory in Pasadena, California, project scientist from start to finish. The umbrella-like antenna designed to return data at 130,400 bits per second just wouldn't unfurl, no matter how hard engineers beat on it from afar.
The fallback antennas' data rate of 10 bits per second “would have been virtually useless” for doing science, notes Johnson. So engineers and scientists teamed up to increase the backup antennas' data rate through hardware upgrades on the ground and other fixes and to decrease the necessary volume of data with tricks such as data compression on the spacecraft. In the end, the mission achieved 70% of its initial science objectives, says Johnson, but “we accomplished far more than 100% of what we anticipated at the start.”
Those achievements ran the gamut from the nanoscale on up, because Galileo carried just about every instrument planetary scientists could wish for. The dust detector discovered streams of smoke-sized particles shot out from the planet by its powerful magnetic field, as well as dust from other stars. The magnetometer detected an ocean beneath the icy surface of the moon Europa, which along with Mars has become astrobiologists's prime focus in the solar system. On the way to Jupiter, the camera found the first satellite of an asteroid, tiny Dactyl circling asteroid Ida. And the three imaging instruments detailed the present state and history of the four surprisingly distinct worlds of the Galilean satellites, from the record magma temperatures of fiery Io to the eons-old surface of cold Callisto.
Galileo may be gone, but its mission lives on. Cassini, an equally well-equipped flagship spacecraft, will reach Saturn on 1 July next year. May it live as long and prosper.
- PLANETARY SCIENCE
Putting Martian Science to the Test
- Richard A. Kerr
The three landers heading for Mars in search of signs of ancient life will also be testing geologic tales spun from decades of orbital data—less glamorous work but no less exciting for planetary scientists
For two generations, planetary scientists have been staring down at the surface of Mars from hundreds of kilometers above, picking out ever-finer details in a wider and wider range of the electromagnetic spectrum. Three times—twice in 1976 with the Viking landers and in 1997 with Mars Pathfinder—they've gotten infinitely closer to their subject through landers. But even then they learned mostly about martian dust and soils and precious little about rocks and the stories they might tell of how the planet has worked over its 4.5 billion years.
That could change with the coming round of landers. The U.S. rovers Opportunity and Spirit, which are scheduled to arrive on Mars in January, carry instruments capable of confirming or denying geologic stories of long-ago water told from orbital data alone. The two NASA landers are “all about testing hypotheses,” says planetary geologist Ronald Greeley of Arizona State University (ASU) in Tempe. The European Space Agency's Beagle 2 lander, which is due to arrive on Christmas Eve, will not be roving, but it will conduct a broader search for life than the Viking landers ever did, while getting a close look at a weird and mysterious martian terrain. “Everybody's excited to be going,” says planetary scientist Wendy Calvin of the University of Nevada, Reno.
But even if all goes according to plan, understanding the geology of just these few spots “may be hard to do,” says planetary geologist Harry McSween of the University of Tennessee, Knoxville. Gusev Crater, where Spirit is headed, “has some complicated geology. Neither of these [NASA] sites is going to be really straightforward.” And even the latest in rover technology has significant limitations (see p. 1834). However, adds McSween, “the complexity does make it fun.”
Rust and water at Meridiani?
The hypothesis testing at Opportunity's landing site on Meridiani Planum—a flat, smooth (and possibly visually boring) plain on the martian equator—will be rooted in the study of color. Readings of the subtle shapes of spectra returned from orbit have generated a range of hypotheses for the origin of Meridiani's minerals. The most dramatic question scientists hope to answer is whether water—a necessity for life—was involved.
As a glance up in the evening sky suggests, the “Red Planet” is actually a yellowish brown. Spectroscopists have long interpreted that color as a sign of nanoscale bits of iron oxide or hematite in the pervasive martian dust. But in 1999, the Thermal Emission Spectrometer (TES) onboard the orbiting Mars Global Surveyor (MGS) returned spectra with such high resolution that researchers could recognize three restricted regions that contained the mineral called gray hematite. Its crystals are large enough to give a gray color rather than the yellow-brown of nanoscale hematite. The largest area by far of gray hematite is Meridiani Planum, where Opportunity is headed.
If Opportunity lands safely on 24 January, it should confirm the existence of gray hematite. That's about all that researchers using orbital data can agree on; how the mineral got there is still up for grabs. On Earth, gray hematite “is almost always associated with water,” says spectroscopist Melissa Lane of the Planetary Science Institute in Tucson, Arizona. By analogy with Earth, the hematite of Meridiani Planum in all likelihood formed with water, she says.
Most researchers would agree that water reacted with other minerals to produce the gray hematite, suggesting an environment conducive to life, at least in the distant past. But a few have suggested it could have formed in lavas without water. Planetary scientist Virgil Sharpton of the University of Alaska, Fairbanks, says that the best images from the camera on MGS show pervasive dunes across Meridiani Planum, suggesting that the hematite grains have been concentrated there by the wind. If so, they could have formed in any sort of environment, including volcanic lavas or ash or in the melted rock of impact sites.
Even if water were involved, as most believe, researchers disagree about what the wet environment was like. It might have been the floor of an ocean or lake, some have suggested, as was the case for Earth's ancient banded iron formations. But the favorite hypothesis is a subterranean, water-logged layer of possibly hot rock later exposed to view by some sort of erosion. Lane sees signs in the shape of spectra from TES that Meridiani's hematite formed as tiny plates aligned with each other. On Earth, such platy hematite crystals form as water alters minerals under the pressure of overlying rock. “It looks as if this whole area was buried in sediment and only recently exhumed” by erosion, says Lane.
Raymond Arvidson of Washington University in St. Louis, Missouri, who will help supervise scientific operations of the landers, can spin a geologic story from all this. In his best-guess scenario, volcanic eruptions laid down 300 meters of debris on top of the 4-billion-year-old cratered Meridiani crust, followed by a heavy layer of wind-blown dust. Water heated by rising magma then flowed through the topmost 10 meters of buried volcanic ash layer, altering some of its minerals to hematite. That would be the prime time for mineral-eating microbes, if any existed, to have taken up residence. Then the wind removed the dust to expose the hematite-rich layer with the occasional crater rim protruding. That's as close to a consensus as anyone comes, but, says Arvidson, “I could be all wrong.”
To test that scenario, “we're really focusing on the rocks and reading the rock record,” Arvidson says. “The rock provides the detailed mineral history. Viking didn't have much in the way of mineralogy [instruments]. Mars Pathfinder had mobility but didn't have very good instruments. Elemental composition [analysis], which Pathfinder had, is good, but mineralogy is even better. We'll have both.”
