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

Chang'e 1 or 2 Moon orbiter artist's concept

Chang'e 2: The Full Story

Posted by Bill Gray on 2012/08/25 10:55 CDT | 4 comments

An update on China's second lunar orbiter, Chang'e 2, which is now heading for asteroid Toutatis.

Pretty picture: Vesta's crater Aelia in high resolution

Posted by Emily Lakdawalla on 2012/08/13 02:59 CDT | 3 comments

I think my favorite features on Vesta are its streaky craters. Today's image release shows one of the streakiest: Aelia, a little crater on the flank of a larger one, near Vesta's equator.

Dawn artist's concept orbiting asteroid Vesta

Dawn journal: The long, slow goodbye

Posted by Marc Rayman on 2012/07/26 12:40 CDT | 1 comments

Dawn has completed the final intensive phase of its exploration of Vesta, and it has now begun its gradual departure for Ceres.

Items 46 - 48 of 97

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.