Crater counts show that the western portions of the Medusae Fossae formation on Mars—an intensely eroded deposit near the northern edge of the cratered highlands-- are much older than previously thought, originating near the end of the Hesperian geologic epoch on Mars, around 3.5 billion years ago, which means that these deposits were emplaced during the epoch that shows evidence for the wide distribution of water at the surface of Mars.
New mapping has revealed the presence of Medusae Fossae (MFF) materials close to Gale crater (image above), the landing site chosen for the Mars Science Laboratory rover Curiosity, en route to its landing the evening of Aug. 5, 2012, PDT (early Aug. 6, EDT). The primary goal for Curiosity 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.
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.
"Gale Crater and its mountain will tell this intriguing story," says Matthew Golombek, Mars Exploration Program Landing Site Scientist from JPL. "The layers there chronicle Mars' environmental history.
Previous work revealed that the layering in the Gale mound is quite different between the oldest layers near the base of the mound and more uniformly layered materials visible at the top of the mound. The layered materials at the top of Gale mound are similar in appearance to uniformly layered exposures of western MFF materials in the areas recently mapped. So, should Curiosity be able to climb up onto the mound and reach some of the uniformly layered materials, the spacecraft will then be able to sample materials that look very much like MFF deposits.
A logical extension of the interpretations in this report suggests that the materials comprising the upper portions of Gale mound might be outliers of MFF (image above) material, much like the ones now identified just outside of the crater. The precise instruments of Curiosity might then show what MFF materials are made of, and thereby open a window onto what happened during the close of the climate-altering Hesperian period.
The findings are reported in a paper by Smithsonian scientists James R. Zimbelman and Stephen P. Scheidt, "Hesperian age for western Medusae Fossae Formation, Mars" scheduled for publication in the June 29 issue of the journal Science.
The image below show portions of global geologic maps of Mars derived from Viking data, with MFF units outlined in red. The equator of Mars runs through the middle of the image; each grid box corresponds to 10 by 10 degrees (roughly 590 by 590 km).
Image credits: Credit: U.S. Geological Survey and NASA/JPL-Caltech/University of Arizona
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