Curiosity has discovered promising organic molecules

On Mars, Curiosity analyzes solidly establish the presence of organic molecules within sedimentary rocks. These organic molecules could be biosignatures of life forms but their origins could also be abiotic. Exobiologists now think that the first interpretation is slightly more likely with thiophenes, which is encouraging.

Two years ago, the Nasa and a publication in the newspaper Science let it be known that the rover Curiosity, which has been rolling since August 2012 on the sedimentary layers inside a Martian crater called Gale, had detected molecules organic in rock samples taken with a drill in mudstone blocks, a fine clayey sedimentary rock cousin of the silt.

Developed by NASA with the participation of the French laboratories Latmos and Lisa, Sat (Sample Analysis at Mars : analysis of samples from Mars) is a set of measuring instruments capable of determining the chemical composition (molecular, elementary and isotopic) of Martian soil, which had in fact identified thiophenic compounds, aromatic and aliphatics. Sure Earth, these compounds can be associated with life form activity and as we know that the analyzed rocks were deposited approximately 3.5 billion years ago in the lake which occupied the crater Gale – lake which was to contain comparable water to that of the Earth's oceans at one time – the news was exciting.

A presentation of the discoveries of organic molecules on Mars by Curiosity. To obtain a fairly faithful translation into French, 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". © Nasa goddard

Biotic or abiotic, that is the question

Unfortunately, these organic molecules could also have been the result of chemical processes. abiotics, therefore having been synthesized without the aid of life forms. Two exobiologists, Dirk Schulze Makuch from Washington State University and Jacob Heinz from the Technische Universität from Berlin, however, have just published an article in the journal Astrobiology which, without deciding between the two interpretations, however, slightly tips the pendulum towards biological syntheses with regard to the thiophenes highlighted with Sam.

As their name suggests, for a chemist, thiophenes are organosulfur compounds found on Earth in the coal and the oil gross, the stromatolites and the microfossils. But on Mars, they may have been brought by meteorites or result from the abiotic thermochemical reduction of sulphates brought to high temperatures billions of years ago by Martian volcanic activity.

However, Dirk Schulze Makuch explains in a statement from Washington State University: "We have identified several biological pathways for thiophenes which seem more likely than the chemical pathways, but we still need evidence" and the researcher to quote one of his famous and late colleagues: " As stated Carl Sagan, extraordinary claims require extraordinary evidence ”.

Dirk Schulze Makuch and Jacob Heinz therefore give in the article ofAstrobiology a brief summary of the imaginable pathways for the generation and degradation of thiophenes as well as their potential to represent the Martian biomarkers of the past activity of bacteria ; they provide suggestions for future investigations on Mars and in terrestrial laboratories to answer the question of whether the Martian thiophenes are of biological origin or not.

For example, for living organisms, it is less costly to energy to use isotopes light from carbon, so that in the remains of organic molecules directly linked to the activity of known life forms on Earth, there is a significant enrichment in carbon 12 compared to the heavier carbon 13. Schulze Makuch and Heinz therefore recommend using the data collected by the next rover to examine the isotopes of carbon and sulfur. We should not be long in knowing more if the rovers Rosalind Franklin of the'Esa and Perseverance of NASA arrive safely on Mars.

Life on Mars: Curiosity and NASA discover intriguing organic molecules

Article by Laurent Sacco published on 08/06/2018

On Mars, the analyzes of Curiosity establish in a way solid the presence of organic molecules within sedimentary rocks. His instruments also confirm the presence of seasonal variations in methane in theatmosphere around him. Methane and organic molecules could be biosignatures of life forms, but their origins could also be abiotic. The discovery of life on Mars is therefore not yet made.

The canvas has been rustling slightly for a few days after Nasa announced a conference for this Thursday, June 7, 2018, presenting a discovery made by the Curiosity rover. Remember that it has been rolling since August 2012 on the sedimentary layers inside a Martian crater called Gale (in honor of a astronomer 19th century Australian amateure century). The announcement had been greeted, however, with a touch of skepticism, even weariness, as it is true that many similar announcements from NASA had given hope for a spectacular discovery when it did not happen. This time, the NASA announcement is fortunately far from the flop that could have been feared.

