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NASA's James Webb Space Telescope:

Obser vations of Mars

Villanueva (CUA / N A SA), Altieri (IFSI), Clancy (SSI), Encrenaz (LESI A), Fouchet (LEISA), Har togh (MP S), Lellouch (LEISA) LСpezValverde (I A A), Mumma (N A SA), Novak (Iona), Smith (N A SA), Vandaele (BISA), Wolf f (SSI)

Does the atmosphere of Mars reveal a more habitable past? Are there unidentified sources of water on Mars? What processes alter the chemical stability of its atmosphere? These are some of the questions that JWST can address by per forming isotopic studies of molecular species (e.g., HDO/H2O), and by investigating the role of trace species in the atmospheric photochemical cycles. The atmosphere acts as a buf fer bet ween the main reser voirs of H, C and O (e.g., regolith, polar caps, rocks) and the exosphere, consequently atmospheric isotopic/abundance ratios and their variabilit y provide key diagnostics quantif ying the exchange bet ween these environments. Characterization of these processes require high-spatial resolution, global coverage, superb spectroscopy and unprecedented time cadences, all qualities provided by the James Webb Space Telescope (JWST ), due to its unique vantage point at the second Sun-Ear th Lagrange point (L2) and its power ful suite of instruments. The broad spectral coverage provided by JWST will permit the characterization of the formation and evolution of global dust storms and cloud systems over volcanoes, while its spectral resolution allows the search for trace photochemical species and isotopic compounds.
Winter

JWST will permit instantaneous measurements disk at ver y high spatial resolutions, allowing transient events near the day/night terminator, seasonal (Nor th-South) phenomena, and the ra ices and of other volatile reser voirs.

of the whole obser vable for the investigation of diurnal (East-West) and pid vaporization of polar

Terminator

Night

Polar Cap

Was Mars habitable? Is it now? How wet was Mars? How much water is currently available?

How is the exchange between the polar caps with the regolith and the atmosphere?

Day


Spectroscopy and Imaging of Mars
10000 Non-saturating with NIRSpec for the night side Non-saturating with NIRSpec for the complete observable disk NIRCam imaging of CO2 non-LTE emission Mars brightness [Jy / square-arcsec]

1000

NIRSpec mapping of O2 nightglow

NIRCam imaging of whole disk

100

10

1

Predicted fluxes (Wolff et al. 2014) for Mars at Ls=285 (dashed), Ls=195 (dotted) and LS=105 (full) as observed with NIRSpec and NIRCam 1 2 Wavelength [m]

Search for organics 3 4 5 6 7

JWST will permit obser vations of Mars at infrared wavelengths with NIRSpec and NIRCam--predicted fluxes are shown for three seasons/aerocentric longitudes (Ls). Specifically, NIRSpec obser vations are feasible with sub-array readouts in the 2.7 to 5.2 m spectral region for the complete obser vable disk, and from 0.7 to 5.2 m in the night regions. Obser vations with NIRCam are accessible with t wo narrow filters near 2 m for the complete disk, and with several filters from 0.5 to 2 m across the night regions. Mapping of CO2 non-LTE emission at 4.3 m will be also possible with NIRCam's filter F430M.

Near-Infrared Spectrograph (NIRSpec)
· Narrow slit spectroscopy · Moderate spectral resolution (/ ~2700) · ~100 km resolution at equatorial latitudes

Observing windows (approaching, receding)
2018 Nov/Dec to Ls:306 (14/Dec) 2020 Ls:206 (22 /May) to Ls:273 (07/Sep) 2020 Ls:319 (21/Nov) to Ls:2 (10/Feb/2021) 2022 Ls:289 (16/Aug) to Ls:333 (04/Nov) 2023 Ls:9 (13/Jan) to Ls:42 (25/Mar)

· 0.7 to 5.2 m accessible with sub-array readouts · Measurements of D/H, O2 nightglow, dust and clouds, CO2 non-LTE emission and sensitive searches for trace species such as organic compounds

Near-Infrared Camera (NIRCam)
· Full disk accessible at 2 m · O2 nightglow mapping at 1.3 m · CO2 non-LTE mapping at 4.3 m · Mapping of the night-side hemisphere
Testing of MIRI performance for Mars is currently underway

Mars viewing geometry
· Most windows will sample the southern cap; polar caps only obser ved when illuminated · M o s t of t h e o b s e r v a b l e d i s k w i l l b e i n d a y t i m e (84-93%) · When approaching, t he evening ter minator will be sampled, while the morning terminator will be sampled when receding
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