Looking Back to Early Mars, Deep Into Earth

AMERICAN GEOPHYSICAL UNION MEETINGSAN FRANCISCO-- Last month, more than 8200 earth scientists gathered here for the fall meeting of the American Geophysical Union. The near-record crowd could choose from sessions on bursts of methane in the ancient ocean, ozone-destroying chlorine in the stratosphere, or a failure of the solar wind on the sun, but more solidly grounded talks included signs of early martian plate tectonics and rocks from the deep mantle.