Did Life Come From An Asteroid? With Harold Connolly Jr.

The Osiris-Rex mission successfully launched from Earth to intersect the asteroid Bennu, collect material, and return to Earth. The mission, an acronym for Origins, Spectral Interpretation, Resource Identification, Security, and Regolith Explorer, was designed to gather pristine samples from a carbonaceous asteroid. These asteroids, unlike metallic ones, are rich in volatiles, including water and prebiotic organic compounds, making them crucial for understanding the early solar system and the origins of life. The motivation for such a mission stems from the fact that meteorites found on Earth, while providing valuable data on the solar system's age, are often contaminated by terrestrial environments. Bringing back untouched samples from space allows for a more accurate analysis of their original composition. Harold Connolly Jr., a co-investigator and mission sample scientist for Osiris-Rex, explained that asteroids like Bennu serve as "time capsules" of the early solar system. They have largely remained unaltered since their formation, preserving conditions that existed 4.567 billion years ago. The term "volatile" in geology refers to compounds like water that evaporate quickly when temperatures rise. These volatiles, present in the asteroid's parent body, circulated within it, contributing to the formation of various minerals and organic compounds. The challenge of bringing back these volatiles, particularly ice, is significant due to the need for extremely cold storage throughout the return journey. Bennu was chosen for the mission because it is a carbonaceous asteroid, aligning with the scientific goals of finding life's precursors, and its orbit crosses Earth's, making it more accessible and cost-effective to reach. Unlike the commonly stereotyped metallic asteroids, carbonaceous asteroids resemble ordinary rocks, but their composition is far more valuable for astrobiological research. Sampling metallic asteroids would be considerably harder, requiring drilling through solid metal. The Osiris-Rex mission employed a "touch-and-go" strategy. The spacecraft was designed to briefly touch the asteroid's surface, fire nitrogen gas to fluidize the regolith, and collect the stirred-up material into a capsule. The mission's success hinged on precise navigation, launching from a moving Earth to intersect a moving Bennu, performing the touch-and-go, and then deploying the sample capsule to a specific landing site in the Utah desert on a rotating Earth. A key challenge encountered during the mission was the unexpected nature of Bennu's surface. Initial data suggested a fine-grained surface, but upon arrival, the team discovered boulders up to 11 stories high. The spacecraft penetrated 48 centimeters into the surface, much deeper than anticipated, revealing that Bennu is a "rubble pile" asteroid held together primarily by gravity, rather than tensile forces between particles. This deeper penetration, while unexpected, was beneficial as it allowed access to "fresher" material less exposed to solar radiation. However, during the sample stowage, several stones got caught, preventing a flap from closing completely, leading to some sample loss each time the arm articulated. Despite this, the mission successfully returned 122 grams of material, exceeding the scientific goal of 60 grams. Upon return, the sample capsule was transported to a facility where it was opened under a nitrogen environment to prevent contamination. Nitrogen was chosen for its inertness with typical minerals and rocks, preserving the sample's pristine state. Geologists first visually examine the rock, then use microscopes, and eventually cut and polish samples for more detailed analysis with electron microscopes to determine mineral composition and arrangement. Other scientists dissolve samples to analyze organics. The context of the rock—its geological history and processes—is paramount for accurate interpretation of results. An "aha moment" in the analysis of Bennu and Ryugu samples was the discovery of evaporite minerals, which form as water-rich solutions evaporate. This finding indicates that water interacted with the asteroid's materials, potentially creating environments where prebiotic compounds could form. The presence of these minerals, which are rare in Earth-found meteorites, highlights the importance of pristine samples. Regarding the search for life's ingredients, the samples from Bennu and Ryugu have yielded significant findings, including 14, possibly 15, of the 20 amino acids essential for life. This discovery supports the idea that the building blocks of life are present in extraterrestrial bodies. The analysis of these asteroid samples also provides crucial context for interpreting potential signs of life found on other planetary bodies, such as Mars. The mission's findings contribute to the broader understanding of how star systems, including our own, form. Asteroids like Bennu are fragments of larger parent bodies that underwent internal geological processes, including heating from radioactive decay and the circulation of fluids, which altered their mineral composition and potentially fostered the formation of prebiotic compounds. These processes were "frozen in time" when the parent bodies shattered due to collisions. The discussion also touched upon phosphorus, a key element for life. It is found in the asteroid samples, incorporated into minerals like phosphates, and is crucial for forming prebiotic compounds. Pre-solar grains, such as diamonds, silicon carbide, and silicates, found within the asteroid samples, predate the solar system's formation. These grains are remnants of earlier stars and provided the "nutrients" for the formation of rocky materials in our solar system, surviving the intense processes of its early development. The collaboration between geologists, astronomers, and biologists is increasingly vital for understanding the universe. The universe does not adhere to human-defined scientific disciplines, and a comprehensive understanding requires interdisciplinary approaches. Sample return missions like Osiris-Rex foster this collaboration, allowing scientists to piece together the complex puzzle of life's origins. The samples returned by Osiris-Rex are not only analyzed by the mission's science team but are also shared with a global community of scientists for further study and verification, embodying the collaborative nature of modern science. Bennu also has implications for planetary defense. It is a near-Earth asteroid with a non-zero probability of impacting Earth in 2182 (estimated at 1 in 2700 chance). Understanding its composition better, thanks to Osiris-Rex, is crucial for developing potential deflection strategies should it become necessary.