New Findings Could Dash Hopes for Past Oceans on Mars

In article ,
(John Curtis) writes:
My reference claims that the largest constituent(next to hydrogen)
of planetay nebulae is carbon monoxide.
http://soral.as.arizona.edu/sofia2/node4.html.

As Henry pointed out, "planetary nebulae" (ejecta of old, evolved
stars) are not the same as "proto-planetary nebulae," or more common,
"proto-planetary disks." In any case, the page you cite describes
the molecular outflow, not the planetary nebula itself. The nebula
itself is ionized and has only trace molecules associated with dust
grains.

CO2 is not a factor unless the temperature of the central star
exceeds 370000 K .

There's something wrong here. A hot central star will dissociate all
molecules, including CO.

Significantly, CO2 was detected in the form of
calcium carbonate, which not only implies aqueous origin but
also a source of oxygen(water) for the conversion of CO into CO2

How did we jump from CO to CO2? Also, where was calcium carbonate
detected, and what is the evidence?

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
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(Steve Willner) wrote in message ...
In article ,
(John Curtis) writes:
My reference claims that the largest constituent(next to hydrogen)
of planetay nebulae is carbon monoxide.
http://soral.as.arizona.edu/sofia2/node4.html.

As Henry pointed out, "planetary nebulae" (ejecta of old, evolved
stars) are not the same as "proto-planetary nebulae," or more common,
"proto-planetary disks." In any case, the page you cite describes
the molecular outflow, not the planetary nebula itself. The nebula
itself is ionized and has only trace molecules associated with dust
grains.

CO2 is not a factor unless the temperature of the central star
exceeds 370000 K .

There's something wrong here. A hot central star will dissociate all
molecules, including CO.

Significantly, CO2 was detected in the form of
calcium carbonate, which not only implies aqueous origin but
also a source of oxygen(water) for the conversion of CO into CO2

How did we jump from CO to CO2?

My interpretation is that CO ignites readily to form CO2.
CO + 1/2O2 --- CO2
Oxygen was derived from the lysis of water.

Also, where was calcium carbonate detected, and what is the evidence?

In the dust shell.
http://www.spaceref.com/news/viewpr.html?pid=7153
John Curtis

In article ,
(John Curtis) writes:
Significantly, CO2 was detected in the form of
calcium carbonate, which not only implies aqueous origin but
also a source of oxygen(water) for the conversion of CO into CO2

How did we jump from CO to CO2?

My interpretation is that CO ignites readily to form CO2.
CO + 1/2O2 --- CO2
Oxygen was derived from the lysis of water.

Also, where was calcium carbonate detected, and what is the evidence?

In the dust shell.
http://www.spaceref.com/news/viewpr.html?pid=7153

Taking the last point first, the original reference is by Kemper et
al., 2002 Nature 415, 295. The main point of the (quite
interesting!) paper is that the carbonate they detect is evidence
for a non-aqueous formation process. The timescale (10^4 years) and
amount of carbonate present (=30 earth masses) are claimed to rule
out the usual aqueous formation processes.

More generally, CO is quite abundant in molecular outflows -- it is
the most abundant molecule after H2. That's because CO has high
energy of formation. CO2 is much less stable and much less abundant
than CO. Neither molecule will exist in significant abundance inside
an ionized region. Molecules are destroyed very quickly by UV
radiation, but solid particles (silicates typically being most
abundant) can last awhile before they are destroyed.

The chemistry of molecular outflows and clouds differs quite a lot
from usual laboratory chemistry. Densities are vastly lower, and
usually there is lots of UV light around. The fact that CO and O
both exist does not mean they will combine. In fact, I deliberately
wrote O and not O2. SWAS did not detect O2 outside the solar system
despite extensive searching and prior expectations that molecular
oxygen should be abundant enough to be detected. (SWAS did detect O2
in Earth's atmosphere, so the instrument was working properly.)

I'm no longer sure what the original point of this thread was, but
perhaps it's useful to clear up some misconceptions about molecular
outflows.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
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