1/5th of Galaxy's stars have earths in the Green Zone

[NOTDilbert]

....That means twenty billion planets of earth-like mass orbiting their stars in the Habitable Zone (liquid water possible on the surface).

http://www.keckobservatory.org/recent/e ... table_zone

All those new neighbors....gonna have to bake some cookies.....

[Jabberwonky]

....That means twenty billion planets of earth-like mass orbiting their stars in the Habitable Zone (liquid water possible on the surface).

http://www.keckobservatory.org/recent/e ... table_zone

All those new neighbors....gonna have to bake some cookies.....

If fresh-baked cookies can't induce first contact, I don't know what will...

[Dave]

The Eddorians claim that the figure is closer to 1 in 3, but they have somewhat looser standards for "inhabitable" planets.

[shadowinthelight]

That sounds awesome for the prospects of life existing elsewhere, but the hypothesis that is gaining traction kind of puts a damper on that. Although our planet is great for sustaining life, according to current models of Earth's early chemistry our planet was lacking in what is believed necessary for life. The funny thing is although Mars is now inhospitable it seems to have had more of what is necessary to create life. Add in a meteor to carry early life forms from one planet to another, stir for a few billion years, and then you get us. It is a little depressing to think this particular combination of planets may be necessary for life to emerge. It really cuts down on the chances of us finding others out there.

[MerchManDan]

All those new neighbors....gonna have to bake some cookies.....

Unless there's an interstellar equivalent to a sign in our front yard that says "BEWARE OF HUMANS."

[bmonk]

Actually, if you can get habitable planets around red dwarfs--then there could be 40 or 50 billion candidates--and they'd have many more billions of years to develop life...

[Mark N]

Actually, if you can get habitable planets around red dwarfs--then there could be 40 or 50 billion candidates--and they'd have many more billions of years to develop life...

Those worlds would have some serious orbital velocity since they will have to be very close to their mother stars to get enough heat and light.

[bmonk]

Actually, if you can get habitable planets around red dwarfs--then there could be 40 or 50 billion candidates--and they'd have many more billions of years to develop life...

Those worlds would have some serious orbital velocity since they will have to be very close to their mother stars to get enough heat and light.

Yep--and probably tidal lock. Still, throw enough mud at a wall, and some is bound to stick...

[Catawampus]

Still, throw enough mud at a wall, and some is bound to stick...

. . .and start to evolve into lifeforms that will then retaliate by throwing you around.

The big question is whether or not we'd recognise alien life as being alive if we saw it. And vice versa.

[Mark N]

Still, throw enough mud at a wall, and some is bound to stick...

. . .and start to evolve into lifeforms that will then retaliate by throwing you around.

The big question is whether or not we'd recognise alien life as being alive if we saw it. And vice versa.

That has been the question ever since the first scientist figured that life may evolve off a different element than carbon.

[txmystic]

That sounds awesome for the prospects of life existing elsewhere, but the hypothesis that is gaining traction kind of puts a damper on that. Although our planet is great for sustaining life, according to current models of Earth's early chemistry our planet was lacking in what is believed necessary for life. The funny thing is although Mars is now inhospitable it seems to have had more of what is necessary to create life. Add in a meteor to carry early life forms from one planet to another, stir for a few billion years, and then you get us. It is a little depressing to think this particular combination of planets may be necessary for life to emerge. It really cuts down on the chances of us finding others out there.

Actually, what are the odds of that very thing happening in a given system? If it is greater than one in 20 billion, there's a pretty good chance there are more earth like planets out there.

[bmonk]

That sounds awesome for the prospects of life existing elsewhere, but the hypothesis that is gaining traction kind of puts a damper on that. Although our planet is great for sustaining life, according to current models of Earth's early chemistry our planet was lacking in what is believed necessary for life. The funny thing is although Mars is now inhospitable it seems to have had more of what is necessary to create life. Add in a meteor to carry early life forms from one planet to another, stir for a few billion years, and then you get us. It is a little depressing to think this particular combination of planets may be necessary for life to emerge. It really cuts down on the chances of us finding others out there.

Actually, what are the odds of that very thing happening in a given system? If it is greater than one in 20 billion, there's a pretty good chance there are more earth like planets out there.

Well, "Earth-like planets" maybe an overstatement. There could be life on very different systems, that don't look much Earthlike. Consider that even here on Earth, we have ecosystems at sub-oceanic thermal vents, we have sub-ice life at both poles, we have desert life and mountaintop life, as well as, say, jungles. Yes, they all use water and carbon (CHON) molecules--but that's about the only constants. Who knows what other systems might come up with?

[shadowinthelight]

Silicon has long been recognized as the best alternative to carbon for building life forms but the fact is the molecular bonds it forms are not nearly as strong. Carbon really is the only viable base for anything that would fit our current definitions of life.

[bmonk]

Silicon has long been recognized as the best alternative to carbon for building life forms but the fact is the molecular bonds it forms are not nearly as strong. Carbon really is the only viable base for anything that would fit our current definitions of life.

Yes--but what sort of trace elements would be used? Which of the millions (billions) of possible carbon compounds would be used, and in what combinations? What sort of climate, especially temperature (and temp range), would be optimal? Would it have a very briny base, especially if it was cold/below freezing? Or some other kind of organic anti-freeze? What if it was well over 50C? Maybe even over 100C, if the atmosphere pressure was high enough? All of those could make the life very different from Earth's biosphere.

[Atomic]

Silicon has long been recognized as the best alternative to carbon for building life forms but the fact is the molecular bonds it forms are not nearly as strong. Carbon really is the only viable base for anything that would fit our current definitions of life.

Yes--but what sort of trace elements would be used? Which of the millions (billions) of possible carbon compounds would be used, and in what combinations? What sort of climate, especially temperature (and temp range), would be optimal? Would it have a very briny base, especially if it was cold/below freezing? Or some other kind of organic anti-freeze? What if it was well over 50C? Maybe even over 100C, if the atmosphere pressure was high enough? All of those could make the life very different from Earth's biosphere.

Different, true, but I suspect only to a point. Consider the range of extremeophiles that currently exist on Earth now -- from sulphur eating bacteria living in the 100C+ environment around deep-sea hydrothermal vents, to the tiny fish living in hugely saline waters around the Great Salt Lake. A species of algae loves hydrocarbons to the point where (as remembered from my youth) it was a problem with diesel trucks -- they had to use an additive to keep the fuel tanks clean. And you think moldy bread was bad?

The anthropic principle has it's uses, and one of them is to consider that in the several billion years of evolution on this world, the effect of trillions upon trillions of bio-chemical experimentation has produced the major Kingoms and Phyla of life on earth. From Viruses to Antelope, they all depend on a well tested set of chemical processes to power them, both aerobic (Oxygen using) and anaerobic (Oxygen shunning) forms. Thus we see the end result of proven life structure which are now shaped by their environment and competition. Consider Puffins and Penguins. Both fill the same ecology, and have generally the same physical form and coloring to fit their environment. But Puffins still fly because of greater threats in their world, but Penguins do not, as their threats are primarily aquatic. Lather, rinse, repeat.

What I would really like to see is a world that has avoided the Oxygen Explosion, and consists of entirely anaerobic life forms! Would they have evolved beyond bacteria into algae, fungi, and perhaps invertebrates or beyond? Perhaps, on a low gravity world, the anaerobic processes would be energy enough!

Ah, to dream...