Beyond Surface Mapping: MEx/HRSC’s New Approach to Monitor Atmospheric Weather on Mars

The High Resolution Stereo Camera (HRSC) onboard ESA’s Mars Express (MEx) has been a cornerstone of global Mars mapping for more than two decades. Originally designed for high-resolution, multi-spectral stereo imaging of the surface, HRSC is now also being used increasingly for systematic monitoring of the Martian atmosphere and weather, whose understanding is essential for scientific investigations and mission planning.

The atmosphere is highly dynamic, showing strong diurnal, seasonal and interannual variability and complex circulation patterns that couple surface and atmosphere. Long-term, multi-instrument observations are therefore required to place atmospheric processes into a global and seasonal context and to support future robotic and human exploration. Continuous monitoring improves knowledge of climate variability, dust activity, and cloud formation, all of which are relevant for landing site characterization and mission safety.

The long operational lifetime and orbital flexibility of Mars Express, combined with HRSC’s imaging capabilities, enable routine weather monitoring alongside continued high-resolution surface imaging. With map scales of 200 to 800 m/px, HRSC’s high-altitude observations bridge the gap between global-scale atmospheric imagers (e.g., MRO/MARCI, MEX/VMC, EMM/EXI) and very high-resolution cameras (e.g., TGO/CaSSIS). This intermediate scale allows detailed analyses of cloud and storm morphology, e.g., for size, speed, and altitude measurements, while still capturing the entire phenomenon.

 

The atmospheric monitoring campaign has yielded several hundred multi-temporal observations of a broad range of phenomena, including synoptic-scale dust storms and cyclones, local- to regional-scale dust lifting events, orographic clouds, atmospheric gravity waves, seasonal water- and CO₂-ice clouds, twilight clouds, and many other cloud types. In addition, HRSC’s high-resolution observations from lower altitudes expand the range of applications by enabling the detection and measurement of small-scale features such as dust devils [1].

Coordinated observation campaigns with the OMEGA spectrometer (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité) and the Visual Monitoring Camera (VMC), both on Mars Express, as well as the Colour and Stereo Surface Imaging System (CaSSIS) on the ExoMars Trace Gas Orbiter, provide complementary observations across multiple spatial and temporal scales, spectral ranges, and viewing geometries, enabling comprehensive multi-instrument studies [e.g. 1,2,3,4] (see Fig. 1–4 for comparative images of exemplary phenomena).

 

To facilitate data discovery and use, the HRSC Cloud Atlas [5] has been developed as a central portal providing curated atmospheric observations, quick-look imagery, and integrated metadata for analysis and outreach. HRSC atmospheric data are openly available through several platforms, including the ESA Planetary Science Archive [6], the FU Berlin map server [7], the MUTED database [8], the data products node of the HRSC team site [9], and DLR’s SFTP distribution service upon request. In addition, the comprehensive dataset of dust devil migration based on HRSC and CaSSIS data [1] is available via the BORIS repository [10]. This multi-platform approach ensures long-term preservation and rapid accessibility.

 

This presentation aims to raise awareness within the scientific community about the availability of these atmospheric monitoring data, describe their key characteristics, illustrate their scientific potential through selected examples, and provide guidance on how they can be accessed. Through dedicated observation strategies, streamlined processing, and improved data access, HRSC now contributes significantly to the multi-mission study of Martian weather.

 

[1] Bickel et al., SciAdv., 2025.

[2] Hernández-Bernal et al., JGR, 2021 and Hernández-Bernal et al., Nature Geoscience (under review).

[3] Sánchez-Lavega et al., Icarus, 2022.

[4] Brasil et al., JGR, 2025. and Brasil et al., JGR (under review).

[5] Tirsch et al., EPSC, 2024 and Tirsch et al., EPSC, 2025.

[6] HRSC @ PSA: https://psaftp.esac.esa.int/#/MARS-EXPRESS/HRSC/

[7] HRSC map server @ FU Berlin: https://maps.planet.fu-berlin.de/#map=3/2074498.35/0

[8] The Multi-Temporal Database of Planetary Image Data (MUTED): https://muted.uni-muenster.de/?z=3.5&d=101 and Heyer et al., PSS, 2018.

[9] HRSC team site @ DLR: https://hrscteam.dlr.de/public/

[10] CaSSIS and HRSC dust devil migration dataset @ Bern Open Repository and Information System (BORIS): https://doi.org/10.48620/87803.

Fig. 1. Typicall annular cyclone at Vastitas Borealis observed by HRSC (left) and VMC (right).

Fig. 2: The Arsia Mons Elongated Cloud (AMEC, [1]), is a special type of orographic clouds appearing each S-spring to summer at the volcano’s edifice. HRSC (left) and VMC (right).

Fig. 3: Weather or storm fronts on Mars as observed by HRSC (top) at Utopia Planitia and by CaSSIS (bottom) at Aonia Terra.

Fig. 4: The composition of the orographically induced lee waves at Phlegra Montes can be determined using spectral information from OMEGA data (left), which compare very well with the visual HRSC observations (right).