Asteroids play the role of time capsules showing what molecules originally existed in our solar system, and may help explain how life started on Earth, a study suggests. Finding complex molecules in asteroids provides the strongest evidence that such compounds were present on the Earth before life formed, said Nicholas Hud from Georgia Institute of Technology in the US.
Knowing what molecules were present helps establish the initial conditions that led to the formation of amino acids and related compounds that, in turn, came together to form peptides, small protein-like molecules that may have kicked off life on our planet. “We can look to the asteroids to help us understand what chemistry is possible in the universe,” said Hud. “It’s important for us to study materials from asteroids and meteorites, the smaller versions of asteroids that fall to Earth, to test the validity of our models for how molecules in them could have helped give rise to life.
“We also need to catalogue the molecules from asteroids and meteorites because there might be compounds there that we had not even considered important for starting life,” he said. NASA scientists have been analysing compounds found in asteroids and meteorites for decades, and their work provides a solid understanding for what might have been present when the Earth itself was formed, Hud said. “Detection of a molecule in an asteroid or meteorite is about the only evidence everyone will accept for that molecule being prebiotic. It is something we can really lean on,” Hud said.
He believes there are many possible ways that the molecules of life could have formed. Life could have gotten started with molecules that are less sophisticated and less efficient than what we see today. Like life itself, these molecules could have evolved over time. “What we find is that these compounds can form molecules that look a lot like modern peptides, except in the backbone that is holding the units together,” said Hud.
“The overall structure can be very similar and would be easier to make, though it does not have the ability to fold into as complex structures as modern proteins. “There is a tradeoff between the simplicity of forming these molecules and how close these molecules are to those found in contemporary life,” said Hud.