Why the idea of ​​extraterrestrial life now seems inevitable and perhaps imminent

Extraterrestrial life, this familiar sci-fi trope, this kitsch fantasy, this CGI nightmare, has become a serious topic of discussion, a "risk factor", a "scenario".

How has ET gone from a science fiction fairy tale to a serious scientific enterprise modeled by macroeconomists, funded by tax conservatives and discussed by theologians?

Because, after a series of remarkable discoveries over the past two decades, the idea of ​​extraterrestrial life is not as far-fetched as it seemed.

The discovery now seems inevitable and perhaps imminent.

It's just chemistry

Although life is a particular type of complex chemistry, the elements involved are not special: carbon, hydrogen, oxygen, etc., are among the most abundant elements in the universe. Complex organic chemistry is surprisingly common.

Amino acids, just like those that make up all the proteins in our body, have been found in the tails of comets. There are other organic compounds in the Martian soil.

And at 6,500 light-years away, a giant cloud of alcohol in space floats among the stars.

Living planets seem to be common too. The first planet beyond our solar system was discovered in 1995. Since then, thousands of astronomers have been listed.

Based on this catalog, astronomers from the University of California at Berkeley calculated that there could be up to 40 billion exoplanets the size of the Earth in the area called "habitable" located around their star, where temperatures are mild enough to allow the presence of liquid water. on the surface.

There is even a potentially Earth-like world orbiting our nearest star, Proxima Centauri. Only four light years away from us, this system could be close enough for us to use current technology. With the Breakthrough Starshot project launched by Stephen Hawking in 2016, projects in this direction are already underway.

Life is robust

It seems inevitable that another life is out there, especially if we consider that life appeared on Earth so soon after its formation.

The oldest fossils ever discovered here date back 3.5 billion years, while clues in our DNA suggest that life could have started 4 billion years ago, when giant asteroids have stopped crushing to the surface.

Our planet was inhabited as soon as it was habitable – and the definition of the term "habitable" has also proved to be a fairly flexible concept.

Life survives in all kinds of environments that seem to us infernal:

• float on a lake of sulfuric acid
• in barrels of nuclear waste
• in superheated water at 122 degrees
• in the Antarctic wastelands
• in rocks five kilometers underground.

It is tempting to think that some of these conditions seem to be replicated elsewhere in the solar system.

Extracts of promise

Mars was once hot and humid and was probably fertile ground for life before Earth.

Today, Mars still has water underground. A gas strongly associated with life on Earth, methane, has already been found in the Martian atmosphere and at levels that rise and fall mysteriously with the seasons. (However, the result of methane is under discussion, with one Mars orbiter recently confirming the detection of methane and another detecting nothing.)

Martian insects could appear as early as 2021, when ExoMars' carrier Rosalind Franklin will search for them with a two-meter drill.

Besides Earth and Mars, at least two other places in our solar system could be inhabited. The moon of Jupiter, Europa and the moon of Saturn, Enceladus, are worlds of frozen ice, but the gravity of their colossal planets is enough to turn inside, to melt water to create vast subglacial seas.

In 2017, pack ice specialists from the University of Tasmania concluded that certain microbes from Antarctica could survive under such conditions. Europa and Enceladus both have underwater hydrothermal vents, as do those on Earth where life may have come into existence.

When a NASA probe tasted the geyser material in space out of Enceladus last June, she discovered large organic molecules. Perhaps there was something that lived among the spray; the probe simply did not have the right tools to detect it.

Russian billionaire Yuri Milner has been so excited by this prospect that he wants to help finance a return mission.

A second genesis?

A discovery, if it were to happen, could upset the world of biology.

All life on Earth is linked, ultimately descending from the first living cell to emerge about 4 billion years ago.

Bacteria, fungi, cacti and cockroaches are all our cousins ​​and we all share the same basic molecular mechanism: the DNA that makes the RNA and the RNA that makes the proteins .

A second sample of life, however, could represent a "second genesis" – without any connection to us. Maybe he would use a different coding system in his DNA. Or he might not have any DNA at all, but another method of transmitting genetic information.

By studying a second example of life, we could begin to understand what parts of the machine of life are universal and which are only the particular accidents of our primordial soup.

Maybe amino acids are still used as basic essentials, maybe not.

We might even be able to develop some universal laws of biology, as we did for physics – not to mention new angles on the question of the origin of life itself.

A second independent "tree of life" would mean that the rapid emergence of life on Earth was not a coincidence; life must abound in the universe.

This would greatly increase the chances that, somewhere among the billions of habitable planets in our galaxy, there is something we could talk about.

Maybe life is contagious

If, on the other hand, the microbes discovered were actually linked to us, it would be a bomb of a different kind: it would mean that life is contagious.

When a large meteorite strikes a planet, the impact can project sputtered rock into space, and this rock can then fall on other planets in the form of meteorites.

The life of the Earth has probably already been taken on other planets – perhaps even towards the moons of Saturn and Jupiter. The microbes may well survive the trip.

In 1969, the Apollo 12 astronauts retrieved an old probe that sat on the moon for three years in extreme cold and vacuum: there were still viable bacteria inside.

Since Mars was probably habitable before Earth, it is possible that life was born there before hitchhiking on a rock of space. Maybe we are all Martians.

Even if we never find another life in our solar system, we could still detect it on one of the thousands of known exoplanets.

It is already possible to look at the light of stars filtered through an exoplanet and to say something about the composition of its atmosphere. an abundance of oxygen could be a telling sign of life.

A verifiable hypothesis

The James Webb Space Telescope, scheduled for launch in 2021, will take these measurements for some of the Earth-like worlds already discovered.

A few years later, space telescopes will directly photograph these planets.

Using a trick a little like the sunshade of your car, the planet's captivating telescopes will be paired with giant umbrellas called starshades that will fly in tandem 50,000 kilometers to the right place to block the blinding light stain from a stink. planet to capture.

The color and the variability of this luminous point could indicate to us the duration of the day of the planet, if it has seasons, if it has clouds, if it has oceans, or even the color of its plants.

This article is republished from The Conversation under a Creative Commons license. Read the original article.