This is planetary radio. Matt Kaplan with another edition of our program about the final frontier, we're glad to have you with us this week.

Sometimes it's what you can't see with your own eyes that changes the world.

In this case, the world is Mars.

We'll talk with Phil Christensen, a planetary geologist who has devoted much

of his life to studying not just the red but the infrared planet. Later Bruce Betts will be here with What's Up and the new trivia contest.

First though, here's Emily trying not to get caught in a flash flood on Mars. years. Hi, I'm Emily Lochuwala with questions and answers.

A listener asked, given the planet's very low atmospheric pressure, how could enough water have existed on Mars to create a flood?

There are two major types of Martian channels, both of which were most likely formed by water.

There are two major types of Martian channels, both of which were most likely formed by water.

The most dramatic channels, called the outflow channels, have features similar to those found in catastrophic flood

channels on earth like the channeled scablands in Washington State.

The amount of water necessary to produce the Martian catastrophic floods is estimated at about 10 to 100 million cubic meters per second,

a flow about 100 times greater than the flow from Earth's largest river, the Amazon.

All of this water most likely came from Benjia. from Earth's largest river, the Amazon.

All of this water most likely came from beneath Mars's surface.

The temperature and pressure at the surface are too low

to allow liquid water to survive long before vaporizing. But conditions underground include higher

pressures and temperatures, probably warm enough for water to exist as a liquid. How could this

water come to the surface to start a flood? Stay tuned to planetary radio to find out. Dr Phil Christensen is the core professor of geologic sciences at Arizona State University.

That's also where he heads ASU's Mars Space Flight Facility.

And if you pick up a copy of the planetary report, the May-June issue of that magazine, which

is just about to appear.

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