Search for Spring Deposits on Mars

Identification of spring deposits on Mars is of major importance to deciphering the history of water on that planet. Martian springs are also potentially important sites for astrobiology, as these could be locations where martian life evolved, where it sought refuge as the climate became colder and drier, and where evidence of that life may have been preserved. Rock and mineral samples from spring deposits, returned to Earth for detailed laboratory analysis, may provide the first compelling, organic signatures of martian microorganisms.

We have recently reported evidence for spring deposits in a large martian crater in Arabia Terra. The martian features are low mounds, each approximately 250 x 500 m in extent, which feature terraced flanks, apical depressions, river-like channels, concentric fractures, and elliptical tonal anomalies. All of these features are common in terrestrial springs such as those in the Dalhousie complex in Australia and Yellowstone National Park. Many of these features on Mars can only be recognized in the full-resolution (28 cm per pixel) images from the HiRISE camera on the Mars Reconnaissance Orbiter (MRO). Additional features on larger scales, identified as potential spring deposits based on morphology and geologic setting, have been reported in craters and valleys by other researchers.

The CRISM hyperspectral imager on MRO, which is bore-sighted with the HiRISE camera, covers the visible and near-infrared wavelengths (0.37 to 3.92 microns) in 545 channels at a spatial resolution of approximately 20 m per pixel. CRISM has demonstrated the capability of identifying many of the minerals characteristically deposited by terrestrial springs including hydrated silica, layered phyllosilicates, hydrated sulfates, iron oxides, and gypsum. Carbonates may also be identifiable in CRISM spectra, though none have been reported to date. Intensive research is underway to correlate potential spring deposits, recognized based on morphology and geologic setting, with CRISM mineral identification.