Modeling Martian Atmospheric Losses over Time: Implications for Exoplanetary Climate Evolution and Habitability

Abstract

In this Letter, we make use of sophisticated 3D numerical simulations to assess the extent of atmospheric ion and photochemical losses from Mars over time. We demonstrate that the atmospheric ion escape rates were significantly higher (by more than two orders of magnitude) in the past at ∼ 4 Ga compared to the present-day value owing to the stronger solar wind and higher ultraviolet fluxes from the young Sun. We found that the photochemical loss of atomic hot oxygen dominates over the total ion loss at the current epoch whilst the atmospheric ion loss is likely much more important at ancient times. We briefly discuss the ensuing implications of high atmospheric ion escape rates in the context of ancient Mars, and exoplanets with similar atmospheric compositions around young solar-type stars and M-dwarfs.

Magnetic Topology Response to the 2003 Halloween ICME Event at Mars

“…This mixed magnetic topological response is consistent with predictions from magnetohydrodynamic simulations for ICME events in previous studies. Key Points: • We analyze Martian magnetic topology response to the 2003 Halloween ICME event and correlate the variation with upstream drivers • A deeper IMF penetration is found over weak crustal regions but more open field lines over strong crustal regions during the event • This mixed magnetic topological response confirms previous predictions from MHD simulations for ICME eventsevents in order to constrain the extrapolation of atmospheric loss back in time, and thus to better understand Mars' atmospheric evolution (e.g., Dong et al, 2018;Jakosky et al, 2018).…”

“…It is reported that ion escape can be enhanced from a factor of a few to two orders of magnitude for different ICME events (e.g., Luhmann et al, ; Ma et al, ). Therefore, it is important to characterize how the Mars' plasma environment responds to present‐day extreme solar events in order to constrain the extrapolation of atmospheric loss back in time, and thus to better understand Mars' atmospheric evolution (e.g., Dong et al, ; Jakosky et al, ).…”

Global Ten‐Moment Multifluid Simulations of the Solar Wind Interaction with Mercury: From the Planetary Conducting Core to the Dynamic Magnetosphere

“…In recent years, our understanding of terrestrial bodies has been significantly advanced by increasingly sophisticated numerical models. A large number of global models based on either fluid or hybrid (kinetic ion particles and massless electron fluid) approach have been developed for both magnetized planets such as Mercury (e.g., Exner et al, 2018;Jia et al, 2015;Kabin et al, 2008;Kidder et al, 2008;Müller et al, 2012;Richer et al, 2012;Trávníček et al, 2010) and unmagnetized planets such as Mars (Dong et al, 2014(Dong et al, , 2015(Dong et al, , 2018a(Dong et al, , 2018bLedvina et al, 2017;Ma et al, 2014;Modolo et al, 2016) as well as exoplanets (Johansson et al, 2011;Dong et al, 2017aDong et al, , 2017bDong et al, , 2018cDong et al, , 2019. However, none of these global models can accurately treat collisionless magnetic reconnection due to their lack of detailed electron physics.…”

Solar Wind Interaction With the Martian Upper Atmosphere: Roles of the Cold Thermosphere and Hot Oxygen Corona

“…At ancient times, the EUV flux and solar wind parameters were much stronger than that of the current epoch (partly resembling those of the M dwarf exoplanets discussed earlier), and Mars also has a much more extensive and intensive hot oxygen corona (Valeille et al, 2010), indicating that hot oxygen exosphere may provide an important source for O + ion escaping billions of years ago. Therefore, the hot oxygen corona may play a crucial role in the long-term evolution of the Martian atmosphere and its composition over its history (Dong, Bougher, Ma, Toth, Lee, et al, 2014;Dong, Lee, et al, 2018). Based on this study, we speculate that the early (e.g., 4 Gya) loss rate of the ionospheric molecular ions (O + 2 and CO + 2 ) may be even lower than the current value due to the strong shielding (i.e., mass loading) effect of high-altitude oxygen ions.…”

“…In recent years, investigations of the Martian thermosphere/ionosphere structure (e.g., Bougher, Jakorsky, et al, 2015;Withers et al, 2015), magnetic topology (e.g., DiBraccio et al, 2018;Liemohn et al, 2017;Luhmann et al, 2015;Xu et al, 2016), and atmospheric ion escape rates (e.g., Egan et al, 2018;Fang et al, 2017;Halekas et al, 2016) have become increasingly important because they are closely related to the evolution of the Martian atmosphere and can affect its climate over the past four billion years (e.g., Bougher, Cravens, et al, 2015;Dong, Lee, et al, 2018;Jakosky, Lin, et al, 2015;Lillis et al, 2015;Mansfield et al, 2018, and the references therein). In situ spacecraft measurements (e.g., Brain et al, 2015;Dong, Fang, et al, 2015;Lundin et al, 2013;Ramstad et al, 2015) have greatly improved our estimates of global ion loss rates at the current epoch.…”