The theory that comets may have kick-started life on Earth four billion years ago in some shape or form is not entirely new. However, this latest research provides fresh evidence for the theory – and it could have implications for finding life on other worlds, too.
The research, conducted by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in Yokahama, suggests that peptides – compounds of two or more amino acids – may have been delivered to Earth by comets. The production of short peptides, leading to longer peptides, is thought to have been a key step in the evolution of complex molecules, and thus life, on Earth.
In the study, the team used a propellant gun to simulate the shock of a comet impact on a frozen mixture of amino acids, water-ice and silicate in cryogenic conditions at 77 Kelvin (–196°C, –321°F). This comet-like mixture was found to form short peptides up to three units long, called tripeptides, when it was hit. It suggests that the impact of a comet hitting Earth could have produced the same building blocks for life.
“Our experiment showed that the cold conditions of comets at the time of the impacts were key to this synthesis, as the type of peptide formed this way are more likely to evolve to longer peptides,” said researcher Haruna Sugahara from JAMSTEC in a statement.
The results suggest that other worlds that have been impacted by comets, such as Jupiter’s icy moon Europa or Saturn’s Enceladus, could have undergone a similar process to Earth. On the NASA Stardust mission in 2004, the amino acid glycine was spotted in the comet Wild 2, providing evidence that they have the necessary ingredients to start life on a planet.
In separate research, published in the journal Earth and Planetary Science Letters, scientists from Tohoku University, the National Institute for Materials Science and Hiroshima University in Japan found that oceanic impacts in particular may have been important. They suggested that meteorites striking an ocean could form amino acids and nucleobases – which are found in DNA and store genetic information – from inorganic compounds.
Both of these studies contribute to the theory that life on Earth owes its beginnings to an extraterrestrial source. As always, though, much more research will be needed to confirm if this theory is true or not.