Asteroid sample collected by NASA mission contains building blocks of life
A portion of the asteroid Bennu sample delivered to Earth by NASA's OSIRIS-REx mission, set into a microscope slide at the agency's Goddard Space Flight Center in Greenbelt, Maryland. Image credit: NASA/Molly Wasser
Asteroids are made from the remnants of planetary formation and give scientists a way of looking back in time in the history of our universe. This makes them a good target of study to understand how life may have started in our solar system. In a paper published in Nature Astronomy scientists found organic molecules, including the 14 amino acids cells use to make proteins, in samples collected from the asteroid Bennu by NASA’s OSIRIS-REx mission.
“This is very exciting because we are seeing increasing evidence that the building blocks of life can form in space,” says Angel Mojarro PhD ’23, an organic geochemist and EAPS alumnus working at NASA Goddard Space Flight Center in Greenbelt, Maryland, and one of the authors on the new paper.
As an organic geochemist, Mojarro is interested in how organic molecules can form in a lifeless environment. One thing he found interesting about the results were the forms the amino acids from the samples took. There are two forms of amino acids, often referred to as left-handed (L-amino acids) and right-handed (D-amino acids), that are identical chemically but mirror images of each other. Mojarro says that life on Earth uses left-handed amino acids, and samples from meteorites found on Earth usually favor those as well. But the Bennu samples were an equal mix of left- and right-handed.
“This indicates other processes, perhaps occurring on planetary surfaces, are responsible for early life’s selection of L- over D- amino acids,” he says.
Most samples until now have been taken from meteorites that have fallen to Earth, which are exposed to Earth-based contamination. So in 2016 NASA launched OSIRIS-REx with the goal of collecting samples from an asteroid in space. The probe (which houses an MIT student-designed instrument) successfully collected samples from the asteroid Bennu in 2020 and returned them to Earth in 2023. Since then, scientists have been hard at work studying the samples while avoiding potential contamination from Earth. While the new results are exciting, there is still plenty of analysis to be done; while scientists may have found the building blocks for life, the next step is seeing if those blocks can be detected assembled in the form of early proteins or DNA.
“We are now investigating whether there is evidence for more complex chemical reactions that may have been responsible for catalyzing the union of single molecules into more complex structures,” Mojarro says.
3 Questions: The first asteroid sample returned to Earth
September 25, 2023
Asteroid grains shed light on the outer solar system’s origins
November 6, 2024