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Did comets bring building blocks of life to Earth? Scientists aren't so sure anymore
With comets out of the picture, attention now turns to asteroids or even Earth itself as the source of prebiotic chemistry.
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The origin of life on Earth remains a mystery. New research shows that comets almost certainly did not bring the chemical building blocks of life to our planet.
Life as we know it is based around carbon chemistry, also known as organic chemistry. Complex organic molecules are the fundamental building blocks of biochemical compounds such as nucleobases, amino acids, sugars and so on that act as the machinery for biochemistry on Earth.
Two big questions are where did this complex chemistry originate? Did these complex organic molecules form on Earth, or were they delivered here from space?
New research led by planetary scientist Richard Anslow of the Institute for Astronomy at the University of Cambridge has now seemingly ruled out comets as the origin of complex organic molecules on Earth.
"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 Anslow in a statement.
Comet impacts on Earth were much more frequent in the first half-billion years of the solar system’s existence, when there were still lots of debris leftover from the formation of the planets.For over a century comet impacts had been considered a prime suspect in the search for what brought the building blocks of life to Earth. However, while comets bringing the building blocks of life to Earth is "kind of a romantic idea," according to Anslow, the University of Cambridge researcher added that the team's results suggest that is highly unlikely.
Anslow and colleagues arrived at this conclusion based upon computer modeling by using the very latest simulations depicting the origin and evolution of comets and their orbits, their interactions with Earth's atmosphere as they enter it, and of the hypervelocity comet impacts themselves.
In particular, they used the fate of hydrogen cyanide as a proxy for what happens to complex organic molecules in comet impacts. Hydrogen cyanide is frequently found in comets and was even detected in the interstellar comet 3I/ATLAS.