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

Comet to whiz past Mars in October 2014

Posted by Emily Lakdawalla on 2013/02/27 05:36 CST | 17 comments

A recently discovered comet, C/2013 A1 (Siding Spring), is going to be passing very close to Mars on October 19, 2014. Does it pose a risk to spacecraft?

Ida and Dactyl in enhanced color (distant view)

Galileo got so many more images of Ida than I realized

Posted by Emily Lakdawalla on 2013/02/22 04:14 CST | 1 comments

While writing up the cruise-phase issues of the Galileo Messenger a couple of weeks ago, I came across a fuzzy montage of images of Ida that I had not seen before. So I decided to spend some time digging into the Planetary Data System to see if there were more images to be found. I found lots and lots pictures that I'd never seen before!

Goldstone radar images of asteroid 2012 DA14

Why don't we have any photos of asteroid 2012 DA14 if it came so close?

Posted by Emily Lakdawalla on 2013/02/19 03:13 CST | 2 comments

A frequently-asked question last week was: if asteroid 2012 DA14 is coming so close to Earth, why hasn't anyone taken any pictures of it? Now that 2012 DA14 has whizzed past us, we do finally have some radar pictures of it, but they still may not satisfy everyone.

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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.