A Bizarre New Mars
Summary (Jan 25, 2004): The first color images from Meridiani, Opportunity's landing site in a flat, volcanic plain, suggest fine-grain soil and the first bedrock ever seen on Mars. The significance of bedrock to geologists can be compared to a history book of the planet, with its binding still ordering the pages to be read. This differs from the scattered page order that other site geology may have offered, because crater impacts and surface flows transport those materials.
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A Bizarre New Mars
Sol 1, Pasadena, CA
By Henry Bortman  |
Opportunity site at Meridiani Planum, a volcanic plain on the opposite side of Mars from Spirit's Gusev crater. Click for large view.
Credit: NASA/JPL |
Shortly after 1:00 am PST on Sunday morning, Opportunity sent back a stunning series of images from its new home in Meridiani Planum. The photos not only confirmed that the rover was safe and healthy on the martian surface, but revealed a bizarre landscape unlike any other previously seen on Mars.
See Opportunity image gallery and slideshow The landscape is flat looking out toward the horizon, although there are small hilly bumps, or hummocks, in the distance. Up close, the surface appears pebbly, but it was easily compressed and smoothed by the lander's airbags.
There is a sizable craggy rock outcrop directly in front of the rover, which is likely to be an early target for the rover's first traverse. By studying the material in the outcrop, scientists will be able to learn unequivocally the geologic history of a specific location on Mars.
Squyres first addressed the rover's location, some 20 to 25 kilometers downrange from the spot scientists initially targeted.
"The place that we thought we were heading, which was a little bit long [past the original target], was very bland looking. We've overshot that by a significant amount and I think we may be into some fairly interesting stuff, in terms of geologic variety, different kinds of materials present [that are close enough for the rover to reach]".
First "we've got to figure out exactly where we are. There may not be a whole lot of landmarks on the horizon in a place like this. It's going to be an interesting challenge to figure out where we are and then decide which direction to go, but we've got time".
"The hematite concentration actually increases toward the east [the direction in which Opportunity is believed to have traveled past the original target]. So we should be deeper into the hematite where we came down than we would have been otherwise".
"We were contemplating a TCM [trajectory correction maneuver, or course correction] that would have nudged us back to the very center of the ellipse. If you look at the hematite region, there are some areas that are more geologically varied than others. There's this hematite-bearing unit, and then there's something else beneath. And the something else beneath it pokes up in some places but not in others".
"Where we targeted the original center of the ellipse was a place where there was a lot of this poking up stuff. It looked like we were going to land a little bit long [past the desired spot], which would have taken us into a place that was much more uniform - it's just the hematite-bearing stuff without a lot of the other stuff".
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Rock Abrasion Tool (RAT), a diamond cutter for removing surface layers from rocks. On the rover's Instrument Deployment Device, or IDD, are four key diagnostic instruments-the RAT, Mossbauer and APXS spectrometer for chemical and elemental determinations and microscopic imager. Meridiani is predicted to have less rock-dust to clear than most previous landing sites. Bottom mosaic shows four perspectives on the Meridiani site. Click lower image to enlarge.
Credit: NASA/JPL |
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"As it is, we overshot that too and are back into [yet another] region that looks like it's got more of the variety. So where we ended up and where we originally put the center of the ellipse may both be equally good".
"I'm thrilled with the landing site. The thing about the Meridiani region is it's very homogeneous over a very large area, so once you get down safe and sound, you kinda can't miss."
"This is the first bedrock outcrop ever seen on Mars," said Squyres. Bedrock, he said, is geologically significant because "you know where it came from.
"One of the problems that we always had at the Viking sites, at the Pathfinder site, and that we're having at Gusev right now, is that we've got these little loose rocks sitting on the surface. Where did they come from and how did they get there? Are they ejecta from out of a crater? If so, where's the crater? Were they brought in by a flood? If so, from how far upstream?
"These rocks grew up right in this neighborhood. This is where they came from."
The lure of Meridiani Planum is a mineral called hematite, a form of iron oxide. Squyres discussed the different ways that hematite can form - many of them involve water - and how the science team plans to learn about the processes that formed the hematite in Meridiani.
"There's lots of different ways you can make hematite. One is you can have these massive deposits like you form in deep-standing liquid water bodies. Then you'd expect to see the hematite uniformly through the rock".
"Another is something hydrothermal. So suppose you got hot water percolating through rocks, through cracks, and you precipitate the hematite, and we see it in veins, in fractures running through the rock. That tells a different story".
"You can form hematite as coatings on the outside of rocks, just by a thin film of liquid water. So suppose we see a hematite-bearing rock, we RAT it, we look underneath and there's no hematite. That's a coating".
"I can't tell you that this is a place where there was ever water. You can take a magnetite-bearing lava and you can oxidize it at high temperature - you get hematite, no water involved."
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Principal investigator, Dr. Steve Squyres, Cornell University, describes the Meridiani landing site and plans for exploration of the flat, basaltic plain. Squyres speculated on Sunday morning that the Opportunity rover may actually be in a shallow crater or depression, if the layered mound in front of the rover is a remnant of the crater rim.
Credit: NASA/JPL |
"The way you tell [how the hematite formed] is by asking yourself what other minerals are present. It's those other minerals, the configuration in which you find it".
"So I don't know what we're going to see. I really don't know. This was a tantalizing place to check, and we're going to check it out. And what we see is what we see. You can't go into this expecting Mars to conform to your wishes. That's asking too much of Mars. You go there and you get what Mars gives you."
And after seeing Opportunity's first photographs, Squyres was quite happy, indeed, with what Mars has given him. "This is exactly what it looked like in my wildest dreams," he said. "And they were pretty wild."
Related Web Pages
Two for Two: Opportunity LandsWater SignsMicroscopic ImagerGusev Crater Pancam- Surveying the Martian Scene
Mössbauer spectrometer Alpha Proton X-ray Spectrometer Mars Rover: The Owner's ManualNASA's RATs Go Roving on MarsReverse Robotic OrigamiNote:
Rocks
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Sunday, January 25, 2004
