Chondritic meteorites, rocks that formed long before Earth existed, could play a fundamental role in the origin of life in the universe, and point to its ubiquity, including on other planetary bodies in our Solar System.
The exceptionality of these unaltered space travelers, who impacted the Earth, makes them the object of meticulous study in multiple laboratories around the world, including the White Room for Meteoritics and Returned Samples of the Institute of Space Sciences (ICE – CSIC). Our studies at the ICE-CSIC, together with the experiments carried out in two separate works in collaboration with the Polytechnic University of Catalonia (UPC) and the University of Tuscia in Italy, have shown that chondrites synthesize complex organic compounds. Recently, in order to investigate the specificity of the minerals contained in these meteorites, we verified that they synthesize hydrocarbons and alcohols and that the reactions produce a large amount of carbon dioxide.
These new features raise the ante in favor of the possibility that the arrival of these catalytic materials on forming planets facilitates the emergence of extraterrestrial life on other worlds.
This time it’s hydrocarbons, methanol and carbon dioxide.
Our latest experiments, carried out by the young astrophysicist Victoria Cabedoindicate that these meteorites, known as chondrites, have reactive mineral phases capable of producing the synthesis of hydrocarbons (methane, ethane and ethylene), as well as alcohols (methanol and ethanol) and also other oxygenated compounds, such as formaldehyde and acetone, even under conditions of reaction without oxygen.
The reactions also produce a large amount of carbon dioxide. We have been able to show that the production of these compounds arises from reactions that occur on the surfaces of meteorites and not as a process of desorption of the organic contents already present in these original materials.
The activity is mainly associated with the metallic phases, since it shows greater productivity than other mineral phases that form the meteorites.
Such experiments preceded others that revealed that Carbonaceous chondrites have surprising catalytic properties unknown in any other rock: they are capable of synthesizing, in aqueous solution and in the presence of nitrogen compounds -we use formamide-, key organic compounds in prebiotic chemistry. This means that, under the right conditions of liquid water, heat, and a nitrogen-rich atmospherethe massive arrival of these materials on a consolidated planet could provide the necessary ingredients to “cook” life as we know it, and not only on Earth.
Rocks tens of millions of years older than Earth
Carbonaceous chondrites are a piled up of the materials that made up the protoplanetary disk: a toroidal-shaped collection of solid materials that gathered the material around the Sun from which the first solid objects in the Solar System formed, including the Earth.
And what is exceptional is that these meteorites usually contain a small percentage by mass of carbon (between 1% and 4%). Carbon is the basis of life because it is present in the biological structures of all living beings.
Its organic content once fascinated chemists of the stature of the Swede Jons Jacob Berzelius (1779-1848) who learned the Chondrite Alaisa meteorite that impacted the Languedoc-Roussillon area, in France, or the German Friedrich Wöhler (1800-1882) who learned the kaba meteorite.
It is not terrestrial contamination
The presence of organic matter in the chondrites was highly controversial: many thought it was the result of terrestrial contamination. The demonstration of its extraterrestrial origin came as a consequence of the space race. In 1969 NASA created fall clean rooms to study lunar rocks and this made it possible to study recently chondrites, two of the most famous meteorites, the allende meteoritethat fell in the city of Mexico that gives it its name, and the Murchison meteoritewhich fell in Australia.
Such falls were studied by one of my mentors and, possibly, one of the most illustrious Spanish biochemists: Joan Gold (1923-2004). His study of the Murchison carbonaceous chondrite, recovered from a fall in Australia in 1969, fueled his fascination with the organic compounds contained in these meteorites and probably his astrobiological interest.
Today we know that a good part of the complex organic compounds, including the soluble ones, arise from the interaction between the primordial minerals incorporated in those meteorites with the hot water that soaked them in the first ten million years after the consolidation of those hydrated asteroids.
We now know its essential role in the origin of organic complexity.
In our studies we have gone one step further. We have shown the properties catalytic of certain minerals in carbonaceous chondrites. And that synthesis of organic compounds would occur by a type of reaction known as Fischer-Tropsch.
The previous experiments that we carried out in close collaboration with the Italian team of Raphael Saladino revealed that the minerals that make up these meteorites synthesize, in aqueous solution and in the presence of formamidekey organic compounds in prebiotic chemistryorganic molecules that may be present on early Earth and give rise to the first forms of life.
These catalytic properties are not known in other rocks on Earth or other planetary bodies in the Solar System, which means that the arrival of such meteorites on Earth could have played a fundamental role in increasing organic complexity in favor of the origin of the life.
The origin of the first living organism
Although the origin of life remains a mystery, today we know that the minerals that make up carbonaceous chondrites are capable of synthesizing increasingly complex carboxylic acids, amino acids, and all the nitrogenous bases that make up ribonucleic acid (RNA), the precursor of the first organism. living: cytosine (the bioisostero isocytokine), guanine, adenine and uracil.
Our work also points to the importance of Krebs cycle whose prebiotic role has been promulgated to explain the fixation of carbon oxides in the Earth’s early atmosphere.
As if that were not enough, among the catalyzed organic products, the appearance of glycine, N-formylglycine and alanine stands out. The evidence suggests that it arises in a synthesis from the form of the Strecker type. On the other hand, from formylglycine, through a process called formylation, the observed urea and guanidine would be generated.
The role of water
That study capped off more than a decade of research into the role of water soaking in the parent bodies of carbonaceous chondrites, a study I began at the Center for Astrobiology and the Institute of Geophysics and Planetary Physics (IGPP) from the University of California (UCLA).
Our planet formed at high temperatures, and its rocky materials are more similar to enstatite chondrites and ordinary waterless chondrites, due to heating that gave them the larger size of their parent asteroids.
However, carbonaceous chondrites usually represent more primitive stages, less affected by the thermal emission that occurred during their transformation, something that affects asteroids hundreds of kilometers in diameter more.
This is the reason why its minerals are more reactive in the presence of water, since its components (silicates, metallic grains, and sulfides) preserve the primordial conditions in which they condensed around the Sun. Chondrites, by preserving the original conditions in their interior, they bring us a valuable message in a bottle of processes that can be key in the first moments after the formation of rocky planets.
Mars, Europa or Enceladus may have conditions conducive to life
In the case of the Earth, the internal heat produced the degassing of the planetary interior to form an atmosphere with water and nitrogen, key components to produce hydrothermal environments that, in the presence of this meteoritic flow, a prebiotic organic broth in which the life.
But our work also suggests that other planetary bodies may also host this primordial organic soup, such as Mars, Europa (Jupiter’s moon) or Enceladus (Saturn’s moon). In the case of Mars, organic deposits around Gale crater suggest that This type of hydrothermal environment may exist during the Noean (between 4,100 and 3,700 Ma ago) and may still harbor “fossil” evidence from that era today.
Thus, perhaps we are facing the discovery of the key chemical processes at the origin of the complexity of organic matter in the universe, processes that may have occurred or may be occurring in other parts of the cosmos that are still waiting to be discovered.
This article was originally published on The conversation. read the original.