Printable Version of Topic

Posted by: BruceMoomaw Jun 23 2005, 12:11 AM

In its latest print issue, the Planetary Society reported the following, in connection with GROZA (the attempted thunder-detecting microphone on Veneras 13 and 14):

"The Planetary Society recently contacted GROZA's principal investigator Leonid Ksanformaliti, an old friend of the society from the Space Research Institute in Moscow, and asked if these data had ever been converted to sound. They had not. At the Society's request, he generously pulled out the old data and has begun the process of converting the data to sound. These Venusian sounds will soon appear on the Planetary Society's website."

Well, Jeffrey Bell -- AKA Mr. Sunshine -- now reports to me:

"Argh! Unpleasant memory blast from former life! Resist powerful urge to smash expensive flat monitor!

"I had some dealings with Comrade Ksanfomaliti back at the time of the PHOBOS fiasco in 1988. I wouldn't trust him to clean my air conditioner. He was one of those all-purpose scientists who made an instrument for every mission, always a different instrument in a different field, and always a disaster. He seemed to have some powerful political influence that kept him in the program. Of course the PS
would latch onto this guy, with their unerring nose for incompetence."
_____________________________________

Well, that's OK -- if no interesting Venusian sounds turn up on those tapes,
the Russians can always fake some. (After all, their "scientific space
program" now consists entirely of ways to continue sponging off NASA's Space
Station budget.) Be on the lookout for Venusian "thunderclaps" that sound
suspiciously like someone shaking a large sheet of tin.

Posted by: Richard Trigaux Jun 23 2005, 07:26 AM

Besides their scientifical interest, sounds carry still much more emotional impact than images or informations. So I think it would be very interesting to hear these sounds, if there are some.

But I remember the famous "Titan sounds" from Huygens, which were not sounds, but just sonograms converted to sound. Are these venusian sounds the same?

Anyway remember that venusian clouds are very high, 60kms, even higher than Titan clouds. When on Earth Lightning sound is seldom heard further than 30kms.

I heard once that Oppy and Spirid had microphones, or at least that such a device was debated during design. Is it true? (Dream not) And if true, did they recorded something? We could perhaps hear whirlwinds. Or meteorite booms. O something unheard before.

To HEAR something from another world!!

Posted by: edstrick Jun 23 2005, 08:30 AM

My recollection from published papers in translated Soviet Journals was that acoustic signal amplitude was recorded at frequent intervals during descent and during brief spots if descent-science instrumentation that interrupted surface science transmission. If I recall correctly, more or less constant high amplitude noise was present during descent and signals were more or less below detectable levels on the surface. I don't recall if any landed hardware mechanical noises were reported.

I think what was transmitted was just the total signal strength during a short period, not the waveform at all. The most you could get out of such data would be very limited. I don't think the Huygens data is much better. I'd have to dig out the atmosphere structure description, but I don't think they recorded any real spectrum of the acoustic noise, maybe coarsely sampled amplitude at (perhaps 4 or something) discrete frequencies.

I'm very underwhelmed by the "Sounds of Titan" recordings that were synthesized and released.

Posted by: Richard Trigaux Jun 23 2005, 09:54 AM

I did not found them back in the ESA site, but the Titan "sound" records were sonograms, giving coarse spectra of frequency, sampled or averaged every 2 seconds, and tremendously compressed to only some 50 bytes per second. To "retranscript" this in sounds requires a white noise source and an equalizer, but in this way we could not distinguist a car noise from an opera. I did not expected to hear birds songs on Titan, but I would have enjoyed very much to hear at least wind whirling around the probe during descent, and a splash noise at landing, as human ear can immediatelly distinguish if the landing is into sand, stones or mud. Afer there was no sound, but we could have got the luck to hear wind, waves or liquid streaming. Or perhaps thunder, as expected.

Why such a compression rate? Because the energy in Huygens (necessary to have large bandwidth) was very restricted. It was probably the same with the russian landers on Venus.

This arises the question of energy in exploring far planets. No sun, long voyages, made nuclear fission or radioisotope cells the only known solution. But to speak frankly I do not like this, we already polluted our planet with this, so we could at least avoid to contaminate all the solar system. The only prospective solution would be small fusion cells.

If we consider the success of Spirit and Opportunity, we note that it is largely based on the availability of several radio relays in orbit, with plenty of solar energy. (and cameras to inspect the further path on the ground). Similarly exploring Titan would first require a large telecommunication satellite in orbit with kilowatts of power, a supercomputer and a life expectancy of 100 years.

Posted by: edstrick Jun 23 2005, 10:57 AM

Things that COULD get turned into real sound:
Viking 2's seismometer could operate briefly in full waveform recording mode. There was also a very compressed mode where it recorded peak amplitude and number of zero-point crossings of the wave in each interval, and a third supercompressed form.