Each rover carries the basic tools of a field geologist. One is the rock abrasion tool, the equivalent of a hammer for exposing fresh rock. The other two field tools are a panoramic camera for the big picture and a microscopic imager for the fine details. Combined, the two should determine whether the hematite comes in Lane's platy form and was formed by the action of subterranean water. They could even see any mineralogical layering indicative of lakebed formation. But if it's all loose sand-and silt-sized grains, Sharpton could be right about the hematite being the winnowed remains of volcanic debris.
Opportunity and Spirit also carry instruments found in a mineralogy laboratory. An alpha particle x-ray spectrometer determines the amount of most elements, a Mössbauer spectrometer identifies and measures the abundance of iron minerals, and a mini-thermal emission spectrometer determines mineral composition spectrally as TES does from orbit. At Meridiani, “it's the minerals in association with the hematite that will be important,” says Arvidson. Minerals such as carbonates, olivine, and iron silicates could tell what minerals water weathered to form the hematite. They could also help tell just what conditions were like during weathering and how conducive to life they might have been.
So far, spectroscopic studies from orbit have failed to find any sign of such accessory minerals on Meridiani Planum. Indeed, Mars has proved to be spectrally bland at the wavelengths examined in varying detail from orbit. “Perhaps Mars is mineralogically impoverished,” says planetary scientist John Mustard of Brown University in Providence, Rhode Island. Even close up, Pathfinder found little spectral diversity, he notes. Opportunity “will allow us to validate the orbital data,” says Mustard, sorting out what part of the martian mineralogical story may have been missed from orbit.
A watery mirage?
At Gusev Crater, Spirit's landing site, the geologists' tales of ancient water will be tested not against spectroscopy and mineralogy but primarily by geological deduction from images. At first glance, images from orbit tell a story of bountiful water flowing into Gusev, ponding, and flowing away. The channel of 900-kilometer-long Ma'adim Vallis cuts through the southern rim of 150-kilometer-wide Gusev, fans of sediment spread across the western half of the crater floor, and a lower cut in the north rim looks like an outlet. Nathalie Cabrol and Edmond Grin of NASA's Ames Research Center in Mountain View, California, have argued that water flowed in, formed a lake, and flowed out the other side.
Gusev as paleolake—a great spot for “following the water” and maybe even stumbling on signs of past life—was the prime justification for selecting the crater as a second landing site. But some are questioning its seemingly straightforward crater-lake history. “Gusev is telling us an interesting story,” says planetary geologist James Rice of ASU; “I just don't think it's the lake story.”
Other craters in the region have no channels running into them but are filled with sediment anyway, Rice notes. Some of it has partially eroded away to expose enticingly regular layering that could be water-lain, windblown, or volcanic sediments. There hasn't been erosion to expose the sediments in the landing area, but Rice suspects that the bulk of Gusev fill got there without a lake forming. What water there might have been running through Ma'adim Vallis could have flowed in and out of Gusev without forming a lake, he says.
Most researchers are not as pessimistic as Rice about finding lakebed sediments, but no one is saying that testing the lake story using a rover is going to be easy. Gusev crater has been sitting there for most of the past 4 billion years collecting whatever has come its way. “I was bowled over” by images from the Thermal Emission Imaging System (THEMIS) on Mars Odyssey, says McSween. They highlight differences between the physical properties of rock, soil, and dust. “Gusev is surprisingly complex.”
Sediment may well have settled out of a lake in nice neat layers from which a history of martian climate could be read. But Rice as well as McSween see in THEMIS images where a slurry of sediment flowed out of Ma'adim Vallis and across the western half of the landing area. If so, there would be no layering there. And unknown amounts of other materials have no doubt collected in Gusev as well: ash from nearby volcano Apollinaris Patera, ejecta from impact craters outside and inside Gusev, dust blown in on the wind, and even lava flows. All that could be on top of any lakebed. “We're going to see evidence of more than one or two processes,” says Greeley. “The results are likely to be complex. Untangling that is going to take time.”
Rover operators will be relying on the panoramic camera and microscopic imager to ferret out the shapes and patterns that can tell a geologic tale. And lacking the martian equivalent of riverbanks and road cuts, they will be searching for some of those impact ejecta blocks for a close look at now-buried deposits. Is there regular layering in the rock, as if sediment fell through a seasonally varying lake, or crosscutting beds typical of flowing water? Are the grains rounded, as water-borne particles would be, or angular, as fresh volcanic ash would be? Are grains sorted by size, as if they fell through standing water? A close look, if Spirit can get one, should tell a tale or two.
A shot in the dark
Beagle 2's primary goal is to test a single, simple question—“whether life began on Mars”—explains consortium leader Colin Pillinger of the Open University in Milton Keynes, U.K. But the compact, 33-kilogram lander built and operated by the British-led consortium has all the tools and instruments for mineralogical study that Opportunity and Spirit carry, with the exception of a thermal emission spectrometer. So it will take the opportunity to test any number of hypotheses prompted by the rocks in the landing area centered in the great Isidis impact basin.
The floor of the impact basin is most often called a lava plain, but scientists have described it as everything from an old sea floor to debris swept off the basin rim by an outburst of carbon dioxide. Moving inward from the rim, “the terrain becomes totally weird,” says planetary geologist Larry S. Crumpler of the New Mexico Museum of Natural History and Science in Albuquerque. “Who knows what that material is?”
Given the general geologic uncertainty in Isidis, the main attraction is a hint of water. Odd strings of cones crisscrossing the floor are up to 50 meters high and are topped by pits. They were possibly formed when volcanic heat boiled subterranean water to steam that drove volcanic explosions, says Beagle 2 team member John Bridges of the Open University. Where there's been water, there may have been life, and life may have left traces of organic matter.
So Beagle 2 is going after the organic matter. “The experiments on the Viking landers were very specifically designed to detect [ongoing] biological activity,” says Pillinger. “Our prime aim is looking for past life.” For that, a “mole” will burrow beneath the surface, even under rocks, to retrieve samples whose organic matter may have been preserved from oxidation on the surface. Any organic as well as inorganic carbon will then be baked off and separately analyzed isotopically for signs of life having shifted the isotopic signature of the organic carbon. The British “have a more imaginative, a more daring payload,” says planetary geologist Michael Carr of the U.S. Geological Survey in Menlo Park, California.
