Major discovery of an abundance of complex organic molecules in young planetary systems

Does life exist elsewhere than on Earth? That’s the question. But if astronomers now know that there are planets everywhere in the Universe, they still do not know if they present the conditions necessary for the emergence of life. Work carried out using the Alma telescope is now providing some answers. They bring to light large amounts of organic molecules in places where planets are formed.

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What if the chemical conditions that led to the emergence of life on Earth were ultimately not uncommon? This is the question posed by recent works published within the framework of the Maps project (Molecules with Alma at Planet-forming Scales). Over 20 scientific articles published in The Astrophysical Journal Supplement Series, the researchers detail how they have just discovered, in the heart of protoplanetary discs surrounding young stars, “Large reservoirs” of molecules organic.

These molecules, specify the astronomers, are not simple molecules based on carbon as the carbon monoxide (CO) found in abundance in space. They are more elaborate. Theories make them “Raw ingredients” to build the molecules that are the basis of biological chemistry on Earth. Laboratory experiments have confirmed this. When the conditions are right, they make it possible to form sugars, from amino acids and even the components of ribonucleic acid – the famous RNA. The bricks essential to life.

Find out if these molecules exist where planets form

Many environments in which researchers have already been able to find this type of complex organic molecule can be qualified as uninteresting. “This time, we wanted to know if these molecules are present in the places where the planets are born, in the protoplanetary discs, explains John Ilee, astronomer at the University of Leeds (United Kingdom), in a communicated .

More organic molecules than expected

These observations were made thanks to telescopeAlma – theAtacama Large Millimeter / Submillineter Array (Chile) -, capable of detecting very weak signals coming from molecules located in cold regions of theUniverse . Signals like fingerprints which inform researchers about the identity of the molecules that emitted them.

Astronomers have thus studied five protoplanetary discs located between 300 and 500 light years of the earth. Their goal: to map the chemical composition of these discs. And see how the molecules are distributed where planets are formed. The researchers thus identified organic molecules simple like hydrogen cyanide (HCN), ethynyl (C2H) or the formaldehyde(H2CO). In the regions of the disc where the rocky planets.

But the researchers mainly found three more complex molecules: cyanoacetylene (HC3N), acetonitrile (CH3CN) and cyclopropenylidene (cC3H2). “Our analysis shows that these molecules are also mainly located in these internal regions of these discs, at size scales similar to our Solar system , with abundances between 10 and 100 times higher than what the models predicted ”, says John Ilee. And it is precisely in these regions that the asteroidsand the comets. These objects which are believed to have seeded our Earth. Astronomers thus imagine that a process similar to that which initiated the appearance of life on our Planet could also occur in these protoplanetary disks.

Understanding how the ingredients of life come together

“If there is such an abundance of such molecules in protoplanetary disks, it may be that even more complex molecules can be observed. We will continue our research in this direction with Alma. If we get results, we’ll be even closer to understanding how the raw ingredients of life can be assembled around other stars ”, notes John Ilee.

What the researchers also observed is a non-uniform distribution of these molecules between and even in protoplanetary disks. This suggests that planets forming in different disks or in different places of the same disk can evolve in radically different chemical environments too. So some planets can be formed with everything it takes to bring out life, while their neighbors cannot. There is no doubt that Alma will allow these fundamental questions to be clarified a little more in the future.

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