Asteroids and Comets

All the Little Things in the Solar System, and the Things They Can Do to Earth

Is there an asteroid or comet out there that poses a risk to life on Earth? The answer is certainly "yes," but we don't yet know where the next major impactor will come from or when it will crash. The best way to reduce this uncertainty is to search the skies for these crumbs of the solar system. The Planetary Society has a long history of supporting amateur and underfunded professional astronomers in their efforts to discover and track potentially hazardous near-Earth objects. This is useful not only for planetary defense, but also for learning about the solar system's origin and evolution.

A fortuitous byproduct of our increasing ability to detect fainter objects is that, for the first time, we now stand a chance of discovering smaller, five- to ten-meter-sized rocks while they are still in space before they burn up in our atmosphere and scatter meteorites along the ground. We are now beginning to link meteorites that we can study in our labs with the data on orbits and compositions that we amass with astronomical observations. Every meteorite, every tiny asteroid has a story, and we can combine these stories together to answer fundamental questions about how the solar system formed and evolved. What were the ingredients that made Earth and the other planets? How are those constituents different now? How have asteroid and comet impacts shaped the origin and evolution of life on Earth (and, potentially, on other planets)? Can asteroids serve as stepping-stones for human travel to farther destinations?

Blogs About Asteroids, Comets, and the Impact Threat

Radar images of asteroid 4179 Toutatis from the 2012 close approach

Asteroid 4179 Toutatis' upcoming encounters with Earth and Chang'E 2

Posted by Emily Lakdawalla on 2012/12/06 12:19 CST | 6 comments

Near-Earth asteroid 4179 Toutatis will be passing within 7 million kilometers of Earth on December 12. Both radio telescopes and the Chang'E 2 spacecraft will be acquiring images.

Mosaic of the asteroid Vesta from the Dawn spacecraft

Images from the long-awaited Dawn Vesta data set

Posted by Daniel Macháček on 2012/11/29 11:55 CST | 4 comments

A few days ago, the Dawn mission finally published their archival data. During the year of delay I often looked with anticipation to the Planetary Data System to check whether or not images were there, and I am delighted that they are finally available. Was the wait worth it? Definitely!

Planetary Radio: A Dawn MIssion Update

Posted by Mat Kaplan on 2012/11/20 12:36 CST

A Planetary Radio status report from the Dawn mission's Marc Rayman, accompanied by a fascinating video tour of Marc's at-home collection of space information and memorabilia.

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Eros' northern hemisphere as seen by the NEAR spacecraft on February 29, 2000. The view is a mosaic of six images.

Asteroids and Comets Visited by Spacecraft

A comparison of all the asteroids and comets ever visited by spacecraft, up to date as of November 10 (when Deep Impact flew past Hartley 2). Vesta is not included.

During the first few hundred million years after oceans appeared on the young Earth, life may have repeatedly begun only to be erased in planetwide sterilization events as very large planetoids were colliding with the larger worlds.

Sizing Up the Threat from Near-Earth Objects (NEOs)

Scientifically, it is useful to divide the impact hazard into two types of events: those with local consequences and those with global consequences. Global events, while much less likely, actually pose a greater risk.

The Torino Scale

The Torino scale is a color-coded advisory system that enables near-Earth object (NEO) researchers to place objects within a potential threat range from zero -- where there is virtually no chance of collision, to 10 -- where global catastrophe is certain.