Mars researchers are tickled by the chance to do any kind of science on Mars, daring or otherwise. “Landing anywhere on Mars, you're going to learn something new and interesting,” says Kenneth Edgett of Malin Space Science Systems Inc. in San Diego, California. “Who knows what we're going to find?” Adds James Head of Brown University: “That's one of the beauties of exploration.”
- PLANETARY SCIENCE
A-Roving We Will Go, Slowly
- Richard A. Kerr
When the Opportunity and Spirit landers arrive at Mars in January, planetary scientists will begin a race against time to unravel geologic mysteries that bear on whether Mars could once have harbored life (see main text). The most demanding clock on that race is the hourglass-like sifting of atmospheric dust onto the rovers' solar panels, which should shut down each rover not long after 90 days of operation. But the race will move very slowly indeed.
Doing field geology by rover “takes time,” says Raymond Arvidson of Washington University in St. Louis, Missouri, who will help oversee the scientific operation of the rovers. It takes so much time that rover team scientists are not counting on Opportunity or Spirit to analyze more than a half-dozen rocks each, about as many as the petite Sojourner rover analyzed in 1997. That would make every rock especially precious in these $400 million missions.
The Sojourner experience illustrates why roving is so slow. “I think Sojourner performed remarkably well,” says Carol Stoker of NASA's Ames Research Center in Mountain View, California, who helped operate Sojourner during the Mars Pathfinder mission. But “we had a lot of occasions when the rover didn't do what we expected.” There was the time it ended up on top of a rock instead of beside it, requiring 4 days to get it down. Another time, rover controllers directed it to place its analyzer arm on a rock and then take data, only to find that it was actually taking data on thin air rather than the rock.
The problem was that things didn't always arrive where scientists and engineers managing Sojourner intended. Stoker says that rovers on the move typically have error rates of about 10%, ending up 1 meter off after 10 meters of travel. Wheels lose traction and slip, especially when turning. Going over a rock can be especially disorienting. “You can't gauge accurately how a command [to a rover] translates into action,” she says. The result is more rounds of commands and actions to get the rover—or its arm—precisely in position.
Repeated commanding of the rover means it can take days to manage an action a human could do in a moment or two. A “command cycle” of downloading data from the rover to Earth, sizing up the rover's situation, deciding on its next action, figuring out how it can take that action, writing up the commands, and sending them back to Mars generally takes all the daylight hours a rover has before shutting down for the night. Practical constraints such as limited rover power and scheduling of the Deep Space Network radio receivers on Earth mean that the command cycle is not likely to be shortened much for these or future rovers, says Stoker. Rather than await development of more capable rovers, she suggests “biting the bullet and putting radioisotope thermal [electrical] generators [RTGs] on spacecraft” instead of solar panels. The two Viking landers had RTGs back in 1976, and they operated for years. In fact, NASA is developing plans to launch a roving science laboratory equipped with an RTG to Mars as early as 2009. The pace would be no quicker, but the race would cover a much fuller course.
- STEVE GOODMAN PROFILE
Madagascar Tames the Bohemian of Biology
- John Bohannon*
After a career that makes him sound like a biological Indiana Jones, Steve Goodman may have settled down, but he is still fighting to save this island's unique wildlife
ANKARAFANTSIKA NATIONAL PARK, MADAGASCAR—Steve Goodman shambles to the top of the hillock where the camp breakfast boils over a fire. “I have a fever,” he mutters between ragged breaths. Just yesterday he was marching through the forest with what seemed like superhuman fitness, striding through the brush and tangle as if it weren't there. After a night writhing and mumbling deliriously in his tent, Goodman's physical transformation is alarming. Now his 6-foot, 8-inch (203-centimeter) frame lies crumpled on a reed mat—pale, trembling, and soaked with sweat—just waiting the fever out. For the first time on this field trip into the northern forests of Madagascar, worry crosses the face of the stoic camp cook Ledada Razafindravao, a friend who has followed Goodman into the remotest parts of his island country. “Steve never complains,” says Achille Raselimanana, a herpetologist with the conservation group WWF, as he opens a medical kit. “So it's serious. Probably malaria.”
It's true that Goodman hasn't complained despite, in the past week, being stung in 10 places by wasps, bitten on the thumb by a tenrec—a mouse-sized mammal—and having parasite-laden bats crawl into his shirt and up his pant legs. “These are the occupational hazards,” says Goodman, a biologist who makes Madagascar his home while holding a staff position with the Field Museum in Chicago.
With self-effacing humor, Goodman describes himself as “a typical American biologist: graying beard, pony tail, sandals, et cetera.” But his colleagues consider him anything but typical. “He has done more to investigate the fauna of Madagascar than any living person,” says Anne Yoder, a biologist at Yale University who has done research in Madagascar for nearly 20 years herself. That's not bad for someone who got his Ph.D. just 3 years ago. Goodman is driven by a sense of urgency to make “a lasting contribution” in a country whose remaining habitats—home to one of the world's most diverse and unique biotas—he has watched dwindle and degrade all around him. “The clock is ticking,” he says.
The reluctant biologist
The course of Goodman's life would have been difficult to predict for those who knew him as a rebellious teenager in Michigan. His interest in science during those years was limited to do-it-yourself rocketry—a hobby that resulted in the accidental torching of a neighbor's garage. At 14 he declared himself “uncomfortable” sleeping with a roof over his head and began spending nights in a sleeping bag outside, even during winters that dropped to an eyebrow-frosting −35°C. “I was a weird kid,” admits Goodman, who is more domesticated now, although he still prefers the outdoors. He did have an obvious talent for sculpture, so his exasperated parents shipped him off to Interlochen Arts Academy, a remote upstate boarding school.
Goodman's sculpture earned him a medal from U.S. President Jimmy Carter, but soon another passion took over. What had begun as a study of birds to capture their movement in sculpture became an interest in their behavior and ecology. Following a gut feeling, Goodman turned his back on a promising artistic career and in 1980 enrolled at the University of Michigan, Anne Arbor, to study biology.
From the start, Goodman followed his own path, skipping half of his required undergraduate classes and instead studying birds in the field. “Steve has never been a conventional academic,” explains Larry Heaney, curator of mammals at the Field Museum who taught at the University of Michigan when Goodman was there. “He has only ever pursued what interests him.” Even as an undergrad, he was crossing into other fields, for example with his study of animal mummies recovered from ancient Egyptian tombs.
