[Murchie85 (OP)]

This post is more an offshoot of the liquid methane post but I thought it would merit its own since some of the points raised were interesting enough to discuss in a different thread.

Firstly what conditions do you think would suite life in our solar system and the local galaxy (obviously ruling out earth). Also what environments would for definite rule out life?

Most of the places I have heard about that have remote possibilities are cold places such as Europa and titan. Even although Europa is a huge ball of ice, its believed that the top layer of the ice sits on tens of kilometres of ocean due to gravitational strains on the planet keeping the ocean liquid. If thermal vents are present near the crust then it may be possible for certain simple life forms to exist/evolve.

Titan on the other hand would require a totally different type of life known from earth as the temperatures are so low that water is frozen solid like steel although methane can flow and rain down on the surface offering a medium for potential life forms.... but wouldn't the lifeforms need energy and isn't energy generally the thermal kind in that it would need to be warm?

Also does a planet HAVE to be in proximity to a star in order to harbour life? Is there another energy source that could offer similar benefits?

p.s I do appreciate this is an astro-biology type post although I would like the focus to be more on the astro part if possible.

Adam

[peppercorn]

I've little doubt that Europa could be 'seeded' with bacterial life - either purposely by an intelligence or by almost infinitesimal odds by 'life' (the right kind to survive) catching a ride there on a meteorite.

I sometimes wonder what happens to NASA's claims of finding remnants of bacterial structures on Mars some years ago. Has that been quietly 'forgotten'?

If life does (of could) exist on moons such as Europa it is essentially driven by gravitation not solar energy.  A 'planet' may be able to experience this hypothetically outside of a solar system environment if it also had a similar enormous mass nearby, but how these 'rouge' objects would have been formed in the first place throws up a million more unknowns.  Add this to the odds of life spontaneously 'firing-up' in the depths of interstellar space and, well, it doesn't even seem considering unless it is a purposeful act.

[granpa]

actually, the odds of life spontaneously 'firing-up' in the depths of the vast molecular clouds of the galaxy seem quite good to me. Certainly not water based bacterial life as we know it but some kind of self-reproducing molecule seems quite likely to form over the eons.

[Murchie85 (OP)]

Is it possible planets orbiting black holes can gain any potential benefits in terms of sustaining reproducing organisms?

[imatfaal]

Murchie - a planet orbiting a black hole would be damned cold.  Unless the black hole was part of a binary. And most binary star/BH systems will have matter moving from star to black hole.  This matter will be spiral down into BH at phenomenal speed and the impacts will generate huge amounts of xrays and gamma rays; neither are exactly conducive to life as we know it 

[syhprum]

Any planet that orbited a large star in the 'Goldilocks's' zone (on which life could have evolved )would suffer a double whammy as the star came to the end of its life.
Firstly as the star went into the giant red stage it would be engulfed by its outer layer and then when it collapsed into a Neutron star on its way to black hole status it would be blasted by Gamma rays and Neutrinos.
It is not likely that life would have had time to develop on this planet as large stars evolve very quickly in cosmic terms.