Organic Molecules in Asteroid Bennu Samples: Clues to Life’s Origins Uncovered

NASA’s OSIRIS-REx mission successfully returned a sample from asteroid Bennu, revealing organic molecules that are essential for life. The analysis showed the presence of all five nitrogen bases required for DNA and RNA, as well as 14 amino acids, formaldehyde, ammonia, and other prebiotic materials. These findings support the panspermia theory, which suggests that asteroids may have delivered the building blocks of life to Earth. The discovery of minerals formed in water-rich environments also hints at the past existence of liquid water on Bennu.

𝑺𝒖𝒎𝒎𝒂𝒓𝒚 𝒐𝒇 𝑭𝒊𝒏𝒅𝒊𝒏𝒈𝒔

• NASA’s OSIRIS-REx mission collected 121.6 grams of material from asteroid Bennu.
• The samples contained all five nitrogen bases crucial for DNA and RNA.
• Scientists detected 14 amino acids, essential for protein formation in living organisms.
• Bennu’s samples also included ammonia, formaldehyde, and N-heterocycles.
• Minerals such as calcite, halite, and sylvite indicate the presence of water in Bennu’s past.
• The presence of vitamin B3 (nicotinic acid) supports the theory that asteroids provided nutrients for early Earth life.
• The results were published in Nature and Nature Astronomy.

𝑵𝑨𝑺𝑨’𝒔 𝑶𝑺𝑰𝑹𝑰𝑺-𝑹𝑬𝑿 𝑴𝒊𝒔𝒔𝒊𝒐𝒏

The OSIRIS-REx mission, launched by NASA in 2016, aimed to study asteroid Bennu and return samples to Earth. The spacecraft reached Bennu on December 3, 2018, mapping the asteroid in detail before collecting a sample in October 2020.

The returned samples were carefully stored and analyzed at NASA’s Goddard Space Flight Center and the Johnson Space Center. The mission’s success has expanded our understanding of early Solar System chemistry.

𝑩𝒖𝒊𝒍𝒅𝒊𝒏𝒈 𝑩𝒍𝒐𝒄𝒌𝒔 𝒐𝒇 𝑳𝒊𝒇𝒆 𝑶𝒏 𝑩𝒆𝒏𝒏𝒖

A major discovery in the Bennu sample was the presence of all five nitrogenous bases used in DNA and RNA: adenine, cytosine, guanine, thymine, and uracil. These are the core components that store genetic information in all life forms on Earth.

Additionally, researchers from Hokkaido University and JAMSTEC found high concentrations of N-heterocycles, which are organic compounds important for biological activity.

“The clues we’re looking for are so minuscule and so easily destroyed or altered from exposure to Earth’s environment. That’s why some of these new discoveries would not be possible without a sample-return mission.”
— Daniel P. Glavin, NASA Goddard Space Flight Center

𝑻𝒉𝒆 𝑹𝒐𝒍𝒆 𝒐𝒇 𝑾𝒂𝒕𝒆𝒓 𝑰𝒏 𝑨𝒔𝒕𝒆𝒓𝒐𝒊𝒅 𝑪𝒉𝒆𝒎𝒊𝒔𝒕𝒓𝒚

Scientists also found 11 types of minerals formed in water-rich environments, including calcite, halite, and sylvite. The Natural History Museum in London confirmed that these minerals could only form in briny water, suggesting that Bennu once had liquid water.

This discovery is important because similar brine chemistry has been observed on Ceres, Enceladus, and Europa, raising the possibility of habitable environments beyond Earth.

𝑪𝒐𝒎𝒑𝒂𝒓𝒊𝒏𝒈 𝑩𝒆𝒏𝒏𝒖 𝒂𝒏𝒅 𝑹𝒚𝒖𝒈𝒖

Scientists compared the Bennu sample with materials from asteroid Ryugu, collected by JAXA’s Hayabusa2 mission.

Feature	Bennu Sample	Ryugu Sample
Amino Acids	14 types detected	Less abundant
Nucleobases	All 5 nitrogen bases	Only uracil and vitamin B3
Water-formed Minerals	High presence	Lower presence
Organic Complexity	More diverse molecules	Less complex compounds

These findings suggest Bennu may have originated in a colder, more water-rich environment than Ryugu.

𝑾𝒉𝒂𝒕’𝒔 𝑵𝒆𝒙𝒕 𝒇𝒐𝒓 𝑨𝒔𝒕𝒆𝒓𝒐𝒊𝒅 𝑺𝒂𝒎𝒑𝒍𝒆 𝑺𝒕𝒖𝒅𝒊𝒆𝒔?

The Bennu samples will continue to be studied for decades, with international collaborations involving NASA, Hokkaido University, and CRESST. Scientists hope to decode the full chemical history of Bennu and confirm whether similar asteroids contributed to life’s emergence on Earth.

The discoveries made by the OSIRIS-REx mission are significant not only for understanding the origins of life on Earth but also for the potential existence of life elsewhere in the Solar System. The building blocks of life—amino acids, nucleobases, and complex organic molecules—have been found on Bennu, supporting the idea that asteroids could have played a critical role in life’s development. As Jason P. Dworkin, one of the researchers on the mission, pointed out:

Scientists are still trying to understand why life developed on Earth and not on other planets. However, findings from Bennu give us important clues. These findings suggest that the Solar System might support life more than we previously believed. The successful mission to Bennu helps us move closer to solving a big mystery in science. This mystery is about how life started and if it can exist outside Earth.

Facts

• OSIRIS-REx is the first mission to return samples from an asteroid since Japan’s Hayabusa2 mission.
• The samples from Bennu are believed to be around 4.5 billion years old, offering a glimpse into the early solar system.
• Asteroids like Bennu are thought to have formed from the remnants of the early solar nebula, the cloud of gas and dust that surrounded the young Sun.

References

• NASA: OSIRIS-REx Asteroid Bennu Sample Reveals Mix of Life’s Ingredients
• Nature Astronomy: Organic Molecules in Bennu Samples
• Hokkaido University: Life’s Building Blocks in Bennu Samples
• Hayabusa2: Japan’s Asteroid Mission
• NASA’s Astromaterials Research
• CRESST: Goddard Center for Research and Exploration

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