Posted on 10/08/2004 2:50:10 PM PDT by ckilmer
Water coursed through Martian hills
NewScientist.com news service
Polygonal cracks were carved on the "Escher" rock by a second wet episode (image: NASA/JPL/Cornell)
The twin rovers on Mars - now reviving having survived the freezing depths of Martian winter - have found new signs that water was once plentiful on Mars.
The Mars rover Opportunity, which has nearly reached the bottom of the 160-metre-diameter Endurance crater, has now found clear signs that the area was drenched twice in the past, say NASA scientists.
Its twin, Spirit, which landed in what was thought to be an ancient lakebed, had failed to find direct signs of water for months as it crossed two kilometres of pure basaltic plains. The rovers landed on the Red Planet in January 2004.
But since Spirit reached Mars’ Columbia Hills in July, the rocks have changed completely, showing evidence of abundant water. "We have not seen a single fresh volcanic rock since we crossed the line" from the plain to the hills, says rover chief scientist Steven Squyres of Cornell University, US. "Every single one shows signs of alteration by water."
The hills, Squyres explains, are like islands of much older rock that stick up from the basaltic lava flows that later filled the basin's depths, creating the smooth plains on which Spirit landed.
Soluble elements
By measuring the differences between the spectra of rocks on the plains and those in the hills - using Spirit’s Alpha Proton X-Ray Spectrometer - the team discovered that the hillside rocks were all significantly depleted in potassium, sulphur, bromine, and chlorine. These are the most soluble elements and would be the first to go if the rocks got wet.
Meanwhile, Opportunity has discovered one of the most interesting rocks seen so far, says Squyres. While attempting to retreat from the lower levels of the Endurance crater, the rover happened upon a slab of rock - dubbed Escher by the team - which is fractured into polygonal shapes (see image). It later found another rock, called Earhart, showing similar shapes.
The rock itself is made up of fine layers that run across the direction of the polygonal cracks, explains John Grotzinger, a sedimentologist at MIT and a member of the science team.
Dry spells
The shapes suggest that the original sedimentary rock formed in a lake or shallow sea - which then dried and solidified - before undergoing a second wet episode and yet another drying out.
And large timescales may have been involved. The latter drying episode must have come after the impact that formed the Endurance crater, Grotzinger says.
Spectral data show that the concentration of chlorine, sodium and other soluble elements is far heavier on the surface of the rock than just beneath it, as it would be if the rock had been bathed in water long after it formed, leaching out the salts.
Both rovers are now heading towards other stimulating targets. Spirit is heading into the hills, towards what appear to be extensive exposures of layered bedrock while Opportunity will attempt to exit its deep crater by way of a steep, heavily layered dark cliff of interesting looking rock.
David L. Chandler
Polygonal cracks were carved on the "Escher" rock by a second wet episode (image: NASA/JPL/Cornell)
bump for later reading with son.
Fascinating stuff. If we brought back some Martian rocks and scraped some stuff onto an agar plate would bacteria possibly grow?
Wow....I forgot all about the rovers. They were supposed to be functional for about 90 days but they'll be closing-in on a year of Martian roving this January.
bump
If we keep looking ,we will eventually find evidence of internal combustion engine use that must have ruined their ozone layer and killed this poor planet and all the inhabitants. This will surely happen to us also.
Once the planet's volcanism died down, the distant Sun became the sole remaining source of heat on the surface, and Mars became the frozen desert it is today.
That's my guess, anyway.
LOL! I hate to be a buzz-kill, but I think it was a combination of Mars' lack of a significant planetary magnetic field (to deflect the solar wind, and its low gravity, that allowed the primorial Martian atmosphere to simply be blown away into space.
FRegrards!
wet episode..?
has there been more than one, I wonder?
Now, if they could just land a rover near Cydonia.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.