A new set of images captured this spring by the ESA-Roscosmos ExoMars Trace Gas Orbiter ExoMars Trace Gas Orbiter (CaSSIS) system shows a number of interesting geological features on the surface of Mars, captured as the planet passed its vernal equinox. This is reported by the European Space Agency.
Dune fields in the Green Crater of Mars
The image below, taken on April 27, 2020, centered at 52.3°S, 351.8°E, shows a portion of an impact crater located within a larger Green Crater in the Argyra Quadrangle in the southern hemisphere of Mars.
This image on the right shows an almost black dune field surrounded by red soils, partially covered with bright white ice. In the center of the image, on the crater wall, you can see ravines, also partially covered with ice. Scientists are currently investigating the link between seasonal ice and the presence of gullies. The picture was taken just after the vernal equinox in the southern hemisphere of Mars when the southernmost part of the crater (right) was almost completely ice-free, and the northern part (center) was still partially covered. The wall of the southern crater was exposed to the sun for a longer time (as on Earth, the slopes facing the equator receive more sunlight), so the ice in this area retreated faster.
Leaf-like structures in the Antoniadi Impact Crater
This image, taken on March 25, 2020, shows the bottom of the 400 km diameter Antoniadi Impact Crater, located in the northern hemisphere of Mars. Blue color of the image centered at 21.0°N, 61.2°E. does not reflect the real color of the bottom but emphasizes the diversity of the rock composition within this impact crater.
In the center of the image are dendritic structures similar to the veins on oak leaves. These structures, which are evidence of the existence of ancient river networks in the region, protrude above the surface, in contrast to the channels, which usually go into the water. The reason is that the channels were filled with harder material – possibly lava – and over time, the softer rocks surrounding these branched channels were eroded, leaving an inverted imprint of this ancient river system.
Spectacular Argyre Pool after the vernal equinox
This image of the Argyra Impact Basin in the southern highlands of Mars was taken on April 28, 2020, when Mars passed the vernal equinox in the southern hemisphere. Seasonal ice in the 800 km impact basin is receding noticeably, while the ridge on the right side of the image is still frosty. Image is centered at 57.5°S, 310.2°E.
The frost-covered ridge faces the pole and therefore receives less solar radiation than the adjacent slope facing the equator. On Mars, solar radiation converts ice to water vapor immediately, without first melting it into water in the process of sublimation. Because the north slope (left) was exposed to solar radiation for longer, its ice sublimated faster.
Composition of rocks in the Ius Chasma canyon
The image taken on May 5, 2020, shows a portion of the bottom of Ius Chasma canyon, part of the Valles Marines canyon system that extends nearly a quarter of Mars’ circumference south of the planet’s equator. The Ius Chasma Canyon, seen in the image rising to the ridge on the right side, is about 1000 km long and up to 8 km deep. This makes it almost twice as long and four times deeper than the famous Grand Canyon in the US state of Arizona. The center of this image is located at 8.8°S, 282.5°E.
The beautiful color variations of Ius Chasma floor are caused by changes in the composition of rocks. Scientists suggest that the light rocks are salts left over from the evaporation of the ancient lake. Information about the composition of the rock is useful for scientists as it allows them to trace the history of the formation of the canyon.