Life must have hitched a lift from Earth to Mars on debris from one of the many meteorites that impacted earth in the first epoch of Earth's biosphere. Or perhaps life originated on Mars, only to find a far more clement home on Earth. We'll never know for sure. - ThreadSky

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nathanielvirgo.bsky.social • 57 days ago

Life must have hitched a lift from Earth to Mars on debris from one of the many meteorites that impacted earth in the first epoch of Earth's biosphere. Or perhaps life originated on Mars, only to find a far more clement home on Earth. We'll never know for sure.

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nathanielvirgo.bsky.social•57 days ago

(This is a reminder that you're listening to Orson Welles' radio adaptation of War of the Worlds. Life on Mars has not in fact been announced.)

nathanielvirgo.bsky.social•57 days ago

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.

nathanielvirgo.bsky.social•57 days ago

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.

nathanielvirgo.bsky.social•57 days ago

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.

nathanielvirgo.bsky.social•57 days ago

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.

nathanielvirgo.bsky.social•57 days ago

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.

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