[ad_1]
The central part of Osuga Valles, which has a total length of 164 km. In some places it is 20 km wide and plunges to a depth of 900 m. Photo: ESA / DLR / FU Berlin, CC BY-SA 3.0 OIG
The surface of Mars bears imprints of structures that resemble river-steam systems on Earth. Scientists therefore assume that there must have been enough water on the red planet to feed the streams that have made their way into the soil.
However, scientists have been discussing for years the source of this water's origin: the rainwater that causes rivers and streams to swell? Or did the water ice in the ground melted because of volcanic activity and infiltrated to form rivers? Each of these scenarios leads to a completely different conclusion about the climatic history of the red planet.
A new study now suggests that the ramified structure of ancient river systems on Mars has striking similarities to arid landscapes. This has been demonstrated in a recent article published in Science Advances by physicist Hansjörg Seybold of the group of James Kirchner, professor at the Institute for Terrestrial Ecosystems, and planetary specialist Edwin Kite of the 39, University of Chicago. 19659003] Valleys eroded mainly by rainwater
Using the statistics of all mapped river valleys on Mars, the researchers conclude that the contours still visible today must have created by superficial runoff. Therefore, the influence of groundwater seepage from the ground can be ruled out as a dominant process for shaping these features.
The distribution of ramification angles of valleys on Mars is very similar to those found in arid landscapes on Earth. According to the lead author, Seybold, this implies that there must have been a similar hydrologic environment with sporadic episodes of heavy rain on Mars for an extended period of time and that this rainwater has run out quickly on the surface shaping the valley networks. This is how river valleys develop in the arid regions of the Earth. For example, in Arizona, researchers observed the same valley network patterns in a landscape where astronauts train for future Martian missions. Valleys in arid regions form a narrow angle fork
The ramification angles on Mars are relatively low. Seybold therefore excludes the influence of groundwater shoots as a major channel-forming process on Mars. The river systems formed by re-emerging groundwater, such as those found in Florida for example, tend to have much wider branching angles between the two tributaries and do not correspond to the narrow angles of the watercourses. water in arid areas.
those found today in arid landscapes have probably prevailed on Mars for a relatively short period of time, there are about 3.6 to 3.8 billion ds. # 39; years. During this period, the atmosphere on Mars may have been much denser than today. "Recent research shows that there had to be a lot more water on Mars than previously thought," says Seybold.
Evaporation Rained
One hypothesis suggests that the northern third of Mars was overlying an ocean at that time. Water evaporated, condensed around high upland volcanoes south of the ocean and resulted in heavy rainfall. As a result, the rivers formed, leaving traces that can still be seen on Mars today.
The big question is where did the water disappear over time? "It is likely that most of it has evaporated into space.But it could still be found in the vicinity of Mars," says the physicist. "But that is a question for a future space mission ".
Reference
Seybold HJ, E Kite, Kirchner JW. Geometry of ramification of valley networks on Mars and Earth and its implications for the early Martian climate. Scientific advances 2018; 4: eaar6692. DOI: 10.1126 / sciadv.aar6692
Source link
