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"We know that there were times when the surface of Mars was frozen; we know that there have been periods of free flow of water, "said Briony Horgan of Purdue University at the Goldschmidt Geochemistry Conference in Barcelona. "But we do not know exactly when these periods were and how long they lasted. We have never sent unmanned missions into areas of Mars capable of showing us these oldest rocks. So we have to use earth science to understand the geochemistry of what might have happened.
"If that's the case, it's important to look for a possible life on Mars. We know that the building blocks of life on Earth developed very soon after its formation and that the presence of living water is essential to the development of life. Thus, the evidence we had early, of the water flowing on Mars, will increase the chances that a simple life has developed at about the same time as on Earth. We hope the Mars 2020 mission will be able to take a closer look at these minerals and begin to respond exactly to the conditions that prevailed when Mars was still young. "
Scientists have known for a long time that water was abundant in ancient Mars, but there was no consensus on whether liquid water was common or whether it was largely frozen in ice.
"The death of Mars" – Ancient climate change caused by an asteroid
The lingering questions are: was the temperature high enough to allow water to flow? Has this happened over a long period of time, or just occasionally? Was the surface desert or frozen? The warm conditions make it much more likely that life would have developed independently on the surface of ancient Mars.
In 2013, planetary scientists from the European Space Agency published 3D images of "the striking upper part of the Reull Vallis region on Mars", revealing a 1,500-kilometer long river from the Promethei Highlands. Terra in the vast basin of Hellas.
Image data from ESA's Mars Express spacecraft show that in some places the river bed is 7 km wide and 300 meters deep. Stereoscopic cameras onboard the satellite also revealed "numerous tributaries" that fed the gigantic river.
On the right of the pictures you can see the Promethei Terra Highlands Mountains, "rising to about 2500 m above the surrounding plains". A spectacular landscape not very different from many on Earth.
Discovery of Mars – Huge liquid water lake observed under the South Pole: "We did not see what was happening under our nose"
The ESA Mars Express team said the river was flowing with abundant water about 3.5 to 1.8 billion years ago, during the hesperian period. After that, the Amazon era began and the Reull Vallis were invaded by a glacier.
Primitive earth as a model
Now, a new comparison of the types of mineral deposits on the red planet with similar deposits on Earth suggests that the beginning of March had one or more long periods dominated by rainstorms and water flow, the water then becoming icy.
Our study of alteration under radically different climatic conditions, such as the Cascades in Oregon, Hawaii, Iceland and other regions of the Earth, can show us how the climate affects the structure of mineral deposits, such as we see it on Mars. Here on Earth, we find silica deposits in glaciers, characteristics of melting waters. On Mars, we can identify similar silica deposits in the youngest areas, but we can also see older areas that resemble the deep soils of hot Earth climates. This leads us to believe that 3 to 4 billion years ago, we had a slow general trend from hot to cold, with periods of thaw and freezing.
"Lost!". How the old ocean of Mars disappeared into space (WATCH Today's "Galaxy" stream)
The analysis of the geology of the surface of Mars confirms a tendency of the hot climate to the cold, but the climate models themselves do not confirm it, because of the limited heat released by the young Sun. "If our conclusions are correct, we must continue to work on Mars' climate models, possibly including a chemical, geological or other process that could have warmed the young planet," Horgan said.
The research team compared Earth data with Martian minerals detected using the NASA CRISM spectrometer currently in orbit around Mars, which remotely identifies surface chemicals containing water. They also took data from the Mars Rover Curiosity. Professor Horgan is a co-investigator of the Mars 2020 mission, expected to be launched in July 2020 and begin exploring the Jezero crater in February 2021.
The image at the top of the page shows the grooved channels of an old threading of the river delta through the Jezero crater on Mars. The paleochannel system is one of the hundred analyzed. Credit: NASA / JPL-Caltech / MSSS / JHUAPL
The Daily Galaxy via the Goldschmidt conference
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