Rover landing site has rocks that tell Mars history

4:07 PM, Aug 3, 2012   |    comments
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PASADENA, California - When scientists were hunting for a landing site for NASA's Mars Science Laboratory and its Curiosity rover, they wanted a place that, geologically speaking, rocked.

In fact, NASA selected Gale Crater -- a chasm 96 miles in diameter -- because of its rocks. It's also, quite simply, a neat place, big enough that it could just about swallow Connecticut and Rhode Island. Equally imposing is its central feature: An 18,000-foot mountain taller than Mount Rainer near Seattle.

It's taller than any mountain in the lower 48 states. But the rocks made it stand out above 60 other candidates as the best site for the Mars rover, which is scheduled to land on the red planet at 1:17 a.m. EDT Monday. "It has two major kinds of rock types that formed in the presence of liquid water on Mars," said Matt Golombek, NASA's Mars Science Laboratory landing site scientist.

The area has: -- Rocks containing significant amounts of sulfates, a telltale sign that they once were awash in water. -- Phyllosilicates, or clays, which also result from contact with water. These rocks can be formed only in the presence of liquid water, and water is one of the key ingredients of the formation of life -- perhaps the single most critical.

But what really makes these rocks rock is that they preserve the history of interaction with water much in the same way amber, tar and paraffin serve to preserve fossils on Earth. Said Golombek: "To geologists, that's gold." Now that's not to say Gale Crater and its towering central mountain aren't scientifically important features themselves.

Certainly, they are. Gale Crater is located just south of the equator on the eastern side of the planet, right in an area that separates Martian northern highlands from its southern lowlands. Planetary scientists for 15 years have been "following the water." Straddling this interesting boundary, Gale Crater is a perfect place to do just that. "Gale Crater is one of the lowest places on Mars, and if you don't know anything else in advance, that's where you want to go find evidence of water," said John Grotzinger, Mars Science Laboratory project scientist at NASA's Jet Propulsion Laboratory here. "Water flows down hill, and that's where we are going."

Planetary geologists are psyched about the prospects of roving around the base of the mountain -- Aeolis Mons. It's informally known as Mount Sharp, a posthumous tribute to pioneering planetary geologist Robert Sharp. He played key roles in earlier robotic Mars expeditions.

Sedimentary rocks, rocks formed from minerals that sunk through water to a planetary surface, form the base of Gale Crater's massive mountain. Topping that foundation is layer after geological layer of material laid down in sequential stacks. Similar strata in the Grand Canyon National Park in Arizona hold evidence of the geological history of Earth.

Planetary scientists expect the layers that make up Mount Sharp to yield evidence of the geological history of the east-central region of Mars, dating back billions of years. "By reading those layers, one after another, we can piece together the history of Mars, or at least in that region," said Ashwin Vasavada, NASA's Mars Science Laboratory deputy project scientist.

"We're really excited because of the size of the stack of layers. That means it's a bigger book, a bigger history book about Mars than anywhere else we could think of to land this rover."

By TODD HALVORSON, Florida Today

Gannett/Florida Today

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