P23B-2142
Analysis of likely Frost Events and day-to-night Variability in near-surface Water Vapor at Gale

Tuesday, 15 December 2015
Poster Hall (Moscone South)
German Martinez1, Erik Fischer1, Nilton O Renno1, Eduardo Sebastian2, Osku Kemppinen3, Nathan Bridges4, Caue Borlina5, Pierre-Yves Meslin6, Maria Genzer3, Ari-Matti Harri3, Alvaro Vicente-Retortillo7, Manuel de la Torre-Juárez8, Miguel Ramos9, Felipe Gomez2 and Javier Gomez-Elvira10, (1)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (2)Centro de Astrobiología, Madrid, Spain, (3)Finnish Meteorological Inst, Helsinki, Finland, (4)Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States, (5)University of Michigan, Ann Arbor, MI, United States, (6)Universite Paul Sabatier, Toulouse, France, (7)Complutense University of Madrid, Madrid, Spain, (8)Jet Propulsion Laboratory, Pasadena, CA, United States, (9)Universidad de Alcalá, Alcalá de Henares, Spain, (10)Organization Not Listed, Washington, DC, United States
Abstract:
We analyze REMS simultaneous measurements of relative humidity and ground temperature with the highest confidence to identify frost events at Gale crater during the first 1000 sols of the MSL mission. The relative humidity sensor has recently been recalibrated (June 2015), providing relative humidity values slightly lower than those in the previous release (Dec 2014). Here we only use relative humidity data obtained with the latest recalibration parameters.

We find that the most likely frost events occurred at four different locations: Dingo Gap during sols 529-535, an unnamed place during sols 554-560, Kimberley during sols 609-617, and an unnamed place during sols 673-676. At these four locations, the terrain features thermal inertia of ~200 SI units, a value much lower than that of 365 ± 50 SI units obtained from satellite measurements at the landing ellipse. We estimate a maximum thickness of the frost layer likely developed at these four locations of the order of tenths of μm, with the precipitable water content (PWC) showing values of a few pr-μm.

Since water vapor pressure values derived from REMS measurements present high uncertainties during the daytime, the day-to-night variability in the near-surface water content at Gale cannot be analyzed using only REMS products. By comparing the nighttime PWC values obtained from REMS with the daytime PWC values obtained from satellite, we estimate a day-to-night ratio of the near-surface water vapor pressure at Gale of about 5.

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