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

Venerable Deep Impact spacecraft has photographed comet ISON

Posted by Emily Lakdawalla on 2013/02/05 05:24 CST | 6 comments

Deep Impact has made the first space-based observations of comet ISON.

Galileo Messengers: Cruise to Venus, Earth, Gaspra, Earth, Ida, and almost to Jupiter

Posted by Emily Lakdawalla on 2013/02/05 08:40 CST | 2 comments

It's taken me a year to face the emotionally draining task of reading and writing about Galileo's cruise phase as chronicled in the mission's newsletters.

Asteroid 2012 DA14 Close Approach Geometry

Guide to Asteroid 2012 DA14 Super Close Approach

Posted by Bruce Betts on 2013/02/04 01:46 CST | 17 comments

The 45 meter asteroid 2012 DA14 will pass closer to Earth than geostationary satellites on Feb. 15, 2013. Learn about the asteroid and what to expect from the close approach.

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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.