A recent discovery on Mars has shed light on the possible origin of life on Earth. Researchers have found that organic material present in the sediments of ancient Martian lake beds points to carbon chemistry widespread throughout the red planet.
This discovery provides valuable insight into how the ingredients of life may have ended up on our planet billions of years ago.
Discovery of organic material on Mars
A decade ago, a robotic rover on Mars uncovered an important piece of evidence by detecting organic material in the sediments of ancient lake beds. This discovery showed that Mars has a rich presence of carbon chemistry, raising intriguing questions about the origin of these organic molecules. While the presence of organic material does not necessarily imply the existence of alien life, it does open up fascinating possibilities about the processes that might produce such molecules.
Planetary scientist Yuichiro Ueno of the Tokyo Institute of Technology led the team that made the discovery. The researchers found that carbon dioxide in the Martian atmosphere it reacts with the sun’s ultraviolet rays, forming a cloud of carbon molecules that descend on the planet’s surface. “Such complex carbon-based molecules are the prerequisite of life, the building blocks of life, one might say,” explained chemist Matthew Johnson of the University of Copenhagen. He further clarified that these organic molecules are formed through atmospheric photochemical reactions without any biological intervention.
The role of photolysis
Photolysis, a process where molecules are broken apart by light, plays an important role in the formation of organic components on Mars. This process produces carbon monoxide and oxygen atoms from carbon dioxide and works faster on lighter isotopes. Consequently, molecules containing carbon-12 are depleted faster than those containing carbon-13, leaving behind an ‘excess’ of carbon-13 dioxide. The notion that photolysis contributes to the organic chemistry found on Mars has been supported by simulations and subsequent investigations.
Johnson and his colleagues published a paper in 2013 hypothesizing this photolysis could explain the presence of organic molecules on Mars. Recent findings provide strong evidence supporting this hypothesis. Atmospheric enrichment of carbon-13 was first identified several years ago when researchers analyzed a Martian meteorite that landed in Antarctica. “The smoking gun here is that the ratio of carbon isotopes in it exactly matches our predictions in quantum chemical simulations,” Johnson said.
Confirmation from the Martian Meteor
A critical piece of evidence was found in the data obtained from Curiosity rover in Gale Crater. The rover samples of carbonate minerals showed a carbon-13 depletion which perfectly mirrored the enrichment of carbon-13 found in the Martian meteorite.
This discovery confirmed that organic material on Mars was formed from carbon monoxide produced by photolysis. “There is no other way to explain the depletion of carbon-13 in the organic material and the enrichment in the Martian meteorite, both relative to the composition of the volcanic CO2 emitted on Mars,” Johnson explained.
Confirmation from Curiosity rover provides strong evidence that photolysis is responsible for the formation of organic material on Mars. This discovery also hints at a possible origin for organic materials on Earth. Billions of years ago, Venus, Earth and Mars all had very similar atmospheres, suggesting that the same processes likely occurred on our home planet.
Implications for the origin of the Earth
The implications of this discovery are far-reaching beyond Mars. The study suggests that organic material found on Mars may provide clues to the origins of life on Earth. During the early stages of the solar system, Earth, Venus and Mars had similar atmospheric conditions. The processes that led to the formation of organic molecules on Mars it could also have happened on Earth, laying the foundations for the emergence of life.
“We have not yet found this ‘smoking gun’ material here on Earth to prove that the process has occurred. Perhaps because the Earth’s surface is much more alive, geologically and literally, and therefore constantly changing,” said Johnson. “But it’s a big step that we’ve now found on Mars, from a time when the two planets were very similar.”
