New discovery in chondrite meteorites raises the stakes in favor of extraterrestrial life

Chondrite meteorites, rocks that formed long before the existence of the Earth, may play a fundamental role in the origin of life in the universe and indicate its ubiquitous distribution, including on other planetary bodies in our solar system.

The exceptional nature of these unchanging Earth-impacting space travelers makes them the subject of scrutiny in many laboratories around the world, including the White Room of Meteoritics and Returned Samples of the Institute for Space Science (ICE – CSIC). Our research at ICE-CSIC, together with experiments carried out in two papers with the Polytechnic University of Catalonia (UPC) and Tuscia University 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 confirmed that they synthesize hydrocarbons and alcohols and that large amounts of carbon dioxide are released as a result of the reactions.

These new discoveries are raising the stakes in favor of the possibility that the arrival of these catalytic materials on forming planets contributes to the emergence of extraterrestrial life on other worlds.

This time it’s hydrocarbons, methanol and carbon dioxide.

Our latest experiments by young astrophysicist Victoria Cabedo show that these meteorites, known as chondrites, have reactive mineral phases capable of synthesizing hydrocarbons (methane, ethane and ethylene) as well as alcohols (methanol and ethanol). as well as other oxygen-containing compounds such as formaldehyde and acetone, even under reaction conditions without oxygen.

The reactions also produce large amounts of carbon dioxide. We were able to show that the formation of these compounds occurs as a result of reactions occurring on the surface of meteorites, and not as a process of desorption of organic content already present in these starting materials.

The activity is mainly associated with the metal phases, since they show higher productivity than other mineral phases that form meteorites.

These experiments were preceded by others that showed that carbonaceous chondrites have amazing catalytic properties unknown to any other rock: they are able to synthesize in aqueous solution and in the presence of nitrogen compounds – we use formamide – key organic compounds in chemistry. . This means that under the right conditions of liquid water, heat, and a nitrogen-rich atmosphere, the massive arrival of these materials on a consolidated planet could provide the necessary ingredients to “cook” life as we know it, and not just on earth.

Rocks are tens of millions of years older than Earth

Carbonaceous chondrites are folded from the materials that formed the protoplanetary disk: a set of toroidal-shaped solid materials that collected material around the Sun, from which the first solid objects in the solar system, including the Earth, were formed.

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 things.

Its organic content once fascinated chemists, such as the Swede Jons Jakob Berzelius (1779–1848), who studied the Ale chondrite, a meteorite that fell in the Languedoc-Roussillon region of France, or the German Friedrich Wöhler (1800–1882), who studied the Kaaba. meteorite.

This is not terrestrial pollution

The presence of organic matter in chondrites was initially a matter of great controversy: many thought it was the result of terrestrial pollution. The demonstration of its extraterrestrial origin was the result of the space race. In 1969, NASA set up clean rooms to study lunar rocks, and this made it possible to study recently fallen chondrites, two of the most famous meteorites, the Allende meteorite that fell in Mexico City, which gives it its name, and the Murchison meteorite that fell in Australia.

Such falls were studied by one of my mentors and perhaps one of the most eminent Spanish biochemists: Joan Oro (1923-2004). His study of Murchison’s carbonaceous chondrite recovered from a crash in Australia in 1969 increased his fascination with the organic compounds contained in these meteorites and demonstrated their astrobiological interest.

Today we know that a significant part of complex organic compounds, including soluble ones, arise as a result of the interaction of the primary minerals contained in these meteorites with the hot water that soaked them in the first ten million years after the consolidation of these asteroids. .

We now know its essential role in the origin of organic complexity.

In our research, we have taken another step forward. We have demonstrated the catalytic properties of some minerals contained in carbonaceous chondrites. And this synthesis of organic compounds will occur according to the type of reaction known as Fischer-Tropsch.

Previous experiments, which we conducted in close collaboration with an Italian group led by Raffaele Saladino, have shown that the minerals that make up these meteorites synthesize in aqueous solution and in the presence of formamide key organic compounds of prebiotic chemistry, organic molecules that may be present on Primordial Earth and give rise to the first forms of life.

These catalytic properties are unknown to other rocks on Earth or other planetary bodies in the solar system, meaning that the arrival of such meteorites on Earth could have played a fundamental role in increasing organic complexity in favor of life.

Origin of the first living organism

Although the origin of life remains a mystery, we now know that the minerals that make up carbon-containing chondrites are capable of synthesizing increasingly complex carboxylic acids, amino acids, and all the nitrogenous bases that make up ribonucleic acid (RNA), the precursor to the first living organism: cytosine (a bioisostero isocytokine), guanine, adenine and uracil.

Our work also points to the importance of the Krebs cycle, whose prebiotic role has been proclaimed to explain the fixation of carbon oxides in the Earth’s early atmosphere.

As if that weren’t enough, the appearance of glycine, N-formylglycine, and alanine stand out among the catalyzed organic products. Available evidence suggests that they result from the synthesis of Strecker-type formamide. On the other hand, from formylglycine, through a process called formylation, the observable urea and guanidine will be formed.

The role of water

This study completes more than a decade of research on the role of water infiltration of carbonaceous chondrite parent bodies, a study that I began at the UCLA Center for Astrobiology (UCLA) and the Institute for Geophysics and Planetary Physics (IGPP). ).

Our planet was formed at high temperatures, and its rocky materials are more like enstatite chondrites and ordinary anhydrous chondrites due to the heat giving them a larger size than their parent asteroids.

However, carbonaceous chondrites are usually more primitive stages, less affected by the thermal change that occurred during their transformation, which affects asteroids hundreds of kilometers in diameter to a greater extent.

For this reason, its minerals are more reactive in the presence of water, since its components (silicates, metal grains and sulfides) retain the initial conditions in which they condensed around the Sun. Chondrites, while maintaining the initial conditions within themselves, they bring us a valuable message about the processes, which can be key in the first moments after the formation of rocky planets.

Mars, Europa or Enceladus may have favorable conditions for life

In the case of Earth, internal heat degassed the planet’s interior to form an atmosphere of water and nitrogen, key ingredients for creating a hydrothermal environment that, in the presence of this meteor shower, turned into a prebiotic organic soup in which life originated. .

But our work also suggests that this primordial organic soup could have been on other planetary bodies, 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 have existed during the Noyan period (between 4100 and 3700 Ma) and may still contain “fossil” evidence of that era.

Thus, perhaps we are facing the discovery of key chemical processes that underlie the complexity of organic matter in the universe, processes that could or could occur in other parts of the cosmos that are still waiting to be discovered.

Josep M. Trigo Rodriguez, Principal Investigator of the Meteorites, Small Bodies and Planets Group at the Institute of Space Sciences (ICE – CSIC)

This article was originally published on The Conversation. Read the original.