Monday, July 25, 2005

New Scientist: Has Huygens found life on Titan?

Now, for the crank story of the day. New Scientist has a story online regarding the possible existence of hydrogen-breathing microbes on the surface of Titan. The story is based on a preprint of an article to be published in Icarus by Chris McKay and Heather Smith. They discuss the possibility that microbes on the surface of Titan could derive their energy from breathing hydrogen and "eating" acetylene that falls from the upper atmosphere on to the surface. They further suggest that depletions in both hydrogen and acetylene near the surface may betray the presence of such organisms. These types of measurements were made by the GCMS instrument on Huygens in January. Hasso Niemann, the PI for the GCMS instrument, stated that the hydrogen abundance is still being worked out and that an upper limit should be arrived at soon.

Of course this article fails to explain how you get around a 94 K surface temperature at the landing site....

11 Comments:

Anonymous jerry said...

I cringe at beating this to death, but I really do think, amoung other things, that the heat shield failed to separate until about 20 minutes later than expected.

With or without odd-ball physics, the parachute was sized to provide a big enough jerk to shake the heat shield free. If the shear winds are as advertised (or Non-Newtonian physics apply) there is no data assuring that the heat shield separated as planned.

This would explain why the probe temperatures stayed so warm so deep into the atmosphere, and why aromatic hydrocarbons, such as benzene were found in aboundances not detected by Cassini - phenols and similar compounds are often release in the pyrolysis of heat shield materials.

In the first audio radar sound track released by the ESA, there was a very peculiar periodic 'ring down' near the end of the track, that sounded exactly like a coin spinning down on a hard surface. Subsequent releases of the sound track filtered this effect out, but I wonder if it was real or an artifact: Real would mean the heat shield was spinning down on the surface of Titan very nearly directly beneath the probe.

...There are also several images of a spherical shaped object that moves from lens to lens early in the descent sequence - I call these the 'Mooning Titanian', but I think it is the heat shield, falling away from the bottom of the probe very close to the surface, and then careening off to the side, possibly striking the probe on the rebound.

...the reluctant cosmologist.

7/25/2005 10:31:00 AM  
Anonymous Pioneer said...

If that was the case, wouldn't the downward-pointing camera's view have been blocked?

7/25/2005 12:01:00 PM  
Blogger Bruce Moomaw said...

Hre we go again:

(1) As "Pioneer" says in that case the early images would have been blocked by the heat shield.

(2) That overabundance of complex organics very high in Titan's atmosphere was also seen by Cassini's mass spectrometer during its flybys of Titan -- in fct, it's much more noteworthy at altitude above those which Huygens' GCMS analyzed.

(3) If Huygens' mildly warmer-than-expected internal temperature was due to the fact that a hot heat shield remained attached for some time, it would also obviously have affected the exterior air temperature measurements from HASI -- which were virtually exactly what was expected.

(4) That "pinging" radar sound track was not a recording of actual sound, but of RADAR echoes translated into sound. It was also very greatly sped up; at the time when your "ringing" first apears, Huygens was still thousands of meters above the surface.

Time to stop beating this, Jerry.

7/25/2005 11:31:00 PM  
Blogger Bruce Moomaw said...

As for Mckay and Smith, I believe what they're suggesting is that Titan might have SUBSURFACE microbes, down at the deeply buried liquid water/ammonia layer (whose existence seems increasingly more likely). They'd be getting the acetylene from the surface indirectly, due to geological vertical transfer processes (which are likely a lot more active on Titan than on, say, Europa, where the idea has also been set forth that microbes in the subsurface ocean are getting radiation-manufactured surface chemicals for nutrients). Right now this speculation is a pure Shaggy Dog story, but it is by no means automatically ridiculous.

7/25/2005 11:35:00 PM  
Anonymous Jery said...

1) 'As "Pioneer" says in that case the early images would have been blocked by the heat shield...'

Some of the early images may have been blocked!

Look at the raw images,

http://esamultimedia.esa.int/docs/titanraw/file5a.html

pages 4-11. It is difficult to tell what-is-what, because many of the early frames (Most pages 1-3, and page 10) are clearly rap-arounds, taken after the landing.

