NASA's Mars Reconnaissance Orbiter has found new evidence of a wet underground environment that once existed on the Red Planet. Using its Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), the orbiter examined the floor of McLaughlin Crater in the Northern Hemisphere of the planet and found evidence of the formation of carbonates and clay in a groundwater-fed lake in the ancient past.

McLaughlin Crater (21.9°N 337.63°E) is located on the western side of the Arabia Terra region of Mars, at a low regional elevation where groundwater-fed lakes are likely to occur. It’s 57 miles (92 km) in diameter and 1.4 miles (2.2 km) deep, which is deep enough to collect ground water. There are no large stream beds feeding into the crater, but there are small channels inside it indicating an ancient lake surface.

Findings indicate the presence of layered, flat rocks at the bottom of the crater. These are partly made of carbonates and clay minerals that require water to form. If a lake was present inside McLaughlin, it would provide a wet environment where life might have existed.

Layers with carbonates inside McLaughlin Crater on Mars (Image: NASA/JPL-Caltech/Univ. of Arizona)

"A number of studies using CRISM data have shown rocks exhumed from the subsurface by meteor impact were altered early in Martian history, most likely by hydrothermal fluids," said Joseph Michalski of the Planetary Science Institute in Tucson, Arizona and London's Natural History Museum. "These fluids trapped in the subsurface could have periodically breached the surface in deep basins such as McLaughlin Crater, possibly carrying clues to subsurface habitability."

The MRO was launched August 12, 2005 from Cape Canaveral Air Force Station, Florida and arrived in Mars orbit on March 10, 2006. Originally scheduled for a two-year mission, the unmanned probe carries a suite of instruments including high-resolution cameras, spectrometers and radar designed to study the climate of Mars with a particular emphasis on the water cycle in the Martian atmosphere and looking for water and water-formed minerals on the surface.

The findings will be published next week in Nature Geoscience.

Source: NASA

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