“I never wanted to do a Ph.D.,” says Goodman, but after graduation he signed up for one anyway because the University of Michigan offered him some financial support. “Goodman was a complete bohemian,” recalls Heaney. “He lived very cheaply, spending most nights sleeping on friends' floors.” Nevertheless, after several years Goodman was as productive as most faculty members twice his age. He was spending months at a time in North Africa doing field research funded by the American Museum of Natural History and the National Geographic Society, he had published 23 papers on topics ranging from evolution and ecology to art history and anthropology, and he had co-written a scholarly book on the role of birds in ancient Egyptian culture. But the graduate administration eventually rumbled that Goodman was doing little work on his thesis and forced him to make a choice: knuckle down, or quit the program. Goodman cut the ties and went his own way as an independent researcher.
Thus began a career that would seem nightmarish to most scientists. Never keeping an address for long nor, indeed, staying in one country for long, Goodman lived precariously from grant to grant, free to roam the world.
One of Goodman's greatest assets in his travels is that he is “exceptionally capable of picking up and instantly using” languages, says Peter Meininger, an ornithologist at the National Institute for Coastal and Marine Management in the Netherlands. While in Egypt researching a definitive book on ornithology in North Africa, he taught himself Arabic and Bishareen, a Bedouin language, adding German so he could read the field notes of a long-dead German ornithologist. He learned Urdu and Balochi while traveling through Pakistan, as well as publishing a set of ethnobotanical papers that helped settle a long-standing question about the transmission of culture in the region. Today Goodman is fluent in French and Malagasy, the two languages spoken in Madagascar, and his list of publications runs into the hundreds.
But Goodman's greatest advantage in the field is that “he just works incredibly efficiently under the worst conditions,” says Brian Fisher, an entomologist at the California Academy of Sciences. In the face of blistering heat, a lack of potable water, or endless treks through muddy jungle, Goodman “always gets the job done.” Fisher recalls wading through stagnant water deep in the forests of Gabon with Goodman, “completely covered in biting tsetse flies.” Their native guides had run off with their supplies, so they were forced to hunt for food. Nonetheless, the trip was “very productive, scientifically”; they identified several animal species new to science and one of the largest pythons ever recorded, which they were then forced to eat.
But after escaping the jungle, Goodman started coughing up a mixture of blood and worms. Luckily, he received medicine through the mail in time to prevent a nematode infestation of his lungs from killing him. This was one of several lucky escapes Goodman has had. In the Philippines, he was comatose and within a few hours of death from scrub typhus before being carried to a hospital. In Sudan, he was ambushed by murderous bandits, but he scared them off with a few shots from his pistol. “I've been extremely lucky,” says Goodman. “But I'm not in it for the thrills. I don't seek out danger in the field.”
At 46, Goodman seems to have settled down at last. He bought a house in Madagascar in 2000 with his wife Asmina, a Malagasy model and fashion designer, and the arrival of a baby boy last year has made him more risk-conscious. He also finally got his Ph.D. in 2000. Because the University of Antananarivo in Madagascar, where he supervises graduate students, technically requires Goodman to hold a higher degree, he flew off to Germany for “a few weeks” to get a Ph.D. at the University of Hamburg based on his recent work.
He even has a steady job now, which signals “the end of bohemianism,” says Goodman. His position at the Field Museum is one of a kind. “He has absolutely no administrative duties,” says Heaney, who was instrumental in bringing Goodman onboard. “We just pay Steve to do whatever research he wants and continue being productive. No other field biologist in the world is better for the job.”
At home in a naturalist's wonderland
It's late afternoon and Goodman is still running a fever. Nonetheless, he's putting in a full day's work in the camp's “lab,” a spot of shade behind a hanging reed mat where a selection of the animals caught in traps are measured, photographed, and dissected.
“Different parts of each specimen go all over the world,” says Goodman as he delicately turns a tiny tenrec inside out. The eyes, for example, go to Frankfurt, Germany, for a study of the development of vision systems. Cornell University's Weill Medical College gets the testicles to investigate the evolution of mammalian gonads. Parasites and blood samples go to the Pasteur Institute in Paris for research on the diseases coevolving with Madagascar's animals. Goodman's work “sustains projects in disciplines as diverse as ecology and phylogeny, physiology and neuroscience,” says Yoder.
Madagascar deserves such attention, says Goodman, because it is one of the best places to study certain evolutionary processes, such as adaptive radiation, the sudden blossoming of new species that made Darwin's finches on the Galápagos Islands famous. Since breaking away from the Indian subcontinent some 88 million years ago, the isolated, France-sized landmass has produced oddities such as the 7-centimeter-long Madagascan hissing cockroach and the lemurs, our big-eyed primate cousins. But the scale and breadth of Madagascar's radiations and their significance to evolutionary biology have become apparent only over the past 5 to 10 years of research, says Goodman. This is in no small part due to Goodman's own research on the phylogeny and distribution of Madagascar's biota. “Steve's genius lies in the combination of his abilities in the field along with his ability to synthesize and communicate,” says Fisher.
In spite of all this biological wealth, Madagascar has remained poorly studied due to political turmoil and creaking infrastructure. Since the Malagasy people forced out their French colonizers in 1960, the country has lurched from dictatorship to dictatorship. Westerners have often been ejected from the country, and when they have been allowed in, field biologists have always had to grapple with the very sparse network of passable roads. Many biological hot spots are still a 100-kilometer walk from any road.
Tenacious researchers like Goodman have opened up to the world the treasures hiding on the island. Since first settling here in 1989, Goodman has himself identified dozens of species new to science, and the biologists he has trained or brought into the field have added hundreds more. When it comes to the challenging terrain of Madagascar, says Fisher, “you can plunk your finger down anywhere on the map, and Steve is the guy who can make it in there and get the data.”
In recent years, liberalization and international aid have made it easier for biologists to study Madagascar in depth. But their work has revealed a bleak picture. Most of Madagascar's species are huddled together in the 10% of the original forest cover that's still intact. These pockets of natural forest are now dying a slow death by degradation and fragmentation. Madagascar's dense biodiversity, combined with looming ecological disaster, has made it the top priority in the eyes of many conservation biologists. Madagascar is home to what biologists call “charismatic megafauna,” such as the lemurs, which have helped conservation initiatives attract hundreds of millions of dollars over the past 3 decades. But much of this money has disappeared into the country's inefficient bureaucracy.
