[pasmembers] Re: Life Beyond Earth
- From: CenturyLink Customer <primefactory@xxxxx>
- To: pasmembers@xxxxxxxxxxxxx
- Date: Mon, 25 Aug 2014 12:43:11 -0400 (EDT)
Had to put my two cents in. O nce the sun ignited it has varied little in
output. I nside of Jupiter's orbit we have asteroids and zodiacal light which
is dust not ices because of the stellar wind and light intensit ies. Even now
this slowly strip s rocky planets of their atmospheres and left only the hea
vier gases (no H & He) . Comets begin to sublimate when they get closer than
Jupiter and quickly lose their mass. Objects like the Earth are a very small
target. The m ost important point against comets is because they formed outside
our solar system they have isotopic ratios that do not match terrestrial
values. Only Io is too hot to have ice of all the moons of the gas giants.
Isotope ratios of ice on these moons are much closer to terrestrial values.
Asteroids beyond Jupiter are also ice covered but not as thick as these moons.
These satellites had close encounters with other moons that reversed the
orbits of the smaller moon and would eject the more massive moon. I have given
lectures on how the Earth was struck 1.8 billion years ago in the Pacific by a
moon of Neptune that had a thick layer of ice and hydrocarbons that made it as
large as Mars. You can double the amount of water the Earth has because the
Moho is a buried mineralized ocean that is still trying to reach the surface
through volcanics.
Mike Marron
----- Original Message -----
From: "Robert Ewing" <rrewing9@xxxxxxxxx>
To: pasmembers@xxxxxxxxxxxxx
Sent: Sunday, August 24, 2014 8:02:10 PM
Subject: [pasmembers] Re: Life Beyond Earth
Sorry I forgot to mention that as the Earth was forming (early on) comets could
have struck it and incorporated water into the Earth as well...the Earth would
have to have accumulated enough mass however so that the escape velocity for
water molecules would not be exceeded.....because the temperature was not cold
at that point......hence difficult for liquid or ice to accumulate here......
On Aug 24, 2014 7:53 PM, "Robert Ewing" < rrewing9@xxxxxxxxx > wrote:
Hey. Bob Ewing here, from PVCC.....
I have always had a difficult time with the comet theory as well, because, the
Earth has been outgassing for 4 billion years plus; (ie: volcanic activity); so
there had to be primordial water inside the Earth from it's formation from the
solar nebula; although maybe in the form of vapor.
H2O is actually a very common molecule in space. But, the Earth has been struck
by many comets as well, so certainly some of the water has come from them
......hard to say what %
Volcanoes emit steam (water) as the primary gas. CO 2 is usually second.
There are hydrated minerals too and maybe some of these have been recycled
inside the Earth over time, as has sediment containing water (marine). When
this material is melted inside the Earth they would release the water as
steam...
Complicated issue!
:-)
Bob
On Aug 24, 2014 5:26 PM, "Alex Vrenios" < axv@xxxxxxx > wrote:
<blockquote>
I just happened to watch the NOVA program, "Finding Life Beyond Earth." The
focus seemed to be on some new thinking about how an exoplanet doesn't have to
be in a "sweet spot," at that not-too-hot and not-too-cold distance from it's
star, to foster life. There are other energy sources, like geothermal, e.g.,
that can suffice, admitting many other, more distant planets and moons to the
potentially inhabited bodies in a solar system. A source of energy, water and
organic compounds were referred to as the "trifecta" of life-forming
ingredients.
Pretty cool, but what caught my interest was the water.
A long time ago, a budding young scientist (in a geology class, I think) asked
one of those questions that stop internationally acclaimed scientists in their
tracks, "Where did all that water come from?" Referring to the fact that about
3/4 of the Earth's surface is covered with water, yet there doesn't seem to be
a reason for that.
The answer for many years has been a bombardment from comets which, as we all
believe, are made mostly of ice: the "dirty snowballs" of stellar objects. I
think that that's a lot of comets! It never seemed to me to be a very
satisfying solution, no pun intended.
This NOVA program referred to an accretion disc as dust, gas and water.
Wikipedia's definition is too vague. Britanica.com says "dust, gas and other
tangled molecules." I don't remember hearing anyone state that water was a
major component of the material from which planets may form before now. But
then I'm not exactly a main-stream astrophysicist, so maybe some of you can
elaborate...
Alex
</blockquote>
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