Mars’s mysterious elongated crater
Orcus Patera is an enigmatic elliptical depression near Mars’s equator, in the eastern hemisphere of the planet. Located between the volcanoes of Elysium Mons and Olympus Mons, its formation remains a mystery.
Often overlooked, this well-defined depression extends approximately 380 km by 140 km in a NNE–SSW direction. It has a rim that rises up to 1800 m above the surrounding plains, while the floor of the depression lies 400–600 m below the surroundings.
The term ‘patera’ is used for deep, complex or irregularly shaped volcanic craters such as the Hadriaca Patera and Tyrrhena Patera at the north-eastern margin of the Hellas impact basin. However, despite its name and the fact that it is positioned near volcanoes, the actual origin of Orcus Patera remains unclear.
Aside from volcanism, there are a number of other possible origins. Orcus Patera may be a large and originally round impact crater, subsequently deformed by compressional forces. Alternatively, it could have formed after the erosion of aligned impact craters. However, the most likely explanation is that it was made in an oblique impact, when a small body struck the surface at a very shallow angle, perhaps less than five degrees from the horizontal.
The existence of tectonic forces at Orcus Patera is evident from the presence of the numerous ‘graben’, rift-valley-like structures that cut across its rim. Up to 2.5 km wide, these graben are oriented roughly east–west and are only visible on the rim and the nearby surroundings.
Within the Orcus Patera depression itself, the large graben are not visible, probably having been covered by later deposits. But smaller graben are present, indicating that several tectonic events have occurred in this region and also suggesting that multiple episodes of deposition have taken place.
The occurrence of ‘wrinkle ridges’ within the depression proves that not only extensional forces, as would be needed to create graben, but also compressive forces shaped this region. The dark shapes near the centre of the depression were probably formed by wind-driven processes, where dark material excavated by small impact events in the depression has been redistributed.
Markus Bauer | EurekAlert!
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes
The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....
Larsen C Ice Shelf rift finally breaks through
A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...
Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision
Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...