Phil StookeIf Venera 10 landed in the hills, I might expect a landscape similar to that at Venera 9's site, lots of blocks where the rock has been broken by dense patterns of faults. But it didn't see that. Tomorrow we will see what the second image of the surface of Venus revealed.
#venus #venera10
OK, what did Venera 10 see? This is the link I gave earlier to Don Mitchell's page about Venus images:
http://mentallandscape.com/C_CatalogVenus.htm
and here is the raw Venera 10 image:
http://mentallandscape.com/C_Venera10.jpg
His expert processing gives us this:
http://mentallandscape.com/C_Venera10_Processed.jpg
(raw, gaps filled from second image, remaining gaps filled by interpolation)
Both of these Venera landers carried a second camera on the opposite side of the lander, but in each case it failed to operate.
#venus #venera10
Here is an old Soviet version of the Venera 10 image, a bit too contrasty so details get lost especially at the horizon. But what we see is different from Venera 9's boulders. This is a nearly flat area with platy slabs of rock interspersed with darker gravelly soil. One of the rocky slabs is cracked. The two objects are a densitometer to measure surface hardness and a lens cover ejected from the camera after landing.
#venus #venera10
#venus #venera10
We have seen the Venera 9 and 10 panoramas, but take a look at this from the Planetary Society:
https://www.planetary.org/space-images/rectified-vs-original-venera-9-and-10-panoramas
(presented without any explanation on that page). This version has more detail:
https://www.planetary.org/space-images/standing-on-venus-with-venera-10
These are artistic re-workings of the panoramas, rearranging bits of the images to create a more understandable view. I show them because they pop up in image searches and are often misrepresented as original images.
#venus #venera10
My pal and occasional co-author Ted Stryk made them - with good intentions, to help people get some idea of what Venus looks like on the surface, because the Russian panorama format is harder to understand. I'm not sure it is really a good idea to do this just because people can get the wrong idea. You do have to be careful taking anything at face value on the internet. Look at me for instance. I could be a total charlatan. (buy my books!!!)
#venus
#venus
Here is a rather crudely reprojected version of the Venera 10 panorama. Once again we don't know the orientation of this map. The lander ended up on a patch of flat rocky slabs, and there seem to be similar rocky areas on each horizon, left and right. Between them are darker gravelly surfaces. The big remaining question would be - where is this in the Magellan radar image we saw earlier? I think this is in the plains, but we can't say exactly where.
#venus #venera10
#venus #venera10
Around the time of Veneras 9 and 10, Earth-based radar mapping was improving. This map is a composite of two radar datasets from this period, reprojected to the azimuthal projection I always use for global maps.
One paper was this:
Campbell, D.B. and Burns, B.A., 1980. Earth‐based radar imagery of Venus. Journal of Geophysical Research: Space Physics, 85(A13), pp.8271-8281.
The other... I think it was in Geophys. Res. Lett. but I haven't tracked it down yet.
#venus #radar
This all looks very nice, but we still don't know much about what is being seen. Take the very bright area Maxwell at the top - is it a mountain range or a canyon like Juventae Chasma on Mars? We only know it's rough. (Now we know it's a mountain) What about the dark smooth area with a bright rim west of Maxwell? Is it a plateau or a depression?. These images suggest lots of tectonic activity but interpretations are very uncertain.
#venus
#venus
The next mission to launch to Venus was NASA's Pioneer Venus mission, with two components. Here is a NASA look back on its 40th anniversary:
https://www.nasa.gov/centers-and-facilities/ames/40-years-ago-pioneers-encounter-venus/
The mission consisted of an orbiter and a multiprobe carrier, launched separately. We will deal with the orbiter first, then look at the probe mission. The image is one of many taken by the orbiter, and here are several more:
https://commons.wikimedia.org/wiki/Category:Photos_by_Pioneer_Venus_1
At first we knew absolutely nothing about the surface of Venus. Then we saw bright radar-reflective spots, but we didn't know if they were high or low or had any relief at all. It took Pioneer Venus to give us our first topographic dataset using a radar altimeter (far less precise than a laser altimeter, but lasers won't work at Venus). Here is an early map, and it comes with the first feature names. Now we can see Maxwell is a high mountain.
#venus #pioneervenus
#venus #pioneervenus
This link:
https://www.lpi.usra.edu/resources/venus_maps/
gives you lots of Venus maps by USGS, but for today we want the top one:
https://www.lpi.usra.edu/resources/venus_maps/1324/I-1324_150.jpg
The map in the previous post was hard to read but this is much clearer. There are 2 obvious continent-scale highland areas (remember Venus is about as big as Earth) Earth. 10 degrees of latitude or along the equator is approx. 1000 km for scale. The poles were not mapped, but our modern view of the planet is becoming clear.
