14:30 〜 14:45
[PPS05-14] The Amazonian declining trends of Martian atmospheric water revealed from surface signatures
キーワード：Mars, Ice deposit, Climate Evolution, Crater Fill Deposit
Martian mid-latitudes are the preferred and most easily accessible location for future missions planning to leverage in-situ water ice. An abundant volume of subsurface water ice is preserved in these regions, and it can serve the purpose (Levy et al., 2014). In this context, there remain three most important questions? 1. Where exactly in the mid-latitudes should we look for? 2. Why the region has abundant water ice? 3. How has this accumulation trend behaved over time? While Sako et al., (JpGU this edition) concentrated on the present-day locations of the subsurface reserves, we concentrated on their depositional patterns during the high-obliquity phases and their evolution through time.
Our observation through high-resolution images and a 1-D radiative-convective model suggest the depositional pattern of the water ice remains similar with variable orbital parameters. Analyzing the images, we statistically quantify that the southwest parts of the craters host a larger volume of water ice than other parts of the craters. This result is supported by the 1-D radiative-convective model derived yearly temperature distribution pattern within the crater floor. The model result suggests that the southwestern parts of the crater floor are the regions of constant low temperature throughout the year. Then following a cold-trap mechanism (colder regions attract more snow and ice to deposit) these regions host more snow or ice when available.
We interpret that the crater floor deposits record the long-term declining water content phase. The net accumulation volume of water ice in the more recent glacial periods (last 10s Ma) was comparatively less than during the intense glacial periods (100s Ma). Nevertheless, the Martian climate still retained a considerable amount of water vapor in the atmosphere, and ice was deposited and accumulated only in the preferred locations, such as the cold southwestern part of the crater. This trend of deposition remained the same for the reported glacial periods on Mars (1 Ga; Soare et al., 2022). This is important because on Mars, environmental reconstruction for more than 20 Ma is impossible because of the chaotic nature of the surface.
Our observation through high-resolution images and a 1-D radiative-convective model suggest the depositional pattern of the water ice remains similar with variable orbital parameters. Analyzing the images, we statistically quantify that the southwest parts of the craters host a larger volume of water ice than other parts of the craters. This result is supported by the 1-D radiative-convective model derived yearly temperature distribution pattern within the crater floor. The model result suggests that the southwestern parts of the crater floor are the regions of constant low temperature throughout the year. Then following a cold-trap mechanism (colder regions attract more snow and ice to deposit) these regions host more snow or ice when available.
We interpret that the crater floor deposits record the long-term declining water content phase. The net accumulation volume of water ice in the more recent glacial periods (last 10s Ma) was comparatively less than during the intense glacial periods (100s Ma). Nevertheless, the Martian climate still retained a considerable amount of water vapor in the atmosphere, and ice was deposited and accumulated only in the preferred locations, such as the cold southwestern part of the crater. This trend of deposition remained the same for the reported glacial periods on Mars (1 Ga; Soare et al., 2022). This is important because on Mars, environmental reconstruction for more than 20 Ma is impossible because of the chaotic nature of the surface.