A geologic mapping project using NASA spacecraft data, offers new  evidence that expansive lakes and seas existed long ago on Mars.

The research points to a series of sedimentary deposits consistent with what would relate to large standing bodies of water in Hellas Planitia located in the southern hemisphere of Mars, said by Dr. Leslie Bleamaster, research scientist at the Planetary Science Institute.

Fine-layered outcrops around the eastern rim of Hellas have been interpreted as a series of sedimentary deposits resulting from erosion and transport of highland rim materials into a basin-wide standing body of water, Bleamaster said. Hellas basin, more than 2.00 km across and 8 km deep, is the largest recognized impact structure on the Martian surface, he said.

The mapping project reinforces earlier research that initially proposed Hellas-wide lakes citing different evidence in the west, he said. The new map and accompanying map pamphlet may be found at http://pubs.usgs.gov/sim/3096/

“This mapping makes geologic interpretations consistent with previous studies, and constrains the timing of these putative lakes to the early-middle Noachian period on Mars, between 4.5 and 3.5 billion years ago,” he said.

A systematic search of high-resolution images revealed that eastern Hellas Planitia, where the fine-layered floor deposits were discovered, is unique in nature representing a confluence between sedimentary sources and sinks. The circum-Hellas highlands represent a significant percentage of the southern hemisphere of Mars and have served as a locus for volcanic and sedimentary activity throughout Martian geologic time. Hellas Planitia preserves the materials shed from these highlands and holds the key to further unraveling some of Mars’ long held secrets.

“Our mapping and evaluation of landforms and materials of the Hellas region from the basin rim to floor provides further insight into Martian climate regimes and into the abundance, distribution, and flux of volatiles through history,” Bleamaster said.

The geologic mapping was published at 1:1,000,000 scale and used Viking Orbiter, Thermal Emission Imaging System (THEMIS) infrared (IR) and visible (VIS) wavelength, and Mars Orbiter Camera (MOC) narrow-angle images, combined with Mars Orbiter Laser Altimeter (MOLA) topographic data, to characterize the geologic materials and processes that have shaped this region and was supported through NASA’s Planetary Geology and Geophysics program.

Source: US Geological Survey
See full maps (PDF)