“It’s in the ‘sweet spot’, the Goldilocks Zone…”

If no-one picks up the phone at Gliese 581d, perhaps someone will be at home on the newly discovered Gliese 581g…  aka the “Goldilocks” planet.  Or, indeed, one of the other exo-planets in the, apparently, increasingly populated Gliese 581 system.  But I tend to agree with the quotes in the level-headed Tom Chivers blog at the Daily Telegraph

Dr Lewis Dartnell, a UCL astrobiologist who specialises in the possibility of microbial life on Mars, says that it’s “undeniably very, very exciting”, but it’s far too early to say anything about life existing on it.

“We don’t know how Earth-like it really is”, he says. “It’s a small rocky planet, but we know nothing about what sort of atmosphere or surface conditions it has.

“It’s in the ‘sweet spot’, the Goldilocks Zone, that would allow for liquid water, but we don’t know if there’s actually water on it – water may never have been present. We really should be cautious.

Further, even if life exists, it is unlikely to be a thriving civilisation of advanced beings who can teach us the secrets of the universe. “The star it orbits is an M-class red dwarf,” says Dr Dartnell, “so it’s cooler and dimmer than our own sun. The habitable zone around it is far closer in, which means that it’s tidally locked – one side always faces its star. It’ll have a pretty weird, extreme climate.

“Basically, delicate creatures like animals and plants might not have had the stability required to evolve. Life, if it exists, is probably nothing more than bacterial pond scum.”

Although I think he overstates the importance of “stability”…  We certainly benefited on this planet from a degree of change.