NASA Discovers Tryptophan on Asteroid Bennu: Crucial Clues to the Origins of Life in Our Solar System

Asteroid Bennu, which orbits near Earth approximately every six years, has been confirmed to contain tryptophan, one of the most complex amino acids vital for life, according to scientists.

This significant discovery was made through NASA's OSIRIS-REx mission. The spacecraft landed on Bennu in 2020, collected approximately 4.3 ounces (122 grams) of rocks and dust, and returned the samples to Earth in 2023, providing researchers with invaluable insights into the early solar system's chemical composition.

Previous research had already established that Bennu, a relatively small asteroid, contains 14 of the 20 amino acids utilized by all living organisms on Earth, as well as five biological nucleobases that form the foundation of DNA and RNA.

Dating back over 4.5 billion years, Bennu originates from the earliest period of our solar system's formation.

Among the most remarkable findings is tryptophan, an amino acid previously undetected in meteorites. Scientists also observed that various rocks in the samples contain different organic chemicals, as noted by NASA in their blog post.

Jose Aponte, an astrochemist at NASA's Goddard Space Flight Center and study co-author, explained to CNN, "Finding tryptophan in the Bennu asteroid is a big deal, because tryptophan is one of the more complex amino acids, and until now it had never been seen in any meteorite or space sample."

"Seeing it form naturally in space tells us that these ingredients were already being made out in the early Solar System. That would have made it easier for life to get started," he added.

The dust collected from Bennu is rich in carbon, nitrogen, and organic compounds, all crucial components for life. Researchers were surprised to discover magnesium-sodium phosphate in the sample, which had not been detected by the spacecraft during its mission.

The asteroid primarily consists of clay minerals, especially serpentine, similar to rocks found at Earth's mid-ocean ridges where water interacts with mantle rock. Perhaps the most exciting discovery is the presence of water-soluble phosphates, which are essential for life on Earth.

Bennu's composition bears similarities to carbon-rich meteorites discovered on Earth. It contains some of the oldest materials in the solar system, formed in dying stars, including supernova explosions, predating our solar system's existence.

Despite containing fundamental building blocks of life, Bennu lacks the necessary conditions to support life as we understand it. Its temperature fluctuates dramatically from approximately 240 degrees Fahrenheit to -100 degrees Fahrenheit. Furthermore, its absence of atmosphere prevents liquid water from existing on or beneath its surface.

Scientists had previously identified amino acids in samples from asteroid Ryugu, collected by Japan in 2019, as well as in meteorites that have landed on Earth. This growing body of evidence suggests that asteroids may have delivered essential ingredients for life to our planet billions of years ago.