The fascinating question of life on Mars is inseparable from that of the past and current existence of liquid water on the red planet.Two planetologists of the famous Caltech in the United States used the data of the Mars probe Recognition Orbiter to determine that several rivers were still to exist on the surface of March just 2 billion years ago.

Let's remember.Just over 50 years ago, the US probe Mariner 9 was the first to put themselves in orbit around March in November 1971.A Martian storm will however prohibit him from photographing the surface of the red planet until January 2, 1972.The images which then sent to the noosphere were already of a significant resolution since it is of the order of the kilometer.They reveal unpublished details of the Olympus Mons volcano but also of a huge canyon which will then be appointed Valles Marineris in honor of the success of the Mission Mariner 9 precisely.

Above all, the probe begins to provide images of structures on the surface of Mars which resemble it to be mistaken for those observed from space on earth, namely dried rivers beds, and which are in the case of our planetblue evidence of erosion and deposits by water.

50 years ago, Mariner 9 marked the history of the exploration of the solar system.To obtain a fairly faithful French translation, click on the white rectangle at the bottom right.English subtitles should then appear.Then click on the nut to the right of the rectangle, then on "Subtitles" and finally on "Translate automatically".Choose "French".© NBC News

To marinate 9 in Mro, a dive into the past of Mars

In 1976, the arrival of the Viking probes will confirm the presence of these structures but also to discover much more.The results are spectacular.Not only are immense river valleys, sometimes extending over thousands of kilometers, are discovered, but there are also traces of massive and rapid liberation from enormous volumes of water with speeds estimated at ten thousand the flowMississippi for certain flows.

Finally, following the calibration of the cellard land thanks to the dates of the lunar rocks brought back by the Apollo missions (the meteoritic bombing and the size of the impactors decreasing since the end of the formation of the solar system there are almost 4.5 billion of'years), these missions have made it possible to constitute an equivalent of the chronology of geological eras on earth.

Planetologists will therefore define approximately three major periods in Martian history named after places on Mars which belong to these periods.We therefore distinguish in general and in chronological order since the birth of March:

Today, an article published in Agu Advances is potentially shaking up this chronology somewhat.The studies of the surface of Mars continued a few decades after the sending of the Viking probes, in particular with the Mars Sounds Orbiter (MRO) of NASA and Mars Express of ESA.The question of habitability in the past in March and especially of a possible appearance of life of which it could remain a few traces still today arises.

As we know, we would like to know if life was born elsewhere than on earth and we can therefore wonder if at least organizations resembling those we know have been able to develop elsewhere in the solar system.This is for this necessary that large quantities of liquid water could have subsist long enough for life to appear and develop if we take for example, there too, the case of the earth.Of course, we can argue that life in the cosmos could be very different from the one we know on earth but after all, what interests us most is how much terrestrial type lifemay appear easily or not in the observable cosmos.

But back to the published article, what does it contain?

Ponds fueled by rivers for billions of years?

The planetologists Bethany Ehlmann and Ellen Leask of the famous Caltech in California explain that they have used the data of the MRO probe accumulated for 15 years to reach the conclusion that rivers would have continued to flow on Mars beyond the Hesperianand for hundreds of millions of years during the Amazonian.

In fact, rivers and ponds could have survived up to 2 to 2.5 billion years ago and therefore for almost a billion years more than expected.

The two researchers concentrated on the study of salt chloride deposits which can only form by evaporation of liquid water.This type of deposits is detected well with the data of the MRO instrument called compact Reconnaissance Imaging Spectrometer for Mars (CRISM).We can in particular map them on the highlands rich in clay of the southern hemisphere of March.

However, these regions are of course cellard and it was therefore a priori possible to try dates by studying the rate of cerassment in a more advanced way than this had been done so far.Two other MRO instruments allow it by giving images of these regions.It is his "contextual camera", with his high-angle lens giving black and white images and her Hrise color camera (High-Resolution Imaging Science Experiment).By combining images of these two devices it was possible to also show that the chloride of salt studied were in depressions which were then shallow ponds on gentle sloping plains, ponds formerly supplied by courseswinding water.

The unimportant density of craters showed that these ponds had only formed on young terrains and whose ages could be estimated by the rate of cellarization.This is how ages as recent as 2 to 2.5 billion years have been advanced.

Water flowed on Mars in a near past

Article by the knowledge published on 06/14/2019

Researchers have identified late aqueous alteration in Martian meteorites that would have occurred on Mars, there are between 227 and 56 million years.This discovery has very strong implications for the evolution of the Martian surface because it shows that liquid water has been available near the surface in a relatively recent past and that, therefore, this could still be the case withThese days.Mars could have been habitable on almost all its history since water is the first ingredient necessary for the emergence of life.

The presence of liquid water on Mars is proven by numerous observations such as the presence of hydrated minerals and old valleys and channel systems, despite highly unfavorable pressure and surface temperature conditions.However, the hydrological activity of the red planet is supposed to be restricted in the first and a half years of its evolution, so up to around 3 billion years ago.Mars would then have experienced an episode of global climate change, leading to the cold and arid conditions that is currently known to him.In order to better understand the evolution of its surface and its habitability -which is one of the main questions of current space exploration programs -, it is essential to document the history of water on Mars.

