Martian atmospheric hydrogen and deuterium: Seasonal changes and paradigm for escape to space

• DOI: 10.1126/sciadv.adm7499
• Publication Date: 2024-07-26T17:58:28Z
• Authors: John T. Clarke; Majd Mayyasi; Dolon Bhattacharyya; Jean-Yves Chaufray; Nicolas Schneider; Bruce Jakosky; Roger Yelle; Franck Montmessin; Michael Chaffin; Shannon Curry; Justin Deighan; Sonal Jain; Jean-Loup Bertaux; Erin Cangi; Matteo Crismani; Scott Evans; Sumedha Gupta; Franck Lefevre; Greg Holsclaw; Daniel Lo; William McClintock; Michael Stevens; Ian Stewart; Shane Stone; Paul Mahaffy; Mehdi Benna; Meredith Elrod
• Keywords: Medical Sciences; Earth, Environmental, Ecological, and Space Sciences; 550; Bioinformatics; 01 natural sciences; 520; Biomedical Informatics; [SDU] Sciences of the Universe [physics]; [SDU]Sciences of the Universe [physics]; Medical Specialties; Medicine and Health Sciences; 0105 earth and related environmental sciences

Mars’ water history is fundamental to understanding Earth-like planet evolution. Water escapes to space as atoms, and hydrogen atoms escape faster than deuterium giving an increase in the residual D/H ratio. The present ratio reflects the total water Mars has lost. Observations with the Mars Atmosphere and Volatile Evolution (MAVEN) and Hubble Space Telescope (HST) spacecraft provide atomic densities and escape rates for H and D. Large increases near perihelion observed each martian year are consistent with a strong upwelling of water vapor. Short-term changes require processes in addition to thermal escape, likely from atmospheric dynamics and superthermal atoms. Including escape from hot atoms, both H and D escape rapidly, and the escape fluxes are limited by resupply from the lower atmosphere. In this paradigm for the escape of water, the D/H ratio of the escaping atoms and the enhancement in water are determined by upwelling water vapor and atmospheric dynamics rather than by the specific details of atomic escape.