Fig. 2: Combined ice precipitation and surface ice distributions from Syrtis Major and Apollinaris Mons.

a–d Precipitation and surface ice distributions broadly overlap with equatorial regions containing high excess hydrogen (i.e., >10 wt% WEH; red lines). Eruptions from Syrtis Major (67.17°E, 9°N) and Apollinaris Mons (174.4°E, −8.5°S) are run according to baseline parameters listed in Table 2. a, b Ice precipitation and surface ice loading represent the resulting distributions at the end of the eruption. c Surface ice loading represents the resulting distribution one year post-eruption with present-day topography and d pre-Tharsis bulge topography. Modeled distributions are overlaid onto a cylindrical projection of Mars. Black lines represent MOLA (a–c) topographic contours and pre-Tharsis bulge (d) topographic contours, with numbers indicating contour elevations in kilometers.