Asteroid Bennu Samples Reveal Ingredients for Life Before Earth Existed
Scientists have uncovered that the building blocks for life were prevalent across the early solar system, a discovery that could reshape our understanding of life’s origins. This revelation comes from the analysis of samples collected by NASA’s OSIRIS-REx mission from asteroid Bennu, led by Dante Lauretta at the University of Arizona.
In 2023, the OSIRIS-REx spacecraft brought back samples from Bennu, which have since been meticulously analyzed by scientists worldwide. These analyses suggest that the conditions necessary to form life’s chemical precursors existed before Earth, possibly increasing the probability of life developing on other celestial bodies.
“These samples from Bennu are an incredible discovery, showing that the building blocks of life were widespread across the early solar system,” stated Dante Lauretta, Regents Professor of Planetary Science and Cosmochemistry at the University of Arizona’s Lunar and Planetary Laboratory. He emphasized that understanding these interactions could guide the search for life beyond Earth.
Bennu formed from remnants of a massive asteroid collision and has been preserved in space since the solar system’s inception about 4.5 billion years ago. The samples provide a window into that era, revealing that Bennu’s molecular makeup indicates its parent body’s origin in the solar system’s cold outer disk.
The extreme cold, reaching minus 400 degrees Fahrenheit, allowed volatile gases like water vapor, carbon dioxide, methane, and ammonia to solidify in Bennu’s parent body. The Nature Astronomy study highlights the “exceptionally high” levels of ammonia in these samples, crucial for forming complex molecules such as amino acids and nucleobases, which are essential for life.
“Besides pointing to the outer solar system origin of abundant ammonia in Bennu’s ancestor, our work also supports the idea that objects that formed far from the sun could have been an important source of the raw ingredients for life throughout the solar system,” noted Danny Glavin from NASA’s Goddard Space Flight Center, a lead author on the Nature Astronomy paper.
The presence of life’s building blocks in Bennu raises the question of how they transformed into biological molecules. According to Tim McCoy, curator of meteorites at the Smithsonian’s National Museum of Natural History, the right environmental conditions are crucial for these ingredients to interact and form life.
McCoy, along with Sara Russell from the Natural History Museum in London, led a team of 66 scientists in examining Bennu’s mineral composition. They identified 11 minerals, including calcite, halite, and sylvite, which form “evaporites” from brine, indicating a potentially life-supporting environment.
“We’re seeing minerals in Bennu samples that we have never seen before in a meteorite or any extraterrestrial sample,” remarked McCoy. These findings suggest that Bennu’s ancestor had warm interiors capable of sustaining liquid water, an essential component for life, which also concentrated molecules necessary for forming complex compounds.
The complete set of evaporites found in Bennu is a first for researchers, representing a long-term evaporation process similar to those in Earth’s drying lakes and shallow seas. This suggests that water on Bennu’s ancestor existed in subsurface pockets, as surface conditions would have caused it to evaporate rapidly due to low atmospheric pressure.
Contributors to this research from the University of Arizona include Jessica Barnes, Harold Connolly, Dani DellaGiustina, Pierre Haenecour, Dolores Hill, Tom Zega, and Zoe Zeszut, utilizing the advanced technologies at the Kuiper-Arizona Laboratory for Astromaterials Analysis. Graduate students Maizey Benner, Kana Ishimaru, Nicole Kerrison, Iunn Ong, Beau Prince, and Lucas Smith also participated in this groundbreaking work.
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