Top Ten Bodies in the Solar System for Extraterrestial Life

I put together this list as an intellectual exercise,
ranking the possibilie places in the solar system
for the existance of Extraterrestial life. I welcome
any non-Guth feedback.

Top Ten Bodies in the Solar System for Extraterrestial Life

1. Earth
Okay, so this may seem like a silly choice at first, but it
is actually serious. Given Earth's viable ecosystem, it
seems likely that if extraterrestial life did exist elsewhere
in the solar system in the past, but not now, there's a
good chance it could have survived if an impact brought
it to Earth. You also have to consider the possibility
of intelligent alien contamination over billions of years.
As to how you'd determine if the life that survived was
actually alien and not native, I don't know, but still, it
is something to consider. Plus, if there's extraterrestial
life both here and on another body, there's a good
chance we'll stumble across it here first.

2. Mars
Energy, water, not too cold or too warm, rich geological
history, complex chemistry, hydrological cycle, a little
atmosphere -- Mars has a alot to offer. A traditional
favorite choice for finding extraterrestial life in other
parts of the solar system.

3. Europa
The recent new favorite, with evidence of subsurface
ocean and interesting chemistry on the surface. Energy
available via tidal heating, so life below the icy surface
is possible.

4. Titan
Very cold, yes, but we don't know yet what's going
on below those clouds. And with all the complex
hydrocarbons floating around and a possible
hydrological cycle as well, chances are slim yet
still realistic.

5. Io
This is the first choice on this list that I expect to be
controversial. However, I think Io has a lot of
possibilities -- complex chemistry, geological activity,
and the surface provides a wide range of termperatures.
I see no reason why life couldn't have developed in a
hot (but not too hot) volcanically heated area... but
Jupiter's radiation is a problem.

6. Jupiter
A questionable entry, but why not micro-celled
organisms floating in the upper atmosphere? Carl
Sagan once speculated on the possibility of more
complex life-forms in gas giants, "floaters", "sinkers",
and "hunters".

7. Saturn
Well, if Jupiter, why not Saturn? Uranus and Neptune
are probably too cold and differ too much in their
composition, but Saturn is enough like Jupiter to
harbor the same possibilities.

8. Triton
Cold and distant, but yet we know it's geologically
active, with liquid subsurface, and possibly some
atmosphere. If life can exist in the oceans of Europa,
why not Triton?

9. Venus
It's hot. Damn hot. And the pressure is deadly.
But microscopic organisms might be able to survive
under the surface, or high up in the atmosphere. The
chances of life on Venus are slim given what we know
today, but I hold out hope.

10. Iapetus
This is my second highly controversial choice, but I
think a defensible one. Frankly, we don't know what
is going on on Iapetus, although there are many theories.
We'll need to get a much closer look to figure out what
the dark material on the surface is, the nature of recent
geological activity, and determine the presence of any
liquid water or atmosphere. However, the planet may
turn out to be a lot like Europa once we learn more, so
I think you can't simply discount it like you can many of
the other rocky/icy airless moons. Alternatively, you
can suggest Callisto or Ganymede.

Bruce

In message , Bruce
Sterling Woodcock writes


6. Jupiter
A questionable entry, but why not micro-celled
organisms floating in the upper atmosphere? Carl
Sagan once speculated on the possibility of more
complex life-forms in gas giants, "floaters", "sinkers",
and "hunters".

Doesn't Jupiter have a lot of turnover and down drafts in the
atmosphere, which means that living things will get sucked down to
levels which are too hot (and too dense ?) to survive.


7. Saturn
Well, if Jupiter, why not Saturn? Uranus and Neptune
are probably too cold and differ too much in their
composition, but Saturn is enough like Jupiter to
harbor the same possibilities.

Having rubbished Jupiter, I'm going to disagree about Neptune as well
:-) It's got an internal heat source, so it could be quite warm at
depth. Unfortunately my copy of "The New Solar System" (3rd ed.)
doesn't have a pressure-temperature graph for Neptune. Saturn looks
inviting though - a nice comfy 300 Kelvin at 300 km below the 100
millibar level. The pressure there is about 10-20 bar. Anyone for SCUBA
gear?
--
Save the Hubble Space Telescope!
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"Jonathan Silverlight" wrote
in message ...
In message , Bruce
Sterling Woodcock writes


6. Jupiter
A questionable entry, but why not micro-celled
organisms floating in the upper atmosphere? Carl
Sagan once speculated on the possibility of more
complex life-forms in gas giants, "floaters", "sinkers",
and "hunters".

Doesn't Jupiter have a lot of turnover and down drafts in the
atmosphere, which means that living things will get sucked down to
levels which are too hot (and too dense ?) to survive.


7. Saturn
Well, if Jupiter, why not Saturn? Uranus and Neptune
are probably too cold and differ too much in their
composition, but Saturn is enough like Jupiter to
harbor the same possibilities.

Having rubbished Jupiter, I'm going to disagree about Neptune as well
:-) It's got an internal heat source, so it could be quite warm at
depth. Unfortunately my copy of "The New Solar System" (3rd ed.)
doesn't have a pressure-temperature graph for Neptune. Saturn looks
inviting though - a nice comfy 300 Kelvin at 300 km below the 100
millibar level. The pressure there is about 10-20 bar. Anyone for SCUBA
gear?

You're probably right about the inner temperature.
My point about the cold was not so much the current
state but how it formed... the internal compositions of
Uranus and Neptune are though to be much different
from Jupiter and Saturn. So the possibility of complex
chemistry seems to be reduced. Also, if the primary
source of organic compounds are cometary material,
Jupiter and Saturn surely gobbled up more than their
smaller cousins. And given the higher possibilities of
life arising on a Galilean or Saturnian moon, then you
have the chance of the parent body being 'seeded' by
the minor one. Still, one could argue the same for
Triton, so...

Personally I think the chance of life in such gas
giants is small at any rate, but given how little we
actually know about their interiors, well, anything is
possible...

Bruce