November 15th 2023.
A new study from the University of Cambridge has proposed an exciting theory - that comets could be key in spreading the building blocks of life to other planets in the galaxy. One long-standing theory for how the basics of life on Earth were delivered suggests comets could be the answer - and now, researchers have shown how comets could do the same for other planets.
"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," said Dr Richard Anslow, from Cambridge's Institute of Astronomy. "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."
In order for the essential molecules to survive, the comets need to be travelling relatively slowly - at speeds below 15 kilometres per second. Some astronomers believe a comet delivered the building blocks for life to Earth. Any faster and the molecules would break apart due to the speed and temperature of impact.
The researchers explain that the most likely places for comets to travel at the right speed are 'peas in a pod' systems - where a group of planets orbit closely together, such as our own solar system. If travelling slowly enough, the comet would crash on a planet's surface, delivering the intact molecules that researchers believe are the precursors for life.
Comets are known to contain a range of prebiotic molecules - for example, samples from the Ryugu asteroid, analysed in 2022, showed that it carried intact amino acids and vitamin B3. Using a variety of mathematical modelling techniques, the researchers determined that it is possible for comets to deliver the precursor molecules for life, but only in certain scenarios - such as planets orbiting a star similar to our own Sun.
"It's exciting that we can start identifying the type of systems we can use to test different origin scenarios," said Dr 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."
This research opens up the possibility of new ways to search for life outside of our solar system. Could comets kick-start life in other solar systems? The researchers say their results could be useful when determining where to look for life - and that's a pretty exciting prospect.
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