Getting all the materials to create alien life may sound difficult, but it may be down to something as simple as the right delivery method. In fact, new research suggests that comets might be the ‘delivery drivers’ of space – ferrying around essential molecules that make life possible.
Scientists have a long-held theory that comets deposited building blocks for life on Earth. Now, researchers from the University of Cambridge’s Institute of Astronomy think this theory could help us find evidence for origins of life on alien planets.
“We can start identifying the type of systems we can use to test different origin scenarios,” said the paper’s first author, Richard Anslow. “It’s an exciting time, being able to combine advances in astronomy and chemistry to study some of the most fundamental questions of all.”
Comets contain prebiotic molecules like amino acids and vitamin B3, as well as large amounts of hydrogen cyanide (HCN). These molecules are important in the synthesis of organic molecules – combining to form proteins and other complex structures that precede the evolution of more complex life.
Published in Proceedings of the Royal Society A, the study describes how the researchers used modelling techniques to calculate the conditions needed for comets to safely deliver their cargo. They found that planets need to have a low mass if they are orbiting stars similar to our Sun, as this makes the planetary atmospheres easier to enter without breaking.
Much like a good courier, comets can’t be travelling too quickly if they want to deliver their packages safely. The study found that comets need to be travelling under 15km (9 miles) per second when they get to their planetary destination – otherwise the speed and temperature of the impact would cause the essential molecules to break up.
But when planets are orbiting lower-mass stars than our Sun – around which speeds are much higher – the comets need a bit of help.
These deliveries are much easier in systems where planets orbit closely together – in the same neighbourhood, if you will. Here, the comets can slow down their speed by ‘bouncing’ between the orbits of the different planets.
How? The comet is pulled in by the gravitational forces of one planet, and then passed to another before making impact with one of them.
If this happens enough times for the comet to approach slowly, it can then crash into the planet’s surface and deliver the essential prebiotic molecules – rather than breaking up in the atmosphere before it gets there.
The researchers now think scientists should be looking for signs of the origins of life in systems like these.
“In these tightly-packed systems, each planet has a chance to interact with and trap a comet,” said Anslow. “It’s possible that this mechanism could be how prebiotic molecules end up on planets.”
Read more: