Researchers at the University of Cambridge have discovered how comets can deliver the molecular building blocks of life to planets in our galaxy, particularly those in the “pea-in-a-pod” system, where the planets orbit each other closely. It was demonstrated that

Cambridge researchers have proposed that comets could carry the building blocks of life to other planets, especially in the “pea-in-a-pod” system. Their findings suggest that these molecules can survive on planets with close orbiting neighbors, providing new insights into the search for extraterrestrial life.

How did the molecules that make up life originate on Earth? One long-standing theory is that they may have been transported by comets. Now, researchers from the University of Cambridge have shown how comets can deposit similar building blocks on other planets in the galaxy.

The role of Comet Speed ​​and the “Peas in a Pod” system

To transport organic material, comets must travel relatively slowly, at speeds of less than 15 kilometers per second. At higher speeds, critical molecules cannot survive. The speed and temperature of the impact causes the molecules to break apart.

The most likely place for a comet to travel at a reasonable speed is in a “pea in a pod” system, where groups of planets orbit closely together. In such systems, comets can essentially pass or “bounce” from one planet’s orbit to another, slowing them down.

If the velocity is slow enough, the comet will hit the planet’s surface, releasing intact molecules that researchers believe are precursors to life. The results were announced on November 15th. Proceedings of the Royal Society A suggests that if the arrival of comets is important for the origin of life, such systems would be promising places to look for life outside the solar system.

Comet: carrier of prebiotic molecules

Comets are known to contain various building blocks of life known as prebiotic molecules. For example, a sample of asteroid Ryugu analyzed in 2022 showed that the asteroid was delivered intact. amino acid and vitamin B3. Comets also contain large amounts of hydrogen cyanide (HCN), another important prebiotic molecule. HCN has strong carbon-nitrogen bonds, making it highly resistant to high temperatures. This means that it can survive and remain intact even if it enters the atmosphere.

Lead author Richard Anslow, from the Cambridge Institute of Astronomy, said: “We’re constantly learning more about the atmospheres of exoplanets, so we’re wondering whether there are planets out there where complex molecules could be transported by comets. I wanted to find out.” “It’s possible that the molecules that brought life to Earth came from comets, and the same could be true for other planets in our galaxy.”

The researchers do not claim that comets are necessary for the origin of life on Earth or other planets, but instead place limits on the types of planets to which complex molecules such as HCN can be successfully transported by comets. I was thinking about it.

Comet path and influence on the solar system

Most of the comets in our solar system are located outside of Earth’s orbit. Neptune,So-called kuiper belt. When comets and other Kuiper Belt Objects (KBOs) collide, they can be pushed toward the Sun by Neptune’s gravity and eventually pulled into the Sun. Jupitergravity. Some of these comets pass through the asteroid belt and enter the inner solar system.

“Earth is currently the only example of a planet with life, so we wanted to test our theory on a planet similar to ours,” Anslow said. “What kind of comet, moving at what speed, could deliver intact prebiotic molecules?”

Using various mathematical modeling techniques, the researchers determined that it is possible for comets to carry precursor molecules throughout their lives, but only in certain scenarios. For a planet to orbit a star similar to our Sun, the planet must have a low mass, and it is beneficial for the planet to be in a close orbit to other planets in the system. The researchers found that nearby planets in close orbits are much more important for planets around low-mass stars, whose typical velocities are much higher.

In such a system, a comet could be pulled in by the gravity of one planet and pass by another before colliding with it. If this “comet pass” occurs enough times, the comet’s velocity will be slow enough that some prebiotic molecules will be able to survive atmospheric entry.

“In these dense systems, each planet has a chance to interact with and capture the comet,” Anslow said. “This mechanism could be how prebiotic molecules reach the planet.”

For planets orbiting low-mass stars like M dwarfs, complex molecules are more difficult to transport by comets, especially if the planet’s density is loose. Rocky planets in these systems are also exposed to higher velocity collisions, which can pose unique challenges for life on these planets.

Implications for the search for extraterrestrial life

Researchers say their results could help determine where to look for life outside the solar system.

“It’s interesting that we can start to identify the types of systems that can be used to test different origin scenarios,” Anslow said. “This is another way of looking at the great work already being done on Earth. What molecular pathways gave rise to the wide variety of life we ​​see around us? Are there other planets with similar pathways? These are exciting times, as we can combine advances in astronomy and chemistry to study some of the most fundamental questions.”

Reference: “Can comets deliver prebiotic molecules to rocky exoplanets?” RJ Anslow, A. Bonsor, PB Rimmer, November 15, 2023. Proceedings of the Royal Society A Mathematical Physics and Engineering Sciences.

DOI: 10.1098/rspa.2023.0434

This research was supported by the Royal Society and part of the Science and Technology Facilities Council (STFC), which is part of UK Research and Innovation (UKRI). Richard Anslow is a Fellow of Wolfson College, Cambridge.