The full sampling rate data could be turned into wind and mechanical activity noise, frequency shifted upwards into the human hearing range. 3-channel stereo, too!

Much the same could be done with the Apollo seismometer data: 3 Long-period axes and 1 vertical short period channel.

Also, the Apollo 14 and 17 Lunar surface experiments, where a geophone array was set out and explosive charges were set off at varying ranges.

You could also "hear' the Surveyor lunar landings: Each leg had strain-guages with a very high readout rate to catch the leg-surface interaction during touchdown. THUMP........ Thump... thump-ump-ump..jiggle-jiggle..... (They rebounded a few inches at the first and second toucheowns)

Posted by: djellison Jun 23 2005, 11:45 AM

I suppose the accelerometers on Pathfinder and MER could be used to so SOMETHING like that - use some white noise and use accel as amplitude

Doug

Posted by: Richard Trigaux Jun 23 2005, 05:13 PM

We could that way record the "noise" or MER's movements. Perhaps the noise of wheels grasping on rocks. But are the accelerometres sensitive enough to record seismic activity, or even wind activity? Enough bandwidth?

A true seismograph is not a small device, so they did not placed one on the MERs. Anyway seisms may be rare on Mars. But perhaps they will try what was done for the Moon: place several seismometres, and send a cruise stage slamming on the ground, to have an artificial seism.

Posted by: edstrick Jun 23 2005, 06:24 PM

Seismometers are pretty useless on rovers. Up in the air <sensative to wind>, not mechanically well coupled to the ground <signals are modified as they travel through the suspension system>, at a location that keeps changing <much interpretation REQUIRES the local propagation of signals doesn't change>, and is utterly irrelevant to rover science.

Always remember, when we grumble "why couldn't the rover carry..."... (which I do), the rovers are the biggest and most crammed with instruments rovers that could fit on the Delta launch vehicles that launched'm.

Posted by: BruceMoomaw Jun 23 2005, 11:44 PM

The thing to do with seismometers is to put 'em on a network of multiple stationary landers simultaneously -- period. You can't even do all that much even with one on a stationary single lander; on rovers they're hopeless. And I agree with Doug Ellison that this -- rather than trying for that ExoMars biorover which would supposedly be both much lighter and more scientifically capable than MSL -- is what the ESA should be doing at Mars; it would be very easy for them to take over the Netlander program from the French.

We also need such a network for meteorology, which appears growingly important to provide preparatory safety data for future landers -- and if subsurface radar sounding from orbit proves impractical at Mars, such network landers, using seismic and/or magnetotelluric sensors, will also be the only workable way to look for subsurface liquid water.

Posted by: Richard Trigaux Jun 24 2005, 04:49 AM

... and to the inner structure of the planet.

The structure of Earth is understood, with its "liquid" inside, different layers, plate tectonics, etc.
The structure and history of the Moon is understood - a former liquid inside led to the gigantic lava flows forming the "seas" billions yeras ago, and since everything is frozen.
Venus may have a similar structure than Earth, except that, for some reason, there is no plate tectonics.

But Mars? It rather ressembles the Moon, with a former "liquid" inner layer. But, as the study of magnetic field showed, there is no "liquid" inside left today. However there are volcanoes. And still active, after recent datations, even if there is an eruption every 50 million years. But, if there is no inner "liquid" core as on Earth, how the magmas are generated?

Recent studies (see http://www.psrd.hawaii.edu/Jan05/MarsRecently.html, where there are several interesting pages) there may be two sources for martian magmas. We have no idea of the inner martian structure, it may even be assymetric.

So a seismometre network is worth trying, to the condition of doing things correctly, with enough network.

Posted by: dvandorn Jun 24 2005, 05:19 AM

A seismometer network is an absolute requirement to understanding Mars' inner structure. The problem with the type of emplacement Viking attempted was that the instrument was mounted to the lander, not in actual, physical contact with the ground.

What with the current state of the art in remote manipulation, do y'all think it would be worth the extra weight to deploy seismometers by unshipping them from the landers and actually emplacing them onto/into the soil? I'm guessing it would require some kind of deployment arm -- but depending on the rest of the science package on a lander (even a netlander-scoped device), such an arm would be useful for other tasks, as well.

-the other Doug

Posted by: edstrick Jun 24 2005, 08:51 AM

The way to deploy a seismometer network is with penetrators, like the two that will be on the Japanese Lunar-A mission, if it every flys.

The Mars-96 mission carried 2 penetrators and 2 hard landers, if I recall correctly. It was total lunacy to send the half-assed Beagle-2 (which could have been a good mission with decent management, quality control and funding) instead of a Mars-96 design penetrator on hard lander on Mars Express.

No..... not lunacy... that'd be a lunar mission. Mars Madness?


Penetrators give maximum coupling with the crust and minimal wind interference.

Posted by: Richard Trigaux Jun 24 2005, 10:18 AM

About sounds of Venus, and generally sounds from outer space, I recomment this link: http://64.233.187.104/search?q=cache:kLZGjtcmTYEJ:www.astrosurf.org/lombry/audiofiles-pulsar.htm+vela+pulsar+sound&hl=fr and other pages on the same site, magnetosphere sounds, satellite sounds, etc. Some are really astounding, other are moving, others are strange or beautiful... Especially pulsar sounds are really unearthy, and, surprinsingly, fast pulsars create a kind of everplaying symphony...



In a general way we should not hide behind rational or utilitary motives when doing science and space exploration. It is the full play of our consciousness exploring the universe. I have no use of Mars, but I really want to know what is there on Mars. The sound of a whirlwind is worth the price to send a microphone.




A strange experiment would be to convert seismic waves into sound. Forinstance, we take the recordings of two seismometres on the Moon, when they sent the cruise stage slamming on the ground, and we send these sounds in a stereo headphone. Given the ability of the human ear to analyse sounds, there may be science data do extract for this, but especially we should hear the Moon resounding like a cymbal under the shock!

Posted by: Bob Shaw Jun 24 2005, 11:22 AM

Well, there are presently two nice, stable platforms sitting on the surface of Mars, doing not a lot. It's not beyond the bounds of engineering to attach a hard-lander style seismometer package to a lander module - even a SkyCrane - and implant the things with a small solid-rocket charge (once Mr Rover has cleared the site!).

Of course, it all weighs...

Posted by: djellison Jun 24 2005, 12:00 PM

Think something could be done with a DS2 type mass/volume budget?

Doug

Posted by: Richard Trigaux Jun 24 2005, 04:57 PM

The landers would have need a radio, solar panels, etc...

Posted by: 4th rock from the sun Jun 25 2005, 12:58 AM

Hi Edstrick,

Is this data avaliable on the net? Some sort of ascii file?
If it is I can give it a try ;-)

Posted by: edstrick Jun 25 2005, 08:18 AM

The Viking and Apollo data *MAY* be available on Planetary Data System geophysics or planetary science nodes. The Viking data was a pretty small volume because of data transmission limitations.

The Apollo data is much more extensive and has been extensively "worked" by a variety of international seismic research teams, I (think) that there have been a number of interesting papers by a (I think) Japanese reararch group who's used more advanced software and faster computers to find weak moonquakes in the data. After all, they are <if they can ever launch it> going to fly a lunar orbiter with 2 penetrators containing seismometers. They need experience working with lunar seismic data.

Posted by: Decepticon Jun 25 2005, 12:49 PM

One sound I would love to hear is Europa's ice surface hev up and down.

Living in Ontario Canada during the winter most of the smaller lakes freeze over. When ice fishing you can sometimes hear the massive slabs of ice cracking and rubbing together. Very eerie sound.

Just imagine being part way threw its Ice crust and hearing this sound on a foreign moon.

Posted by: Richard Trigaux Jun 25 2005, 02:24 PM

This needs a high frequency seismometre on Europe.

Posted by: edstrick Jun 25 2005, 08:19 PM

We do *NOT* know how well the Europa ice-crust is decoupled from the underlying rocky crust. Two things that have been massively ignored by press coverage of Europa are as follows:

1.) The geological activity patterns imply a thickening of the crust and declining activity patterns in each area. Thin-ice-pack breakup and rifting, followed by narrow cracking and/or hot-spot formation.

2.) Post Voyager models suggested that tidal heating in Europa may be inadequate to keep a steady state ocean liquid under a crust, but there may be cyclic heating and activity. The crust largely freezes, tidal energy loss is low, and the orbit builds up eccentricity under pumping from Io and Ganymede. That pushes up tidal heating rates till the crust starts to soften and you get runaway heating, massive melting, an outburst of activity, and the orbit rapidly circularizes, shutting off the heating and starting the next cycle as the crust freezes.

I think the geology is entirely consistent with such models. The one thing from Galileo that pretty much proves the crust isn't frozen down to rock is the magnetic field data that shows there's a conductive, probably brine layer, in the near-subsurface. Probably the crust concentrates salts and acids as it freezes till it can't freeze any deeper.

There's probably a lot of this in the technical planetary geology literature in the last decade that's totally below the horizon of press-release driven reporting which is most everything we see with few exceptions, like Bruce Moomaw's reporting.

