An article published in the journal “Nature Geoscience” reports a study on the mounds in Mawrth Vallis, a valley on the planet Mars considered very interesting for the traces of the ancient presence of liquid water. A team of researchers from the Open University and the Natural History Museum in London used data collected by various space probes to perform geomorphological and spectroscopic analyses of the mounds. Their conclusions are that they’re the remains that were formed by erosion by the retreat of the plateau in the Noachian period, between 4.1 and 3.7 billion years ago. For this reason, they believe that they constitute a sort of stratigraphic record of the changes in the presence of water in Mawrth Vallis.
Researchers who are reconstructing the geological history of Mars have been studying the Mawrth Vallis for years. It’s part of the Oxia Palus quadrangle, is connected to the Arabia Terra highland, and ends in the Chryse Planitia lowland. Photos of this area were captured several years ago by ESA’s Mars Express space probe, and this is just one of the occasions the region was photographed from orbit. There are more than 15,000 mounds scattered across the area that extends to Chryse Planitia of uncertain origin, but this new study offers an answer to the mystery.
The presence of clay materials throughout the area has been well-known for years and is a starting point for this new study. In this new reconstruction, the highlands were once immersed in water, but the collapse of the Martian atmosphere led to the retreat of the plateau and the erosion that left only the present-day mounds.
The clay layers that formed due to the interaction between water and rocks appear to be squeezed between older non-clay layers below them and younger ones above them. According to the researchers, this type of formation represents a record of the geological events that occurred during the Noachian.
Studies about the presence of water are important but there are also those about the so-called Martian dichotomy, that is, the difference between the geological characteristics of the northern and southern hemispheres of Mars. The authors of this study offer evidence of a strong connection between the formation and alteration of the mounds, the plateau, and the morphology of the dichotomy in that region.
The ExoMars mission’s Rosalind Franklin rover should land in the region of Oxia Planum, also in the Oxia Palus quadrangle and not far from the Mawrth Vallis, with which it shares the past presence of water. This mission began as a collaboration between ESA and the Russian space agency Roscosmos but the stop of collaboration with Russia forced design changes with the involvement of NASA.
The hope is that the Rosalind Franklin rover will be launched in 2028 to join the TGO (Trace Gas Orbiter) space probe, the first vehicle of the ExoMars mission already in orbit around the red planet. A key goal is to search for organic materials that may have been preserved underground. There, it’s more likely that possible traces of life, present or past, exist. New information on the geological history of Mars will certainly be found.
