There are also different oxygen isotopes in this meteorite than in younger Martian meteorites.

FORBES: Meteorite Shows Evidence Of Water On Ancient Mars

To find out how warm the earth was before that, climatologists have had to resort to indirect methods, such as measuring tree-rings, or counting the different isotopes of oxygen in layers of polar ice.

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The researchers looked at the different types, or isotopes, of oxygen atoms trapped in the samples and, using a well-established technique, were able to infer water temperatures at the time the organisms built their shelly parts.

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