Scientists from Nasa and Universidade of Arizona identified tryptophan in fragments of the asteroid Bennu collected by the OSIRIS-REx mission. The finding, published in a study led by geochemist Angel Mojarro, from Goddard Space Flight Center, marks the first detection of this essential amino acid in extraterrestrial material. The discovery reinforces the hypothesis that asteroids delivered fundamental organic compounds to the primitive Terra.
Tryptophan is used by the human body to produce serotonin, a neurotransmitter linked to mood regulation, and melatonin, a sleep hormone. Because it is a fragile molecule, it had never been found in meteorites that pass through the Earth’s atmosphere.
Why Tryptophan Never Appeared Before
Tryptophan degrades easily with intense heat. Meteoritos that fall into Terra undergo extreme atmospheric friction, reaching thousands of degrees Celsius, which destroys delicate compounds.
Samples of Bennu were collected directly in space in 2020 and returned to Terra in September 2023 inside a protected capsule. Esse method avoided atmospheric burning and preserved sensitive molecules.
The detection occurred in analyzes carried out in 2025 using high-precision techniques in a terrestrial laboratory.
What else was found in Bennu
The researchers confirmed the presence of 14 previously reported amino acids. Também detected all five common nucleobases (adenine, guanine, cytosine, thymine and uracil).
- Non-biological amino acids reinforce the extraterrestrial origin of compounds
- Several chemical pathways, many involving ancient liquid water, formed the molecules
- Asteroid’s heterogeneous composition indicates multiple chemical processes over billions of years
Importance for the origin of life
The presence of tryptophan in Bennu expands the inventory of biological precursors delivered by celestial bodies. Asteroides and comets may have provided greater amounts of organic ingredients than previously estimated.
The finding shows that complex molecules form naturally in lifeless environments. Isso requires caution when searching for biological signs on other worlds.
Varied composition of the asteroid
Bennu is a breccia, that is, a cluster of fragments of different origins. Scientists analyzed portions with different mineral compositions.
Some regions showed signs of alteration by liquid water in the remote past. Outras maintained more primitive chemistry.
These variations indicate that no single process generated all of the observed molecular diversity.
Next steps of the research
The authors recommend additional analyzes to confirm the origin of the detected tryptophan. Técnicas of enantiomeric and isotopic composition can determine whether the amino acid has a clearly extraterrestrial signature.
Future missions to return samples from other asteroids and comets are considered essential. Elas allow us to study fragile molecules that are lost during natural falls in Terra.
The discovery reinforces the importance of continuing to collect material directly in space to understand the prebiotic chemistry of Sistema Solar.
