Either way, some of the adaptations that made life so successful on Earth had only arisen after that, with the result that Earth-life and Mars-life differed in fundamental ways.
Comments
Log in with your Bluesky account to leave a comment
They shared much of the same machinery for DNA replication and translation into proteins, as well as some of the core metabolic reactions, but the Martian genetic code used four base pairs to code for an amino acid rather than three.
This meant that Martian life could use many more than the 21 amino acids used by Earth-life, but it came at the cost that the code was more error prone and constantly subject to change, making it difficult for genes to be transferred between lineages.
In many ways Mars-life was better at evolution than Earth-life; by some measures Mars had a higher biodiversity than Earth. But Earth-life had an advantage despite that. It had found a set of 20 amino acids that worked and fixed them once and for all, allowing it to innovate in other areas.
Although the discovery of Mars-life had taught us much about the nature of life and its history on Earth, it hadn't done much to dispel the idea that the origin of life was a unique event that only occurred once. Both biospheres shared a common ancestor, after all.
There were three things that began to dispel that idea. The first was increasing evidence of biosignatures on exoplanets, although there was much debate about that and it would take more than 20 years to reach even a tentative agreement on the right interpretation of the data.
The second was the discoveries in the oceans of Europa and Enceladus and on Titan and the asteroids, and the resulting long-raging disagreements about what exactly had been discovered and the nature of the boundary between chemistry and biology, if there even was one at all.
Comments