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When Life Went Global


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False Start on Earth’s Sisters?

Grinspoon’s work focuses on the evolution of climate and atmosphere on Earth-like planets. At a recent conference themed Habitable Worlds Across Time and Space, held at the Space Telescope Science Institute in Baltimore, MD, he discussed the implications of this viewpoint for Earth’s nearest neighbors: Venus and Mars.

Just like Earth, Venus and Mars may once have been watery worlds. Image Credit: ESA

Just like Earth, Venus and Mars may once have been watery worlds. Image Credit: ESA

The three rocky planets formed around the same time, some 4.5 billion years ago. Just like Earth, Venus and Mars may once have been watery worlds. Today they seem dry and barren, but several lines of evidence suggest they both had oceans in their early days.

“Everything we know about them points to an early environment that was hospitable for life,” Grinspoon says in an interview with Astrobiology Magazine.

- See more at: http://www.astrobio.net/news-exclusive/life-went-global/#sthash.ru7ORt5U.dpuf

Somehow only Earth held onto its water, and eventually burst out with the self-sustaining fire of life.

“Maybe what’s rare is not the formation of watery planets, but the persistence of habitable environments over cosmological timescales,” he says.

By the end of his talk, titled “Venus and Mars as Failed Biospheres,” Grinspoon raises an intriguing question. Is a biosphere necessary for the long-term survival of life?

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