Ambiguous biosignatures of Martian life

The biogeochemist and geologist Jennifer Eigenbrode has just revealed that Curiosity has detected in sedimentary rocks dating back about 3.5 billion years the undeniable presence of several organic molecules dating from this period. More specifically, they are thiophenic, aromatic and aliphatic compounds. However, we know that these rocks were deposited at that time in a lake.

The presence of Curiosity in the Gale impact crater for several years also made it possible to follow the unexplained methane fumes. The fact is now proven: they are cyclically modulated by the seasons Martian. More important in summer, they are reduced in winter. On Earth, these seasonal seeps can be produced by methanogenic bacteria.

Jennifer Eigenbrode however at the outset put the dots on the "i". The organic molecules identified as well as the seeps of seasonal methane are not necessarily of biological origin. Abiotic phenomena, therefore arising from physicochemical processes, could explain them. As it stands, the Curiosity instruments do not make it possible to decide.

But these results are still very encouraging, especially for the mission ExoMars 2020, from ESA, currently in preparation. She should drop a 300 rover on the surface of the Red Planet kg equipped with a drill capable of bringing a carrot taken up to 2 meters deep. A laboratory capable of analyzing the sample and identifying biochemical markers planned on board the machine could therefore make a revolutionary discovery.

A presentation of the Gale crater explored by Curiosity. To obtain a fairly faithful translation into French, 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". © NASA Jet Propulsion Laboratory

In the meantime, you can consult the two scientific articles published in the journal Science and which give more details on the discoveries made by Curiosity. They were made possible by Sam (Sample Analysis at Mars, or analysis of samples from Mars in French), a set of measuring instruments capable of determining the chemical composition (molecular, elementary and isotopic) of the atmosphere of Mars and of Martian soil, developed by Nasa with a participation from the French laboratories Latmos and Lisa.

  • Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars

  • Background levels of methane in Mars ’atmosphere show strong seasonal variations

The rock samples studied were taken with a drill in mudstone blocks, a fine clay sedimentary rock cousin of the silt. Sam therefore detected organic molecules present under the surface of Mars. The previous detections made with Curiosity were open to criticism because they were ambiguous. This is no longer the case with the new protocol for the use of Sam's instruments implemented by researchers.

Organic molecules and kerogens 3.5 billion years ago?

These molecules are old because they are found inside rocks (notably one called Mohave 2) dating from around 3.5 billion years. But, as Jennifer Eigenbrode explains in the first ehealth above, these molecules could have been brought to Mars by meteorites like the chondrites carbonaceous, rich in biological molecules, such as amino acids such asadenine where the guanine, but which are the result of abiotic processes. These molecules prebiotics could also have contributed to the appearance of life on Earth and perhaps on Mars.

Despite a meteor bombardment which brings from 100 to 300 tons of matter per year for billions of years, the surface does not seem to be strongly enriched in these organic molecules, as exobiologists and planetologists discovered with disappointment in the 1970s with Viking missions. Martian soil has been found to be very oxidizing and in conjunction with radiation UV which is not strongly attenuated by one ozone layer, as is the case on Earth, these organic molecules would therefore be quickly destroyed, degraded into simple forms.

The molecules discovered by Sam would have been preserved for billions of years because they were deep in the rocks and also because they contained sulfur compounds that help conservation. These molecules, like the benzene and the toluene, coming from samples brought to hundreds of degrees, could be fragments of much longer carbonaceous molecules fragmented by heat, like the kerogens.

On Earth, it is an intermediate material between dead organisms in sediment and coal or petroleum. But these molecules could just as easily have been synthesized on Mars by interactions between rocks and hot water in hydrothermal systems.

Clathrates or methanogenic bacteria for Martian methane?

Now let's come to the discovery of seasonal methane seeps. Photochemical models of the Martian atmosphere predict that this gas would have a duration life of about 300 years, so any detection involves a very recent injection into the atmosphere on a geological scale. Indications of the presence of methane in the atmosphere of Mars have in fact existed since 2003 and have in particular been the subject of a publication in Science of Therese Encrenaz and colleagues who had spotted traces of this gas using European probe instruments Mars Express.

