What Shaped the Surface of Mars?

When the Phoenix lander arrives on Mars, what can it expect to see? And what processes shaped the face of Mars as we see it today?
25 May 2008

Interview with 

Susan Conway, the Open University


Chris - Susan Conway is from the Open University. She's studying the processes that have helped to shape the surface of Mars over the last four-and-a-half billion years. Hello Susan.

Susan - Hello there.

The Martian LandscapeChris - Thank you for joining us. What does Mars actually look like if you were to go and stand there? We have actually got pictures from it.

Susan - We have, that's right. Where the Mars Phoenix lander is going to land is up near the North pole. It's getting on for about late spring there so if someone was on the space ship and they touched down they'd obviously need a pretty good space suit because the atmosphere's quite thin. It would be pretty cold and what they'd see when they got there? Probably quite a bit of white frost. This is not water. This would be CO2, carbon dioxide, and they'd be looking about them . You might see black rock. You might see reddish sand as well, in amongst the bits of frost.

Chris - Why is it so red?

Susan - It's the iron content of the material so the dust is actually quite high in iron. As you know when you expose iron to the atmosphere it forms rust. That's the red colour. It's basically a rusty planet.

Chris - And the sky? We're used to the sky on Earth being a nice blue colour during the day. What do you see on Mars?

Susan - Well, it depends on the atmospheric conditions. On a really bad day: completely black. You wouldn't be able to see anything at all. You wouldn't be able to see you hand in front of your face.

Chris - Why not?

Susan - Well, the winds on Mars create these huge dust storms. They kick up all this dust and basically just like being in fog but instead of it being water it's all this really fine, red dust. You wouldn't be able to see your hand in front of your face.

Chris - Do we know what drives those dust storms, because you were saying the atmosphere is very thin. If you've got virtually no atmosphere, how do you get such strong winds?

Susan - Well, the temperatures on Mars have a huge difference. To compensate for the thin atmosphere you've got these huge temperature differences. We're talking -60 up to 25 degrees in different hemispheres in Mars. That drives these extremely strong winds that pick up this really fine dust making these huge dust storms.

Atmosphere of Mars taken from low orbitChris - One of the interesting things when the 2003 Mars Express mission from the ESA (European Space Agency) got to the red planet it started to give us these amazing pictures of the surface of the planet. There are gullies, there are ridges. It's the most extraordinary sort of surface scape, isn't it?

Susan - It is amazing, yes. Not only the Mars express but we've got the MRO, the Mars Reconnaissance Orbiter is sending back images of 25cm per pixel . You'll be able to see this studio, you'd be able to see a car on Mars, that sort of thing. This is bringing back amazing pictures of some weird landscapes that you just wouldn't expect. Big dunes, gullies that look like they've been formed by water. Just some really amazing stuff.

Chris - And it's also home to the biggest volcano in our solar system, isn't it? Olympus Mons.

Susan - Yes, that's right. Absolutely massive.

Chris - Those gullies that you mentioned look like they've been carved by water because if you compare them to what we have on Earth, say the Grand Canyon or something. Although they're on much bigger scale they do look very similar, don't they? Is it water?

Susan - That's up for debate. There are two features we're looking at. There's a huge feature that you can see that's a Grand Canyon Vallis Marineris kind of feature. The massive one you can see on Mars. That's thought to have been carved by water a really long time back in Mars' history so we're talking 2.5 billion years ago.

Chris - That is a long time ago. I thought some of these things looked a bit more recent than that.

Susan - That's right, these are smaller features. A couple of kilometres long and you can only see them in the most high resolution images. They're sinuous. They've got no craters on at all which shows that they're really recent. They look just like gullies that you would find in a ploughed field that's just got water washed over it or on the badlands. If you imagine a desert scenario and you've got the gullies formed in the badlands. It kinda looks like that.

Chris - If it's not water, what else could do that?

Susan - There's a couple of other theories. Scientists think that maybe it could be dry mass wasting. That's where material just breaks off and falls down the slope in response to gravity. People have difficulty with that because the morphology is not quite the same. The shape is not quite right. That could be due to the different sediment properties and gravity on Mars. It could be some kind of CO2. Maybe a CO2 avalanche that picks up material and takes it down slope; maybe a CO2 explosion so suddenly the CO2 gets heated up and then that explodes something like a volcano and picks up loads of stuff and tumbles down-hill because it's denser than the atmosphere.

Chris - Are you doing experiments here on Earth to model how that would occur so that you can then match up what you find in the laboratory with the pictures we've got to see which of these explanations it's most likely to be.

Susan - Yes, we're doing experiments in a Mars chamber that has the same atmospheric pressure and the same temperature and we're running water downhill there to test the water hypothesis. To see if water could actually be stable – because obviously it's outside the stability field for water – it's too cold, too little pressure for water; to see if water can stay active and mobile for long enough to form these features. We're testing that hypothesis.

Chris - What's your gut feeling at the moment?

Susan - I think it's water, personally. It's all up for debate, we'll have to see.

Chris - If it is water, looking at the terrain, when do you think water last ran?

Susan - It could be anything in the last 100,000 years.

Chris - Which is very recent, isn't it?

Susan - it is very recent, yes.

Chris - Which means, if there was life there it could still have been viable up until 100,000 years ago which is a blink of an eye isn't it?

Susan - Yeah. If the water formed these features and then has gone back into the ground and we still have liquid water beneath the ground little micros still could be living there in the rock, eating the rock, eating the water and still sitting there waiting for us to discover them.


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