Presentation #213.02 in the session “Mars the Gathering!”. Cross-listed as presentation #206.05.
We report results from continuing searches for organic molecules (such as CH4, CH3OH, C2H6, C2H4) in the atmosphere of Mars. We have identified methane and water and have obtained upper limits for the other molecules listed. We used the L3 setting on iSHELL (NASA-IRTF) to sample ten orders ranging from 3.20-3.48 microns that encompass absorption bands of the molecules listed along with bands of water and ozone. We acquired data with the slit oriented N/S and centered on the sub-Earth point on Mars (~9:40 local time); time serial data were taken as the planet rotated under the slit. Data were taken on UT 10-12 December 2020 (Ls~329°, 70°-126°W) and UT 25 February 2021 (Ls~9°, 37°-81°W). Approximately ten minutes of data were stacked for each data point in this presentation. The Mars atmospheric spectrum was isolated from the solar and terrestrial spectra, including terrestrial signatures of H2O, CH4, O3, and related species. Extracts were taken at 0.6 arc-sec intervals in the latitudinal direction. Simulations based on atmospheric models generated for Mars were created to match the observed spectrum. Column densities for CH4 and H2O were thus determined. For other molecules listed above, upper limits were measured. Results for the column density of water were consistent with other measurements, such as NOMAD-TGO, for the same season and location. We have found column densities of methane to vary between its detection limit (2 ppbv) to ~ 25 ppbv. These values are consistent with previously detected column densities of methane (Mumma et al., Science, 2009). Column density maps for methane and water will be presented for both seasonal dates and compared with previously presented measurements at Ls ~ 122° and 293°. This work was partially funded by a grant from NASA’s Mars Fundamental Research Program (11-MFRP11-0066) to RN. NASA’s Mars Exploration Program supported this work under WBS 604796.01.12.01.03 to MJM. We thank the administration and staff of the NASA-IRTF for awarding observing time and for coordinating our observations.