posted 03-01-2004 01:46 PM               

Bernie
http://www.space.com/scienceastronomy/opportunity_evidence_040229.html

posted 03-01-2004 02:11 PM               

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Big news from Mars: After a weekend of escalating buzz, NASA has scheduled a rush news conference at 2 p.m. ET Tuesday at its Washington headquarters to announce dramatic new findings about water on Mars.

The specifics are being held back for the briefing, but clearly they have to do with evidence sent back from the Mars rovers relating to the role liquid water played — and may still be playing — on the Red Planet. If there is even a bit of salty liquid water beneath the surface of Mars, as hinted last month, that theoretically could open the way for life to exist there even today.

Among the clues are the threadlike features seen in some of the microscopic imagery, which could have been laid down by mineral-rich water percolating through the soil; the fine-layered appearance of Martian bedrock around Opportunity's landing site, which points toward a sedimentary origin; and fancifully nicknamed geological features such as blueberries and macaroni.

The rover missions' principal scientific investigator, Cornell astronomer Steve Squyres, will be among the speakers at Tuesday's briefing, NASA spokesman Don Savage told MSNBC.com. Arrangements for the briefing were firmed up over the weekend — and Savage said the plans were made so hastily because the news couldn't be held back much longer, "not that we would want to hold it." So stay tuned for the news as it happens, via MSNBC's live video coverage.

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posted 03-01-2004 08:46 PM               

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First, we're nowhere near a "Mars = dead planet" conclusion yet.  For example, the outcrop in this particular crater might be layers of bedded volcanic ash, as you say, but for all we know there might be a layer of limestone from an ancient seabed five feet below that!  So one outcrop does not a dead planet make.  

Second, in our five landings so far, this outcrop is a unique opportunity because it is the first place where we really look edge on at what seems to be bedrock layering.  We're SO lucky to have landed in this little crater, because the impact punched thru the strata and exposed it in the crater wall, but as I say, we see only a few layers of the stratigraphic column.  You couldn't judge all the strata of the Grand Canyon by what you see in the top few feet!   Other places, we looked at randomly scattered boulders (tossed there by impacts??), which seemed to be basically lava fragments.  Here are some examples of what we are looking for, and what might be found:

a:  it could be layers of dust blown in long ago and cemented into layers -- in which case the composition might be similar to all other soils and dust sampled so far in Mars lander missions.

b:  it could be layers of volcanic ash blown in and laid down in beds from some nearby eruption, perhaps from a volcano within 100 km.  Often on earth, ash beds are different composition than the lavas, and this might give us better understand of the range of volcanic eruption types on Mars. 

c:  it could be (to take a wild possibility) layer of limestone-like calcium carbonates, layed down in ancient lake beds.  This would be strong evidence of ancient lakes on Mars, and the question would shift to how long they lasted.  Were they just one-time ponds that evaporated in a month, or hundred-million year long lakes that were there for quite a while. 

I have no idea to what extent they are waiting for the best data or trying to resolve data-taking issues, but I'm sure they'd like to get a nice clean answer to what ever they find, to distinquish among these kinds of possibilities. 

To make another point:  its often said in science that it is hard to prove a negative.  For example, if we drive up to a rock in one of these sites and it is loaded with fossils (again an unlikely possiblity) that proves that, yes, there was life on Mars.  But if we drive up to 100 rocks and find no fossils, it does not prove that there was never life on Mars.  The negative conclusion usually materializes slowly as understanding gets better and better and we've looked in many kinds of environments. 

So this is really an exciting time -- we're assembling just the first bits of data on what kinds of bedrock outcrops exist on Mars!

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posted 03-02-2004 01:08 PM               

I find this all very exciting and am eagerly anticipating the news conference!

posted 03-02-2004 02:22 PM               

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Opportunity Rover Finds Strong Evidence Meridiani Planum Was Wet
March 2, 2004

Scientists have concluded the part of Mars that NASA's Opportunity rover is exploring was soaking wet in the past.

Evidence the rover found in a rock outcrop led scientists to the conclusion. Clues from the rocks' composition, such as the presence of sulfates, and the rocks' physical appearance, such as niches where crystals grew, helped make the case for a watery history.

"Liquid water once flowed through these rocks. It changed their texture, and it changed their chemistry," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the science instruments on Opportunity and its twin, Spirit. "We've been able to read the tell-tale clues the water left behind, giving us confidence in that conclusion."

Dr. James Garvin, lead scientist for Mars and lunar exploration at NASA Headquarters, Washington, said, "NASA launched the Mars Exploration Rover mission specifically to check whether at least one part of Mars ever had a persistently wet environment that could possibly have been hospitable to life. Today we have strong evidence for an exciting answer: Yes."

Opportunity has more work ahead. It will try to determine whether, besides being exposed to water after they formed, the rocks may have originally been laid down by minerals precipitating out of solution at the bottom of a salty lake or sea.

The first views Opportunity sent of its landing site in Mars' Meridiani Planum region five weeks ago delighted researchers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., because of the good fortune to have the spacecraft arrive next to an exposed slice of bedrock on the inner slope of a small crater.

The robotic field geologist has spent most of the past three weeks surveying the whole outcrop, and then turning back for close-up inspection of selected portions. The rover found a very high concentration of sulfur in the outcrop with its alpha particle X-ray spectrometer, which identifies chemical elements in a sample. "The chemical form of this sulfur appears to be in magnesium, iron or other sulfate salts," said Dr. Benton Clark of Lockheed Martin Space Systems, Denver. "Elements that can form chloride or even bromide salts have also been detected."

At the same location, the rover's Moessbauer spectrometer, which identifies iron-bearing minerals, detected a hydrated iron sulfate mineral called jarosite. Germany provided both the alpha particle X- ray spectrometer and the Moessbauer spectrometer. Opportunity's miniature thermal emission spectrometer has also provided evidence for sulfates.

On Earth, rocks with as much salt as this Mars rock either have formed in water or, after formation, have been highly altered by long exposures to water. Jarosite may point to the rock's wet history having been in an acidic lake or an acidic hot springs environment.

The water evidence from the rocks' physical appearance comes in at least three categories, said Dr. John Grotzinger, sedimentary geologist from the Massachusetts Institute of Technology, Cambridge: indentations called "vugs," spherules and crossbedding.

Pictures from the rover's panoramic camera and microscopic imager reveal the target rock, dubbed "El Capitan," is thoroughly pocked with indentations about a centimeter (0.4 inch) long and one-fourth or less that wide, with apparently random orientations. This distinctive texture is familiar to geologists as the sites where crystals of salt minerals form within rocks that sit in briny water. When the crystals later disappear, either by erosion or by dissolving in less-salty water, the voids left behind are called vugs, and in this case they conform to the geometry of possible former evaporite minerals.

Round particles the size of BBs are embedded in the outcrop. From shape alone, these spherules might be formed from volcanic eruptions, from lofting of molten droplets by a meteor impact, or from accumulation of minerals coming out of solution inside a porous, water-soaked rock. Opportunity's observations that the spherules are not concentrated at particular layers in the outcrop weigh against a volcanic or impact origin, but do not completely rule out those origins.

Layers in the rock that lie at an angle to the main layers, a pattern called crossbedding, can result from the action of wind or water. Preliminary views by Opportunity hint the crossbedding bears hallmarks of water action, such as the small scale of the crossbedding and possible concave patterns formed by sinuous crestlines of underwater ridges.

The images obtained to date are not adequate for a definitive answer. So scientists plan to maneuver Opportunity closer to the features for a better look. "We have tantalizing clues, and we're planning to evaluate this possibility in the near future," Grotzinger said.

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