Another problem is that biologists have tended not to include Malagasy scientists in their projects, although their involvement is required for any lasting conservation. Goodman's inclusive work ethic has helped reverse this trend, says Robert Dewar, an ecologist and conservation biologist at the University of Connecticut, Storrs. “No one has done as much to train Malagasy biologists as Steve.” Working with WWF-Madagascar, Goodman created the Ecological Training Program (ETP) in 1993, which is the first of its kind and is now being replicated elsewhere in Africa. More than 30 Malagasy field biologists have gone through the ETP, including Raselimanana, who is now the chief biodiversity scientist for WWF-Madagascar. Goodman still directs the program, spending about 6 months of the year in the forests. Starting next month, he is taking the only substantial break from the field in years, but not for a vacation. He is putting the finishing touches on a book that he hopes will change the fate of Madagascar (see sidebar).
Back at camp, night has fallen and Goodman is telling a joke in Malagasy, French, and English so no one is left out. He looks a little healthier. “I come down with a fever once a month or so,” he says nonchalantly, due to the malaria and other parasites he carries for life. Would he trade it all in for a comfy teaching job in the States? “Not a chance.” At long last, Goodman feels at home.
- STEVE GOODMAN PROFILE
A Biological Bible for Madagascar
- John Bohannon*
Aside from holding the occasional megaconference or sequencing a genome, biologists rarely join forces to do something big. But biologists Steve Goodman of the Field Museum in Chicago and Jonathan Benstead of the Marine Biological Laboratory in Woods Hole, Massachusetts, are about to pull off a collective feat: They have persuaded nearly everyone with a scientific stake in the island of Madagascar—nearly 300 scientists with expertise spanning paleobotany to bat phylogeny—to collaborate on a single book, to be published by the University of Chicago Press in January. At nearly 1800 pages, The Natural History of Madagascar is a scientific milestone and by far the largest synthesis of tropical biology research ever. The authors have a strong incentive to team up: to save their workplace.
An estimated one in 31 plant species and one in 36 vertebrate species exist solely in Madagascar's unique habitats, but they could be gone within decades. “A book can make a difference,” says Benstead, who along with Goodman is contributing chapters and editing the tome. A similar book about half its size proved to be a huge boon to Costa Rica in 1983. Like Madagascar now, Costa Rica in the 1980s had one of the highest rates of deforestation. The publication of Costa Rican Natural History provided a catalyst for research and ecotourism, says Benstead, and today the country is a model for tropical conservation. To make Madagascar's biological bible flush with color photography as well as affordable to students and tourists, charitable subsidies have poured in from the Field Museum, WWF, science funder Schlinger Foundation, and even QMM, a Canadian mining company.
But another unique aspect of the book, says Goodman, is revealed by its table of contents: There are nearly 70 Malagasy authors. “For decades these national biologists have been in the shadows of their foreign colleagues,” but their work now speaks for itself. This shift of scientific expertise shows that “we have reached a new era,” says Goodman, in which the biological riches of the developing world can be studied and protected by those who live there rather than by foreigners.
- MEIOTIC DRIVE
Bickering Genes Shape Evolution
- Elizabeth Pennisi
Not all genes follow the rules of inheritance; now researchers are discovering how organisms adapt to the troublemakers
Reproduction is supposed to be an equal opportunity event. Consider humans: In developing sperm, the sex chromosomes sort 50:50 such that half the sperm carry the male-defining Y chromosome and the rest sport an X. Only the randomness of fertilization leads to families of nine girls and no boys, for example. The same supposedly holds true for the rest of the genome.
But in humans, flies, mice, and perhaps many other organisms, guerrilla warfare within the genome sometimes pits one element against another. This often takes on the appearance of a battle between the sexes, but it is really a fight between genes. In this struggle, typically one or more of the X chromosome's genes strike out against the Y's genes. Genes on other chromosomes also can get caught up in this struggle, causing an escalating arms race.
Researchers have caught glimpses of these so-called intragenomic conflicts ever since the 1920s. They dubbed the phenomenon “meiotic drive.” But only in the past decade have they come to appreciate just how devious and pervasive the aggressive genes—called drivers—are, and how dogged the counterattacks can be. This interplay “may markedly affect the evolution of the whole genome,” says Catherine Montchamp-Moreau, an evolutionary biologist at CNRS, the French basic research agency, in Gif-Sur-Yvette. As such, the work is leading evolutionary biologists to see patterns in what once was considered a fluke of nature.
Genes usually work together. Their survival depends on their collective ability to make an individual run fast, eat well, reproduce efficiently, and ward off infections. Still, as biologists are increasingly coming to realize, not all versions—called alleles—of each gene are alike. Some appear to look out for themselves. Somehow, they are more adept at passing copies of themselves on, sometimes even crowding other alleles out. It's a game of numbers, and the more prolific the DNA, the greater its evolutionary success.
In recent years, researchers have discovered a few mechanisms by which one gene can thwart a rival. During meiosis, chromosomes copy themselves, line up with their matching partners, and then split up. First the partners head into different halves of the dividing cell; then the duplicates—so-called sister chromatids—separate as that new cell splits in two. In 2000, Montchamp-Moreau and her group unraveled one cellular mechanism behind meiotic drive, a technique that seems to be particularly widespread among insects. They found that certain fruit fly driver genes caused a misstep when Y chromosome chromatids parted ways. “As a result, the corresponding [precursor sperm] did not develop into functional Y-bearing sperm,” she says. But in mice and possibly humans, other researchers have since determined that the action takes place in the egg rather than the sperm.
To counter a selfish driver gene, one or more genes often evolve the ability to gang up against it to keep it from proliferating more than it should. The defensive behavior appears by chance, but if effective, it is selected for through time. In other cases, new research is showing, meiotic drive can spur the evolution of sexual selection or other adaptations to quell selfish genes.
Thomas Hunt Morgan of Columbia University in New York City first observed skewed genetic inheritance patterns in the fruit fly Drosophila melanogaster. Some populations had more females than males, and through breeding experiments he linked this bias to the sex chromosome. In the 1950s, Yuichiro Hiraizumi and James Crow of the University of Wisconsin, Madison, observed biased inheritance wherein certain crosses between white-eyed and red-eyed flies yielded only red-eyed offspring, rather than a mix of the two. Thirty years later, Mary Lyon, a geneticist at the Medical Research Council's Mammalian Genetics Unit in Harwell, U.K., discovered a similar phenomenon wherein a chromosome bearing the “T” version of a group of immune system genes called the T locus was transmitted more often than the “t” version, another example of what Hiraizumi and Crow called segregation distortion. Now researchers know that meiotic drive exists in more than 20 species of flies, two species of mosquito, an arachnid, a lemming, mice, humans, and some plants and fungi.
