Les humains ont-ils accidentellement détruit la vie potentielle sur Mars ? C'est une idée audacieuse, mais les scientifiques commencent à se demander si nos actions pourraient avoir anéanti une vie microbienne avant même que nous réalisions qu'elle existait. Mars est incroyablement sèche aujourd'hui, mais il y a des milliards d'années, elle avait de l'eau et aurait pu accueillir de minuscules organismes. Si l'un de nos rovers ou modules d'atterrissage a introduit des microbes terrestres ou perturbé l'environnement martien délicat, cela pourrait avoir perturbé les formes de vie qui auraient pu s'accrocher. De plus, certaines expériences destinées à tester la présence de vie ont peut-être accidentellement provoqué sa mort, par exemple en exposant des échantillons à des produits chimiques agressifs. Ce n'est pas certain, mais cela rappelle qu'explorer d'autres planètes nécessite une prudence accrue, notamment en ce qui concerne la protection de leurs écosystèmes - si toutefois ils existent ! Animation créée par Sympa.
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FunTranscript
00:00Mars is the Earth's space cousin.
00:02Fourth planet of our solar system, it is about half the size of our blue ball.
00:07It also has two small moons, Phobos and Deimos.
00:12These moons have the shape of an earth apple.
00:14Phobos is a dramatic character who approaches Mars
00:18and plans a catastrophic landing in about 50 million years.
00:22Deimos is much calmer and stands at a good distance from Mars.
00:26Mars has been nicknamed the Red Planet.
00:29Because of its rusty red surface.
00:31This color was so vivid that it was spotted by astronomers many years ago.
00:36We can even sometimes see it with the naked eye in the sky,
00:39in the form of a small squint.
00:42This planet may look warm,
00:45but in reality it is a very cold desert.
00:48Temperatures can go down to 153 degrees Celsius.
00:53But has it ever been a rusty desert?
00:56In fact, no.
00:57Scientists think that a long time ago,
01:00this planet may have been similar to ours.
01:03Here is Curiosity, the detective rover of NASA's Jet Propulsion Laboratory.
01:08Scientists want to know everything about the climate,
01:11the landscape and the other characteristics of the planet.
01:14Curiosity is a robot the size of a car.
01:16It weighs about 900 kg.
01:19It started its journey on November 26, 2011.
01:22And it managed to land on Mars on August 6, 2012.
01:26Originally, Curiosity's mission was supposed to last two years,
01:30but it is still going on today.
01:32Curiosity is actually a space laboratory on wheels.
01:35It is equipped with cameras, spectrometers,
01:38radiation detectors and sensors to study the Martian environment.
01:42While traveling, Curiosity rewinds the history of Mars.
01:45During its mission, our rover discovered something incredible.
01:49Traces of lakes and rivers dating from a distant time.
01:53Curiosity's favorite place to have fun is the Gale Crater.
01:57It is a prehistoric Martian oasis,
02:00where we think there used to be water.
02:02There is a huge mountain in the middle.
02:04Mount Sharp.
02:06This place is higher than 10 Eiffel Towers stacked on top of each other.
02:10It contains layers of rocks that contain a whole bunch of secrets.
02:13Recently, scientists have found something amazing
02:17by studying Curiosity data.
02:20What is so surprising?
02:22It is not just any crack.
02:24These are messages from the past.
02:26They mean that the Martian soil was moistened,
02:29then dried alternately.
02:31During the drying phases,
02:32the tip of the soil shrank and cracked,
02:35creating these junctions in the shape of T.
02:38It would seem that the Martian soil
02:40has undergone several cycles of humidity and dryness.
02:43This would have happened up to 10 times.
02:46Thus, the junctions took the shape of cracks in the shape of I.
02:50When a group of cracks in the shape of I come together,
02:53they form a super cool pattern,
02:56something like a patchwork of hexagons.
02:58It looks like bee nests, or the skin of a dragon.
03:01Each of these hexagons is the size of a candy.
03:04Similar cycles have occurred on Earth,
03:07and they are linked to the appearance of life.
03:10When the water dries,
03:12it leaves behind concentrated substances
03:14that are conducive to chemical reactions.
03:16And these reactions could be those
03:18that give you the biological kick.
03:20These hexagons have existed for a very long time,
03:23billions of years.
03:24This means that Mars has already had a climate
03:26similar to that of the Earth,
03:28and perhaps even life.
03:30In fact, the red planet even presents traces of water
03:33at the current time,
03:34in the form of ice hidden in the poles.
03:37Mars has a north pole and a south pole,
03:40which, like on Earth, are ice caps.
03:43Imagine the north pole as a large ice cream
03:45about 1,000 km wide.
