Can there be life on Mars today?

Search for life on Mars should not focus exclusively on the distant past, say some researchers.

Four billion years ago, the Martian surface was apparently quite habitable, with rivers, lakes and even a deep ocean. Indeed, some astrobiologists consider ancient Mars as a cradle of life even better than Earth, and they suspect that life on our planet may have come a long time ago. aboard the Martian rocks blown into space by a powerful impact.

Things changed when Mars lost its global magnetic field. The charged particles dripping with the sun were then free to remove the particles formerly thick. Martian atmosphereand strip him they did. This process has transformed Mars into the cold, dry world we know today. about 3.7 billion years ago, suggest observations from NASA's MAVEN orbiter. (The Earth still has its global magnetic field, explaining how our planet remains so livable.)

Related: The search for life on Mars (Chronology of a photo)

But this turn of events does not necessarily mean that Mars is a dead planet today.

"If Mars had life 4 billion years ago, Mars still has life, it did not happen on Mars that could have destroyed life," said Michael Finney, co-founder of The Genome Partnership, a non-profit organization that manages genome progress. Conferences on Biology and Technology.

"So, if there had been life on Mars, maybe she'd have moved, maybe she's hidden a little bit, but she's probably still there," said Finney the month. last at a roundtable held at the Breakthrough Disc Lecture at the University of California. Berkeley.

Go underground?

One of the most promising hiding places is the Martian metro. Although the surface of the red planet no longer contains liquid water these days – aside, perhaps, from temporary flows on warm slopes – there is probably a lot of wet matter in the buried aquifers. For example, observations from the European Mars Express orbiter suggest that a large lake could be hiding under the south pole of the red planet.

The various residents of the Earth announce their presence in a spectacular and obvious way. an advanced extraterrestrial civilization could probably understand quite quickly, simply by scrutinizing our atmosphere, that our planet is inhabited.

We do not see any evidence so clear in the Martian air, but scientists have recently spotted intriguing clues. For example, NASA's Curiosity mobile has gone through two plumes of methane inside the Gale Crater, 154 km wide (154 km), that the six-wheeled robot has been exploring since the touchdown of 2012. The mobile mission also determined that the baseline methane Gale's air follow seasonal cycles.

More than 90% of the Earth's atmospheric methane is produced by microbes and other organisms, so it is possible that gas is a signature of modern Martian life.

But the jury is certainly still on this issue. Abiotic processes can also generate methane. the reaction of hot water with certain types of rocks is an example. And even though Mars' methane is biogenic, the creatures that created it could have been dead for a long time. Scientists believe that methane plumes from the red planet have leaked from the subsoil, and it is impossible to know how long the gas was trapped there before reaching the surface.

Related: 5 bold claims of extraterrestrial life

In search of DNA

From NASA Rover 2020 of Mars, whose launch is scheduled for next summer, will be looking for signs of a long dead life on the red planet. The same is true of the European-Russian ExoMars rover, a mission that will take off at about the same time.

But some researchers are pushing to expand the hunt for existing Martian life. One of them is the molecular biologist Gary Ruvkun, based at the Massachusetts General Hospital and Harvard Medical School.

Ruvkun is one of three leading researchers in the SETG project (Search for Extra-Terrestrial Genomes), which is developing an instrument to detect life in or on DNA or RNA on Mars. and in other extraterrestrial worlds.

He was part of the Breakthrough Discute discussion group with Finney and several other researchers. He also delivered a speech at the conference, in which he explained SETG instrument on future Martian rovers and other robotic explorers.

Part of this case is centered on panspermia, the idea that life has spread widely in the solar system, and perhaps in the galaxy, by natural or artificial means. If life has indeed come from elsewhere elsewhere on Earth, there is a good chance that it has blossomed once on Mars too, it is thought. The red planet could have been the source, or it could have been "seeded" like the Earth.

Ruvkun considers panspermia as very probable; During his discussion speech, he described himself as a "religious fanatic" of this idea. Ruvkun cited as evidence to support the very early emergence of ATP synthase, the enzyme that makes adenosine triphosphate, a molecule energy storage.

The ATP synthase goes back to the base of the tree of life on Earth, which means that this complex and complex molecule was already operational about 4 billion years ago, said Ruvkun.

"It's not fair that life is put to work," he said. "It's like it has to be super-evolved very quickly, which is why panspermia is so appealing."

If panspermia is really a thing, all the life forms we'll find on Mars – or anywhere else in our solar system – will probably be related to us, reasoned Ruvkun and others. That is, such organisms will use DNA or RNA as a genetic molecule. So we should go hunt for that.

"It seems really silly not to look for DNA on Mars," Ruvkun said during his interview. "It's a worthwhile experience, would we say."

Related: The old Mars could have endured life (Photos)

Not only Mars

Mars is not the only place in our solar system where alien life could flourish today. Indeed, most astrobiologists would put a little less the red planet behind the moon of Jupiter Europa and satellites Saturn Enceladus and Titan.

Europa and Enceladus harbor deep oceans of salty liquid water under their ice shells. It is thought that Titan also has an ocean of buried waters and also sports lakes and liquid hydrocarbon seas on its surface. (NASA is developing a Europa flyby mission characterizing the oceans which will be launched in the early or mid-2020s. The agency also aims to soon send a hunt lander to life on the surface of the moon. And a mission Titan is one of two finalists for the launch of "New Frontiers" by NASA in 2025, with a project to return samples of comets. We should know which of NASA will have chosen by the end of the year.)

Even Infernal Venetian, a warning against climate change on Earth, could still harbor habitable redoubts, according to scientists.

Just like Mars, Venus once had abundant surface water, but an uncontrolled greenhouse effect took it away and left the planet with surface temperatures high enough to melt lead. However, the conditions seem rather mild about 50 km above the Venusian surface.

Penny Boston, director of NASA's Institute of Astrobiology at the agency's Ames Research Center in California, said she thought she the modern life of Venus are weak because of the "dehydration" of the planet.

Anyway, the possible existence of a cloudy life on Venus "must absolutely be questioned," said Boston during the same discussion-debate under discussion.

Mike Wall's book on the search for extraterrestrial life, "Over there"(Grand Central Publishing, 2018, illustrated by Karl Tate), is out now. Follow him on Twitter @michaeldwall. Follow us on twitter @Spacedotcom or Facebook.