P033-0018
The Highly Variable Ratio of D/H in Atoms Escaping from Mars

Thursday, 10 December 2020
Poster
John T Clarke1, Majd Mayyasi2, Dolon Bhattacharyya3, Nicholas McCord Schneider4, Bruce Martin Jakosky5, Roger V Yelle6, Jean-Loup Bertaux7, Michael Chaffin8, Jean-Yves Chaufray9, Justin Deighan8, Sonal Jain8 and Franck Montmessin10, (1)Boston University, Boston, MA, United States, (2)Boston University, Center for Space Physics, Boston, MA, United States, (3)University of Illinois at Urbana-Champaign, Electrical and Computer Engineering, Urbana, IL, United States, (4)Univ Colorado, Boulder, CO, United States, (5)University of Colorado Boulder, Boulder, CO, UNITED STATES, (6)University of Arizona, Lunar and Planetary Laboratory, Tucson, AZ, United States, (7)Univ. Versailles St Quentin, Guyancourt, France, (8)Laboratory for Atmospheric and Space Physics, Boulder, CO, United States, (9)LATMOS/IPSL, UVSQ Université Paris-Saclay, Sorbonne Université, Guyancourt, France, (10)LATMOS Laboratoire Atmosphères, Observations Spatiales, UVSQ Université Paris-Saclay, Sorbonne université, CNRS, Paris, France
Abstract:
The constituent atoms of water are known to escape the weak Martian gravity into space, and the lighter isotope H escapes faster than D leading to a long term increase in the D/H ratio of the remaining water. The present D/H ratio is proportional to the total amount of water that has escaped, but deriving the depth of water on a warmer and wetter primordial Mars requires understanding the factors that control escape processes today. In particular, it is important to measure the escaping atoms H and D, rather than rely on the D/H ratio in water and modeling. Observations of UV Lyman-alpha resonance line emissions from H and D atoms has been carried out with the MAVEN and Hubble Space Telescope (HST) missions, providing direct measurements of the H and D densities and escape rates from the upper Martian atmosphere. The H and D densities and the ratio of D/H in the escaping atoms are found to consistently increase by a factor of 5-10 around southern summer (perihelion) across several Martian years. This is consistent with an influx of hydrogen species from lower atmospheric water around perihelion, at which times the D/H ratio also increases from the higher escape flux of H compared with the heavier D atoms. A scenario is proposed to explain these changes that can be verified by future measurements.
<< Previous Abstract | Next Abstract >>