Signs of life..

I've often wondered about which atmospheric gases are an
indication or proof of life.
Metane and Oxygen seem to be two candidates.
Now, I just noticed that Titan (Saturn's moon into which ESA will
launch a probe in January 2005) contains 6 % Methane.
Also, we recently have found traces of Methane and Ammonnia on Mars.
And exo-planets might soon (in a decade or so) be scanned for
signs of life based on atmospheric gases such as oxygen.
I wonder what conclusions we can draw if any of these gases are
actually found anywhere... Are there many (if any) non-life originations
for oxygen, methane and ammonia ? If so, why do we think we
can draw any conclusion from finding these on other planets ?
And if not, is there bacterial life on Titan ?

Rob

Wasn't it Rob Dekker who wrote:
I've often wondered about which atmospheric gases are an
indication or proof of life.
Metane and Oxygen seem to be two candidates.
Now, I just noticed that Titan (Saturn's moon into which ESA will
launch a probe in January 2005) contains 6 % Methane.
Also, we recently have found traces of Methane and Ammonnia on Mars.
And exo-planets might soon (in a decade or so) be scanned for
signs of life based on atmospheric gases such as oxygen.
I wonder what conclusions we can draw if any of these gases are
actually found anywhere... Are there many (if any) non-life originations
for oxygen, methane and ammonia ? If so, why do we think we
can draw any conclusion from finding these on other planets ?
And if not, is there bacterial life on Titan ?

Volcanoes emit methane.

It's theoretically possible for oxygen to be produced by dissociation of
water vapour without any organic process being involved. The energy
could come from UV light or from lightning. If the gravity isn't too
strong, some of the dissociated hydrogen leaks away into space before it
can recombine, leaving a surplus of oxygen.

However, we conjecture that at atmosphere of a lifeless planet would
either be almost entirely oxygenating or almost entirely reducing
(methane and ammonia are reducing). If we detected an atmosphere that
contains more than trace amounts of both types of gas, then we'd be
fairly confident that there are organic processes in operation.

The inorganic processes for creating the gasses that I mentioned above
are rather slow processes. If such a process is generating oxygen in an
atmosphere that contains an excess of methane, then the oxygen and
methane will react with each other over a few thousand years to produce
water and carbon dioxide. If there isn't any methane, or any other
reducing gas) for the oxygen to react with, then the oxygen levels
could, theoretically, build up to significant levels over billions of
years.

[Past experience suggests that when we do find a planet with significant
amounts of oxygen and methane in its atmosphere then there'll be a
sudden rush of scientists with explanations of how this could happen
without life being present. At present anyone with such an explanation
is keeping quiet.]

--
Mike Williams
Gentleman of Leisure

Wasn't it Rob Dekker who wrote:
I've often wondered about which atmospheric gases are an
indication or proof of life.
Metane and Oxygen seem to be two candidates.
Now, I just noticed that Titan (Saturn's moon into which ESA will
launch a probe in January 2005) contains 6 % Methane.
Also, we recently have found traces of Methane and Ammonnia on Mars.
And exo-planets might soon (in a decade or so) be scanned for
signs of life based on atmospheric gases such as oxygen.
I wonder what conclusions we can draw if any of these gases are
actually found anywhere... Are there many (if any) non-life originations
for oxygen, methane and ammonia ? If so, why do we think we
can draw any conclusion from finding these on other planets ?
And if not, is there bacterial life on Titan ?

Volcanoes emit methane.

It's theoretically possible for oxygen to be produced by dissociation of
water vapour without any organic process being involved. The energy
could come from UV light or from lightning. If the gravity isn't too
strong, some of the dissociated hydrogen leaks away into space before it
can recombine, leaving a surplus of oxygen.

However, we conjecture that at atmosphere of a lifeless planet would
either be almost entirely oxygenating or almost entirely reducing
(methane and ammonia are reducing). If we detected an atmosphere that
contains more than trace amounts of both types of gas, then we'd be
fairly confident that there are organic processes in operation.

The inorganic processes for creating the gasses that I mentioned above
are rather slow processes. If such a process is generating oxygen in an
atmosphere that contains an excess of methane, then the oxygen and
methane will react with each other over a few thousand years to produce
water and carbon dioxide. If there isn't any methane, or any other
reducing gas) for the oxygen to react with, then the oxygen levels
could, theoretically, build up to significant levels over billions of
years.