In the early 1990s, researchers began to uncover just how complex this jockeying during reproduction could be and glimpse its potential consequences. Some who never intended to look at meiotic drive became the most avid researchers. Montchamp-Moreau stumbled across female-biased progeny in Drosophila simulans while looking into how mobile elements, short stretches of DNA that hop from one part of a genome to another, might interfere with mating. At about the same time, Gerald Wilkinson, an evolutionary biologist at the University of Maryland, College Park, discovered something strange about tiny stalk-eyed flies that he and his colleagues had collected in Malaysia. “Some males were producing all daughters,” he explains. And Jeanne and David Zeh, evolutionary biologists at the University of Nevada, Reno, unsuspectingly headed in this direction with Jeanne's work on a pseudoscorpion found in Central and South America. Still others were drawn to mammals that demonstrated unequal inheritance of certain genes and chromosomes.
Montchamp-Moreau and her colleagues were the first to discover meiotic drive in D. simulans. Typically, reproduction in these fruit flies yields about equal numbers of males and females. But her experiments upset the détente that maintained a balanced sex ratio. To look at mobile elements, she had begun to breed flies from isolated populations. Sometimes offspring of males and females from different places had skewed sex ratios.
Driver genes were at fault, she discovered. These genes were normally undetectable because other genes—the suppressors—had evolved ways to keep the driver in check. But in these experiments, the second-generation flies often inherited suppressors from one population and drivers from another. The suppressors were unequipped to neutralize new aggressors— uncloaking meiotic drive.
Suppressors had been found in other species. However, “for the first time, we described a complete suppression of drive, which restored an equal sex ratio in the populations even though the drivers were at high frequency,” says Montchamp-Moreau. The cloaking had fooled her and others into thinking that this species was free of drivers, and so were most others.
The discovery helped explain why drivers persist. Uncontrolled, drivers can be their own worst enemy. Theoretical work indicates that aggressive alleles can cause a population—and the driver it hosts—to go extinct. Each generation would have fewer males, until none would be left to mate with females. A suppressor diverts a driver from its destructive path. Montchamp-Moreau's discovery prompted others to search for this hidden antagonism. And, according to David Hall, an evolutionary biologist at the University of Texas, Austin, “a lot of cryptic drivers are now showing up.”
The evolution of meiotic drive can take different trajectories, Montchamp-Moreau has found. In some D. simulans populations, the drivers seem to be spreading; in others, drivers show signs of becoming ineffective; and in a few, drivers are completely disarmed and are probably breaking down within the genome.
Laboratory breeding studies also alerted the University of Maryland's Wilkinson to meiotic drive. He became curious about why some male stalk-eyed flies produce only female young. He ruled out infections with Wolbachia, a bacterium that distorts sex ratios in its hosts. More breeding experiments traced the cause of the skewed sex ratio to the X chromosome. Then, in 1998, he and his colleagues discovered a connection between meiotic drive and a male ornament: the eye stalk. But suppressor genes weren't keeping the drivers in check, the team found—sexual selection was.
Males have longer eye stalks than females, and females often prefer males with particularly long stalks. This favoritism allows females to avoid driver genes, which are associated with short stalks, Wilkinson and colleagues found. Stalk length is determined largely by a gene on the X chromosome. That gene is close to the driver gene—so close that the two are inherited as a unit, Wilkinson's postdoctoral fellow Philip Johns reported in June at the Evolution 2003 meeting in Chico, California. The allele for a shorter stalk is hooked up to the allele causing meiotic drive, whereas that for a longer stalk is joined to the nondriving allele.
“Our results surprisingly implicate meiotic drive as a potent evolutionary agent that can catalyze sexual selection,” Wilkinson points out. Before, researchers thought that females evaluate ornamental male traits as a way to tell which males are the healthiest. In this case, general health seems to be secondary. Instead, this preference seems to have evolved in reaction to a selfish gene. Meiotic drive “might have a fairly significant input on behavior,” concludes Laurence Hurst, a genetic evolutionary biologist at the University of Bath, U.K.
In addition to luring more females, stalk-eyed males without the driver genes have a second defense, Wilkinson's graduate student Catherine Fry reported at the Evolution meeting. She mated the same female with males that carried the driver and other males that didn't. When sperm from both are in the female reproductive tract, “less than 10% of the offspring are fathered by the [male with the] driver,” says Wilkinson. Fry's work indicates that seminal fluid from the nondriver male is toxic to the driver male's sperm.
Meiotic drive can affect another behavioral aspect of mating behavior, says Jeanne Zeh. During the 1990s, she and her colleagues began studying paternity patterns in a strange arachnid—a pseudoscorpion—that hitches rides on the abdomens of harlequin beetles. “The results were quite unexpected,” she recalls. Females, which brood their young in translucent sacs carried under their abdomens, mated with an unusually large number of males. In one case, there were four fathers for seven young. Moreover, females that had just one or two mates tended to abort their embryos.
Zeh's group studied the literature and found that spontaneous abortion is common soon after fertilization, particularly in mammals and live-bearing arachnids. She blames incompatibility between the male and female contributions to the offspring's genome, some of which may be caused by driver or suppressor genes. To hedge against losing her embryos, the female has evolved to take sperm from multiple males into her reproductive tract. There the immune system weeds out unsuitable sperm, Zeh speculates.
Although studies such as these follow the effects of meiotic drive on the natural history of organisms, geneticists Fernando Pardo-Manuel de Villena of the University of North Carolina, Chapel Hill, and Carmen Sapienza of Temple University in Philadelphia have been homing in on how meiotic drive affects evolution within the genome. Meiotic drive in mammals, they're finding, seems to shape the genome in a different setting and through a different mechanism. Mammalian drivers bias inheritance patterns by exerting their effects in the egg; in insects, sperm bear the brunt of a driver's power.
Pardo-Manuel de Villena, Sapienza, and colleagues have begun to focus on a chromosomal rearrangement called a Robertsonian translocation, common in both humans and mice. In some individuals, two chromosomes merge to form a single long one—causing the total number in humans to drop to 45 from 46. In 1991, Sapienza and Pardo-Manuel de Villena reported that such translocations could foster meiotic drive in females. The Siamese-twin chromosome, with its sole working centromere, somehow gets the jump on the two individual chromosomes during meiosis and is more likely to survive.
