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Was this great riverside on Mars the place where its oceans finally disappeared?

Mars Orbiter image of stone once carved by water. Credit: NASA

For a while, scientists have known that Mars once was a much warmer and warmer environment than it is today. But between 4.2 and 3.7 billion years ago, its atmosphere was slowly removed, which turned the surface into the cold and dehydrated place we know today. Even after several missions have confirmed the existence of old seaside beds and rivers, there are still unanswered questions about how much water Mars once had.

One of the most important unanswered questions is whether large seas or oceans have ever existed in the northern lowlands. According to a new study by an international team of researchers, Hypanis Vallée's old river system is actually the remains of a river delta. The presence of this geological property is an indication that this river system once emptied into an old Marian sea on Mars northern hemisphere.

For their study entitled "The Hypanis Valles Delta: The Last Highest Part of an Early March Sea", recently featured in the journal Earth and Planetary Science Letters the International Team consulted data from Mars Reconnaissance Orbiter (MRO) and Mars Odyssey probe 2001

to investigate morphology, sedimentary architecture and landfill of Hypanis Valles region.

This delta is what separates the southern highlands from the northern lowlands, where an old sea is once thought to have existed – a theory that has remained unjustified. Based on data from MRO's High Resolution Imaging Science Experiment (HiRISE) and 2001 Odyssey's Thermal EMISSION Imaging System (THEMIS), the team found compelling evidence that a large water source once covered the northern third of Mars.

<en rel = "lightbox" href = "https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/2018/1-wasthishuger.jpg" title = "A picture from the study showing Hypanis Valles sediment fan. Credit: Peter Fawdon et al. / Science Direct / Earth and Planetary Science Letters ">
 Was this huge river delta on Mars the place where its oceans finally disappeared?
A picture from the study showing Hypanis Valles sediment fan. Credit: Peter Fawdon et al. / Science Direct / Earth and Planetary Science Letters

As Joel Davis – a postdoctoral researcher in the planetary surface of the Museum of Natural History and a co-author of the paper – is explained in a recently published NHM press release:

"A marine sea means that Mars probably had a very terrestrial water cycle, with rivers , lakes and now oceans, all of which probably are intercepted as part of a planet-wide system. We think this terrestrial hydrological cycle was active 3.7 billion years ago and began to close down sometime after. Our study is not a definitive evidence for a sea, but these geological characteristics are very difficult to explain without one. "

It was not an easy challenge to determine if Mars had standing bodies of water, or not, mainly because Mars lacks the obvious indications of lakes and oceans on its surface (like fine sandy beaches or clear beaches). As a result, researchers must look for other ways of identifying the water that flowed and sand dropped, which is where sedimentary fans come to play.

In this case, the fan was identified as a river slope which formed when a river slows down in the presence of a slower or still water body. This causes small sediments carried by the river to settle on the ground and form geological properties (such as small islands at the mouth of the river) over time. Previously, the rivers were found on Mars, but only in craters where water flowed into a lake.

 Was this huge river division on Mars the place where its oceans finally disappeared?
Artist distribution of how "Lake" on the Gale Crater on Mars may have looked millions of years ago. Credit: Kevin Gil

The case, curiosity of curiosity, who has studied the Gale Crater since it landed there in 2012, has discovered ample evidence that the crater once was a lake. This evidence included clay minerals at the base of Mount Sharp, as well as sedimentary deposits and channels discovered in the craters wall and Mount Sharp, which can only be explained by water flowing into the crater.

Thanks to his study, scientists can now assure that Hypani's sedimentary fan is proof of a standing body of water large enough to be an ocean. Their study also indicates how the ocean returned as the climate gradually becomes colder and drier. Basically, when sea levels fell by almost 500 meters, the Hypanis delta began to grow outward as a result.

Finally, they decided about 3.6 billion years ago, the water system dried and disappeared, which is similar to when Mars lost most of its old atmosphere. Since then there has been no water on the surface in any form other than ice – with the exception of an underground lake recently discovered.

As doctor Peter Fawdon, a postdoctoral research from Open University and leading authors associate with the study, explained:

Researchers were able to measure the amount of water loss on Mars by measuring the relationship between water and HDO from today and 4.3 billion years ago. Credit: Kevin Gill

"The research has made a significant contribution to our understanding of the early March climate, which we now know went from having a water club similar to the Earth to be a cold desert-like landscape in a relatively short period. Would like to get a better understanding of how many of these fluvial divisions are on Mars so that we can determine the position and size of their old sea. "

This study has not only provided final proof that they are a sea on Mars, but it is also important to The coast of this ancient sea is close to where ExoMars 2020 and the March 2020 robbers will land in the next few years. The fact that a sea once existed there increases the odds that these robbers will find evidence of the last march life – which is their main goal.

Over the last century, our collective understanding of Mars has changed dramatically. Once you believed to be a planet crossed by canals and inhabited by little green men, the first robotic mission to the red planet revealed a frozen landscape that was hostile in life. But in recent decades, evidence has emerged that shows that Mars may have supported life earlier.

And although there may be a life there today, Mars is still a dynamic and fascinating place that can teach us a lot about the history and development of our solar system. But if there are still microbes present on the red planet, ExoMars 2020 and the March 2020 robbers are likely to find it.

Explore further:
A large floating water lake under the southern pole of Mars

More information:
Peter Fawdon et al. Hypanis Valles Delta: The Last Elevation of an Early March Sea?, Earth and Planetary Science Letters (2018). DOI: 10,1016 / j.epsl.2018.07.040

Journal Reference:
Earth and planetary letters

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