Even though Mars turned dry and cold long ago, researchers at the University of Colorado Boulder have discovered evidence of an ancient lake that likely represents some of the last potentially habitable surface water ever to exist on the Red Planet.
In a study published in the journal Geology, scientists detailed an 18-square-mile chloride salt deposit, roughly the size of the city of Boulder, in the planet’s Meridiani region near the Mars Opportunity rover’s landing site. Much the same as on Earth in locations such as Utah’s Bonneville Salt Flats, large-scale salt deposits are considered to be evidence of evaporated bodies of water.
Lead author Brian Hynek, research associate at the Laboratory for Atmospheric and Space Physics (LASP) at CU-Boulder, said:
“This was a long-lived lake, and we were able to put a very good time boundary on its maximum age. We can be pretty certain that this is one of the last instances of a sizeable lake on Mars.”
Digital terrain mapping and mineralogical analysis of the features surrounding the deposit indicate that this one-time lakebed is no older than 3.6 billion years old, well after the time period when Mars is thought to have been warm enough to sustain large amounts of surface water planet-wide (planetary scientists believe that the solar system formed approximately 4.6 billion years ago).
“By salinity alone, it certainly seems as though this lake would have been habitable throughout much of its existence,” said Hynek.
He added, however, that other factors such as acidity levels were not included in the scope of the study.
Brian M. Hynek, Mikki K. Osterloo, and Kathryn S. Kierein-Young
Late-stage formation of Martian chloride salts through ponding and evaporation
Geology, G36895.1, first published on August 5, 2015, doi:10.1130/G36895.1
Illustration: LASP / Brian Hynek