"TomHendricks474"  wrote in message
news:cjepv4$1rg4$1{at}darwin.ediacara.org...
> >> Whether Mars sized planet in earth orbi is large enough to contain the
> >> necessary ingredients? I don't know.
> >But you've ruled it out in the rest of this thread.  Why (if you don't
> >know)?  And by implication, you've ruled out planetary object 2x,
> >4x and 6 times Mars' size, as well as 2x and 4x Earth's size.
> >You're arguing for too many limitations given the unknowns, IMO.
> I ruled it out at its present placement. Putting it in earth orbit
> is not the same thing.

Ah.  Then perhaps this thread's been unnecessary and we're in argreement far
more tham I had thought.  I've always taken your "same sized planet" (as
Earth) as being ruling out any planet of significantly different size in any
orbit.

> (snipped)
> >Planets spin regardless of moon(s).  Mars, for example, spins almost
> >the same as Earth (40 minutes longer for a Martian day.) You're
> >aruing for too many limitations given the unknowns, IMO.
> But present day earth spin is different from that 4 billion years
> ago which was probably much much faster such that a day was
> 5-6 hours, and night was 5-6 hours - due to the closer moon.

And are you arguing for this as a limitation?  (I wouldn't rule out the
possibility of life based on a 5-6 hour spin *or* a 24-25 hour spin.)

> (snipped)
> >But you just said "OK" for planets with a range of 1/10
Earth's mass
> >to 10x Earth's mass (which seems reaonable to me without facts
> >against it). Which is it?
> Didn't mean to. They have to be pretty close to earth's size  -
specifically
> close enough to retain the same atmosphere. I can't be more exact than
> that with what I know.

But above you said you only eliminated Mars in Mars' orbit (TH: "I ruled it
out at its present placement. Putting it in earth orbit is not the same
thing").  I took that to say a Mars-sized planet in Earth's orbit might
possibly support OOL.

But OK, I see with your atmosphere where you're coming from.  I'd guess,
though, that the atmosphere can be pretty different (thinner, thicker,
composition, etc.), too.

> >Where are you getting this? At
> >http://brahms.phy.vanderbilt.edu/~rknop/classes/a250/fall2002/pellish/tab
> >le_of_distances.pdf
> >it gives the following eccentricity values (other sites roughly agree):
> >  Planet      Eccentricity
> >  Mercury      .21
> >  Earth           .02
> >  Neptune      .01
> It's not so much their orbit is where the sun is. In earth's it is in the
> center

I thought that was the same thing.  By an an orbit eccentricity of .01,
"Neptune's orbit, for example, is closer to circular than Earth's" (.02)
"and Mercury's is less so" (.21).  What do these values mean, otherwise?
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