This is planetary radio. Hi everyone I'm Matt Kaplan. Last week we heard from Peter Smith and Lori Leshin. Now it's time to meet the other two finalists

for NASA's Mars Scout mission in 2007.

Joel Levine is principal investigator for Ares, the Mars Airplane, while Mark Allen heads the

Marvel Orbiter team. Later, Astrobot's Biff Starling and Sandy Moon Dust, we'll check in from the Mars Exploration Rovers. It's a jam-packed show and

we'll begin it with Emily's explanation of Jupiter's psychedelic colors. That's planetary

radio. Far out, man. Hi, I'm Emily Lochuwala with questions and answers. A listener asked, what causes the different

colored bands in Saturn's and Jupiter's atmospheres?

Jupiter and Saturn are giant balls of rapidly rotating gases.

Their atmospheres are heated from above by the sun and from below by internal heat sources.

The contrast between their inside and outside temperatures causes powerful currents to rise through Jupiter's and Saturn's atmospheres.

These currents can carry interesting chemical

compounds from the planet's depths to higher levels. As in the Earth's atmosphere, the rotation

of the belts. Zones are thought to be regions of upwelling air, which become capped by bright white

cirrus clouds made not of water but instead of ammonia.

Belts, on the other hand, are thought to be regions of downwelling.

Because there are fewer ammonia clouds over belts, we can see deeper into the atmosphere.

What causes the colors that we can see in Jupiter's and Saturn's belts?

Stay tuned to planetary radio to find out.

As I'm recording this, NASA HQ is still struggling with a tough decision.

Which of four unique finalists will be named as the first Mars Scout mission, slated for a 2007 launch.

By the time you hear this, that decision may... slated for a 2007 launch.

By the time you hear this, that decision may have been made.

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