Extraterrestrial organic matter: A look at the cosmic signatures of life

Meteorites, comet dust, asteroid samples and particles obtained from space missions reaching Earth from all over the universe carry unique information about the past of the universe, not only physically but also chemically. The most notable of these materials are “extraterrestrial organic materials”. These complex carbon-based compounds can be the product of biotic or abiotic processes and are among the strong evidence suggesting that life is not unique to Earth in the universe.

Extraterrestrial organic matter is a group of molecules found in samples from meteorites, comets, planetary surfaces, and interstellar environments that are carbon-based and contain elements such as hydrogen, oxygen, nitrogen, sulfur, and phosphorus. These compounds are generally described as amino acids, carbonyl compounds, PAHs (polycyclic aromatic hydrocarbons), nucleobase-like structures, and short-chain carboxylic acids.

These materials are critical for investigating the universality of life and the possibility of extra-planetary life. They also contribute to our understanding of the formation process and early chemistry of the Solar System. The presence of these organic compounds in meteorites such as carbonaceous chondrites suggests that these molecules may have been synthesized in interstellar clouds before the formation of the Solar System. For example, a wide variety of organic compounds have been found in carbonaceous chondrites (especially CM and CI types). In addition, organic materials preserved with traces of liquid water in some salt crystals indicate the interplanetary transport of these molecules.

DISCOVERY AND CHARACTERIZATION METHODS

Thanks to advanced analytical techniques, detailed information about the existence, structure and origin of extraterrestrial organic matter is obtained:

• Mass spectrometry (especially high-resolution FT-ICR MS) is widely used in the resolution of complex organic mixtures.

• Laser desorption/ionization techniques allow the samples to be examined without being damaged.

• NMR spectroscopy elucidates the structural features of organic molecules.

• Raman spectroscopy and infrared spectroscopy are used to determine the mineralogical and organic composition of samples.

• Multimodal imaging techniques provide chemical and structural data simultaneously, allowing samples to be detailed at the nanometer scale.

5. COSMIC ORIGIN OF ORGANIC SUBSTANCES: ASTROCHEMICAL PERSPECTIVE

Some of these organic compounds are thought to have formed in the interstellar medium, in dust and gas clouds, in the presence of ultraviolet radiation and cosmic rays. Chemical reactions on ice grains in dense molecular clouds have paved the way for the formation of complex molecules over time. These processes may have been carried to planetary systems by comets and meteorites.

There are some fundamental similarities and differences between extraterrestrial organic matter and biological molecules naturally found on Earth. Although the amino acids found in meteorites overlap in some ways with those found in living organisms, these amino acids are generally found in both right- and left-handed (L and D forms). However, life on Earth is specific to the L form. This is an indication that the organic matter in meteorites is not of biological origin but rather formed by abiotic processes.

THE ROLE OF ORGANIC MATTER IN THE SEARCH FOR EXTRATERRESTRIAL LIFE

The study of extraterrestrial organic matter forms the basis of astrobiology. These studies form the scientific framework for the search for life on bodies such as Mars, Europa, and Enceladus. Although the presence of organic carbon alone is not evidence of life, it does indicate that the building blocks necessary for life are present. Recent studies have shown that some bacteria can grow by feeding on organic carbon sources from outer space. This reinforces the idea that life on Earth could sprout elsewhere in the universe.

Missions such as OSIRIS-REx, Hayabusa2, Perseverance, and Dragonfly are designed to directly analyze the presence of organic matter by collecting surface samples. Data from these missions reveal not only the presence of organic matter, but also their formation conditions and potential biological relevance.

There are several difficulties in interpreting extraterrestrial organic matter:

• Protecting samples from contamination may be difficult.

• It is difficult to decide the source of organic molecules (biotic or abiotic?).

• Changes that may occur during entry into the Earth's atmosphere may disrupt the original structure.

Therefore, multidisciplinary studies, advanced analysis methods and controlled laboratory experiments are very valuable in this field.

Extraterrestrial organic matter plays a critical role in our understanding of the cosmic evolution of life. Their discovery, analysis, and comparative studies not only shed light on the possibility of life in the universe, but also allow us to question the universality of the chemical basis of life. Future research will provide a better understanding of not only the relevance of these structures to life, but also the extent of chemical diversity and molecular evolution in the universe.