Scientists have long suspected that comets helped kickstart life on Earth by seeding it with organic molecules. But new research may bring the idea to a screeching halt.A team of researchers led by the University of Cambridge found that a comet’s entry into the Earth’s atmosphere is too violent for the molecular building blocks of life to survive, as detailed in a new study published in the journal Scientific Reports. Any stragglers would be vaporized upon impact with the ground.“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,” said lead author and Cambridge astronomer Richard Anslow in a statement about the work.“It’s kind of a romantic idea,” he added, “but our results suggest it’s highly unlikely.” Pseudo-panspermia, the idea that life’s building blocks came from space, has gained credence in recent decades. It’s a “romantic idea” because it also suggests that life may be a common occurrence. Astronomers have frequently found organic molecules on comets and asteroids, suggesting they’re abundant throughout the cosmos. Samples taken from one asteroid called Bennu contained 14 of the 20 amino acids that life uses to build proteins and all five of the molecules that make up DNA and RNA. That discovery in particular supported the “RNA world” hypothesis which posits that the earliest forms of life relied on self-replicating RNA molecules before the advent of DNA and proteins.In a previous study, Anslow suggested that comets could be “bouncing” between planets whose orbits are close together, allowing the comets to slow down to a speed — below nine miles per second — that allows them to deliver organic molecules without destroying them.But the new work shows that the likelihood of this working on Earth is extremely slim. In simulations of comet entries, they focused on hydrogen cyanide (HCN), a prebiotic molecule that’s commonly found on solar system comets. What they discovered was that there’s just too many conditions that would need to be perfect for hydrogen cyanide to survive the trip in one piece.“It would really have to be a one-in-a-million occurrence,” Anslow said, “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,” he added. “But it seems to be a really rare occurrence — at best, a one-off fluke.”Any HCN molecules that did survive wouldn’t exist in great enough quantities, proividing “an insignificant source of the concentrated feedstock molecules required for prebiotic chemistry,” the researchers wrote in the study.It might be a considerable blow for the theory on Earth, but the researchers suggest that comets could have seeded life-giving molecules on Mars, which has a thinner atmosphere and makes for a smoother entry.“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,” said Anslow. “Or the other, perhaps more likely, alternative, is that it didn’t happen on either planet.”More on biology: Astronomers Spot Mysterious Object Lurking Beyond PlutoThe post We Were Totally Wrong About How Life on Earth Started, Study Suggests appeared first on Futurism.