The reduced chromosome number thus becomes ever more common: In humans, for example, “a female with 45 chromosomes has more offspring with 45 than with 46,” Pardo-Manuel de Villena points out. Males with this reduced number of chromosomes father equal numbers of offspring with 45 and 46 chromosomes, indicating that the chromosomal competition is being played out in eggs rather than sperm. He thinks that meiotic drive at Robertsonian translocations might explain why humans have two fewer chromosomes than chimps. And it might help explain why in some European mice, as other geneticists have shown, the chromosome number has dropped from 40 chromosomes 5000 years ago to 22 today.
Sometimes the opposite process can also fuel meiotic drive. When a chromosome breaks apart, causing an uneven distribution of centromeres, offspring may be more likely to inherit the newly enlarged set. Here again meiotic drive seems to have influenced speciation. For example, on Madeira Island off Portugal, where mice landed less than 500 years ago, mouse chromosome numbers now range from 22 to 28. When those with 22 breed with mice carrying 28, the offspring are infertile. “This is really evolution working fast,” says Pardo-Manuel de Villena.
Gradually researchers are homing in on the identity of drivers and the strategies that let them proliferate more than other DNA. Pardo-Manuel de Villena's lab is now busy searching for genes involved in meiotic drive in mammals. In one case, “we have mapped the first gene to a region of 200,000 bases,” he says. They must check out the functions of the half-dozen genes in that region to pinpoint the right one. Driver strategies vary from species to species, but usually a malfunctioning protein is involved.
It doesn't take much to mess up chromosomal inheritance, Barry Ganetzky, a geneticist at the University of Wisconsin, Madison, and his colleagues reported in the 14 May 2002 issue of the Proceedings of the National Academy of Sciences. A signaling molecule called ranGAP helps transport molecules into and out of the nucleus. His team had already shown that mutated forms of this protein spell trouble for developing Drosophila sperm. But recently the researchers found that even the normal protein distorts the inheritance of certain chromosomes if it is present in excess. In this case, a driver gene—possibly just a second copy of the fruit fly's ranGAP gene—increases the amount of ranGAP in competitor sperm, which is enough to cause problems.
Prions, too, get caught up in intragenomic conflict, Henk Dalstra of Wageningen University, the Netherlands, and his colleagues reported earlier this year. Spores produced during the sexual phase of reproduction in the filamentous fungus Podospora anserina contain either an allele that prompts prion formation or one that codes for a normal protein. Spores containing the prion-forming allele somehow get rid of spores with the other allele, they reported in the 27 May 2003 issue of the Proceedings of the National Academy of Sciences.
The accumulation of examples of meiotic drive suggests that deep inside every individual—and in more species than researchers realize—there's a lot of conflict going on. “It's like kids at dinner,” Hurst explains. “Underneath that lovely perfection of the 50:50 sex ratio, there's a lot of kicking under the table.”
- WILDLIFE BIOLOGY
In Search of the Ivory Gull
- Kevin Krajick*
A symbol of the High Arctic has almost disappeared, and scientists are on a quest to understand why
For the last two summers, Grant Gilchrist has paid $1000 per hour for a helicopter to take him into the realm of the ivory gull: the interiors of High Arctic islands circling the pole, where the glacial terrain is too harsh for any other creatures. Gilchrist, a biologist at the Canadian Wildlife Service (CWS) in Ottawa, sought the rare, nomadic ivories at sites where researchers once reported hundreds, but he spotted only cliffs stained orange from lichens nourished by the dung of gulls past. He saw no birds and no other sign of them, not even a broken eggshell. After his rare human venture into this territory, he concludes that the gulls' numbers in Canada have plummeted 90% over the past 20 years.
Ivory gulls are the ultimate survivors: They are thought to hunt largely in the dark and eat almost anything, including other gulls and the blood of wounded polar bears, and they winter on the frozen seas while other birds head south. But they are already on the Canadian list of vulnerable species and are considered uncommon in the rest of the north. Now, the birds' worldwide status seems less certain than ever. Monitoring programs in Norway and Russia—where the largest population was once thought to reside—have fallen apart, and researchers there are worried too.
Some fear that the near disappearance is a warning that climate change or other human intrusion has upset arctic ecosystems faster than previously thought. Others hold out hope that the gulls have simply fled to secret refugia. Gilchrist sees the gulls as a possible leading indicator of the health of arctic ecosystems, yet, he says, “I can't think of a bird we know less about.”
Alone in the Arctic
Because of the remoteness and danger of the birds' haunts, literature on the ivory gull can be as much legend as science. Early arctic mariners viewed the graceful, pure-white birds, weighing only half a kilogram, as phantoms that soared out of nowhere with disembodied cries, then melted away. Eventually explorers found nesting colonies on inland cliffs and plains in Russia, Norway, and east Greenland, but the Canadian breeding sites remained largely a mystery right into the 1970s and '80s, when geologists newly equipped with helicopters spotted them. The birds were nesting on nunataks— sheer-cliffed islands of rock surrounded by vast glacial icefields—up to 50 kilometers inland from the frozen seas where they scavenge carrion and hunt fish and invertebrates through cracks in the ice. Biologists have since located other Canadian colonies amid polar deserts of jumbled rock fragments just as barren as the glaciers. These hideouts apparently offer chicks protection from predators such as bears and foxes, which can't make the long trek from the sea ice.
In the few years following these finds, a brief burst of research saw hundreds of the birds banded. The total world breeding population was estimated at about 30,000, with perhaps 5000 in Canada, 20,000 on Russian islands including the archipelago of Franz Josef Land, and smaller populations in Norway and Greenland. But many Canadian colonies were never visited again after their discovery, and no one has ever set foot on the nunataks, says Gilchrist.
Then, in 2000, Canadian Inuit hunters told researchers that they no longer saw the birds at sea or at town garbage dumps. That was ominous news, given increasing evidence that thinning sea ice from a warming climate is stressing many arctic marine creatures, from ice-dwelling algae to polar bears (Science, 19 January 2001, p. 424).
Gilchrist and his colleagues scraped together money to recheck the three dozen known Canadian colonies, and in July 2002 and 2003 they flew to the sites, dodging treacherous snow and fog and landing unexpectedly more than once when visibility was lost. This summer they also searched some 7000 square kilometers of likely habitat by plane and helicopter, including sea-ice regions where gulls once foraged. Their colleagues interviewed sailors and hunters who might have seen the birds.