[Past experience suggests that when we do find a planet with significant
amounts of oxygen and methane in its atmosphere then there'll be a
sudden rush of scientists with explanations of how this could happen
without life being present. At present anyone with such an explanation
is keeping quiet.]

--
Mike Williams
Gentleman of Leisure

Mike Williams wrote in message ...
indication or proof of life.
Metane and Oxygen seem to be two candidates.
Now, I just noticed that Titan (Saturn's moon into which ESA will
launch a probe in January 2005) contains 6 % Methane.
Also, we recently have found traces of Methane and Ammonnia on Mars.
I wonder what conclusions we can draw if any of these gases are
actually found anywhere...

Comets hve frozen methane. When they crash onto Titan or fall apart in
Saturn space, part of the methane could be added to the atmosphere.

Same for Mars.

Regards

Carsten Nielsen
Denmark

Mike Williams wrote in message ...
indication or proof of life.
Metane and Oxygen seem to be two candidates.
Now, I just noticed that Titan (Saturn's moon into which ESA will
launch a probe in January 2005) contains 6 % Methane.
Also, we recently have found traces of Methane and Ammonnia on Mars.
I wonder what conclusions we can draw if any of these gases are
actually found anywhere...

Comets hve frozen methane. When they crash onto Titan or fall apart in
Saturn space, part of the methane could be added to the atmosphere.

Same for Mars.

Regards

Carsten Nielsen
Denmark

Carsten Nielsen wrote:
Mike Williams wrote in message ...

indication or proof of life.
Metane and Oxygen seem to be two candidates.
Now, I just noticed that Titan (Saturn's moon into which ESA will
launch a probe in January 2005) contains 6 % Methane.
Also, we recently have found traces of Methane and Ammonnia on Mars.
I wonder what conclusions we can draw if any of these gases are
actually found anywhere...

Comets hve frozen methane. When they crash onto Titan or fall apart in
Saturn space, part of the methane could be added to the atmosphere.

Same for Mars.

That would suggest the claim the spots on pictures of earth are not
defects but are in fact very small comets to replenish it frequently
and in some quantity. While that would certainly apply to Mars because
of the thin atmosphere it is not clear that would apply to Titan.

One explanation that may apply to Titan is everything that can react
with methane has reacted and there is still some left over. I don't
know that is possible.

--
The Mossad brags of subborning treason by Jews against
their own countries. Whom are we to believe?
-- The Iron Webmaster, 3218

Carsten Nielsen wrote:
Mike Williams wrote in message ...

indication or proof of life.
Metane and Oxygen seem to be two candidates.
Now, I just noticed that Titan (Saturn's moon into which ESA will
launch a probe in January 2005) contains 6 % Methane.
Also, we recently have found traces of Methane and Ammonnia on Mars.
I wonder what conclusions we can draw if any of these gases are
actually found anywhere...

Comets hve frozen methane. When they crash onto Titan or fall apart in
Saturn space, part of the methane could be added to the atmosphere.

Same for Mars.

That would suggest the claim the spots on pictures of earth are not
defects but are in fact very small comets to replenish it frequently
and in some quantity. While that would certainly apply to Mars because
of the thin atmosphere it is not clear that would apply to Titan.

One explanation that may apply to Titan is everything that can react
with methane has reacted and there is still some left over. I don't
know that is possible.

--
The Mossad brags of subborning treason by Jews against
their own countries. Whom are we to believe?
-- The Iron Webmaster, 3218

"Rob Dekker" wrote in message m...
I've often wondered about which atmospheric gases are an
indication or proof of life.
Metane and Oxygen seem to be two candidates.

Methane ice trapped in oceans and peridically leaching out (like the
methane ice in the Gulf of Mexico) comes to mind as one source of
regulated methane releases into an oxygen rich environment over long
periods of time. Can non-biogenic primordial accretion methane do the
same?

Now, I just noticed that Titan (Saturn's moon into which ESA will
launch a probe in January 2005) contains 6 % Methane.
Also, we recently have found traces of Methane and Ammonnia on Mars.
And exo-planets might soon (in a decade or so) be scanned for
signs of life based on atmospheric gases such as oxygen.

