Aerospace Science & Intelligent Technology

Tantalus Fossae – a glimpse into the volcanic past of Mars

These images, which were created using data acquired by the High Resolution Stereo Camera (HRSC) (HRSC) show part of the large Tantalus Fossae graben system in the northern hemisphere of the Red Planet. The network lies to the east of the four-kilometre-high Alba Patera volcano and gives an idea of the enormous forces that acted on the Martian crust from below through local and regional stress fields and led to volcanic and tectonic activity. HRSC, which has been mapping the planet on board ESA’s Mars Express spacecraft since 2004, was developed at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and is operated by its Institute of Planetary Research in Berlin-Adlershof. The data are an important resource for current and future Mars research.

Opening and sinking – a crust under tension

The Tantalus Fossae (Lat. for ‘Troughs of Tantalus’) are a vast network of graben systems surrounding the Alba Patera volcano. They extend over 1000 kilometres in a north-south direction and are between two and 10 kilometres wide and up to 350 metres deep. They were most likely created as a result of tension in the Martian crust generated by the arching of the Alba Patera volcano, which protrudes from its surroundings like a gigantic shield. The Tharsis uplift in the south of this area, a 4000-kilometre-wide ‘bulge’ in the Martian crust reaching up to ten kilometres high and home to the largest Martian volcanoes, may have also played a role in the formation of these structures. Due to the stretching of the crust when a volcano rises, large blocks of terrain sink into the resulting spaces and form a tectonic graben system.

The graben structures seen in these HRSC images run roughly from south to northeast along the north-eastern flank of the volcanic uplift. However, these structures did not all form at the same time. The large impact crater in the centre of the image, for example, is intersected by several grabens. This means that it already existed before the volcanic uplift was finished, which led to the formation of graben within the crater as well. Almost all of the smaller craters appear superimposed on top of the graben, suggesting later impact dates, after the tectonic activity. Some of them are filled with material, most likely lava, making them very shallow and lacking the bowl-shaped profile typical of relatively young craters. From such observations, geologists can reconstruct the chronological sequence of events that gave rise to this landscape.

On closer inspection, especially in the south (left in image 1), numerous river valleys branching like a tree can be seen intersecting several of the grabens. They must be older than the grabens, as they were not diverted by the grabens , but seem to run directly through them. The area in the northern (right) part of the picture is much lower than the southern part, clearly visible on the topographic survey map (image 6). Therefore, these valleys should run along this gradient, from south to north and not, as can be seen here, from west (above) to east (below). This is evidence that these valleys were formed earlier, before the volcanic rocks in the south began to arch about 3.5 billion years ago. This conclusion also fits the type of valley branching, which indicates surface run-off typical of early Mars.

King Tantalus – eponym for a ‘tortured’ landscape

This region was named after King Tantalus, son of Zeus, father of the gods, and Pluto, daughter of the Titans in Greek mythology. When he tried to test the gods’ omniscience by serving them his youngest son as a meal, they banished him to Tartarus, the deepest region of Hades. There he had to suffer eternal torments, the proverbial ‘Torment of Tantalus’. He stood in a pond with water, but it always seeped away as soon as he tried to drink from it. Likewise, fruit trees surrounded him. If he reached for their branches, they were blown out of reach by the wind. Thus, he suffered eternal thirst and hunger. But his son, who had been killed, was brought back to life by the gods.

Image processing

These images were created using data acquired by the High Resolution Stereo Camera (HRSC) on 19 July 2021 during orbit 22,173 of the Mars Express spacecraft. The image resolution is approximately 18 metres per pixel. The centre of the image is located approximately 257 degrees east and 43 degrees north. The perpendicular colour view was generated using data acquired by the nadir channel, the field of view which is aligned perpendicular to the surface of Mars, and the colour channels of HRSC. The oblique perspective views were computed using a Digital Terrain Model (DTM) and data acquired by the nadir and colour channels of HRSC. The colour-coded topographic view is based on a DTM of the region from which the topography of the landscape can be derived. The reference body for the HRSC DTM is a Martian equipotential surface (areoid).

HRSC was developed and is operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) in cooperation with German industry. The systematic processing of the camera data was performed at the DLR Institute of Planetary Research in Berlin-Adlershof. Personnel in the Department of Planetary Sciences and Remote Sensing at Freie Universität Berlin used these data to create the image products shown here.

The HRSC experiment on Mars Express

The High Resolution Stereo Camera (HRSC) was developed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and built in collaboration with partners in industry (Airbus, Lewicki Microelectronic GmbH and Jena-Optronik GmbH). The science team, which is headed by Principal Investigator (PI) Thomas Roatsch, consists of 50 co-investigators from 34 institutions in 11 countries.

All images in high resolution and more images acquired by the HRSC instrument can be found in the Mars Express image gallery on flickr.

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