PerspectivePlanetary Science

The Earth and the Sun

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Science  24 Jun 2011:
Vol. 332, Issue 6037, pp. 1509-1510
DOI: 10.1126/science.1206965

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For more than 2 years, NASA's Genesis mission collected atoms of the solar wind (charged particles ejected from the Sun's atmosphere). Positioned at the Sun-Earth L1 Lagrange point about 1.5 million km from Earth, the spacecraft was well beyond the complicating effects of Earth's atmosphere and magnetic field, which hinder accurate ground-based astronomical measurements. The balance of gravitational forces at the Lagrange point allowed the spacecraft to maintain a fixed relationship to the Earth and the Sun with minimal expenditure of propellant. The highest priority of the mission was to determine the abundances of the stable isotopes of oxygen (16O, 17O, and 18O) and nitrogen (14N and 15N) in the Sun and, by inference, in the whole solar system (1). However, on returning to Earth with its payload, the capsule suffered an unplanned hard landing in Utah in 2004, shattering most of the collector materials and thereby greatly complicating the initial sample analysis. After years of developing analytical techniques, McKeegan et al. and Marty et al., on pages 1528 and 1533 of this issue (2, 3), reveal that these goals have now been accomplished.