Exoplanets: The planet with 100% life has 0% existence?

A recent news story featured an astronomer whose personal feelings about the chances for life on a recently discovered planet orbiting a star other than our sun were - 100%:

Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say, my own personal feeling is that the chances of life on this planet are 100 percent," said Steven Vogt, a professor of astronomy and astrophysics at the University of California, Santa Cruz, during a press briefing today.

"I have almost no doubt about it.”

He might have done with a few doubts about planet Gliese 581 g, which has a 37-day orbit around a dim, red dwarf star. The
latest story is that other astronomers can’t establish that Gliese exists.

Two weeks after one team of astronomers announced finding the habitable planet Gliese 581 g, another team says it can find no evidence of the world in its data.

Last month, a team of astronomers announced the discovery of the first alien world that could host life on its surface. Now a second team can find no evidence of the planet, casting doubt on its existence.

[ ... ]

But it might be too early to claim a definitive detection. A second team of astronomers have looked for signals of Gliese 581 g in their own data and failed to find it.

"We easily recover the four previously announced planets, "b", "c", "d", and "e". However, we do not see any evidence for a fifth planet in an orbit of 37 days," says Francesco Pepe of the Geneva Observatory in Switzerland. He presented the results on Monday at an International Astronomical Union symposium in Turin, Italy.

Although the Geneva team cannot find evidence for the new planet, they cannot exclude the possibility that Gleise 581 g exists. "We are not trying to prove the nonexistence of a planet," Pepe says. "It's really difficult to prove that something does not exist. We are just saying we do not see a significant signal that is really different from noise."

- Rachel Courtland, "First life-friendly exoplanet may not exist", 1(3 October 2010)

Well, as we, and they, all know, one cannot prove that a physical thing really does not exist. One simply reaches the point where one considers its existence too improbable to spend more time looking.

If Gliese is not found, the episode will demonstrate one important thing: Many people badly need to believe in life on other planets, and many more people are eager to hear them tell about it. The legendary caution of science stands no chance against the onslaught of such yearnings.

See also Exoplanets: The recent pilgrimage to Darwin's shrine.

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Serious push to find more exoplanets

Exoplanets: Will intelligence be common or rare?