“All the sources tell the same story,” says Mark Mallory, a CWS biologist in Iqaluit and Gilchrist's partner. The birds are gone almost everywhere. The researchers spotted a few previously unknown nest sites, but they averaged only a few birds each. Their new estimate of the Canadian population: 500 to 700. Their preliminary work appears in this month's Arctic; they plan to submit their latest results to Biological Conservation.
Researchers suspect long-term declines in other regions too, but Russian and Norwegian fieldwork largely stopped for lack of funds in the mid-1990s. The last Russian estimate of 10,000 breeding pairs was published in 1996, but it is probably too high, says Hallvard Strøm, a marine bird biologist at the Norwegian Polar Institute who has worked in the Russian arctic. In a 1996 survey of known nesting sites in western Franz Josef Land, a major breeding region, he could not find a single extant colony. “Now, we hope to get back out next year, partly because of what Grant has found,” he says. The 1000 or so birds nesting in east and north Greenland appear to be stable or increasing, says Olivier Gilg, chair of the nonprofit Arctic Ecology Research Group in Dijon, France, which mounted an expedition this summer that banded some 270 birds. But, he says, “we don't know too much about the movements of these birds” and whether they are related to those in other countries.
Seeking the smoking gun
With the gulls scarce or missing, researchers are scouring the north for clues to what has happened. Climate change would seem a prime suspect, but the links may be complicated, say Gilchrist and Mallory. Some bird species that nest at the lower edges of the ice pack, such as black guillemots, have indeed seen drastic declines in recent years, apparently because their food sources have moved or died out with the melting of the ice. But ivory gulls nest at such high latitudes that they still seem to have plenty of ice for summer hunting. Instead, the researchers think the problem may be at the gulls' wintering grounds, thought to include the waters between Greenland and Canada.
There, sea ice has actually increased in extent and concentration since the 1950s, due to changed winds and water currents and a regional temperature drop, says Mads Peter Heide-Jørgensen, a senior scientist at the Greenland Institute of Natural Resources. The gulls need a delicate balance of ice and open water to get at prey, so this near-total freezeup may be starving them, says Heide-Jørgensen, who has a paper in review at Ambio. In the past few years, startled amateur birders have reported hundreds of ivory gulls in Newfoundland in winter, which suggests they could be displaced southward in search of food; in 1996, one lost and exhausted-looking specimen turned up near Los Angeles, California—the most southerly sighting recorded.
Warming could be more directly spoiling the birds' splendid isolation. Unpublished work by glaciologists Roy Koerner of the Geological Survey of Canada in Ottawa and Martin Sharp of the University of Alberta in Edmonton shows that icecaps on the Canadian islands where the gulls nest have shrunk 15% to 20% since the 1960s. Some icefields are now losing up to a meter in elevation per year, says NASA's director of cryosphere sciences, Waleed Abdalati, in a paper in review at the Journal of Geophysical Research. As a byproduct, the rugged topography of the ice around some nunataks is smoothing out, making it easier for predators to walk there. Some nunataks are ceasing to be nunataks at all, as the ice around them disappears and they rejoin the coastal bedrock. And “one fox can take out a whole colony,” points out Gilchrist.
Other possibilities involve more direct human disturbance. Although the birds are not known to nest in western Greenland, they pass through in fall and spring, where they are hunted by a fast-growing Inuit population armed with long-range boats and high-powered weapons. Heide-Jørgensen thinks that shooting is helping wipe out other birds, including common eiders, king eiders, and thick-billed murres. Indeed, says Tony Gaston, a CWS ornithologist in Hull, most recoveries of banded ivory gulls have come from west Greenland hunters.
Chemical contaminants carried long distances on winds are another suspect. Five gulls shot by researchers off Canada's Ellesmere Island in 1998 carried relatively high burdens of PCBs, pesticides, and lead, says Aaron Fisk, an ecotoxicologist at the University of Georgia in Athens. He doubts that the chemicals are enough to affect the population—other birds carry similar amounts without apparent harm—but admits that the gulls' habit of scavenging carcasses, blood, and dung puts them high on the food chain and probably magnifies the effect.
A more optimistic possibility is that the birds have simply gone elsewhere. “I would like to believe in some magic refugium, and that is possible,” says Keith Hobson, a CWS ornithologist in Saskatoon. Ellesmere Island alone covers 213,000 square kilometers, with uncountable nunataks. And the observations of Gilchrist and others suggest that unlike most other colonial seabirds, ivories may not use the same colonies each year, perhaps to keep predators off their trail. Biologists have actually seen a few nesting on icebergs, the ultimate temporary rookeries. “It's hard to tell if the number is changing if they don't return to where they're supposed to,” says population ecologist Robert Rockwell of the American Museum of Natural History in New York City, who studies arctic seabirds.
However, most bird species that relocate don't go more than about 200 miles, asserts Camille Parmesan, a population biologist at the University of Texas, Austin. And Gilchrist believes that the gulls' predilection for the most barren possible habitat limits their options to surprisingly few places. After the extensive recent searches, “I don't think they're hiding anywhere,” he says.
Douglas Causey, an ornithologist at the Harvard Museum of Comparative Zoology, says he has observed comparable crashes in the past 20 years—the same time frame as the ivories—in two species of cormorants in the Aleutian Islands. “It's astounding and unprecedented,” he says. “I believe something is going on in the environment. We just don't know what it is yet.”
Gilchrist and Mallory hope to continue their studies, but the challenges are daunting. Canada's arctic research budget has dropped since the 1980s. And the work is dangerous: Helicopters, the only way in, are a leading cause of death among arctic scientists. In 2000, two Canadian wildlife experts were killed when their pilot lost his orientation in snow and fog and hit the ice in the same region where Gilchrist and Mallory work.
This summer Gilchrist managed to land by helicopter a kilometer from one small ivory gull colony on a great, rolling plain of broken-up limestone on Baffin Island. Even he, a polar-travel veteran, was shocked at the utter lifelessness of the place. He picked his way through razor-sharp cobbles and spent a couple of enchanted hours watching gulls from as close as 8 meters. Unfortunately, they were not alone: Just 4 kilometers away was a fly-in team of geologists drilling for diamonds. As northern waters grow progressively more ice-free in the summer, industrial shipping and exploration for minerals and oil are growing—bad news for a species that seems to thrive on isolation. The South African De Beers Corp. and others have recently staked out huge positions, including at one coastal base camp on Baffin near where three ivory gull colonies used to exist. There, as elsewhere this year, the gulls were nowhere to be seen.