This is planetary radio.

This is planetary radio. less than three weeks until the human spirit once again visits the Martian

surface.

Hi everyone I'm Matt Kaplan.

The Deputy Project Scientist for the Mars Exploration Rovers Spirit and Opportunity provides a mission

update for us.

Later, it's Bruce Betts and family on what's up. Never ask a

woman her age but you can ask Emily how we tell the age of a planet from its surface. I'll be right back with Albert Haldeman of JPL.

Hi, I'm Emily Luwala with questions and answers.

A listener asked, I've heard that the Northern Plains of Mars are 2 billion years younger than the

Southern Highlands. How can one part of Mars are two billion years younger than the southern highlands.

How can one part of Mars be younger than another part?

Once a planet forms, wouldn't it all be the same age?

When scientists talk about the age of Mars's planes and highlands, they're not talking about the whole planet, but instead about the surface of the planet.

Our own planet is over 4.5 billion years old, but its surface is continually changed by the action of

weathering and erosion so that there is no landscape on the Earth that is older than

a few hundred million years. On the other hand the Moon's surface has not really changed much in over 3 billion years.

How do we tell how old these surfaces are?

For the Earth and a few other places in the solar system, we have rock samples that can be dated directly using

radiometric age dating. But the way we really get a handle on the ages of places in the

solar system is using craters. How do we do that? Stay tuned to planetary radio to find out. Dr Albert Haldeman is the deputy project scientist for the Mars Exploration Rover Mission.

He's not the only person with a Caltech PhD in planetary science, but he may be the only jet propulsion lab researcher

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