Cometary Delivery of Prebiotic Molecules: A Key to Life’s Origins in Other Galaxies, Cambridge Finds

Artist’s impression of a meteor hitting Earth
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(IN BRIEF) Researchers from the University of Cambridge have conducted a study suggesting that comets could play a role in delivering the molecular building blocks for life to planets in other galaxies. The study proposes that comets, which contain prebiotic molecules, must travel at slow speeds to effectively deliver organic materials to planets. The ideal conditions for this are found in planetary systems where planets orbit closely together. In such systems, comets can be passed from one planet’s orbit to another, gradually slowing down and ultimately crashing onto a planet’s surface, delivering intact molecules that could be precursors to life. This research has implications for the search for extraterrestrial life beyond our Solar System and the understanding of life’s origins.

(PRESS RELEASE) CAMBRIDGE, 15-Nov-2023 — /EuropaWire/ — In a groundbreaking study, researchers from the University of Cambridge, a public collegiate research university in Cambridge, England, have presented compelling evidence on how comets, celestial objects often associated with their icy tails and celestial wanderings, could play a crucial role in delivering molecular building blocks for life to planets in other galaxies. The study offers intriguing insights into the potential origins of life beyond our Solar System.

The prevailing theory suggests that comets may have transported the molecular foundations of life to Earth, and now, scientists have demonstrated how similar processes could occur on planets throughout the galaxy.

To effectively deliver organic materials, comets must travel at relatively slow speeds, typically below 15 kilometers per second. At higher speeds, the essential molecules would disintegrate upon impact due to the combination of speed and temperature.

The research suggests that the most suitable environments for comets to travel at the required slower speeds are found in systems where planets orbit closely together, akin to “peas in a pod.” In such systems, comets could be effectively passed from one planet’s orbit to another, gradually reducing their speed.

When comets reach slow enough speeds, they could crash onto a planet’s surface, delivering intact molecules believed to be precursors for life. These findings, published in the Proceedings of the Royal Society A, imply that such planetary systems with closely packed planets could be promising candidates for the search for extraterrestrial life, assuming cometary delivery played a role in the emergence of life.

Comets are known to contain a range of prebiotic molecules, the essential building blocks of life. For instance, the analysis of samples from the Ryugu asteroid in 2022 revealed intact amino acids and vitamin B3. Comets also harbor substantial amounts of hydrogen cyanide (HCN), a crucial prebiotic molecule known for its durability at high temperatures, making it resilient enough to survive atmospheric entry.

Richard Anslow, the first author of the study from Cambridge’s Institute of Astronomy, noted, “We’re learning more about the atmospheres of exoplanets all the time, so we wanted to see if there are planets where complex molecules could also be delivered by comets. It’s possible that the molecules that led to life on Earth came from comets, so the same could be true for planets elsewhere in the galaxy.”

The researchers emphasize that comets may not be an absolute necessity for the origin of life on Earth or other planets, but they aim to establish limits on the types of planets where complex molecules like HCN could be successfully delivered by comets.

Most comets in our Solar System are located beyond Neptune’s orbit in the Kuiper Belt. Occasionally, interactions with Neptune’s gravity push some comets toward the Sun, leading them into the inner Solar System.

“We wanted to test our theories on planets that are similar to our own, as Earth is currently our only example of a planet that supports life,” said Anslow. “What kinds of comets, travelling at what kinds of speed, could deliver intact prebiotic molecules?”

Through mathematical modeling, the researchers concluded that comets could indeed deliver life’s precursor molecules under specific conditions. In systems where planets orbit a star similar to our Sun, it is essential for the planet to be low in mass and closely located to other planets in the system. For planets orbiting lower-mass stars, like M-dwarfs, where speeds are generally higher, nearby planets are even more critical in facilitating the gradual reduction of comet speeds for molecule survival.

“In these tightly-packed systems, each planet has a chance to interact with and trap a comet,” explained Anslow. “It’s possible that this mechanism could be how prebiotic molecules end up on planets.”

The implications of this study may guide future investigations into potential habitats for life beyond our Solar System and deepen our understanding of the origins of life in the universe.

The researchers say their results could be useful when determining where to look for life outside the Solar System.

“It’s exciting that we can start identifying the type of systems we can use to test different origin scenarios,” said Anslow. “It’s a different way to look at the great work that’s already been done on Earth. What molecular pathways led to the enormous variety of life we see around us? Are there other planets where the same pathways exist? It’s an exciting time, being able to combine advances in astronomy and chemistry to study some of the most fundamental questions of all.”

The research received support from the Royal Society and the Science and Technology Facilities Council (STFC), a part of UK Research and Innovation (UKRI). Richard Anslow is a Member of Wolfson College, Cambridge.

Reference:
R.J. Anslow, A. Bonsor and P.B. Rimmer. ‘Can comets deliver prebiotic molecules to rocky exoplanets?’ Proceedings of the Royal Society A (2023). DOI: 10.1098/rspa.2023.0434

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SOURCE: University of Cambridge