Solubility of C-O-H volatiles in graphite-saturated martian basalts and application to martian atmospheric evolution
Loading...
View/Download File
Persistent link to this item
Statistics
View StatisticsJournal Title
Journal ISSN
Volume Title
Title
Solubility of C-O-H volatiles in graphite-saturated martian basalts and application to martian atmospheric evolution
Published Date
2012-12-12
Publisher
Type
Conference Paper
Abstract
The modern martian atmosphere is thin, leading to surface conditions too cold to support liquid water. Yet, there is evidence of liquid surface water early in martian history that is commonly thought to require a thick CO2 atmosphere. Our previous work follows the analysis developed by Holloway and co-workers (Holloway et al. 1992; Holloway 1998), which predicts a linear relationship between CO2 and oxygen fugacity (fO2) in graphite-saturated silicate melts. At low oxygen fugacity, the solubility of CO2 in silicate melts is therefore very low. Such low calculated solubilities under reducing conditions lead to small fluxes of CO2 associated with martian magmatism, and therefore production of a thick volcanogenic CO2 atmosphere could require a prohibitively large volume of mantle-derived magma. The key assumption in these previous calculations is that the carbonate ion is the chief soluble C-O-H species. The results of the calculations would not be affected appreciably if molecular CO2, rather than carbonate ion, were an important species, but could be entirely different if there were other appreciable C-species such as CO, carbonyl (C=O) complexes, carbide (Si-C), or CH4. Clearly, graphite-saturated experiments are required to explore how much volcanogenic C may be degassed by reduced martian lavas.
A series of piston-cylinder experiments were performed on synthetic martian starting materials over a range of oxygen fugacities (IW+2.3-IW-0.9), and at pressures of 1-3 GPa and temperatures of 1340-1600 ÂșC in Pt-graphite double capsules. CO2 contents in experimental glasses were determined using Fourier transform infrared spectroscopy (FTIR) and range from 0.0026-0.50 wt%. CO2 solubilities change by one order of magnitude with an order of magnitude change in oxygen fugacity, as predicted by previous work. Secondary ion mass spectrometry (SIMS) determinations of C contents in glasses range from 0.0131-0.2626 wt%. C contents determined by SIMS are consistently higher than CO2 contents determined by FTIR. This difference, termed excess C, is attributed to the presence of other reduced C-species, such as carbonyls and amides (which have C=O and N-H bonds), detected using FTIR in reduced graphite-saturated martian basalts. An atmosphere produced by degassing of magmas similar to this study would be richer in C-O-H species than previously modeled using only CO2 and could create a much warmer climate that stabilizes liquid water on the ancient martian surface.
Keywords
Description
Fall AGU meeting, 2012.
Related to
Replaces
License
Collections
Funding information
NASA Mars Fundamental Research Program Grant 10-MFRP10-0069
Isbn identifier
Doi identifier
Previously Published Citation
Suggested citation
Stanley, Ben D.; Hirschmann, Marc M.; Withers, Anthony C.. (2012). Solubility of C-O-H volatiles in graphite-saturated martian basalts and application to martian atmospheric evolution. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/140767.
Content distributed via the University Digital Conservancy may be subject to additional license and use restrictions applied by the depositor. By using these files, users agree to the Terms of Use. Materials in the UDC may contain content that is disturbing and/or harmful. For more information, please see our statement on harmful content in digital repositories.