A few years ago, Curiosity had already detected transient low concentrations of methane in the Martian atmosphere. But this could be explained by a continuous supply of meteorites with organic matter. Methane would then be produced by the degradation of this material under the effect of intense UV radiation on the surface of Mars.

The new data from Curiosity seems to exclude this hypothesis, in particular because the variations are too large and therefore cannot be produced, moreover cyclically, because of this bombardment of matter. But the methane detected is not necessarily a sign of the current activity of methanogenic bacteria living in pockets of maintained water. liquid by the heat of the residual volcanic activity.

It could come from clathrates fossils, methane-rich ice well known at the bottom of the oceans on Earth, present just below the surface of Mars. During the spring and especially the Martian summer, the rise in temperature would vaporize ice in cracks on the surface allowing this methane to be released.

The XXIe century is just beginning. We bet that we will have the answers to all the questions raised by this discovery before 2050.

Curiosity and its discovery on Mars? NAS according to NASA …

Article by Laurent Sacco published on 11/30/2012

Regarding the enigmatic discovery made by Curiosity on Mars, we should not know more than at the next conference, from December 3 to 7, 2012. NASA has just canceled the suspense by denying any discovery " likely to enter history books " The Curiosity instruments just work exceptionally well, which excites researchers.

More than a week ago, we learned that one of the main responsible for the Martian Curiosity Mission, the geologist John P. Grotzinger, allegedly told a journalist to be enthused by mysterious measurements of the results of analyzes of samples of Martian soil carried out using the instrument sat ((Sample Analysis at Mars). He couldn't say more, probably awaiting confirmation, but it was a discovery "likely to enter the history books".

Obviously, a rumor that the rover was able to discover traces of the existence of life on Mars immediately spread.

Patrice Coll (Lisa) and Michel Cabane (Latmos), important members of the French team strongly involved in Sam, quickly reacted by declaring: "Contrary to what one can read in certain media, Sam cannot find a living organism, since this analytical laboratory has its mission is to define the chemical composition of the samples it analyzes, whether they are soil or atmosphere samples. Obviously, if Sam detects or identifies organic compounds, it will be necessary to try to answer the question of their origin (s), and in this case it will not be up to Sam alone to answer this question but to all the instruments of MSL which by crossing their results will make it possible to better understand this origin, whether biological or other … In summary, Mars' investigation with Sam has barely begun ".

Thanks to the rovers Spirit and Opportunity and especially the probes in orbit Mars Express and MRO, it was confirmed that water flowed on Mars and that oceans existed there. We now know where future robotic or human missions will have to look for possible traces of a life, even in the form of fossils. © Insu, Dailymotion

Curiosity: too full of enthusiasm?

JPL spokesperson Guy Webster followed suit when commenting on John Grotzinger's remarks to the journalist. radio NPR public in these terms: "Regarding his remark on the history books, the mission as a whole is likely to enter the history books … there is nothing specific to come that is upsetting. John was delighted with the quality of the analyzes on the samples from the robot while a reporter was in his office. He has been enthusiastic about previous results in the past, and he will be again in the future. ”

Unless the truth is elsewhere, NASA has just coldly showered those who hoped that at least clues of an appearance of the life on Mars in the distant past, were found by Sam. In an online statement on his site since yesterday, we can read the following statements: "Rumors and speculation that a major discovery has been made in connection with the Curiosity mission which is in its infancy is wrong. At this stage of the mission, the robot's instruments did not provide any evidence of the presence of Martian organic matter ”.

For traces of methane or amino acids, we will have to keep looking …

This will also interest you

The ExoMars mission begins its quest for Martian life Is there life on Mars? The ExoMars mission should soon answer this question. Having left for the Red Planet not long ago, the European Space Agency (Esa) probe will arrive in October 2016. The Euronews channel tells us about its journey and its objectives in this new episode of Space.

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