NASA's OSIRIS-REx mission collected samples from the asteroid Bennu, revealing molecules important to life, including amino acids and nucleobases in DNA and RNA. The presence of ammonia and formaldehyde suggests conditions are ripe for the formation of complex molecules in space.
The scientists also discovered a suite of evaporite minerals that suggest Bennu once had a water-rich environment that could have supported pre-biochemistry. The mission highlights the possibility that the building blocks of life are widespread in the solar system, while also raising questions about why Earth remains the only known host of life.
The secret of asteroid Bennu: the ingredients for life?
NASA's OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification and Security - Rock Explorer) spacecraft brought back rock and dust samples from the asteroid Bennu, revealing molecules essential for life on Earth. Scientists have also found evidence of ancient brine, which may have been the "broth" that helped these molecules interact and evolve into more complex compounds.
While these findings don't show evidence of life itself, they suggest that the early solar system had the right conditions for life to emerge, making it more likely that life could form on other planets and moons.
Nicky Fox, associate administrator of the Science Mission Directorate at NASA Headquarters, said: "NASA's OSIRIS-REx mission is already rewriting our understanding of the origin of the solar system. Asteroids provide a time capsule into our Earth's history, and Bennu's samples are critical to our understanding of what was present in the solar system before life began on Earth."
The origin of life is one of science's deepest mysteries, but clues to the mystery are buried in plate tectonics, the water cycle, and even life itself. To find answers, scientists are looking to primitive asteroids beyond Earth, such as Bennu, the target of NASA's bold OSIRIS-REx sample return mission. OSIRIS-REx collected raw material from Bennu in 2020 and returned it to Earth in 2023. Now, rocks from Bennu are revealing a lost world from the birth of the solar system that had the right conditions for life. Image Credit: NASA Goddard Space Flight Center Unveils Building Blocks of Life in Space
In research papers published in the journals Nature and Nature Astronomy, scientists from NASA and other agencies share the results of the first in-depth analysis of minerals and molecules in Bennu samples that OSIRIS-REX will send to Earth in 2023.
The most striking detections, detailed in the Nature Astronomy paper, include amino acids - 14 of the 20 amino acids used by life on Earth to make proteins - and all five nucleobases used by life on Earth to store and transmit genetic instructions in more complex macromolecules of terrestrial organisms such as DNA and RNA, including how to arrange amino acids into proteins.
Scientists also described extremely high levels of ammonia in Bennu samples. Ammonia is important to biology because, under the right conditions, it can react with formaldehyde (which was also detected in the sample) to form complex molecules such as amino acids. When amino acids are linked into long chains, they form proteins, which power nearly all biological functions.
Original samples uncontaminated by the earth
These building blocks of life detected in the Bennu samples have been found previously in extraterrestrial rocks. However, the discovery of these components in pristine samples collected in space supports the idea that objects far from the sun may have been an important source of the original precursor components of life throughout the solar system.
Danny Glavin is a senior sample scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and co-first author of the Nature Astronomy paper. "That's why some of these new discoveries would not have been possible without sample return missions, meticulous contamination control measures, and the careful custody and storage of these precious materials from Bennu."
Tracing Bennu’s watery past
As Glavine's team analyzed Bennu samples for clues about compounds related to life, their colleagues, led by Tim McCoy, curator of meteorites at the Smithsonian's National Museum of Natural History in Washington, and Sara Russell, a cosmological mineralogist at the Natural History Museum in London, looked for clues about the environment in which these molecules formed. Writing in the journal Nature, the scientists further describe evidence of an ancient environment suitable for kick-starting the chemistry of life.
Scientists found traces of 11 minerals in Bennu samples, from calcite to glauconite and albite, which are formed when water containing dissolved salts evaporates over time, leaving the salts behind as solid crystals.
Similar brine has been found or hinted at throughout the solar system, including on the dwarf planet Ceres and Saturn's moon Enceladus.
A never-before-seen complete set of minerals
Although scientists had previously detected several types of evaporites in meteorites that fell to the Earth's surface, they had never seen a complete set of evaporites that preserved an evaporation process that could have lasted thousands of years or more. Some of the minerals found in Bennu, such as trona, have been found in extraterrestrial samples for the first time.
"These papers really go hand in hand, trying to explain how exactly the ingredients for life came together to create what we see on this water-altered asteroid," McCoy said.
Uncovering the mystery of left-handed life
Although the Bennu samples provide all the answers, several questions remain to be answered. Many amino acids can be produced in two mirror-image forms, like a left-handed and a right-handed pair. Life on Earth produces almost exclusively the left hand, but the Bennu sample contained an equal mixture of the two amino acids. This means that on the early Earth, amino acids may have started out as equal mixtures. Why life "turns left" instead of right remains a mystery.
"OSIRIS-REx was a very successful mission," said Jason Dworkin, OSIRIS-REx project scientist at NASA's Goddard Division and co-first author of the Nature Astronomy paper. "The data from OSIRIS-REx add to a picture of a solar system full of potential for life. Why, so far, we have only seen life on Earth and not elsewhere is the really tantalizing question."
Compiled from /ScitechDaily