Subject:
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Re: Question about 7101
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Newsgroups:
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lugnet.off-topic.fun
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Date:
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Sun, 20 Jun 1999 22:22:54 GMT
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Viewed:
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470 times
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Jeff Stembel wrote:
> [Moving to off-topic.fun]
>
> In lugnet.starwars, Lindsay Frederick Braun writes:
> > Alan G. Carmack wrote:
> >
> > I think a Pod Race on the moon would be really boring, since turbojets
> > don't work really well without an atmosphere. Well, OK, the moon does
> > have an atmosphere, but it's got a pressure of about 0.2mm Hg (Sea level
> > Terran average is 1013mm Hg) and it's sodium, not exactly good for it.
> > I think that for a planet to maintain an atmosphere *and* be of the age
> > where an oxygen-nitrogen mix would develop, it would have to be Earth-
> > sized or larger.
>
> Where did you hear about the moon's atmosphere? I try to keep up on Astronomy
> news, but I've heard nothing about it. It can't be pure sodium, as I'm pretty
> sure the moon's gravity isn't strong enough to hold it (although I may be
> wrong).
That's why I thought it was so weird when I first saw it. Supposedly it was
detected through spectroscopy, not by the instruments actually sent to the
surface--and it's so tenuous that it's almost not an atmosphere. I recall reading
it in Jay Pasachoff's general intro text but I'll have to take another look.
> Also, the orbital distance will determine what a planet's atmosphere is like.
> The elements settle out at different distances from the star they orbit, which
> is why the first four planets are composed primarily of heavy elements and
> compounds (iron, silicon), and the second four are composed primarily of light
> elements and compounds (helium, hydrogen). Pluto is, of course, an anomoly.
> ;)
That's if you buy that particular model of planet formation, of course.
I vaguely remember one that suggests all of the planets have nickel-iron cores
and silicon bases, but that only the outer planets had access to enough light gases
to accrete their envelopes. The sodium atmosphere is really an ionosphere--why
it's that, I don't know. I'll see what I can dig up.
LFB.
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