Annual Water Cycle at Jezero Crater Based on Observations and Column modeling

Water vapor in the Martian atmosphere and its interactions with the soil have influenced the evolution of the planet’s climate and informs on its current and past habitability. However, water vapor has been directly observed in situ only by moisture sensing instruments in three landed spacecrafts: The Phoenix ’07 lander, the Mars Science Laboratory rover Curiosity and the Mars 2020 mission rover Perseverance (Polkko et al 2023). Perseverance was launched on 30 July 2020 by NASA, and landed successfully on 18th February 2021 at Jezero Crater, Mars (Lon. E 77.45° Lat. N 18.44°).

We analyze here annual and diurnal water cycles at Jezero crater on Mars during the first thousand sols of humidity observations by the Perseverance rover, bit over one and a half Martian years. The primary data source is the Mars Environmental Dynamics Analyzer (MEDA, Rodriguez-Manfredi et al 2021) sensor suite sensors: the MEDA-HS relative humidity (RH) sensor, which is located in the rover’s Remote Sensing Mast and operates at 1.5 m above the surface (Hieta et al 2022). MEDA-ATS atmospheric temperature sensors (ATS) provided air temperature at 1.5 m above the surface for modeling (Munguira et al 2024). Optical depth needed also for modeling is provided by Mastcam-Z camera (Lemmon et al 2023).

ATS observations over sol are used to calibrate an adsorptive single column model (SCM) diurnal temperature profile which also gives areal thermal inertia and albedo (Savijärvi, Harri 2021). Nocturnal RH observations are then fitted with the SCM, which then reconstructs the full diurnal water vapor cycle and its vertical distribution, which also results precipitable water column (PWC). Our modeling work focuses on locations where the rover remained stationary or within a small area for an extended period of time, thus ensuring stable soil properties and allowing for more robust averaging of HS observations over multiple sols.The SCM effectively reproduces the observation-based nighttime water vapor amounts at the modeled locations. The PWC estimated by the SCM, when adjusted to the MEDA near-surface observations, aligns well with  Emirates Mars Mission (EMM) EMIRS instrument satellite data observed over Jezero at the same time (Smith et al 2022). Both SCM simulations and MEDA-HS observations produce an annual water vapor peak around Ls 150^◦ - Ls 160^◦ on Mars years (MY) 36 and 37.

Local topography appears to influence near-surface water vapor levels, suggesting that terrain effects should be considered when modeling the diurnal cycle in heterogeneous landscapes. On the flat Jezero crater floor, the SCM directly reproduced observed nocturnal water vapor volume mixing ratios (VMR). After the Perseverance rover began climbing out from the crater floor to higher elevations, an anomaly at early morning hours in the nocturnal VMR curve was observed. Our ”flat surface” SCM version could not reproduce this observed behavior. However, using only early night observations for SCM calibration in these cases still produced PWC which aligned well with the satellite observations.

References:

Jouni Polkko, Maria Hieta, et. al. 2023, Initial results of the relative humidity observations by MEDA instrument onboard the Mars 2020 Perseverance Rover. Journal of Geophysical Research: Planets, doi.org/10.1029/2022JE007447

Rodriguez-Manfredi, J. A., de la Torre Ju´arez, et al. 2021. The Mars Environmental Dynamics Analyzer, MEDA. A Suite of Environmental Sensors for the Mars 2020 Mission. Space Science Reviews, 217 (3), doi.org/10.1007/s11214-021-00816-9

Hieta, M., Genzer, M., Polkko et al. 2022. MEDA HS: Relative humidity sensor for the Mars 2020 Perseverance rover. Planetary and Space Science, 223 , 105590. doi: 10.1016/j.pss.2022.105590

Munguira, A., Hueso, R. et al. 2024. One martian year of near-surface temperatures at Jezero from MEDA measurements on Mars2020/Perseverance. Journal of Geophysical Research: Planets, 129 . doi: 10.1029/2024JE008385

Lemmon, M., Wolff, M., & Bell, J. 2023. Results from the optical depth imaging campaign of the Mars-2020 Perseverance rover. Bulletin of the AAS, 55 (8). https://baas.aas.org/pub/2023n8i213p09

Savijärvi, H. I., & Harri, A. M. (2021, March). Water vapor adsorption on Mars. Icarus, 357 , 114270. doi: 10.1016/j.icarus.2020.114270

Smith, M. D., Badri, K., Atwood, S. A. et al. (2022). EMIRS observations of the aphelion-season Mars atmosphere. Geophysical Research Letters, 49 . doi: 10.1029/2022GL099636