Boulder, Colorado - For the first time, conclusive evidence has been found of shorelines on Mars.
A University of Colorado at Boulder research team has identified a lake which covered as much as 80 square miles, and was up to 1,500 feet deep. The shoreline evidence includes a series of alternating ridges and troughs thought to be remnants of beach deposits.
"This is the first unambiguous evidence of shorelines on the surface of Mars," said CU-Boulder Research Associate Gaetano Di Achille, who led the study. "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."
Images used for the study were taken by a high-powered camera known as the High Resolution Imaging Science Experiment, or HiRISE. Riding on NASA's Mars Reconnaissance Orbiter, HiRISE can resolve features on the surface down to one meter in size from its orbit 200 miles above Mars.
Analysis of the images indicates that water carved a 30-mile-long canyon that opened up into a valley, depositing sediment that formed a large delta. This delta and others surrounding the basin imply the existence of a large, long-lived lake, say the researchers. The lake bed lies within a valley known as the Shalbatana Vallis.
The evidence shows the lake existed during a time when Mars is generally believed to have been cold and dry, said CU-Boulder Assistant Professor Brian Hynek. "Not only does this research prove there was a long-lived lake system on Mars, but we can see that the lake formed after the warm, wet period is thought to have dissipated."
The deltas adjacent to the lake are of high interest to planetary scientists because deltas on Earth rapidly bury organic carbon and other biomarkers of life. Most astrobiologists believe any signs of life on Mars will take the form of subterranean microorganisms.
Di Achille said the newly discovered lake bed and delta deposits would be would be a prime target for a future landing mission in search of evidence of past life.
A paper on the subject has been published online in Geophysical Research Letters.