Mars may have been a nice place to visit once, but that was a long, long time ago.
Researchers at the University of Colorado (CU) at Boulder studying recent images from the Mars Reconnaissance Orbiter (MRO) are reporting that they've found the remnants of a primordial lake on the Red Planet. Calling the satellite photos "the first definitive evidence of shorelines on Mars," the CU-Boulder team, led by Research Associate Gaetano Di Achille, said in aprepared statement
that the lake would have contained water more than 3 billion years ago.
The researchers said the lake would have measured 80 square miles in circumference and have had a depth of 1500 feet, making it roughly the size of Lake Champlain in North America. They also observed that the ancient lake would have been an integral part of a broad delta, suggesting the presence of a large river.
Evidence for their conclusions, which will be published in the latest issue of Geophysical Research Letters, came from a powerful camera aboard the MRO called the High Resolution Imaging Science Experiment, or HiRISE. Their analysis of the HiRISE images in question suggested to them that they were looking at a a 30-mile-long canyon, which opened up into a valley, depositing sediment that formed a large delta in what planetary scientists now call the Shalbatana Vallis.
"This is the first unambiguous evidence of shorelines on the surface of Mars," said Di Achille. "The identification of the shorelines and accompanying geological evidence allows us to calculate the size and volume of the lake, which appears to have formed about 3.4 billion years ago."
The age estimate runs at odds with standard theories of the timeline for the development of Mars, which hold that the planet's surface water would have dissipated much earlier.
Di Achille said the newly discovered lakebed and delta would be a prime target for a future landing mission to Mars in search of evidence of past life.
"On Earth, deltas and lakes are excellent collectors and preservers of signs of past life," said Di Achille. "If life ever arose on Mars, deltas may be the key to unlocking Mars' biological past."
[For more on the prospects of exploring the Red Planet in the future, please see IEEE Spectrum'sSpecial Report: Why Mars? Why Now?
in this month's issue.]