We know that there are dense and cold molecular clouds at the heart of about 1% of the dust formed by stars at the end of their life and which are surrounded by a mantle of ice. Prebiotic chemical reactions take place there, the full complexity of which is not yet known. This dust is also the basic material for the formation of planets and the James-Webb telescope can observe it like never before. These observations should help us understand whether the appearance of life and Earth-like planets is a rarity or not in the observable cosmos.
In the interview he gave to Futura about his latest book, Jean-Pierre Bibring explained to us that the discovery of the diversity of the planets of the Solar systemSolar systemand in particular mondaymonday of JupiterJupiterhad led to the realization that many points of bifurcationbifurcation between evolutionary paths determined by chance and necessity existed in the formation and evolution of planets. Similar conclusions could be reached with regard to the exoplanetsexoplanets and the chemistrychemistry prebiotic of mattermatter in the cloudsclouds dense and cold dusty molecules which by their collapsecollapse gravity can give starsstars surrounded by protoplanetary discsprotoplanetary discs and finally planets.
We could therefore ask ourselves the question of the universal character or not of the appearance of life and also of planets similar to the Earth in theUniverseUniverseat least in the Milky WayMilky Way. The question remains open. To progress, we need to clarify many points such as the one concerning the formation and evolution of molecules prebioticsprebiotics in molecular clouds and in protoplanetary discs.
Exobiology and cosmic ice
Radio astronomy has taught us that there are many moleculesmolecules organic in these clouds. Elementary astrochemical models have been constructed in which grains of silicatessilicates and carbonaceous materials are surrounded by a gangue of ice, mainly water, gangue in which under the effect of photons ultravioletultraviolet young stars, shock wave heating and bombardment of cosmic rayscosmic raysof the chemical reactionschemical reactions occur leading to molecules already observed by radio astronomers.
In models of planet formation in the Solar System, icy giants like Jupiter and NeptuneNeptune first form with a core of rocks and ice resulting from a snowball-like agglomeration process of icy dust. The telluric planetstelluric planets like the Earth and Mars undoubtedly received an initial stock of water but we do not know in what quantity or in what form. In the case of the Earth, which is all the same in the end poor in water if we compare it to the heart of Neptune for example, it is not clear whether its oceans are due to primordial degassing with a main water reservoir at the heart of our Blue Planet or if the water of its oceans came later with the last major bombardments ofasteroidsasteroids and of cometscomets at the start of theHadesHades.
(embed)https://www.youtube.com/watch?v=4Cs6qUHz3yA(/embed)
The Solar System is a laboratory for studying the formation of giant planets and the origin of Life that can be used in conjunction with the rest of the observable Universe for the same purpose. Mojo: Modeling the Origin of JOvian planets, i.e. modeling the origin of the Jovian planets, is a research project that has resulted in a series of videos presenting the theory of the origin of the Solar System and in particular of the gas giants by two renowned specialists , Alessandro Morbidelli and Sean Raymond. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The 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”. © Laurence Honnorat
We do not know if the molecules of life, such as sucressucres, DNA and RNA, were brought to Earth initially by comets and asteroids or whether they were born in the famous primitive hot soup of the famous Miller-Ulrey experiment. In short, the formation of planets and the appearance of life are unquestionably conditioned at the beginning by simple ices coating dusts and which become more and more complex over time through a variety of chemical pathways which depend on their environmental conditions. . Much remains to be discovered and understood about it and only by combining new astronomical observations, cutting-edge laboratory experiments on this icy dust and a modelizationmodelization complete chemical that we can see more clearly.
It is with all these considerations that researchers came together within the framework of the Ice Age project with among them and at their head, Melissa McClure, astronomerastronomer at the Leiden Observatory. They just let know in particular via a recent publication in Nature Astronomy that they had used the penetrating gaze in theinfraredinfrared of telescopetelescope James-Webb to dive like never before into the icy and dark heart of a famous molecular cloud in the Milky Way in order to unlock some of the secrets of these protoplanetary and prebiotic ices.
A rich cocktail of organic molecules
Remember that the organic molecules of life as we know it are composed of only four elements:hydrogenhydrogen (H), l’oxygenoxygen (Of the carbonecarbone (C) and thenitrogennitrogen (NOT). These elements represent 99.4% of the human body while the rocks of the Earth are largely dominated by minerals refractoryrefractory containing essentially as elements, the ferfer (Fe), the siliconsilicon (Yes), the nickelnickel (Ni) and oxygen.
In fact, we often collectively speak of organic molecules in terms of CHON, or even CHONS, because some add as a fifth important element, the sulfursulfur. They are found as important ingredients both in atmospheresatmospheres planets and in molecules such as sugars, alcoholsalcohols and the amino acidsamino acids simple. They are also found in the icy dust at the origin of comets and carbonaceous asteroids.
What the James-Webb telescope has just made possible, according to a joint press release to the NasaNasa et al’ESAESA, it is an in-depth inventory of the ice located in the deepest and coldest parts studied to date in a molecular cloud. In this case, it is the Chameleon I cloud (abbreviated to Cha I for Chamaeleon, in English), one of the closest active star-forming regions to the Solar System and containing a few hundred stars and protostars.
Astrochemists have thus identified a wide range of molecules ranging from sulphursulphur carbonyl,ammoniaammonia and methane, to the simplest complex organic molecule already identified by radio astronomers for decades: methanol CH3OH.
In this press release, Melissa McClure explains that the studies conducted have provided results that “ provide insight into the initial dark chemistry phase of ice formation on grains of interstellar dustinterstellar dust which will turn into pebbles of centimeter sizes from which the planets are formed in discs. These observations open up a new windowwindow on the pathways of formation of the simple and complex molecules that are needed to make the building blocks of life ».
A key to determining the place of life in the cosmos
« Our identification of complex organic molecules, such as methanol and potentially ethanol, also suggests that the many star and planetary systems developing in this particular cloud will inherit molecules in a fairly advanced chemical state. This could mean that the presence of prebiotic molecules in planetary systems is a common result of star formation, rather than a feature unique to our own Solar System. adds his colleague Will Rocha, also an astronomer at the Leiden Observatory and who contributed to this discovery.
« This is just the first in a series of spectral snapshots we will get to see how the ices evolve from their initial synthesis to the comet-forming regions of protoplanetary disks. This will tell us what mixture of ices and therefore what elements may possibly be delivered to the surface of terrestrial exoplanets or incorporated into the atmospheres of giant planetsgiant planets of gazgaz or ice cream McClure also adds.
(embed)https://www.youtube.com/watch?v=mrCEiBi67Go(/embed)
STScI Webinar by Melissa McClure on IceAge: Chemical Evolution of Ices during Star Formation (program ERS 1309), recorded on March 11, 2020. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The 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”. © JWST Observer
