>
>> 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.


(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 arguing 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.

(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.

>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

.
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