[X] My Assistant

[Webscientist]

An interesting news release on the website of the Cassini Equinox Mission:
http://saturn.jpl.nasa.gov/news/cassinifea...feature20090904

I had noted that propane (C3H8) could also be present as a liquid on Titan. So, we have, at least, three potential candidates for pools of liquids on Titan: methane, ethane and propane.

If the data of wikipedia are correct, propane has a boiling point ( in normal, terrestrial conditons) of -42.09°C and a melting point of -187.6°C.

With environmental conditions similar to those in the landing site of the Huygens probe ( 1467hPA, -179°C), I suppose that propane can form liquid pools, as well.

[nprev]

Well, I'll just get this out of the way right now:

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[Hungry4info]

Feeling an excessive need to rant.

"Titan's atmospheric inventory would fuel about 150 billion barbecue cookouts, enough for several thousand years of Labor Days."

Really? This doesn't tell me a darned thing about the amount of propane on Titan. Unless that's the new unit for measuring the propane abundance.

I can see it now.


Propane on Titan
Abstract:
"Using high resolution mass spectroscopy from instruments aboard the Cassini spacecraft, we are able to measure a C3H8 abundance of 150 +/- 3% Giga-BBQ'-cookouts within three sigma confidence."

(made some of that up, but you hopefully get the point).

[centsworth_II]

...This doesn't tell me a darned thing about the amount of propane on Titan....

They do give this specific estimate: "We estimate there are nearly 700 million barrels of propane on Titan, said Nixon. "That is enough to fill six-billion 20-pound tanks of liquefied propane gas."

[titanicrivers]

Well, I'll just get this out of the way right now:

Ya got that right ....

[Juramike]

[i]"We estimate there are nearly 700 million barrels of propane on Titan, said Nixon.

1 American barrel = 0.15899 m3 (Source: Unit Conversions: Oil Industry Conventions: http://www.eppo.go.th/ref/UNIT-OIL.html)

Soooo....1.1E8 m3 of propane on Titan's surface.

Amount of estimated propane = 0.11 km3 propane. (1E9 m3 = 1 km3)

Estimated condensed organic materials volume inventory of Titan (from upper end of estimates in Table 1 by Lorenz et al., 2008: http://www.lpl.arizona.edu/~rlorenz/organicinventory.pdf):

1.9E6 km3 of total condensed material volume inventory on Titan (atmospheric methane, methane/ethane lakes, dune sands, etc.)

If I got the math right, percentage-wise, there's not much propane "in da mix" (58 ppb)

[ElkGroveDan]

I can just see it years from now, fleets of spacecraft landing on Titan with cargo holds full of oak barrels to collect propane, while back on Earth distilled spirits are transported in steel propane canisters due to the global barrel shortage.

[Greg Hullender]

Feeling an excessive need to rant.

Have some sympathy for the folks who write these "outreach" pieces. It doesn't help their careers at NASA, but only scientists can do it without it being total drivel. They do it because they know it's important to involve the public, and they go to great lengths to find things ordinary people can relate to.

ADMIN EDIT: lets leave it at that.

--Greg

[Hungry4info]

Juramike, thanks for that. That puts it into something I can grasp

About the public, though I agree that one should put it in a way that the average Joe will understand, the 150 billion BBQ cook-outs is a bit hard to grasp mentally, compared to, say, "enough to fill lake [name] [number] times." Sort of like saying that my house weighs as much as a trillion paper-clips would be less preferable to saying how much more it weighs than my car or something.

The discovery of propane is neat (even at 58 ppb), though I thought propane was already detected at Titan?

[centsworth_II]

About the public, though...

I don't think the objective in the second paragraph is to give a real idea of how much propane there is, but to at least fix the idea that propane is there. Here in the US, with the foremost thing on many peoples' minds being the labor day weekend and the last big cookout of summer, the propane grill reference is a natural. Many casual readers won't get past the second paragraph. The only thing that would cause them to remember the mention of propane at all would be the reference to the grill.

For those more interested, the rest of the article gives more detailed information.

[Ron Hobbs]

The discovery of propane is neat (even at 58 ppb), though I thought propane was already detected at Titan?

Interesting. I did a quick Google search, expecting to find just information on the Cassini finding. The 4th item was this:

Propane on Titan, Astrophysical Juournal, 2003, Nov. 1

Roe et al. claim "the first observations of propane on Titan that unambiguously resolve propane features ..."

Is propane on Titan going to be like water on Mars; discovered every time a new instrument finds it?

[centsworth_II]

Is propane on Titan going to be like water on Mars; discovered every time a new instrument finds it?

Why do we insist on maligning and nit picking every news item? The situation is clearly stated in the article linked in the opening post:

"This gas of many terrestrial uses was first discovered in Titan's atmosphere back in 1980 when NASA's Voyager 1 spacecraft flew past the Saturnian system. Over the years, both ground and space-based instruments have added to the research, but accurately quantifying the amount of propane on Titan has proved elusive."

[remcook]

The elusiveness is mostly caused by the lack of (Earth-based) laboratory spectra of propane at relevant temperatures in the past, not so much by the measurements themselves. There should be about 0.5 ppm of propane in the stratosphere, but I can't access the Nixon paper at the moment...

[Webscientist]

They do give this specific estimate: "We estimate there are nearly 700 million barrels of propane on Titan, said Nixon. "That is enough to fill six-billion 20-pound tanks of liquefied propane gas."

Regarding the abundance of Propane (700 million barrels of propane), I made a few calculations to get a better idea:
700 millions barrels=11 291 110 m3
If this amount of propane (C3H8) appeared in a lake of pure propane on Titan's surface, it would only represent the equivalent of twice the size of "Lac de Saint-Cassien" ( Var, France ) which has a mean depth of 16 meters and a surface area of 3.7 km².

Therefore, I guess that the potential for lakes of pure propane on Titan's surface is very unlikely.
Traces of propane in the ethane/methane lakes of Titan ? Answer before the lander?