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Differential Scanning Calorimetry and Evolved Gas Analysis of HydromagnesiteVolatile-bearing minerals (e.g., Fe-oxyhydroxides, phyllosilicates, carbonates and sulfates) may be important phases on the surface of Mars. In order to characterize these phases the Thermal and Evolved Gas Analyzer (TEGA) flying on the Mars'98 lander will perform analyses on surface samples from Mars. Hydromagnesite [Mg5(CO3)4(OH)2.4H2O] is considered a good standard mineral to examine as a Mars soil analog component because it evolves both H2O and CO2 at temperatures between 0 and 600 C. Our aim here is to interpret the DSC signature of hydromagnesite under ambient pressure and 20 sccm N2 flow in the range 25 to 600 C. The DSC curve for hydromagnesite under the above conditions consists of three endothermic peaks at temperatures 296, 426, and 548 and one sharp exotherm at 511 C. X-ray analysis of the sample at different stop temperatures suggested that the exotherm corresponded with the formation of crystalline magnesite. The first endotherm was due to dehydration of hydromagnesite, and then the second one was due to the decomposition of carbonate, immediately followed by the formation of magnesite (exotherm) and its decomposition to periclase (last endotherm). Evolution of water and CO2 were consistent with the observed enthalpy changes. A library of such DSC-evolved gas curves for putative Martian minerals are currently being acquired in order to facilitate the interpretation of results obtained by a robotic lander.
Document ID
20000084336
Acquisition Source
Johnson Space Center
Document Type
Preprint (Draft being sent to journal)
Authors
Lauer, H. V., Jr.
(Lockheed Martin Space Mission Systems and Services United States)
Golden, D. C.
(Hernandez Engineering, Inc. United States)
Ming, Douglas W.
(NASA Johnson Space Center Houston, TX United States)
Boynton, W. V.
(Arizona Univ. AZ United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Geophysics
Meeting Information
Meeting: Science Serving Agriculture and Natural Resources: Past/Present
Location: Salt Lake City, UT
Country: United States
Start Date: October 30, 1999
End Date: November 4, 1999
Sponsors: American Society of Agronomy
Funding Number(s)
PROJECT: RTOP 131-50-20-23
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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