This is planetary radio. We're headed back to Mars and we know where we're going.

We're headed back to Mars and we know where we're going.

Hi everyone, I'm Matt Kaplan.

Dr. Matt Gollumbeck of JPL will be here to tell us where two big rovers will land and

a little about the just completed site selection process.

Too bad those rovers won't get there as fast as sun-grazers.

Emily will tell us about these comets that hold the solar system speed record.

And Bruce Betts has traded his shirt and tie for a loud aloha shirt and a trivia question

about a famous Mars mission of several years ago. We're glad you've selected our site. I'll be back with

Matt Gollumbek right after this. Hi, I'm Emily Lochuwala with questions and answers. A listener asked, what are the fastest moving objects in the solar system?

Comets are the solar system's fastest solid bodies.

The speed of a comet depends on the size of its orbit and its proximity to the sun.

An object in space will reach its fastest

orbital speed when it passes closest to the sun at a position in its orbit called perahelian.

Among short period comets and asteroids, an asteroid called 1995 CR and a comet named

Mockholz 1 are the fastest. At parahelian, both of these objects are eight times closer to the sun than the Earth is

and reach speeds above 110 kilometers per second.

You can see animations of both objects on our website at planetary.org.

For comparison, the better known comets, Halion, Hale Bop, reach more leisure leak maximum

speeds of only around 50 kilometers per second.

But these short period comets and asteroids are left in the dust

by another class of solar system speed demons, the Sun Grazers.

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