Restoration and Recalibration of the Viking MAWD Datasets

Abstract:

High-resolution HIRISE images of transient albedo dark features, called Recurring Slope Lineae (RSL), have been interpreted to be evidence for current hydrological activity [1]. If there are surface sources of water, then localized plumes of atmospheric water may be observable from orbit. The Viking MAWD column water vapor data are uniquely valuable for this purpose because they cover the full range of Martian local times, and include data sampled at high spatial resolution [2]. They also are accompanied by simultaneously acquired surface and atmospheric temperatures acquired by the Viking Infrared Thermal Mapper (IRTM) instruments. We searched the raster-averaged Viking Orbiter 1 and 2 MAWD column water vapor dataset for regions of localized elevated column water vapor abundances and found mid-latitude regions with transient water observations [3]. The raster averaged Viking Orbiter 1 and 2 MAWD column water vapor data available in the Planetary Data System (PDS), were calculated from radiance measurements using seasonally and topographically varying surface pressures which, at the time, had high uncertainties [4]. Due to recent interest in transient hydrological activity on Mars [2], we decoded the non-raster averaged Viking MAWD dataset, which are sampled at 15 times higher spatial resolution than the data that are currently available from PDS. This new dataset is being used to recalculate column water vapor abundances using current topographical data, as well as dust and pressure measurements from the Mars Global Circulation Model.

References: [1] McEwen, A. S., et al. (2011). Seasonal flows on warm Martian slopes. Science (New York, N.Y.), 333(6043), 740–3. [2] Farmer, C. B., & Laporte, D. D. (1972). The Detection and Mapping of Water Vapor in the Martian Atmosphere. Icarus. [3] Nuno, R. G., et al. (2013). Searching for Localized Water Vapor Sources on Mars Utilizing Viking MAWD Data. 44th Lunar and Planetary Science Conference. [4] Farmer, C. B., et al. (1977). Mars: Water vapor observations from the Viking orbiters. Journal of Geophysical Research, 82(28), 4225–4248.