Fig. 1 Diffusive separation by mass above the homopause. Examples of the ratio of N2 to 40Ar, both measured by MAVEN NGIMS, during a single orbit. The altitude at which the ratio equals the lower-atmosphere value, shown by the vertical dashed line, is the nominal homopause altitude. (A) Well-behaved example showing the ability to extrapolate the ratio down to the surface value to derive the homopause altitude. (B) Example showing structure at lower altitudes that complicates the extrapolation.
Fig. 3 Solar-zenith–angle dependence of upper-atmosphere structure. Panels show the argon exobase altitude, homopause altitude, separation between the homopause and exobase, and atmospheric scale height derived from 40Ar measurements, as a function of the solar zenith angle throughout the mission. Points are color coded by Martian season (Ls) and show the effects of changing seasons.
Fig. 4 Derived fraction of atmospheric Ar lost to space. Data points represent values derived for 40Ar scale height and separation between the homopause. Each point represents a single orbit and is color coded by SZA. Dashed lines represent the fraction of 36Ar lost to space, integrated through time, including the effects of outgassing of juvenile gas, release of gas from impacting asteroids, and weathering of crustal materials.
Supplementary Materials
www.sciencemag.org/content/355/6332/1408/suppl/DC1
Materials and Methods
Supplementary Text
Figs. S1 to S3
References (38–41)
Additional Files
- Mars' atmospheric history derived from upper-atmosphere measurements of 38Ar/36Ar
B. M. Jakosky, M. Slipski, M. Benna, P. Mahaffy, M. Elrod, R. Yelle, S. Stone, N. Alsaeed
Materials/Methods, Supplementary Text, Tables, Figures, and/or References
- Materials and Methods
- Supplementary Text
- Figs. S1 to S3
- References