03:48The south pole is a little smaller,
03:50about 350 km wide.
03:53But its layer of ice is thicker,
03:55a bit like a snowball with a solid envelope.
03:58When it's winter at the poles,
04:00the night is incredibly long.
04:02There is no light,
04:03and the darkness is glacial.
04:05During these periods,
04:06about 30% of the air turns into frozen CO2.
04:10Carbonic ice,
04:11like the ones we often see in horror movies.
04:14But when the light of the sun comes to wake up the poles,
04:17this dry ice turns into gas again.
04:20All these cycles of freezing and thawing
04:22produce clouds and frost, like on Earth.
04:25Once, a rover named Opportunity
04:28even surprised clouds of water ice.
04:30But that doesn't necessarily mean
04:32that Mars was once as prosperous as Earth.
04:35Life needs more than simple cycles of humidity
04:38and dryness to appear.
04:40It needs an adequate atmosphere
04:42and other specific ingredients.
04:44We are not sure that Mars had all these elements.
04:47And even if it was the case,
04:49nothing can affirm that life really developed there.
04:52But that raises another very important question.
04:55Did Mars ever shelter tiny living creatures?
04:59Curiosity is not the only robot
05:01to try to answer this question.
05:03There is also a rover called Perseverance.
05:06It tries to find clues about Martian life.
05:09It digs into an ancient Martian crater,
05:11once filled with water.
05:13And, like a space archaeologist,
05:16Perseverance searches for fossilized traces of ancient creatures.
05:20And the funniest thing is that some scientists
05:23think that we discovered what was to be discovered
05:27nearly half a century ago.
05:28But that unfortunately,
05:30we accidentally destroyed what we had found.
05:33This happened even before Curiosity
05:35started to roll on Mars.
05:37In the 1980s,
05:38two NASA landers,
05:40Viking 1 and Viking 2,
05:42made a stop on Red Planet.
05:44These landers took a selfie.
05:46Then they also did weird experiments
05:49on Martian soil.
05:50All in order to find signs of life.
05:53What they found was a strange organic substance
05:56called perchlorate.
05:58It is a compound used in fireworks
06:01or rocket fuel.
06:03But most of the results did not seem very promising.
06:06They even mixed soil with water and nutrients,
06:09hoping that if there were Martian microbes,
06:11they would feed on these substances
06:13and produce radioactive gases.
06:15Unfortunately, this did not happen.
06:17Here is the problem now.
06:19Some scientists think that the water added at the time
06:22may have destroyed these little Martian creatures.
06:25The poor microbes that were hanging there
06:27were suddenly sprinkled with a strange liquid.
06:29Such a situation would not be very pleasant
06:32for terrestrial microbes.
06:33They live inside rocks
06:35and absorb the water in the air.
06:38Pouring water on them would be a real disaster.
06:41So, of course, giving them nutrients afterwards
06:44would be useless.
06:46If you have survived a flood,
06:48you are probably not in a good mood.
06:51The cells of these hypothetical Martian creatures
06:54may contain hydrogen peroxide,
06:56which would allow them to survive in an extreme environment.
07:00If this is the case,
07:01this could explain the results of the experiments.
07:04The instruments have heated the samples.
07:07So, if there was hydrogen peroxide,
07:10it would have exploded,
07:11eliminating the little creatures
07:13and destroying their environment instantly.
07:15Imagine how ridiculous it would be
07:18if it turned out that we accidentally destroyed
07:20the only signs of life on Mars.
07:22Ideally, we would need a new mission on Mars
07:25to test this theory.
07:27Let's hope it is not confirmed.
07:29Anyway, the trip is not over.
07:32Other missions are planned for Mars,
07:34and man could even visit this planet one day.
07:37The next mission is the Mars Sample Return.
07:40It is a super cool collaborative project
07:42between NASA and ESA.
07:44They work together to bring back memories of Mars,
07:47collected by the faithful rover
07:49Mars Perseverance of NASA.
07:51There will be a whole bunch of spaceships.
07:53They will work together to bring back
07:55these precious Martian samples.
07:57The samples should arrive on Earth
08:00at the beginning or middle of the 2030s.
08:03But we will not stop on such a good path.
08:06Our Martian missions are a kind of warm-up
08:08for an even bigger adventure.
08:10The exploration of the icy moons of Saturn and Jupiter.
08:14These moons hide oceans under their surface.
08:16And who knows what secrets they conceal.
08:19But whether it's Mars,
08:20icy moons or something else,
08:22our extraterrestrial life quest continues.
08:26In addition, we are slowly starting to find
08:28more and more organic material on Mars.
08:31And maybe one day,
08:32we will finally find microbes in our solar system.
08:35Let's hope so and stay tuned.