Asteroid Bennu May Hold Clues On How Life Began As NASA Detects Tryptophan

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.

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.

The dust from Bennu is full of carbon, nitrogen, and organic compounds, all important ingredients for life. Scientists were surprised to also find magnesium-sodium phosphate in the sample, which wasn't detected by the spacecraft before.

The asteroid's rocks are mostly clay minerals, especially serpentine, similar to rocks found at Earth's mid-ocean ridges, where water meets mantle rock. The most exciting find is water-soluble phosphates, which are essential for life on Earth.

Bennu's composition is similar to carbon-rich meteorites found on Earth. It contains some of the oldest materials in the solar system. These materials were formed in dying stars, including supernova explosions, long before the solar system existed.

Even though it contains important building blocks of life, Bennu does not have the conditions needed for life as we know it. Its temperatures swing from a scorching 240 degrees Fahrenheit to a freezing -100 degrees Fahrenheit. Also, because it has no atmosphere, liquid water can't exist on or under its surface.

Scientists had also found amino acids in samples from another asteroid, Ryugu, collected by Japan in 2019, as well as in meteorites that have landed on Earth. All this evidence suggests that asteroids may have brought key ingredients for life to our planet billions of years ago.