This is planetary radio. Mars Day has come and gone, but the season of Mars continues.

Hello everyone, I'm Matt Kaplan.

What would you want to take along with you on a Mars voyage?

Air, water, food, and maybe a traveler's guide to Mars?

Luckily, Dr. William Hartman has just written exactly that.

He'll be with us in a minute. Bruce Betts will help wrap up the Mars Day festivities

and present a new trivia contest question and Emily returns with this

week's question and answer segment. As you're about to hear, she's following the

water. And the Hi, I'm Emily Lochuwala with questions and answers. A listener asked, what if Mars never had a thick

atmosphere and warm climate?

How could the outflow channels on Mars be carved without liquid water?

At present temperatures and atmospheric pressures,

liquid water exposed at the surface of Mars would rapidly freeze or boil away,

so it doesn't seem likely that vast floods of liquid water could have carved the Martian outflow channels without a different climate.

But it turns out that there are several possible scenarios for floods of liquid water on Mars,

even if the temperature and pressure has always been the same.

Scientists have long suspected, and the Mars Odyssey spacecraft has recently proved

that a great deal of water is trapped beneath Mars's rocky surface

in the form of ground ice or even groundwater.

The interior of Mars is still hot,

so water trapped several kilometers underground

is probably liquid.

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