(Without time stamps, any image interpretation is very speculative.)

But ALL of the down-facing images on page four are very weak gray scales. Allowing for the jpeg processing that occurred before transmission, these images could be very dark - blocked!

The 'Mooning Titanian first shows up on page five, and there is no other detail in the bottom lens between pages five and ten, where obvious 'post-landing' images reappear. The 'Titanian' shows up again on page 11, Sliding across all three imagers, but discernable features do not appear in the down-facing camera again until the middle of page 12.

Extremely low contrast clouds, or extremely low light?

Is the "Mooning Titanian" the heat shield? Hiding the surface of Titan until it slide away on page 11? If not, what is it?

2) The salient question here is are the same hydrocarbons idendified by Cassini and Huygens? (You are correct, Bruce, I could be completely up-in-the-night on this one, because I do not know.)

3)I have not seen an exterior or interior temperature vs time plot- but I don't understand how the temperature could vary 'as expected' when the speed of sound did not - there should be a direct correlation between the speed of sound and the temperature-even more so if both the pressure and temperature curves are nominal. Very unphysical.

4)Yes, the 'ring down' I described could have been sped up from the actual event time, I have yet to see radar altitude vrs T-zero entry time plots - perhaps this is the 'small hill' you described, but the 'ring' sounded periodic - artificial - I suppose if Huygens was swinging or rotating in a tightening spiral over a natural feature, it may have induced this type effect. Fascinating!

It is interesting to see how prior expectations shape the interpretation of data, including my own. To someone who is certain there is life out there, the surface of Enceladus has to be a gold mine.

Rocks!

7/26/2005 09:24:00 AM  
Blogger Jason said...

While I love lively debate, this is getting a little out of hand:

1) You don't see anything because of the HAZE!! If the heat shield where there, it would be black. You're right, though, having the images out of order and in some cases missing an frame out of the triplet, does make it difficult to see what is going on. But the fact the GCMS and DISR instruments got data at all during their entire mission profile again tells us that the heat shield jettisoned as it should, at the right time. Again, I have heard no suggestion from anywhere other than from Jerry here that the heat shield didn't jettison at the right time or that the descent profile was anything but nominal, other than the horizontal wind speed being less than expected in the lower 40 km of the atmosphere and the haze extending down to the surface.

The dark spot you refer to on page 5, is a condensation droplet in three images that are exactly the same image. The first set of images are post-landing images because there were more than 1000 images taken, more than expected and thus started wrapping in their scripts to 0.

2) I remember Benzene.

3) I have a temperature and pressure plot produced from Huygens data here. They are screen shots from a press conference so they are a little blurry, but the left plot is a pressure profile from HASI. The vertical axis is altitude and goes from 140 km at the top to 0 km at the origin. The horizontal axis is pressure in hPa and ranges from 0 at the origin to 1500 at the right end.

The left plot is the temperature profile from HASI. Again the vertical axis is altitude and goes from 140 km at the top to 0 km at the origin. The horizontal axis is temperature in Kelvin and ranges from 60 K at the origin to 180 K at the right end.

Again, sorry for the blurriness, but this is the best plot I have from Huygens available to me. Again, both plots are consistent with expectations both in altitude and temperature. I don't know how this squares with speed of sound, but this is the data we have on hand now.

4) I'll need to listen to the radar sound again.

5) Why would the appearance of the surface of Enceladus be a gold mine to those certain there is life out there? I don't understand. How does life have anything to do with fascinating features on Enceladus?

7/26/2005 10:37:00 AM  
Blogger Bruce Moomaw said...

(1) I was wrong about the sound track you are apparently referring to being produced by the radar altimeter -- that was only one such track released at that press conference. There were one or two actual acoustic-noise soundtracks released there, too, and presumbly you're referring to one of them -- but the team has not noted anything unusual turning up on any of them.

For a complete compendium both of these and of later, better-processed versions of the acoustic sound track, see http://www.planetary.org/sounds/huygens_sounds.html . Then you can tell me which track you're specifically referring to -- but, again, there seems to be absolutely nothing unexpected, or even interesting, on any of them. Titan, as expected, is a very quiet world -- and in any case the transformation of the HASI microphone's noise-level measurements into sounds is very indirect and unrealistic.

