SPACE.com -- The Chemistry of Mars

Among the signs of water at Opportunity's location are the round, BB-sized particles like these seen in a mosaic from the microscopic image taken at the rock outcrop dubbed 'Guadalupe.' These spherules are not concentrated at particular layers within the rock, as they would likely be if they originated outside the rock and were deposited onto accumulating layers while the rock was forming. Image Credit: NASA/JPL/US Geological Survey

This spectrum, taken by Opportunity's Moessbauer spectrometer, shows the presence of an iron-bearing mineral called jarosite in the collection of rocks dubbed 'El Capitan.' El Capitan is located within the rock outcrop that lines the inner edge of the small crater where Opportunity landed. The pair of yellow peaks specifically indicates a jarosite phase, which contains water in the form of hydroxyl as a part of its structure. These data suggest water-driven processes exist on Mars.

'El Capitan' is being studied in great detail using the scientific instruments on Opportunity's arm; images from the panoramic camera help scientists choose the locations for this compositional work. The millimeter-scale detail of the lamination covering these rocks can be seen. The face of the rock to the right of the mosaic may be a future target for grinding with the rover's rock abrasion tool. Image Credit: NASA/JPL/Cornell

Opportunity's Microscopic Imager found this intriguing object, lookingmore like Rotini pasta. Its odd shape has stirred up Mars researchers,both inside and outside of the NASA Mars Rover Exploration team. Whetheror not this object is related to biology has prompted a variety ofviews.

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	The Chemistry of Mars By Tariq Malik Staff Writer posted: 07:00 am ET 03 March 2004

One of the foundations supporting NASA's case for water on Mars is the presence, at least near the red planet rover Opportunity, of the salty chemical forms of sulfur known as sulfates

One of the foundations supporting NASA's case for water's past presence on Mars, at least near the rover Opportunity, is salty chemical forms of sulfur known as sulfates.

These mineral salts were found in abundance during Opportunity's studies of a rock outcrop sitting in its Meridiani Planum landing site.

"With this quantity of sulfates, you kind of have to have a lot of water involved," explained Steven Squyres, principal investigator of Opportunity's science package and a professor at Cornell University.

The sulfates were detected with Opportunity's alpha particle X-ray spectrometer, which identifies the chemical elements of a sample, detected high amounts of sulfur in the nearby outcrop during three weeks of intense study by the robust robot. Among the chemical forms of sulfur present were magnesium, iron and other sulfate salts.

Chief among the sulfates found is jarosite, a hydrated iron sulfate detected by Opportunity's Moessbauer spectrometer, a device that scans for iron-bearing minerals.

"On Earth, the only place we see this mineral is in areas where there is liquid water," said Cathryn Weitz, a program scientist with the Mars Exploration Rovers program, which includes Opportunity, and Mars Express. Jarosite is typically found in acidic lakes or such as hot springs, she added.

Opportunity's rock outcrop could also have once sat in an acidic lake or a hot springs environment, NASA officials said.

The detection of magnesium sulfate kieserite, which is similar to epsom salt, and bromide salts were also telltale signs that water existed on the red planet. Both are evaporite minerals, and found on Earth in regions where seas evaporate over time.

Benton Clark III, a Mars Exploration Rover team member, said Opportunity's observations showed that the levels of bromide salts increased towards the bottom of the outcrop, but the sulfur levels increased towards the top.

"This is a classic signature of an evaporite," he told SPACE.com. "Here, water is evaporating, and the salt comes out in these deposits."

Opportunity's handlers can't say for certain that Meridiani Planum was up to its armpits in a salty sea in eons past. It's just as possible that groundwater percolated through the rocky outcrop on the way into the ground. Rover scientists are busy planning further studies over a broader area may help determine what depth, on the surface or otherwise, Martian water may have reached.

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