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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

An active comet, from a distance

Posted by Emily Lakdawalla on 2015/02/13 01:27 CST | 4 comments

Rosetta has closed to within 50 kilometers of Churyumov-Gerasimenko, on its way to a very close, 6-kilometer flyby of the comet tomorrow. To prepare for the flyby, Rosetta traveled much farther away, allowing it to snap these amazing photos of an increasingly active comet from a great distance.

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Rosetta shifts from sedate circular orbits to swooping flybys

Posted by Emily Lakdawalla on 2015/02/10 12:35 CST | 9 comments

For the period of time before and after the Philae landing, Rosetta was able to orbit the comet close enough that it was in gravitationally bound orbits, circling the comet's center of gravity. As the comet's activity increases, the spacecraft has to spend most of its time farther away, performing occasional close flybys. The first of these is at 6 kilometers, on February 14.

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Planet Formation and the Origin of Life

Posted by Dante Lauretta on 2015/02/09 10:47 CST | 4 comments

To understand the possible distribution of life in the Universe it is important to study planet formation and evolution. These processes are recorded in the chemistry and mineralogy of asteroids and comets, and in the geology of ancient planetary surfaces in our Solar System.

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Asteroids, Comets, and the Threat

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.

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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.

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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.

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