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The Planetary Report
Facing the Impact Hazard 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.

Volume 20, number 3
May/June 2000

Facing the Impact Hazard

Download this issue as a PDF
(Planetary Society members only)


4 Astronomy: Eyes Wide Shut: Astronomer David Jewitt addresses the threat of near-Earth objects and humanity's lukewarm response.

6 Shoemaker Grants: A Little Money, Lots of NEOs: Dan Durda reports 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.


3 Members' Dialogue Faster, better, cheaper...pick two.

18 World Watch Small errors, huge losses.

20 Q&A Does Eros have any surface gravity?

22 Society News Expanding our Board of Directors.

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Planetary Defense

An asteroid or comet headed for Earth is the only large-scale natural disaster we can prevent. Working together to fund our Shoemaker NEO Grants for astronomers, we can help save the world.


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