( r mapping early habitat divergences ont...)Map of life on Earth could be used on Mars

r mapping early habitat divergences onto the tree, Blank observes that the ancestors of each of the three kinds of prokaryotes inhabited one of Earth's three types of hydrothermal systems, which include sulfurous steam vents like those which smatter the Yellowstone caldera, hydrothermal deep-sea vents, and boiling silica-depositing springs.

"Is it a coincidence, then, that we have three hydrothermal habitats and three major groups of prokaryotes? We aren't sure, " she said. "This could suggest that we have some really ancient habitat specialization. These lineages specialize in these three habitats, and diverge in these habitats for many hundreds of million years before they start moving into other types of habitats."

The 'peculiar' ancestor

It isn't clear why bacteria diversified later, though environmental changes, like periods of global glaciation nicknamed "snowball Earth," could have provided the impetus that demanded microbial adaptation. Whatever the cause, new adaptive microbial traits can be very different from those of their "peculiar" ancestors. It seems that, on some level, humans and bacteria can relate.

"If we see these major patterns of divergence on Earth, we should expect to see similar patterns on life on Mars, that is, if life ever existed there," Blank said. "Not the same patterns, because Mars has had a different history, but we should see trends that are analogous. You would expect to see a peculiar ancestor specialized to a unique niche, eventually diverging into descendants that have very different traits than their ancestor did. These descendents would have adapted to changes that would've happened in Mars's history."

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Source:Washington University in St. Louis


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