“Early Mars was The Water Planet” –Will NASA’s August 5th Science Mission at Gale Crater Provide Proof?




"We can now say that the planet was altered on a global scale by liquid water about four billion years ago." John Carter of the University of Paris

Will the newly defined search zone for The Mars Curiosity rover following its Aug. 5th touchdown prove Carter right? The Curiosity Science Mission goal is to look for chemical evidence of ancient life preserved within exposures near the base of a five-kilometers high mound of layered materials at the center of Gale crater.**

"Layering at the top of the large mound at the center of Gale crater [landing site] is similar to layering visible in western Medusae Fossae Formation exposures, so Curiosity may be able to examine these materials up close, providing the first direct evidence of how they were formed," said Jim Zimbelman, geologist at the National Air and Space Museum’s Center for Earth and Planetary Studies. "This is exciting because so far none of our orbiting spacecraft have been able to measure the composition of MFF materials, something crucial to any explanation of its origin."

Because of its history, 96-mile wide Gale Crater crater with its strangely sculpted mountain –three times higher than the Grand Canyon is deep–is the ideal place for Curiosity to conduct its mission of exploration into the Red Planet's past. Researchers plan to use Curiosity to study layers in the mountain that hold evidence about wet environments of early Mars.

"This may be one of the thickest exposed sections of layered sedimentary rocks in the solar system," said Joy Crisp, MSL Deputy Project Scientist from NASA's Jet Propulsion Laboratory. "The rock record preserved in those layers holds stories that are billions of years old — stories about whether, when, and for how long Mars might have been habitable."

An instrument on Curiosity can check for any water that might be bound into shallow underground minerals along the rover's path. Today the Red Planet is a radiation-drenched, bitterly cold, bleak world. Enormous dust storms explode across the barren landscape and darken Martian skies for months at a time. But data from the Mars Reconnaissance Orbiter suggest that Mars once hosted vast lakes and flowing rivers.

Minerals in northern Mars craters observed by two NASA orbiters suggested that a phase in Mars' early history with conditions favorable to life occurred globally, not just in the south. Southern and northern Mars differ in many ways, so the extent to which they shared ancient environments has been open to question.

In recent years, the European Space Agency's Mars Express orbiter and NASA's Mars Reconnaissance Orbiter have found clay minerals that are signatures of a wet environment at thousands of sites in the southern highlands of Mars, where rocks on or near the surface are about four billion years old. Until this week, no sites with those minerals had been reported in the northern lowlands, where younger volcanic activity has buried the older surface more deeply.

French and American researchers report that some large craters penetrating younger, overlying rocks in the northern lowlands expose similar mineral clues to ancient wet conditions. Other types of evidence about liquid water in later epochs on Mars tend to point to shorter durations of wet conditions or water that was more acidic or salty.

The researchers used the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), an instrument on the Mars Reconnaissance Orbiter, to check 91 craters in the northern lowlands. In at least nine, they found clays and clay-like minerals called phyllosilicates, or other hydrated silicates that form in wet environments on the surface or underground.

Earlier observations with the OMEGA spectrometer on Mars Express had tentatively detected phyllosilicates in a few craters of the northern plains, but the deposits are small, and CRISM can make focused observations on smaller areas than OMEGA.

"We needed the better spatial resolution to confirm the identifications," Carter said. "The two instruments have different strengths, so there is a great advantage to using both."* CRISM Principal Investigator Scott Murchie of Johns Hopkins University Applied Physics Laboratory, said that the findings aid interpretation of when the wet environments on ancient Mars existed relative to some other important steps in the planet's early history.

The prevailing theory for how the northern part of the planet came to have a much lower elevation than the southern highlands is that a giant object slammed obliquely into northern Mars, turning nearly half of the planet's surface into the solar system's largest impact crater. The new findings suggest that the formation of water-related minerals, and thus at least part of the wet period that may have been most favorable to life, occurred between that early giant impact and the later time when younger sediments formed an overlying mantle.

"That large impact would have eliminated any evidence for the surface environment in the north that preceded the impact," Murchie said. "It must have happened well before the end of the wet period."

The three-dimensional image at the top of the page shows a trough in the Nili Fossae region of Mars shows a type of minerals called phyllosilicates (in magenta and blue hues) concentrated on the slopes of mesas and along canyon walls. The abundance of phyllosilicates shows that water played a sizable role in changing the minerals of a variety of terrains in the planet's early history.

The Daily Galaxy via NASA/JPL

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