Life exists on Earth but its existence has not been definitively proven on other planets/worlds. Biological activity might have existed on Mars and, in this respect, the ancient environments of the Red Planet may shed light on the environmental conditions of the ancient Earth. How life developed on our planet is far from fully understood. Whether the origin of life was exogenous (Section 7) or developed in peculiar and transient niches on Earth is still vigorously debated. However, planetary sciences and the geological record provide significant insight into relevant environmental conditions and timing. Although life can develop and persist in...

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