(2) At that press conference, no sound track was released of the echoes from the separate sonar sounder (which only began detecting the surface several hunded meters up). Instead, a graph was shown of the data from this instrument. Unfortunately, this graph seems never to have been put on the web -- but it visually showed a very clear double echo during the last part of the descent, which turns out to have been due to the fact that during its last few dozen meters of descent Huygens drifted over a 4-meter bluff, so that the sounder's broad beam was echoing off terrain at two different heights. (I don't know yet whether the radar altimeter also detected this bluff.)

(3) The HASI team leader stated explicitly at that same press conference that both the pressure and temperature graphs with altitude were virtually exactly as predicted in advance on the basis of Voyager and Cassini data -- indeed, it seems to have been one of the few respects in which Titan met advance expectations precisely.

7/26/2005 06:04:00 PM  
Blogger Bruce Moomaw said...

For a good brief summary (and graph) of Cassini's mass spectral analysis of the organics in Titan's extremely high-altitude atmosphere, see the last part of http://www.planetary.org/news/2005/cassini_titan05_results_0504.html .

7/26/2005 06:07:00 PM  
Anonymous Jerry said...

Thanks Bruce,

The clearly NATIVE complex hydrocarbons represent a great puzzle: Why are they there, and where did they come from? If the presences of these molecules was the only fact we knew about Titan chemistry, the first hypothesis would be there is indeed some form of life on Titan!

(NO! I do not think that is likely to be true - )

I haven't tried to do anything with the acoustic plots, but we have played a lot with the radar audio. I can't correlate radar pulse or space widths from the audio with Bird's graphs, so any interpretation I happen upon is blind and somewhat futile until the full data release. Likewise, pressure and temperature data plotted against entry time, rather than altitude, would be very helpful.

The 'ring down' I described is still in the ESA version: http://esamultimedia.esa.int/images/huygens_alien_winds_descent_radar.mp3

53 seconds into the track - it is very low level - tight headphone stuff, and I'll admit it does not sound as much like a 'spinning coin' as I heard (or imagined) in the middle of the night a day or two after the landing. Peculiar, to say the least.

7/28/2005 09:43:00 AM  
Blogger Bruce Moomaw said...

Well, since it's radar (and on a tremendously sped-up sound track, which covers the entire 2 hour 27 minute descent), it certainly isn't due to anything like the heat shield spinning. The initial switchover from a quiet first part of the sound track -- with only occasional pulsing clicking noises -- was explained at the press conference as being due to the fact that this is the recording of the data from the radar altimeter BEFORE it locked onto the surface. The fast crescendo of stuff during the later part is the actual echoes off Titan's surface.

7/30/2005 10:28:00 PM  
Anonymous Jerry said...

According to the ESA: "This recording was produced by converting into audible sounds some of the radar echoes received by Huygens during the last few kilometres of its descent onto Titan." - minutes at most, not hours

They do not not mentioned whether this audio is time-compressed, but a compression factor of 5 or 10 would actually make the period of the sound more compatible the ring-down of an object the size of the heatshield.

However, on the same page the ESA explicitly states that the microphone data was both edited and compressed.

http://www.esa.int/SPECIALS/Cassini-Huygens/SEM85Q71Y3E_0.html

The radar plots I have seen in presentations show meaningful radar data for less than one hour. The time is charted only in unreferenced relative time, and there are drop-outs and a great deal of noise in BOTH radar channels.

The way this altimeter data is presented, with altimeter lines over-layed by a thick unrelated line; and no absolute time scale, doesn't inspire confidence in the time-at-altitude profile.

I am still HOPING someone will publicly post time-stamped altimeter, sonar, temperature and pressure data, without which it is impossible for us to resolve this issue on Jason's blog.

Sorry about the clutter, Jason, but if the imaging teams have been assured the descent profile is 'rock solid', the DWE data should be presented in a way that demostrates this, and includes reference times and error bars.

On another, but related subject, the graph of the accelerometer associated with the penetrometer stablizes after penetration at a value of about -0.5 g(Earth). Shouldn't it 'zero' at about 0.17 g (Earth)? What is with that?

8/05/2005 12:16:00 PM  

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