Sailing to the solar system's most massive asteroids this week on planetary radio. Hi everyone, welcome to Public Radio's travel show that takes you to the final frontier.

I'm Matt Kaplan. As we speak, a little spaceship with great big

wings is flying toward a big rock called Vesta. It will stick around a while once it gets

there and then leave for an even bigger world called

series. After that who knows where dawn might head. Not even principal investigator

Chris Russell is entirely sure. Chris will join us today to talk about this first ever

mission that will orbit two different bodies driven by the steady thrust of its

ion engines. We'll also hear from Emily Lochuwala about whether New Horizons had to be the first probe to visit Pluto.

Could one of the voyagers have been directed there?

And we'll wrap up this holiday edition of our show by letting Bruce Betts once again play Santa Claus.

He'll tell us what to watch for in the crowded night sky and send a planetary radio t-shirt down someone's chimney.

2007 has been one of the busiest and most productive years ever for space exploration,

with spacecraft headed almost everywhere from Mercury to Pluto.

Unfortunately, our lead story this week is about an all-to-earthbound problem for an upcoming

mission to Mars.

NASA says a conflict of interest discovered within a panel of experts must be resolved before the winning candidate

for the Mars Scout program can be selected.

And since Mars missions launched during a window that only opens up every 26 months. It will be 2013, not 2011, before this trip to

sample the red planet's upper atmosphere gets underway. You can learn the details in

Emily's blog at planetary.org.

Speaking of Mars, somebody should warn the Martians to watch for falling rocks.

It's just possible that the planet will take a moderate pasting from an asteroid called 2007

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