This is on the planetary radio.

It made it.

Our spirit is on its way to Mars.

Spirit, the Mars Exploration Rover, that is,

and with luck spirit will soon be followed by opportunity.

And no one's happier about that than Joy Crisp.

Welcome back everyone. I'm Matt Kaplan.

Dr Crisp is the Murr Project Scientist at GPL.

She joins us on today's planetary radio.

Bruce Betts will be here with another trivia contest

and an update on his friend Biff Starling, the Astrobot.

Before all that, Emily wants us to know where all the Martian air has gotten off to.

I'll be back in a minute.

Hi, I'm Emily Loch Duwala with questions and answers.

A listener asked, what happened to Mars's ancient atmosphere?

Most but not all scientists agree that during Mars's early history,

the atmosphere was much thicker than it is today.

This argument is commonly based on the observation of dry riverbeds on the oldest Martian terrain.

At some point, water ran freely on the Martian surface, but today the low atmospheric pressure precludes the possibility.

Where did all that gas go?

One possible place is the rocks themselves.

Carbon dioxide can dissolve in water and combine with

...