Posted by: Richard Trigaux Jun 25 2005, 09:31 PM

As a matter of facts when salty water freezes, it concentrate salt. And thus, the freezing point gets lower. So that an equilibrium is reached with a certain salt concentration.

But to have a cyclical activity, in your model, needs to have the water completelly frozen.

Perhaps Ganymede is more salty than Europe.

My idea about Europe is that the activity is rather due to accumulation of volcanic gasses from the rocky core. The gas dissolves in the water, until enough concentration is reached, and then the limnic eruption breaks the ice crust, lefting the blocks chaos which are observed in many places.

You speak of the decoupling of the ice crust from the rocky core. Two extreme cases are possible:
-The water is completelly frozen, we have an ice shield allowing eventual ice mountains to form
-there is a completely free water layer, and ice mountains cannot form

intermediary cases would be:

-the ice layer is free, but can be occasionally blocked by the summit of some rock mountains. In such case, the whole ice raft could break
-The ice layer is not free, but a thin water layer allows it to flow like a glacier.

The point of Decepticon was to hear the creaking of the ice crust, thinking that it floats on liquid water. To hear earthquakes in the underliying rock layer is another story, especially if there is a liquid layer. This is not impossible, this situation occurs on Earth, where seismic waves can travel through the liquid core, or through magma chambers. But I never heard of seismology through the ocean, frozen or not. There is a huge difference of density between water and rock, which makes the coupling low.

Posted by: edstrick Jun 26 2005, 06:55 AM

A network of small penetrators with seismograph/geophones + magnetometers + heatflow sensors would be enormously valuable.

Ice-sounding radar has enormous potential at Europa, but from an entirely different radar methodology, so does radar interferometry. The sort of thing that takes dual radar images <as on the shuttle radar topography mission or with the european ERS-1 and 2 satellites flying nearly identical groundtracks> and generates an interferogram from the data. Interference fringes show down to millimeters of relative ground deformation with some 10 meters horizontal resolution. Europa's crust, whether grounded, partially free, or free-floating, *MUST* flex under orbital tidal flexing and should be visible in interferometry data. I know the studies have been done in the context of detailed geophysical models of Europa for what amplitude effects are expected, but I don't know the results of the studies.

There's more than one way to skin the Europan cat <catfish>, all of them well give different views on crustal thickness and dynamics and be of complementary value... too many to fly on single missions, especially limited ones like the pre- and post-Prometheus missions using chemical propulsion must be.

Posted by: Richard Trigaux Jun 26 2005, 07:29 AM

Why not sonar sounding, or provoked explosions? As on Earth with seismometres, we should detect easily a liquid layer.

Such penetrators could be VERY small, just an arrow with a piezo detector and a radio. playback of interesting events would require little power, but it would also require a permanent satellite around Europa.










I noted tremendous images of volcanoes or seisms on Earth, with interferometry fringes showing deformations of only centimetres. We could see Europa "breathing" with tides. Perhaps active faults, if there are.

If there are points where the ice crust is linked to the rock core, these points should be very visible as lower deformation points surrounded with very active zones. A case I did not noted is that the crust would move relative to the rock, while touching it in some points, generating friction on these points. If this happens, or happened in past, we should find volcanoes or mountains with a flat summit (ice movement being the most efficient erosion mean).

Posted by: tty Jun 26 2005, 06:17 PM

Seismology does work through the Earth's core which is liquid and the low-velocity layer that is partly melted. However note that S-waves don't propagate through a liquid but P-waves do, so an analysis of the waves received from a number of seismic events at known distances from a seismometer will yield a profile through Europa. A known azimut would also be valuable if there are local differences in the profile.
The problem with this is that it requires either a network of seismometers or impacts/explosions at known locations relative to the seismometer. Either way means a lot of weight to be moved to Europa.
The most cost-effective solution would probably be one seismometer and a number of small nuclear charges (which can weigh less than 100 lb each). However I imagine the political and ethical problems would be considerable.

tty

Posted by: Richard Trigaux Jun 26 2005, 09:52 PM

useless: simply projecting some weights at high speed would produce the same effect, as on the Tempel comet.

As for the pollution, it is unacceptable on Earth, and, for weaker reason but still strong enough, also inacceptable on other planets. Remember that many expect that Europa may host life, and, until we have not found evidence of the countrary, for instance after drilling into its ocean, we should treat it as an inhabited world. Even lifeless, we cannot expect what we shall do -or even be- in millions of years, while the nuclear wastes will be still hot, perhaps we shall have some need of Europa. With my opinion having engaged Earh in millions of years of storing and monitoring nuclear wastes was at least not good management, but this is off topic on this forum... and in too many places elsewhere.

Anyway your idea (one seismometre, several explosions) seems fine, and it could be done with one lander, and later a rocket sending a well timed string of bullets.