Science  23 Dec 2011:
Vol. 334, Issue 6063, pp. 1611

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  1. Is Jupiter Eating Its Own Heart?

    Sophisticated new calculations indicate that Jupiter has destroyed part of its own core. Jupiter consists primarily of an atmosphere of hydrogen and helium, with a liquid hydrogen-helium interior surrounding a metallic-rocky-icy core.

    Conditions at the interior of the gas giant—with temperatures of about 16,000 kelvin and pressures at about 40 million atmospheres—are so extreme that no experiment can reproduce them. So, planetary scientists Hugh Wilson and Burkhard Militzer of the University of California, Berkeley, used quantum mechanical calculations to simulate how materials in the core might interact with the liquid mantle. They found that magnesium oxide (MgO)—a key ingredient in Jupiter's core—dissolves readily when it encounters the hydrogen-helium fluid surrounding the core, they report in a paper submitted to Physical Review Letters.

    How quickly this is happening is unclear—for example, it is unknown whether convection in Jupiter's interior is vigorous enough to dredge up dissolved core material and toss it into the hydrogen-helium envelope. If so, Jupiter's core has been shrinking since the planet's birth, notes Militzer. That core erosion could happen even more rapidly at more massive gas giants with even hotter cores, he adds—perhaps so rapidly that some of the largest gas giants might be completely coreless.

  2. A Shirt That Cleans Itself


    Washing your clothes may someday be as easy as hanging them in the sun: Researchers have developed a type of self-cleaning cotton. Titanium dioxide coatings have been known to have self-cleaning properties; when ultraviolet light strikes the compound, it emits oppositely charged particles known as electron-hole pairs, which encourage so-called oxidation reactions that break down organic material such as dirt. But now, researchers have made this process work in visible light, by coating cotton with nitrogen-doped titanium-dioxide (N-TiO2) and an extra layer of silver-iodide (AgI). In visible light, the N-TiO2 and AgI seem to work together, forcing any generated electrons and holes to separate so that they stand less chance of recombining—ultimately making them more efficient at oxidation. In their report, due to be published later this month in Applied Materials & Interfaces, the researchers describe how a piece of treated cotton stained with orange dye self-cleaned when exposed to a 1000-watt lamp for 2 hours.