Scientists have confirmed that asteroid Bennu — a near-Earth object that passes close to the planet roughly every six years — contains tryptophan, one of the most complex amino acids essential for life.
The finding comes from samples collected by NASA's OSIRIS-REx mission. The spacecraft touched down on Bennu in 2020, gathering about 4.3 ounces (around 122 grams) of dust and rocks before returning the material to Earth in 2023. The samples provide an unprecedented glimpse into the chemistry of the early solar system.
Previous analyses revealed that Bennu holds 14 of the 20 amino acids used by all living organisms, as well as five biological nucleobases — the molecular foundations of DNA and RNA. The asteroid, which is estimated to be over 4.5 billion years old, is considered a relic from the solar system's earliest era.
Researchers say the latest discovery is particularly significant because tryptophan has never before been detected in meteorites. NASA also noted that the sample contains rocks with varying compositions of organic molecules, highlighting the chemical diversity present on the asteroid's surface.
The findings suggest that Bennu may hold valuable clues about how the building blocks of life may have been delivered to Earth in its formative years.
Jose Aponte, an astrochemist in the Astrobiology Analytical Laboratory at NASA's Goddard Space Flight Center and co-author of the study, told 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.
Carbon, nitrogen, and organic compounds—all essential components of life—are abundant in Bennu dust. The presence of magnesium-sodium phosphate in the sample, which the spacecraft had not previously detected, shocked scientists.
The majority of the asteroid's rocks are clay minerals, particularly serpentine, which resemble rocks found at the mid-ocean ridges on Earth, where mantle rock and water meet. Water-soluble phosphates, which are necessary for life on Earth, are the most fascinating discovery.
Asteroid Bennu May Hold Clues On How Life Began As NASA Detects Tryptophan
Asteroid Bennu, which passes near Earth roughly every six years, contains tryptophan, one of the most complex amino acids essential for life, scientists have confirmed.
- Edited by:NDTV News Desk
- World News
- Nov 28, 2025 15:23 pm IST
Asteroid Bennu, which passes near the Earth roughly every six years, contains tryptophan, one of the most complex amino acids essential for life, scientists have confirmed.
This discovery comes from NASA's OSIRIS-REx mission. In 2020, the spacecraft landed on Bennu, collected about 4.3 ounces (around 122 grams) of rocks and dust, and brought it back to Earth in 2023, which gave a snapshot of the early solar system's chemistry.
Earlier studies found that Bennu, a small asteroid, contains 14 of the 20 amino acids used by all living beings on Earth, and five biological nucleobases, the building blocks of DNA and RNA.
Benno is over 4.5 billion years old and is from the early days of our solar system.
One of the exciting discoveries is tryptophan, an amino acid never seen before in meteorites. Scientists also noticed that different rocks in the samples have different organic chemicals, NASA said in its blog post.
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Jose Aponte, an astrochemist in the Astrobiology Analytical Laboratory at NASA's Goddard Space Flight Center and co-author of the study, told 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."
The composition of Bennu is comparable to that of Earth's carbon-rich meteorites. Some of the solar system's oldest materials can be found there. Long before the solar system existed, these materials were created in dying stars, including supernova explosions.
Bennu lacks the conditions necessary for life as we know it, despite having vital components of life. It can get as hot as 240 degrees Fahrenheit or as cold as -100 degrees. Furthermore, liquid water cannot exist on or beneath its surface since it lacks an atmosphere.
Amino acids have also been discovered by scientists in meteorites that have fallen to Earth and in samples from another asteroid, Ryugu, that Japan collected in 2019. All of this evidence points to the possibility that billions of years ago, asteroids may have introduced essential components for life to our planet.
