Scientists have announced the unprecedented discovery of Tryptophan, a complex essential amino acid, on samples from asteroid Bennu, bolstering theories that life’s fundamental building blocks may have originated in space.
This marks the first time Tryptophan, an amino acid vital for human diet and protein synthesis, has been identified in extraterrestrial material.
The findings come from analyses of rock and dust collected by NASA’s OSIRIS-REx mission, which successfully returned samples to Earth in 2023.
Dr. Jose Aponte, a NASA astrochemical chemist, highlighted the significance of Tryptophan’s presence. He stated its complex nature suggests the “formula for the origin of life” might have been produced in the early solar system, not exclusively on Earth.
The discovery adds Tryptophan to 14 other amino acids and all five nucleobases, components of DNA and RNA, previously identified in Bennu’s samples. This brings the total to 15 out of the 20 amino acids used by terrestrial life.
Asteroid Bennu is believed to have formed from meteorite fragments between 200 and 700 million years ago. Its composition reflects the solar system’s genesis 4.5 billion years ago.
Its constituent elements are thought to have originated from an ancient supernova, subsequently processed by heat, collisions, and solar radiation.
Researchers also noted the presence of ammonia and various minerals on Bennu, which are crucial raw materials for creating basic life molecules. These are considered important building blocks that have not yet been assembled.
Initial analyses were conducted on a small 50-milligram sample. Further verification is ongoing.
Experts are confident that the risk of contamination from Earth is minimal, given the pristine condition of the retrieved samples.
While other amino acids have been detected on celestial bodies like asteroid Ryugu, Tryptophan had not been found until now.
Scientists from a NASA research center announced these findings on November 28, 2025.