Oxygen rich atmospheres with Ozone can build up without life from
water and carbon dioxide photolysis, but water photolysis also
destroys ozone, so some scientists have argued that if Oxygen, Ozone,
Carbon Dioxide and Water were found together, one could discriminate
photochemical dissociative Oxygen production from biological
photosynthesis.

Also, I've read that Methane, Nitrous Oxide, Ammonia, Sulfur or
Nitrogen would also be of interest during a biomarker search.

I wonder what conclusions we can draw if any of these gases are
actually found anywhere...

Judging from the recent claimed finds of Mar's methane and ammonia
(and I heard a rumor on the radio the other day of yet another
interesting gas) no conclusions can or will be made.

Are there many (if any) non-life originations
for oxygen, methane and ammonia ?

Yes. Volcanism is one source. Also, one scenario could be that life
could create an atmosphere of Oxygen and then become extinct via
permanent ice age or the reverse. Also, as you probably know, there
also has been some fairly complex chemistry detected in space over the
decades, including life-necessary gases, elements and amino acids.
They are most probably abiotic agglomerations in space, but I would
suppose that it is not preposterous that a terrestrial planet could
sweep up such gases during formation, where an original Oxygen rich
mix could be preserved in an abiotic frozen world.

If so, why do we think we
can draw any conclusion from finding these on other planets ?

I don't think that anyone could draw conclusions, but it might be an
interesting planet to keep an eye on.

And if not, is there bacterial life on Titan ?


If there is, perhaps we will not know it for a thousand years (based
on the current pace of discovery, as there are no probes even
contemplated for such an investigation.) I think the big argument (I
not being a proponent of it) is the Earth-centric perspective of most
'Earth life' could not live on such a cold, gasoline planet. Looking
back to the origins of life on Earth, the proto-extremophiles who
populated the Earth and made the air we breath were in some fairly
different starting conditions, so I don't think there will be any
'ruling-out' of exoplanets for quite some time (millenia.)

Rob

Back in 1998 an Astrobiology Conf. identified one of NASA's
Astrobiology mission objectives as being to resolve the very questions
that you have asked (IMO biomarker gas investigations and abiotic
geological contributions of those same gases have not be fully
explored.)

This link talks a little bit about it at

http://astrobiology.arc.nasa.gov/roa...iomarkers.html

"Extrasolar Biomarkers
Objective 13: Define an array of astronomically detectable
spectroscopic features that indicate habitable conditions and/or the
presence of life on an extrasolar planet."


This link talks about a paper "Relevance of O2 and O3 as biomarkers in
terrestrial exoplanet atmospheres"

http://www.aas.org/publications/baas...ps2001/382.htm


Also, Oxygen alone is not a good indicator, as is shown by this
seeming case of Oxygen photolysis in the atmosphere of the planet HD
209458b

"Oxygen and Carbon Found in Atmosphere of an Extrasolar Planet"

http://hubblesite.org/newscenter/new...ets/1075730400
"...(the first transiting (extrasolar) planet discovered, the first
extrasolar planet known to have an atmosphere, the first extrasolar
planet observed to have an evaporating hydrogen atmosphere, and now
the first extrasolar planet found to have an atmosphere containing
oxygen and carbon.

Lastly, it is possible that planets without Oxygen or Methane could
also have life on them, so to re-state the answer to your question,
while the presence of Oxygen, Ozone, Methane, Water and CO2 might be
convincing (to some) if found together, no one could rule out life
being on a planet lacking some of these gases.

Best regards, Jason H.

"Rob Dekker" wrote in message m...
I've often wondered about which atmospheric gases are an
indication or proof of life.
Metane and Oxygen seem to be two candidates.

Methane ice trapped in oceans and peridically leaching out (like the
methane ice in the Gulf of Mexico) comes to mind as one source of
regulated methane releases into an oxygen rich environment over long
periods of time. Can non-biogenic primordial accretion methane do the
same?

Now, I just noticed that Titan (Saturn's moon into which ESA will
launch a probe in January 2005) contains 6 % Methane.
Also, we recently have found traces of Methane and Ammonnia on Mars.
And exo-planets might soon (in a decade or so) be scanned for
signs of life based on atmospheric gases such as oxygen.

