Loss of the Martian atmosphere to space: Present-day loss rates determined from MAVEN observations and integrated loss through time

• Published in: Icarus (New York, N.Y. 1962) Vol. 315; pp. 146 - 157
• Main Authors: Jakosky, B.M., Brain, D., Deighan, J., Grebowsky, J., Halekas, J., Luhmann, J.G., Andersson, L., Andre, N., Andrews, D., Baird, D., Baker, D., Bell, J., Benna, M., Bhattacharyya, D., Bougher, S., Bowers, C., Chamberlin, P., Chaufray, J.-Y., Clarke, J., Combi, M., Connerney, J., Correira, J., Crabb, K., Crary, F., Cravens, T., Delory, G., Dewey, R., Dong, C., Dong, Y., Dunn, P., Egan, H., Eriksson, A., Evans, S., Fallows, K., Fogle, A., Fowler, C., Fujimoto, M., Garnier, P., Girazian, Z., Groeller, H., Gruesbeck, J., Hamil, O., Hanley, K.G., Hara, T., Harada, Y., Hermann, J., Holsclaw, G., Houston, S., Kotova, A., Lee, Y., Lee, C., Lentz, C., Lo, D., Lugo, R., Ma, Y.-J., Mahaffy, P., Marquette, M.L., Matsumoto, Y., Mayyasi, M., Mazelle, C., McClintock, W., McFadden, J., Medvedev, A., Mendillo, M., Meziane, K., Milby, Z., Mitchell, D., Modolo, R., Nagy, A., Nakagawa, H., Narvaez, C., Olsen, K., Pawlowski, D., Peterson, W., Rahmati, A., Roeten, K., Romanelli, N., Ruhunusiri, S., Russell, C., Sakai, S., Seki, K., Sharrar, R., Shaver, S., Siskind, D.E., Slipski, M., Steckiewicz, M., Stewart, I., Stiepen, A., Stone, S., Tenishev, V., Terada, N., Terada, K., Tolson, R., Toth, G., Trovato, J., Vogt, M., Xu, S., Yelle, R., Yiğit, E., Zurek, R.
• Format: Journal Article Web Resource
• Language: English
• Published: Elsevier Inc 15-11-2018; Elsevier; Academic Press Inc
• Subjects: Astrophysics; Atmosphere; Aérospatiale, astronomie & astrophysique; Magnetospheres; Mars; Mars atmosphere; Mars climate; Physical, chemical, mathematical & earth Sciences; Physique, chimie, mathématiques & sciences de la terre; Sciences of the Universe; Solar wind; Space science, astronomy & astrophysics; Mars; Mars atmosphere; Solar wind; Magnetospheres; Atmosphere; Mars climate
• ISSN: 0019-1035; 1090-2643; 1090-2643
• DOI: 10.1016/j.icarus.2018.05.030

•MAVEN has observed the Martian upper atmosphere for a full Martian year, and has determined the rate of loss of gas to space and the driving processes; 1–2 kg/s of gas are being lost.•The loss rate extrapolated back in time gives an estimate of the total loss of gas to space and its impact on Martian climate history; an estimated 0.8 bars or more of CO2 likely has been lost.•Loss to space has been the major process driving climate change on Mars.
Observations of the Mars upper atmosphere made from the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft have been used to determine the loss rates of gas from the upper atmosphere to space for a complete Mars year (16 Nov 2014 – 3 Oct 2016). Loss rates for H and O are sufficient to remove ∼2–3 kg/s to space. By itself, this loss would be significant over the history of the planet. In addition, loss rates would have been greater early in history due to the enhanced solar EUV and more-active Sun. Integrated loss, based on current processes whose escape rates in the past are adjusted according to expected solar evolution, would have been as much as 0.8 bar CO2 or 23 m global equivalent layer of H2O; these losses are likely to be lower limits due to the nature of the extrapolation of loss rates to the earliest times. Combined with the lack of surface or subsurface reservoirs for CO2 that could hold remnants of an early, thick atmosphere, these results suggest that loss of gas to space has been the dominant process responsible for changing the climate of Mars from an early, warmer environment to the cold, dry one that we see today.