Opportunity rover set for 'coolest geologic field trip'
Posted: January 27, 2004

The discovery of layered rocks in the Martian bedrock next to the Opportunity's landing platform has scientists anxiously awaiting the rover's exploration of the terrain beginning next week.

"Opportunity has now sent us the most striking image yet obtained by the Mars Exploration Rover mission. We have discovered some wonderful finely-layered rocks in the outcrop at Meridiani Planum," Steve Squyres, the principal investigator announced Tuesday.

This is Opportunity's view of layered rocks in an outcropping near the lander. Credit: NASA/JPL/Cornell
Download larger image here; 3-D version can be seen here.

The rocks are about 25 feet away from the lander where Opportunity came to rest early Sunday. The craft landed in a small crater on the plains of Meridiani along the Martian equator.

"In my day job, I study the history of the Earth, and the documents in that kind of history are layered rocks that are stacked one atop another. Each one of those layers records an event in the history of the planet. And by stringing them together we develop a sense of history," said Andrew Knoll, a rover science team member from Harvard.

"We have a familiar type of document just in front of us at Opportunity. That is truly exciting, better than we could have hoped for and something every geologist in the world is probably developing opinions about right now."

With its package of science instruments, the Opportunity rover will determine if the rock layers were created by water or volcanic activity.

"Many of you look at that scene and say 'I have something a lot like that in my backyard.' And that is true. The problem is if you live in Kentucky what you see in your backyard is a sedimentary rock. That is a rock made by the stripping down of some pre-existing rock unit and then the transport of those materials to another place where they are deposited again. But if you live in Hawaii, you could see a similar scene and it could be the product of volcanic activity," Knoll said.

"So at this point, there are really only two candidate suites of processes that are on the table. One is the layering you see represents fine-scale volcanic events, not lava flows but ash materials that have been spewed from a volcano. The other option is that these are sediments that have been transported here from somewhere else.

"If they are sediments, there are only two, I think, plausible mechanisms for transporting that material -- one would be wind, the other would be water. These are, I think, not ice-borne sediments.

"Those two hypotheses would bring us to very different conclusions about the nature of the history of this site. The good news is that over the set of sols we should be able to distinguish between those two hypotheses -- the volcanic and sedimentary.

"They each make a set of predictions for what we should see. They differ in the predictions for what we might see when we really get close to these and look in detail at the chemistry. They differ in the sets of predictions they make in the types of textures that we will see."

The rover missions were launched to search for evidence of past water on the planet to help answer the larger question of whether Mars ever had life.

This is illustration shows Opportunity in relation to the rock outcrop. Credit: NASA/JPL/Cornell/Ames/Maas Digital LLC
The layered rocks are located in a 12- to 18-inch tall bedrock outcrop that extends around a portion of the crater wall where Opportunity sits.

"The rover drivers when they first saw this went 'yikes!' And then when they realized the scale of this thing, it was not quite the imposing obstacle that it initially appeared to be," said Squyres.

"One of the wonderful things about this though is when you look at this and you realize the scale of it you get a sense of how thin those layers are. I mean the layers are like a centimeter thick. These are very, very small layers and that really puts some constraints on what it could be. These aren't lava flows. These are something we've never seen on Mars before.

"We are about to embark on what is arguably going to be the coolest geologic field trip in human history."

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