A low temperature aqueous alteration in the Martian meteorite zircon

De récents travaux ont mis en évidence le fait que des cristaux de zircon (ZrSiO₄) dans des météorites martiennes avaient été altérés par l'eau et que cette altération datait de 1,5 à 1,7 milliard d'années.Zircon is an extremely robust mineral to most geological processes.Its training can be precisely dated thanks to the U-PB isotopic system and therefore represents a very reliable temporal archive.However, the radioactive isotopes (U and TH) that it contains are also his Achilles heel since they damage its crystalline network.

The latter can in some cases regenerate, but in other cases deteriorate to the point of returning the zircon porous to fluids, which can be deduced by examining its internal texture using a scanning electron microscope (imagebelow).This is precisely what happened to certain Hadéens zircon crystals of Jack Hills (Australia). Dans ces cristaux, le rapport Th/U mesuré est bien supérieur à celui intégré dans le temps, c'est-à-dire déduit des isotopes du Pb (²⁰⁶Pb et ²⁰⁸Pb) qui sont les produits de désintégration de l'U et du Th. Le découplage visible dans certains zircons de Jack Hills (Th/U mesuré > Th/U intégré) ne peut pas être provoqué par des processus connus autres que de l'altération aqueuse de basse température.The two researchers from the Magmas and Volcanoes Laboratory (LMV, Clermont-Auvergne University, CNRS, IRD / University Jean Monnet) and the Center for Petrographic and Geochemical Research (CRPG, University of Lorraine, CNRS) therefore used these differences as trackersAqueous alteration outside the earth.

The data published on lunar zircons do not indicate any trace of low -temperature aqueous alteration.However, the results for Martian zircons from Black Beauty meteorites (NWA 7533 and 7034) show that part of the available data presents the same decoupling of the measured and integrated TH/U reports as the land zircons of Jack Hills.

Mars would have liquid water available throughout its history

This result therefore suggests that alteration by low -temperature aqueous fluids occurred on Mars.The modeling of the evolution of U-Th-PB systems in the zircon allowed researchers to show that an alteration episode had actually taken place between 1.7 and 1.5 billion years but that the strong divisionsBetween TH/U reports measured and integrated into time were linked to a much more recent, estimated alteration episode (thanks to the model) between 227 and 56 million years.This episode therefore intervenes on the late Amazonian which is a period generally considered to be cold and dry for Mars.

These results, published in Nature Communications, are very important because they demonstrate that, in a near past, Mars still had liquid water available on its surface or sub-surface for long enough and in sufficient quantity to alter mineralssuch as zircons.The origin of this water is still vague but it could have been released by the local melting of the Martian cryosphere under the effect of a meteoritic impact or a recent magmatic activity.

The discovery of liquid water in a past close to Mars implies that this planet may have had a hydrosphere during almost all its history, even locally, and that it may still be the case today.Liquid water being linked to earthly life, the conclusions of this article make it possible to suppose that Mars may have owned the first ingredient necessary for the emergence of life throughout its history.

Liquid water would have flowed on Mars a few years ago!

Article by Jean Etienne published on December 7, 2006

The recent modifications of the appearance of several ravines covering the ramparts of certain craters suggest that liquid water has passed on the surface of Mars very little ago.

For several years, the American probe Mars Global Surveyor (unfortunately lost for about a month), has transmitted detailed images of the surface of the red planet, showing among others ravines which seemed to have been dug by a element.Nevertheless, nothing was less certain and many scientists attributed its training to a geological process, at most to flows of sand.However today, by comparing high resolution photographs taken from the same places and under identical conditions, they can only face the facts: in several places, modifications have appeared in a very short period of time, suggestinga water flow.

" Nous nous sommes longtemps préoccupés de la présence ancienne d'eau sur Mars ", déclare le chercheur Kenneth Edgett, " mais aujourd'hui nous parlons bien de l'eau qui est présente en ce moment même en surface de la Planète rouge ".Edgett and his colleagues based on the images of Mars Global Surveyor (MGS) in order to revisit regions likely to have been the scene of an aqueous event.And their research turned out to be fruitful, since two ravines, whose views had been taken in 1999 and 2001, then again in 2004 and 2005, present a clear evolution which seems to have been caused by a flow on the surface surface.

In the two places, each located on the internal rampart of a crater, brilliant deposits appeared during this brief period, perhaps caused by a deposit of salt, mud or frost.

Philip Christensen, researcher at the State University of Arizona, suggests carrying out detailed spectral analyzes in order to confirm the photographic evidence of liquid water or its deposits, while being enthusiastic that the system D'Thermal imagery (Thermal Emission Imaging System - Themis) on board the Mars Odyssey probe currently in Martian orbit, and of which he is the main director, can perform these measures.

" Je pense que nous nous trouvons bien face à un écoulement d'eau liquide, mais quelle qu'en soit la source, nappe aquifère à fleur de terre, fonte de glace ou de neige, cela importe peu, le fait qu'il s'agisse bien d'eau est essentiel ", ajoute Philip Christensen.

Martian water

The evidence of the presence of water in the past in March was revealed in 2004 by the Opportunity robot, and has since been confirmed to be confirmed.Scientists have long associated the search for liquid water on the red planet with the possibility of life, since the two are closely linked here on earth.The existence of liquid water on the surface or shallow depth can also serve as a potential source of supply to future Martian explorers.

But the proof that the modifications of aspect of the Martian ravines have been caused by liquid water may not be without consequence on the continuation of the exploration program, by raising the problem of contamination.Indeed, an accidental contribution of terrestrial microorganisms in a place rendered to the development of life would risk definitively ruining any subsequent research relating to a possible Martian biology.