Topic: Average star has TWO potentially Earth-like worlds

[Nemesis]

Link to full article

Boffins in Australia have applied a hundreds-of-years-old astronomical rule to data from the Kepler planet-hunting space telescope. They've come to the conclusion that the average star in our galaxy has not one but two Earth-size planets in its "goldilocks" zone where liquid water - and thus, life along Earthly lines - could exist.

“The ingredients for life are plentiful, and we now know that habitable environments are plentiful,” says Professor Charley Lineweaver, a down-under astrophysicist.

[Tulwar]

If Earth's size and position relative the sun were the only factors!  That's not to say this isn't good news, but the Earth is an unusually dense planet with a freakishly large moon.  Perhaps closer to the core of the galaxy would be some good candidates.  In a denser part of the galaxy, comet strikes would happen more often, increasing the pace of evolution, as well....  Then, maybe that could over-do it.

I wonder what the odds are of an earth-like moon occuring around a Jupiter-like planet in the Goldilocks Zone.  It has been postulated that Mars lost most of its atmosphere, because, lacking a Van Allen Belt, the Sun blew it away.  Were it a moon of Jupiter, and Jupiter were in Mars' orbit, Mars could still have an atmosphere, like Titan, around Saturn.

[Nemesis]

The word potentially takes that into account.

However is the Earth unusually dense or is it more typical for its position in the solar system?  We don't have enough details for other systems to be sure.  The same for the moon.  Some of the "massive" terrestroid planets found may actually be binaries that have Earth mass moons that make the planet seem even bigger than it actually is.  There are super jovians in the goldilocks zone that could easily have Earth mass moons but we can't yet tell that level of detail.

As to closer in meaning more comet impacts that could be a bad thing as according to some theories for our complex cells a long period of time with fairly stable conditions was needed for current cell to form by smaller cells colonizing larger ones and passing from parasite to symbiote to a unified whole. 

We can't even be sure if the large moon was needed.  Wave actions and solar tides might have had the same effects to sufficient degree.  It could also be irrelevant and the theories that claim it is needed may be proven wrong.  Insufficient data to decide this like much else.   

[Tulwar]

In our solar system, the Earth is more dense than any other planet.  The current theory is that a collision with a mars-sized object blew a much of the silica off the Earth, forming the moon.  This gives the Earth pleanty of nuclear fuel and conductive iron to produce the Van Allen Belts.  There is a theory that Venus does not have plate techtonics, but because the crust is so hard and thick, the entire planet melts every so often.  This would cause serious problems for life as we know it.  Were Earth to consist of more rock and less iron, a periodic meltdown would cause life to have to start from scratch, over and over again.  Just because earth-sized planets in the Goldilocks Zone may be common, doesn't negate the Rare Earth Theory.

Still, different solar systems are probably likely to have different average densities.  As smaller stars are formed from debris of super novi, a lot of variation is possible.  I merely think that density is more likely toward the core, but it can be completely random.

From there, I go to look on the bright side.  Earth might not have even been the ideal womb for intelligent life.  It was just good enough.

As far as the bombardment by comets goes, I merely suggest that our case may not have been the ideal.  Toward the core of the galaxy, with stars being closer together, interference with the obects in the Oort cloud.  Comets would cause mass extinction events more often, putting evolution could be on the fast track.  Then again, that could be a fast track could be to a dead end.   Not to mention, a slower mass extinction pattern could very well be a better situation to promote intelligent life.  This is the epitome of idle speculation on my part.

[Nemesis]

I seem to recall reading some time back on the Venus plate tectonics issue that Venus just misses on a critical temperature being able to have them.