Scientists Explain Exactly How Alien Life May Have Begun

Comets may have played a major role in bringing life to Earth—and now, researchers have discovered that they may be doing the same thing for other, faraway planets.

For a planet to sustain life, it must have organic material built from the elements carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. These elements combine to create the organic molecules essential for life on Earth—and potentially, other planets.

The real question is how these elements end up being delivered to these planets.

Scientists already know that comets contain a range of molecules essential for life. But they can only deliver these molecules in certain scenarios.

In the new research, published in Proceedings of the Royal Society, scientists explain that in order to deliver organic material to exoplanets—planets outside our solar system—, comets need to be traveling at a slow speed. Otherwise, high speed would destroy these essential molecules, the study reported.

The most likely place where comets would travel at a speed low enough to preserve the living-giving molecules is within a system where planets orbit closely together. These systems would allow the comet to pass slowly through the orbit of different planets.

At these slow speeds, the comet could then impact with a planet’s surface, delivering the building blocks for life.

“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,” first author Richard Anslow, from the Institute of Astronomy at Cambridge University in the U.K., said in a release detailing the findings. “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.”

Scientists used mathematical modeling techniques to analyze the likelihood of this happening.

They found that for this to happen for planets orbiting a star similar to the sun, it needs a low mass, the study reported. And only when the “comet passing” happened enough times, would it slow enough to pass on the life-giving molecules.

“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. What kinds of comets, traveling at what kinds of speed, could deliver intact prebiotic molecules?” Anslow said. “In these tightly-packed systems, each planet has a chance to interact with and trap a comet. It’s possible that this mechanism could be how prebiotic molecules end up on planets.”

Prebiotic molecules contain the chemical elements needed for life.

These findings could eventually help scientists in their search for extraterrestrial life. Astronomers are a long way from discovering it, but each new find on the possibility of life-giving molecules leads them a step closer.

“It’s exciting that we can start identifying the type of systems we can use to test different origin scenarios,” Anslow said. “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.”