Life Found on Asteroid Bennu, but Very Simple 0 11

Analysis of soil brought back from asteroid Bennu by NASA's OSIRIS-REx mission has shown that amino acids in space can form not only in the hot interiors of celestial bodies but also in deep cold. By comparing Bennu samples with the Murchison meteorite, scientists found that the simplest amino acid—glycine—has a different chemical history. While it was synthesized in warm liquid water in the meteorite, on Bennu it formed in primordial ice before the Solar System was created.

Asteroids and comets are rich in organic matter, including amino acids. The main mystery lies in the mechanism of their appearance. It is believed that organic matter is synthesized inside asteroids when ice melts and reacts with rock. A similar reaction (Strecker synthesis) is currently used for the industrial production of amino acids.

However, this had to be tested on meteorites that fell to Earth, such as Murchison (in Australia in 1969). After 50 years of storage, they could have been contaminated by Earth's atmosphere or bacteria. The samples from Bennu, delivered in a sealed capsule, provided the first opportunity to study the chemical processes of the early Solar System.

The authors of the study published in the journal PNAS conducted ultra-precise isotopic analysis. Instead of simply weighing molecules, they applied the method of intramolecular isotopy.

The specialists literally broke down glycine molecules into parts and measured the content of heavy carbon (13C) separately in the "tail" of the molecule (the carboxyl group) and in its base. The distribution of isotopes between different parts of a single molecule indicates which specific chemical reaction gave rise to the substance. In the product of the Strecker reaction, there is an imbalance of isotopes: the tail of the molecule becomes heavy, rich in carbon-13, while there is little in the head.

In glycine from the Murchison meteorite, the isotopic ratio between the two parts of the glycine molecule was characteristic of synthesis in warm liquid water, as in the Strecker reaction. In samples from asteroid Bennu, the carbon atoms within glycine turned out to be isotopically similar. This indicates that the molecules formed through radical reactions in cosmic ice under the influence of radiation.

Additional analysis of nitrogen confirmed this version: the amino acids from Bennu are saturated with heavy nitrogen (15N), which is typical of objects formed in the cold outskirts of the Solar System or even in the interstellar medium.

The scientists also encountered an unexpected mystery. Mirror copies of the same amino acid (L- and D-glutamic acid), which should be identical in non-living nature, had different isotopic compositions on Bennu. This discovery calls into question old methods of searching for life based on the chirality (symmetry) of molecules.

The study proves that early Earth received organic molecules from two sources. Part of the organic matter arrived ready-made, from hydrothermal sources on asteroids, while part came from the primordial cloud that birthed the Sun. This confirms that the chemistry necessary for the emergence of life is a standard process in the Universe, functioning under a wide range of conditions.