Science Seminars

11/10/2011 – Mars Chloride-Bearing Materials – Signatures of Aqueous Environments

Speaker: Mikki Osterloo
Date: Thursday, Nov 10, 2011
Time: 4pm
Location: Duane Physics Bldg Room D-142

Seminar Abstract:

The Thermal Emission Imaging System (THEMIS) on the 2001 Mars Odyssey Spacecraft has provided thermal infrared (IR) spectra of materials dispersed throughout the low albedo Noachian and Hesperian-aged southern highlands plains units that show a featureless slope towards longer wavelengths. Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) visible/near infrared spectral observations for the sites indicate that they are composed of a relatively high albedo anhydrous material, which lacks distinct spectral absorptions. Supported by additional observations such as elevated thermal inertia, location in topographic lows, and distinctive morphology (e.g., light-toned and polygonally fractured), there is compelling evidence for a mineralogical component of chloride salt within the materials. Results of our global survey of THEMIS IR daytime data indicate there are hundreds of local exposures spread throughout the southern highlands plains units. Although these chloride materials may only be representative of relatively short-lived bodies of water, such as the salt pans of Death Valley, the fact that the hydrologic and climatic conditions permitted their formation is important and indicates that many locations throughout the southern highlands must have been substantially warmer and wetter in the past. I will discuss the results of our survey investigating the geologic context of the materials, highlighting the materials’ geologic diversity and prevalence across the southern highlands. Additionally, I will discuss our ongoing efforts to investigate and characterize the proposed chloride-bearing materials and their potential formation mechanisms, including crater age-dating of the materials, detailed stratigraphic investigations, and structural analyses of the polygonal fractures identified within many of the sites. Understanding these materials has implications for the hydrological history of the planet and can provide clues to the evolution of regional and global climate.