Water Evidence from Mars' Spirit
|Mazatzal rock in Gusev crater, Spirit site. The bright color and scalloped shape have inspired Mars' geologists to drill and uncover interior layers. Credit: NASA/JPL/MER
This approximate true-color image (right) taken by the panoramic camera on the Mars Exploration Rover Spirit shows the rock dubbed "Mazatzal" before the rover drilled into it with its rock abrasion tool. The rock "has clearly been altered by interaction with fluids,' said Hap McSween, science team member from the University of Tennessee, Knoxville.
On sol 82, Spirit ground into a circular patch of the rock called "New York," then repeated this operation on sol 85 to complete the hole. Several observations were made during this grinding process with the rover's suite of scientific instruments. Preliminary results suggest that fluid may have been present during Mazatzal's formation.
"The indications are that this rock has experienced multiple periods of alteration,' McSween said. The combination of evidence from the rover's on-board science package "suggest very strongly that Gusev did have its own water supply,' he said. This suite of tools includes instruments to measure chemical composition, a microscopic imager and multiple diagnostics to pick up water-formed minerals and salts.
Mazatzal is a highly coated rock, containing at least four "cake layers": a top coat of dust, a pinking coating, a dark rind and its true interior. The latest grind by Spirit's rock abrasion tool (the RAT) resulted in that tool's deepest hole yet, nearly 8 millimeters (0.31 inches).
Although all the Mazatzal drilling operations were completed successfully on Mars, the rover team spent most of the March 30th morning and afternoon on Earth worrying. After the team sent the uplink to Spirit, they waited for the standard "beep" that confirms the sequence reached Spirit and was activated. This beep, and an expected one 10 minutes later were not acquired, and engineers proceeded to trouble-shoot what might have gone wrong.
No errors could be found, and finally a successful afternoon Odyssey communications pass provided 75 megabits of data, indicating that all the sequences were in fact onboard the rover and that all the planned sol activities had completed successfully. The rover team members breathed a collective sigh of relief, and are now looking into possible causes of the failure to detect the beep.
|X-ray spectrometer (APXS) graph showing the expected ratio of bromine and chlorine. Where on Earth, an evaporative process takes place, these ratios can diverge, as shown at the Dead Sea.
Image Credit: JPL/MER/APXS Team
When images were downlinked successfully, the false-color, close-up image taken by the Mars Exploration Rover Spirit's microscopic imager (banner) showed a section of the hole drilled into the rock dubbed "Mazatzal" after the hole was ground for a second time. The first drilling by the rover's rock abrasion tool left an incomplete hole, so a second one was performed.
The reddish-yellow material on the left side of the banner image is the original dust coating. The darker, blue-grey surface on the right side was exposed after brushing. The crack in the rock may have once contained fluids from which minerals precipitated along its walls.
One of the most curious features found so far with the composition of the martian rocks has been their relative concentrations of salts, particularly bromine and chlorine. Typically, bromine and chlorine stick together in a fixed ratio, as in martian meteorites and Earth seawater.
So a graph of bromine vs. chlorine concentrations will be a straight line, not one that flattens out or diverges from a fixed chemical ratio. But sometimes the elements split apart and their relative quantities diverge. This separation is usually caused by evaporation processes, as in the Dead Sea on Earth.
On Mars, at Meridiani Planum and Gusev Crater, this split has been observed to an even greater degree than seen on Earth. This puzzling result is currently being further explored by Mars Exploration Rover scientists.
On March 30th, Spirit also took some images to try to catch a dust devil in action. These tiny tornadoes are frequent in Gusev crater and chaotically track across the flat plains, typically appearing in the early afternoon (1-2 p.m. locally) when solar heating is maximum and when warm air rises and collides with other pressure fronts to cause circulation.
|Active Martian dust devil caught in the act of creating a sandblast track in Promethei Terra, December 11, 1999.
Credit: NASA/JPL/Malin Space Science Systems
The sheer geographical scope of a Martian storm can cover a hundred times the size of an Earth dust devil. Martian tornadoes span up to 10 km (6 miles) high with a moving and circulating center nearly 10 football fields across (one kilometer, or six-tenths of a mile). Familiar to many in the American Southwest, these intriguing dust devils are notable as one of the few visible kinds of surface weather on any planet in our solar system.
Sol 87, which ended at 3:00 p.m. PST on April 1, 2004, was a driving day for Spirit as it begins what could be a record-breaking journey toward the Columbia Hills. So far, Spirit holds the driving distance milestone of having travelled more than a quarter-mile and maneuvered through some of the more rugged terrain of sharp, volcanic rocks yet encountered.
Related Web Pages
Spirit's Sol images and slideshow
Opportunity image gallery and slideshow
Mars Berries Once Rich in Iron-Water
NASA's RATs Go Roving on Mars
Pancam- Surveying the Martian Scene
Alpha Proton X-ray Spectrometer