Oxygen rich atmospheres with Ozone can build up without life from
water and carbon dioxide photolysis, but water photolysis also
destroys ozone, so some scientists have argued that if Oxygen, Ozone,
Carbon Dioxide and Water were found together, one could discriminate
photochemical dissociative Oxygen production from biological
photosynthesis.

Also, I've read that Methane, Nitrous Oxide, Ammonia, Sulfur or
Nitrogen would also be of interest during a biomarker search.

I wonder what conclusions we can draw if any of these gases are
actually found anywhere...

Judging from the recent claimed finds of Mar's methane and ammonia
(and I heard a rumor on the radio the other day of yet another
interesting gas) no conclusions can or will be made.

Are there many (if any) non-life originations
for oxygen, methane and ammonia ?

Yes. Volcanism is one source. Also, one scenario could be that life
could create an atmosphere of Oxygen and then become extinct via
permanent ice age or the reverse. Also, as you probably know, there
also has been some fairly complex chemistry detected in space over the
decades, including life-necessary gases, elements and amino acids.
They are most probably abiotic agglomerations in space, but I would
suppose that it is not preposterous that a terrestrial planet could
sweep up such gases during formation, where an original Oxygen rich
mix could be preserved in an abiotic frozen world.

If so, why do we think we
can draw any conclusion from finding these on other planets ?

I don't think that anyone could draw conclusions, but it might be an
interesting planet to keep an eye on.

And if not, is there bacterial life on Titan ?


If there is, perhaps we will not know it for a thousand years (based
on the current pace of discovery, as there are no probes even
contemplated for such an investigation.) I think the big argument (I
not being a proponent of it) is the Earth-centric perspective of most
'Earth life' could not live on such a cold, gasoline planet. Looking
back to the origins of life on Earth, the proto-extremophiles who
populated the Earth and made the air we breath were in some fairly
different starting conditions, so I don't think there will be any
'ruling-out' of exoplanets for quite some time (millenia.)

Rob

Back in 1998 an Astrobiology Conf. identified one of NASA's
Astrobiology mission objectives as being to resolve the very questions
that you have asked (IMO biomarker gas investigations and abiotic
geological contributions of those same gases have not be fully
explored.)

This link talks a little bit about it at

http://astrobiology.arc.nasa.gov/roa...iomarkers.html

"Extrasolar Biomarkers
Objective 13: Define an array of astronomically detectable
spectroscopic features that indicate habitable conditions and/or the
presence of life on an extrasolar planet."


This link talks about a paper "Relevance of O2 and O3 as biomarkers in
terrestrial exoplanet atmospheres"

http://www.aas.org/publications/baas...ps2001/382.htm


Also, Oxygen alone is not a good indicator, as is shown by this
seeming case of Oxygen photolysis in the atmosphere of the planet HD
209458b

"Oxygen and Carbon Found in Atmosphere of an Extrasolar Planet"

http://hubblesite.org/newscenter/new...ets/1075730400
"...(the first transiting (extrasolar) planet discovered, the first
extrasolar planet known to have an atmosphere, the first extrasolar
planet observed to have an evaporating hydrogen atmosphere, and now
the first extrasolar planet found to have an atmosphere containing
oxygen and carbon.

Lastly, it is possible that planets without Oxygen or Methane could
also have life on them, so to re-state the answer to your question,
while the presence of Oxygen, Ozone, Methane, Water and CO2 might be
convincing (to some) if found together, no one could rule out life
being on a planet lacking some of these gases.

Best regards, Jason H.

"MW" == Mike Williams writes:

MW Wasn't it Rob Dekker who wrote:
I've often wondered about which atmospheric gases are an indication
or proof of life. Metane and Oxygen seem to be two candidates. [...]

[...]
MW [Past experience suggests that when we do find a planet with
MW significant amounts of oxygen and methane in its atmosphere then
MW there'll be a sudden rush of scientists with explanations of how
MW this could happen without life being present. At present anyone
MW with such an explanation is keeping quiet.]

I just heard one. Imagine an ice-covered planet, about the mass of
the Earth. Water vapor in the atmosphere is disassociated into
hydrogen and oxygen. The hydrogen escapes. As the planet is ice
covered, there are no rocks exposed with which the oxygen can react.
Ergo, the oxygen concentration of the atmosphere increases over time,
as the ice sublimates. (Of course, no quantitative predictions of the
oxygen level in such an atmosphere were made in the talk.

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