Asteroid Bennu reveals life's building blocks from space
Scientists discovered numerous organic compounds in samples from the asteroid Bennu, including key amino acids, DNA, and RNA. This finding suggests that the chemical components essential for life might have been commonly present in the early Solar System, and the first asteroids may have "delivered" these ingredients to Earth.
A team of scientists, studying samples from the asteroid Bennu, identified numerous organic molecules, including important ingredients of life. According to NASA, these key samples were collected by the OSIRIS-REx probe, which launched in 2016. The probe gathered dust, soil, and rocks from the asteroid and returned them to Earth in 2023. Since then, research has been ongoing. Here are the key findings.
What did the asteroid formed 4.5 billion years ago conceal?
Bennu is an asteroid discovered in 1999 that particularly interests scientists due to its age and composition. Considered potentially hazardous to Earth, it formed about 4.5 billion years ago at the beginning of the Solar System's formation. Thanks to the mission by NASA, samples were delivered to Earth that serve as a "cosmic time capsule" offering insights into the early stages of our planetary system's development.
The data from the analysis of samples from Bennu were published in the journal "Nature" and "Nature Astronomy". The research, ongoing since 2023, revealed that the samples contained thousands of organic compounds. The most crucial among them include:
- Amino acids - Thirty-three different amino acids were identified, including 14 of the 20 standard proteinogenic amino acids, which are the basic building blocks of proteins. They are crucial because they combine to form proteins that perform many vital functions in organisms, including catalysing chemical reactions, transporting molecules, and forming cellular structures.
- Nitrogenous bases - All five nitrogenous bases that make up DNA and RNA were detected in the samples: adenine, guanine, cytosine, thymine, and uracil. They are fundamental for storing and transmitting genetic information, essential for the functioning and reproduction of organisms.
- Also detected were 19 non-proteinogenic amino acids, which are rare or not present in Earth's biology.
All these molecules found on Bennu, researchers believe, are necessary for life formation. The fact that they are present on the asteroid suggests that life might have originated somewhere in space and arrived on Earth. It might not necessarily have formed through living organisms but through chemical processes on the asteroid itself.
The first asteroids might have "delivered" life to Earth
Although scientists did not find evidence of life on Bennu, their findings support the hypothesis that asteroids that fell on Earth in its early days might have brought essential ingredients for life. Discoveries also suggest that life might have existed on other planets and moons in the Solar System.
Similar organic molecules, including amino acids, have been detected in meteorites before. According to scientists, samples from Bennu are unique because they were not contaminated during their passage through the atmosphere. Unlike space samples, meteorites often undergo Earth's conditions, affecting research outcomes. Directly retrieved samples from the asteroid are a valuable "time capsule" from the early Solar System.
The asteroid also holds a lot of ammonia and remnants of water
In Bennu's samples, scientists discovered some surprises, including very high concentrations of ammonia—about 100 times greater than in Earth's soils. Ammonia is a key component of many biological processes, including the production of amino acids that can form proteins. Additionally, traces of 11 minerals were found, part of brines formed during the evaporation of water on Bennu and its parent asteroid.
Tim McCoy from the Smithsonian National Museum of Natural History, cited by NASA, indicated that the salt left after evaporation resembles the sodium structures found in places on Earth like Searles Lake in California. McCoy noted that the raw ingredients for life on Bennu combined in interesting and complex ways, which might be considered another step towards life. Similar brines may exist on the moon Enceladus and the dwarf planet Ceres.
Previously, scientists, after initial analyses of Bennu's samples in 2023, pointed to the presence of carbon and water enclosed in clay minerals. The current analysis results are even more surprising. Scientists emphasise that further research is needed to understand why life arose on one planet or moon and not others. Jason Dworkin of NASA pointed out that the question of what Bennu lacked compared to Earth remains, and this will be the next research area for astrobiologists around the world.
