New Delhi: Scientists believed that the ingredients for life on earth were brought to our planet by comets. However, new research has shown that those molecules would not have survived the journey through space.
Researchers at the University of Cambridge used computer simulations to test if prebiotic molecules could withstand the speed and intensity with which comets collided with the Earth. Their findings were published in Scientific Reports on 28 October.
“Historically, scientists thought that comets were important for the origin of life on Earth, because they carried carbon and nitrogen-bearing molecules, so these giant space snowballs were almost like a ‘get out of jail free card’ that brought all the molecules a planet would need to seed life. It’s kind of a romantic idea, but our results suggest it’s highly unlikely,” lead author Richard Anslow from Cambridge’s Institute of Astronomy, said in a statement.
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Why comets could have failed
Comets are icy masses made up of frozen gases, dust, and rock. They contain molecules that could have led to the chemical reactions needed to create life. However, scientists have now found that carrying these ingredients through space and bringing them to the earth in an intact condition, is not that simple.
To study whether these ingredients would have survived the journey to Earth, the team focused on the hydrogen cyanide (HCN) molecule found on comets. HCN is a key ingredient in prebiotic chemistry. It might be toxic to human beings but it participates in chemical reactions leading to other compounds essential for life.
Researchers created computer models that could simulate how comets would have interacted with the Earth’s atmosphere and surface. They found that comets would have been moving at speeds and angles which would make it difficult for fragile organic compounds to survive the journey. The extreme heat generated during the comet’s entry into the Earth and the collision itself would likely destroy many of these molecules. Even if some of the HCN molecules survived, researchers say that the likelihood of it being useful in a chemical reaction is extremely low.
“It would really have to be a one-in-a-million occurrence, because not only would you need an impact at just the right speed and just the right angle, you would also need everything to happen after that point, in terms of the concentration and the speed at which the chemical origins of life got going. We can’t rule out for certain that it happened that way. But it seems to be a really rare occurrence – at best, a one-off fluke,” said Anslow.
According to researchers the chances of such molecules surviving the impact of comet-planet collisions is more likely on Mars. The planet is smaller than the Earth, has a thinner atmosphere, and makes it easier for objects in space to reach its surface during the early phases of the solar system when such collisions were more common.
“This is not to say it definitely happened on Mars, of course, but suggests it would be unlikely if it happened on Earth and didn’t happen on Mars. Or the other, perhaps more likely, alternative, is that it didn’t happen on either planet,” Anslow added.