New Findings Could Dash Hopes for Past Oceans on Mars

You have to know where to look, and when the 2500 mile long, 5 mile deep
Valles Marineris Canyon System is explored, undoubtedly, life, and water
will be found.

Nothing much is on the surface, with the conditions there, except
remnants of when the sun was hotter, and the climate better, that
astronomers and others will disagree with anyway.

At that time the earth was more like Venus, another fact, they'll
disagree with, but, that time period is farther back in time than they
comprehend at the present.

http://pds.jpl.nasa.gov/planets/capt...ars/valmar.htm

=DF=83--=B9=B9

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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In article ,
Eric Crew writes:
Only a minority of planetary nebulae are like small rings or disks -
brightly glowing shells of gas, as C E R Bruce discovered many years
ago. Most are more like small galaxies with spiral shapes and arms -
generally two or four.

Could you post the names of a few examples of PN that look "like
small galaxies with spiral shapes and arms?"

--
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
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In sci.astro Steve Willner wrote:
In article ,
Eric Crew writes:
Only a minority of planetary nebulae are like small rings or disks -
brightly glowing shells of gas, as C E R Bruce discovered many years
ago. Most are more like small galaxies with spiral shapes and arms -
generally two or four.

Could you post the names of a few examples of PN that look "like
small galaxies with spiral shapes and arms?"

Have a look at NGC 4361 - I'm pretty sure that's the one that a Famous
Astronomer mistook for a Virgo-cluster galaxy in a classification
assignment based on Crossley plates, about 20 years ago. Pretty
convincingly like a Seyfert galaxy, even - bright, very pointlike
nucleus and dim spiral features. These are much less tightly wraped
than the features in NGC 6543 (from the famous Hubble images).

Bill Keel

(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
email may be sent to your ISP.)

In article ,
"William C. Keel" writes:
Have a look at NGC 4361 - I'm pretty sure that's the one that a Famous
Astronomer mistook for a Virgo-cluster galaxy in a classification
assignment based on Crossley plates, about 20 years ago.

There's a nice picture at
http://crux.astr.ua.edu/goodies/misc...s/ngc4361h.gif
although the caption gives a somewhat different slant on the story.
Of course both could be true: Famous Astronomer gets fooled, then
sees how many students fall into the same trap.

A color image at
http://www.3towers.com/ngcB.htm
shows that the gas is brightest in the green [O III] lines.

Pretty
convincingly like a Seyfert galaxy, even - bright, very pointlike
nucleus and dim spiral features. These are much less tightly wraped
than the features in NGC 6543 (from the famous Hubble images).

Based on the image, it looks like the bulk of the gas is in the
(apparently) spherically symmetric shell, but I see what you mean
about the spiral features. Very nice!

--
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
email may be sent to your ISP.)

In sci.astro Steve Willner wrote:
In article ,
"William C. Keel" writes:
Have a look at NGC 4361 - I'm pretty sure that's the one that a Famous
Astronomer mistook for a Virgo-cluster galaxy in a classification
assignment based on Crossley plates, about 20 years ago.

There's a nice picture at
http://crux.astr.ua.edu/goodies/misc...s/ngc4361h.gif
although the caption gives a somewhat different slant on the story.
Of course both could be true: Famous Astronomer gets fooled, then
sees how many students fall into the same trap.

They should be the same story, if one notices where the picture is from...

Bill Keel