Twilight Mesospheric Clouds in Jezero as Observed by MEDA Radiation and Dust Sensor (RDS)

Abstract

The Mars Environmental Dynamics Analyzer instrument, on board NASA's Mars 2020 Perseverance rover, includes a number of sensors to characterize the Martian atmosphere. One of these sensors is the Radiation and Dust Sensor (RDS) that measures the solar irradiance at different wavelengths and geometries. We analyzed the RDS observations made during twilight for the period between sol 71 and 492 of the mission (Ls 39°–262°, Mars Year 36) to characterize the clouds over the Perseverance rover site. Using the ratio between the irradiance at zenith at 450 and 750 nm, we inferred that the main constituent of the detected high‐altitude aerosol layers was ice from Ls = 39°–150° (cloudy period), and dust from Ls 150°–262°. A total of 161 twilights were analyzed in the cloudy period using a radiative transfer code and we found: (a) signatures of clouds/hazes in the signals in 58% of the twilights; (b) most of the clouds had altitudes between 40 and 50 km, suggesting water ice composition, and had particle sizes between 0.6 and 2 µm; (c) the cloud activity at sunrise is slightly higher that at sunset, likely due to the differences in temperature; (d) the time period with more cloud detections and with the greatest cloud opacities is during Ls 120°–150°; and (e) a notable decrease in the cloud activity around aphelion, along with lower cloud altitudes and opacities. This decrease in cloud activity indicates lower concentrations of water vapor or cloud condensation nuclei (dust) around this period in the Martian mesosphere.

Geometric Properties of Water-ice Clouds as Observed from Jezero Crater in the First 600 sols with the NavCam Instrument On Board the Mars2020 Rover, Perseverance

“…The first cloud movie was captured on sol 173, L S 83.7°, and faint clouds were initially observed on sol 236, L S 111.9°, followed by a period of heightened activity with numerous cloud features between sols 279-299 (L S 132.1°and 141.9°). This trend has also been reported by Toledo et al (2023) However, it is important to acknowledge that a higher incidence of cloud structures in the NavCam images does not necessarily signify peak cloudiness or high water-ice activity. Throughout the ACB season, water-ice is expected to be present in the atmosphere (Tamppari et al 2003;Smith 2004;Wolff et al 2019).…”

“…Using the Emirates Mars Infrared Spectrometer (EMIRS) on board the Emirates Mars Mission (EMM), Atwood et al (2022) observed ACB clouds to be thicker and more widespread in the early to mid-morning compared to the mid-afternoon to earlyevening period. Similarly, using the RDS on the MEDA instrument on Perseverance, Toledo et al (2023) reported that for twilight cloud observations, 65% of the observations during sunrise contained cloud detections compared to 52% of the observations. Furthermore, the MEDA thermal infrared sensor, TIRS, has shown that atmospheric opacities during the ACB decay over Jezero during the hours when the cloud movies were taken (Smith et al 2023).…”

“…(1) Setup of the 3D Point Grid We established a grid of 3D points representing a virtual plane positioned h km above the Mars2020 rover, where h represents the height of the plane. Based on vertical profiles of the water ice obtained with the Mars Climate Sounder (see Section 4.3.1) and twilight cloud heights observed using the Perseverance Radiation and Dust Sensor (RDS; Apestigue et al 2022;Toledo et al 2023), heights ranging from 30 to 50 km were selected. We assumed that all clouds exist within a single layer at the given cloud height, neglecting the curvature of the plane at the cloud base within the field of view.…”

The Uranus Multi-Experiment Radiometer for Haze and Clouds Characterization

“…A number of simulations using a Monte-Carlo radiative transfer code (Toledo et al 2017(Toledo et al , 2023 were performed to define the dynamic range of channels 17 and 18. In these simulations, the photons are emitted from a singular source (the lamp) and collected by a bin next to it whose area is equivalent to the detector's.…”

One Martian Year of Near‐Surface Temperatures at Jezero From MEDA Measurements on Mars2020/Perseverance

“…At L S 153°, a regional dust storm passed across Jezero, with this location being an active dust lifting location (Lemmon et al., 2022), while at L S ∼213° and ∼313°, the large A and C yearly storms (Kass et al., 2016) reached Jezero, respectively. In turn, clouds produced the greatest increase in the measured atmospheric opacity around L S ∼145°, during the Aphelion Cloud Belt season (Patel et al., 2023; Smith et al., 2023; Toledo et al., 2023). This increase in atmospheric opacity was accompanied by an apparent increase in daily mean air temperatures (Figure 4a).…”