Two papers published at the end of January in Nature and Nature Astronomy provide evidence about the origin of life. The analyses and inferences from their results affect the disciplines of biology, astronomy and geology overall, and research at the University. 

The reports detail the mineralogy and chemistry of a sample taken from the near-Earth asteroid Bennu, which was brought home by the National Aeronautics and Space Administration’s Origins, Spectral Interpretation, Resource Identification, and Security – Regolith Explorer in September 2023.

OSIRIS-REx launched in 2016 and returned its capsule to Earth around seven years later — and with it, extraterrestrial rocks dating back about 4.5 billion years. 

Bennu’s shining brilliance

Preliminary tests determined that the asteroid is carbon-rich and once contained water — two essential components of life. It would take two more years to discover the full extent of Bennu’s chemical similarities to Earth.

The Nature Astronomy paper describes the discovery of all five nucleotide bases in rock samples from Bennu. The bases are the information-carrying parts of DNA and RNA that enable the self-replication of cells and hold the instructions to build proteins out of amino acids. 

The sample also contained 14 out of the 20 amino acids that all living organisms use — from bacteria to archaea and eukaryotes.

While these molecules have been found or detected in other asteroids before, this mission is significant as it eliminated the chance that the sample was contaminated. 

That is typically the case when looking at meteorites — small pieces of asteroids that reach  Earth’s surface. Much of their material is burned up as they travel through the atmosphere and are then exposed to Earth’s surface conditions. 

This can skew the results of any experiments on meteorites, making grabbing a sample directly from the source important.

Even more promising to answering questions about the origin of life is Bennu’s mineral composition. Scientists found 11 minerals that form from evaporated water on Earth in areas like the Great Salt Lake, Utah, or Searles Lake, California. 

This suggests that Bennu’s parent asteroid had tiny pockets of briny water in the space between dust particles of the regolith. The regolith is the loose debris layer covering the surface of most asteroids, caused by innumerable collisions against other objects in space or by solar winds.

These pockets gave atoms a surface of sorts to come together to create more complex, biological molecules. 

“Bennu shows that the origin of life could’ve easily happened in our solar system,” said Leslie Looney, professor in LAS. “The building blocks are there, the ‘Lego pieces’ are there; you just need the manual to put them together properly.”

Looney’s research is in protostellar and protoplanetary systems, or the clouds of dust and gas that collide to form stars and eventually mature solar systems. In particular, he analyzes how dust particles smaller than the width of a human hair condense and grow into planets. 

“Star formation is happening today; it’s happening right now, not even very far away from us,” Looney said. “We’re just understanding how that’s happening today, and then we’re saying that’s probably what happened 4.6 billion years ago too. As we learn more about these systems, we’re learning more about ourselves.”

Since asteroids formed alongside planets in the protoplanetary disk, almost anything found in asteroids is likely to have also been present in the early forms of planets. As such, the Bennu sample analyses add another layer to Looney’s research, connecting the very beginnings of our solar system to the present.

Making Earth a little ‘meteor’

Conditions were not calm in our early solar system. From about 4.1 to 3.8 billion years ago, Earth experienced an era called the Late Heavy Bombardment, where it was continually impacted by leftover objects not absorbed in planet formation.

Whatever was present in these objects would have been added to Earth’s composition. It’s suggested that Bennu’s composition is similar to that of these absorbed objects, as they all formed at the same time from similar materials. 

If this is correct, then the Late Heavy Bombardment might have brought the building blocks of life to Earth, or at least increased their concentration in just the right places for them to come together into the first replicating molecule, and later, a single-celled organism. 

“It wasn’t until the end of the Late Heavy Bombardment that everything kind of got to the point where it wasn’t so volatile, so hot, so dangerous, so impossible for life to live,” said Bruce Fouke, professor in LAS. “Right now, we put the oldest life at about 3.8 billion (years).”

Fouke has dedicated his career to studying the interactions of life, water and minerals. 

Having researched coral reefs, Mammoth Hot Springs in Yellowstone National Park, Roman aqueducts, oil fields in Alaska, the formation of kidney stones and the calcification of heart valves and breasts, he deeply understands the relationship between these three tenants.

In particular, he presents the Mammoth Hot Springs as an analog for “the early cradle of life,” as its present environment is likely similar to Earth’s thermal vents shortly after the Late Heavy Bombardment. Fouke expressed anticipation in seeing where the Bennu results will propel science in the near future, including his interdisciplinary research. 

While still under investigation, the current scientific consensus is that asteroids, including Bennu, do not necessarily have living organisms on them. Only, they could have transported the components for life to Earth. Once here, however, those molecules could have formed cells and their constituents.

To infinity and beyond! — In pursuit of extraterrestrial life

NASA is actively looking for alien life, both in our own solar system and further. The Bennu sample analyses are crucial in this search, as the apparent commonness of biological molecules in our solar system and the similar elemental composition across the universe imply that the same chemical reactions that created life on Earth could occur elsewhere in the universe. 

This is a main aspect of Looney’s ASTR 330: Extraterrestrial Life and ASTR 150: Killer Skies: Astro-Disasters courses. After hearing about the results at the end of January, he explained the findings to his students in almost all of his classes.

“People need to know this,” Looney said. “It’s kind of a thing that everyone needs to know, that the monomers of life are out there in the solar system, and that it’s not unique. We don’t expect there to be any reason why life isn’t more common.” 

This hunt for extraterrestrial life includes looking not only for the molecules that make up organisms, but also for planets and other objects that can host life for long periods. In the context of water-based life like our own, this means searching for habitable zones, the area in an object’s orbit around a star where liquid water can exist. 

Finding these zones is complicated, however. It’s more common in the universe for stars to exist in multiple star systems, unlike our lonely sun. One kind of these systems is binary, where two stars orbit each other.

Siegfried Eggl, professor in Engineering, studies the habitable zones of binary systems. He has mapped the possible orbits of planets depending on how far apart the stars are from each other. 

“What the OSIRIS-REx results mean for this (my research) is that now the odds of finding life somewhere else have been really bumped up,” Eggl said. “We showed that you can actually have habitable planets in binary stars also.” 

The chances for extraterrestrial life increase when the molecules to create it are more prevalent and areas life can exist are more common. Eggl’s research broadens the ever-growing pile of evidence for finding life beyond Earth, aided by OSIRIS-REx and other missions.

“It’s a very important step towards making sure we understand that we are not alone, most likely, and now it’s just up to us to find who else is out there before they find us,” Eggl said.

After dropping the capsule containing the Bennu sample back on Earth, the OSIRIS-REx craft was left to finish its orbit around the sun. Due to an extra bit of fuel and luck, the renamed Origins, Spectral Interpretation, Resource Identification and Security – Apophis Explorer craft will remain in space to observe the physical changes to the asteroid Apophis as it passes by Earth in 2029.

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