On the Cover: Might these faint circles be the scars of past blows to Earth's surface? The concentric ring structure left of center is the Aorounga impact crater in northern Chad. Scientists are using radar imagery to study the possibility that Aorounga is part of a "crater chain" formed several hundred million years ago by pieces of an asteroid or comet. A second crater appears to sit in the middle of this picture, and the dark, partially circular trough at right of center could be a third. The area shown is 45 by 40 kilometers (28 by 25 miles) in size. This image, captured in 1994 by the Spaceborne Imaging Radar-C/X Band Synthetic Aperture Radar onboard the space shuttle, penetrated the Sahara's sand to reveal these otherwise invisible geologic features. JPL/NASA
4 Astronomy: Eyes Wide Shut: Astronomer David Jewittaddresses the threat of near-Earth objects and humanity's lukewarm response.
6 Shoemaker Grants: A Little Money, Lots of NEOs: Dan Durdareports on the third round of grants currently underway, funded entirely from donations by Planetary Society members.
10 Human Exploration of Near-Earth Asteroids: Dan Durda considers the possible role of NEOs as targets for spacefaring explorers.
12 NEAR Shoemaker Goes to Work:Charlene Anderson shares some the first findings from NEAR at the asteroid Eros.