#venus #pioneervenus
Pioneer Venus also made a very low resolution radar image of the equatorial region of Venus. If I can find it I will post it tomorrow. But let's look now at the probes it dropped into the atmosphere. There were 3 small probes, one on the day side of the terminator, one on the night side, one in the north near the Maxwell radar feature (not known during mission design). A large probe and the carrier spacecraft ('bus') also entered the atmosphere.
#venus #pioneervenus
#venus #pioneervenus
Here is a map showing their target points and actual sites. They were pretty close to the targets. These were studying the atmosphere, not the surface, and were not expected to survive landing (they just fell, no parachutes except for the large probe). However, the Day probe transmitted from the surface for over an hour and the night probe for 2 seconds (it probably fell over). The bus had instruments too and gave data until it burned up.
#venus #pioneervenus
#venus #pioneervenus
Here are a set of close-up views of the Pioneer Venus sites. First the large probe (which operated down to the surface) and the bus or carrier spacecraft which burned up in the atmosphere (having no heatshield). And surviving fragments of the bus fell in the area indicated. The close views at right (100 km across) show the large probe fell in a region of extensive lava flows and the bus broke up over over a heavily faulted region.
#venus #pioneervenus
#venus #pioneervenus
Here are the remaining 3 Pioneer Venus probe sites. Remember that these were targeted for atmospheric, not geological observations and the geology was unknown. Only the Day probe survived on the surface for any significant time. All 3 sites are lava plains crossed by ridges and fractures, a very common landform on Venus. The night probe is close to Maxwell Montes - how interesting it would be to land on top of it...
#venus #pioneervenus
#venus #pioneervenus
The temperature and pressure would be significantly lower on top of Maxwell - still hellish for us but a little bit less hellish than elsewhere, maybe allowing a longer survival time on the surface. The composition of these bright mountain tops seems to be different as well, so it would be interesting to probe it. But there are more exciting targets - the favourite goal for future landers is the tesserae (fractured uplands) which may be bits of older crust.
#venus #pioneervenus
#venus #pioneervenus
I am a cartographer, so all I want to do all day and half the night is mark things on maps. Pioneer Venus orbited Venus and eventually entered the atmosphere and burned up. The chances of anything reaching the surface are slim, but that's not the point - I would like to be able to say 'Pioneer Venus burned up over ----- Planitia, Magellan burned up over ---- Terra, Venus Express burned over --- Tessera. It should be simple, but it's not. Let's look at the problem.
#venus
#venus
These orbiters were all in quite elongated high inclination orbits, so they can only enter the atmosphere at (or near) their periapsis latitude, and we know what that is for the final phase of each mission, so the latitude is fixed quite easily. The longitude is much more complicated. The orientation of the orbit plane in space would be known. The question is, which bit of the planet was under the periapsis at the time of atmospheric entry on the last orbit?
#venus
#venus
I'm not clever enough to put all this together and answer my own question, and I have asked the internet at least once (on unmannedspaceflight.com) but to no avail. I might have an answer for Pioneer Venus so let's look at it. I jotted these notes down years ago and don't recall where my information was from. But this is what I have:
Last contact was on 8 October 1992. The last orbit was on 22 October...
#venus
Last contact was on 8 October 1992. The last orbit was on 22 October...
#venus
The periapsis was near midnight on Aug. 28, when the subsolar longitude was about 208 degrees east, so periapsis longitude was about 28 east. On the last orbit, 40 days later, the periapsis long. should be about 86 east. Therefore the place where Pioneer Venus burned up should be about 11 south (periapsis latitude) and 86 east, on the south edge of Ovda Regio (you can find it on my probe location map). I don't have similar data for other orbiters and am not confident about this one.
#venus
#venus
The next events in our Venus story were the Venera 11 and 12 missions. These were upgraded landers with colour cameras and better analytical instruments for the atmosphere and surface. They were not accompanied by orbiters this time, but their carrier spacecraft flew past Venus, and relayed data from the landers. Two landers, two cameras each... but not one of the 4 cameras worked. We don't have pictures, but let's see where they went - tomorrow!
#venus
#venus
When we have seen the most recent Venus lander (it wasn't very recent) I will post a map showing all lander locations on the planet. Meanwhile, here is the region where Veneras 11 and 12 landed in December 1978. When I was making these illustrations I did not know the figure numbers so they are omitted here. I can reveal that Venera 11 was --B and Venera 12 was --C. This is a complex region of rough uplands and smooth plains south of Beta Regio.
#venus #venera11 #venera12
#venus #venera11 #venera12
Here is the Venera 11 landing site in a context map and a closeup at full Magellan resolution. The 2nd map spans about 100 km side to side and is roughly centred in the 300 km circle in the context map. This is a very smooth plains site: lava flows with a veneer of sediment, most likely. White lines are rough-faced fractures (faults), and there are also some fine dark lines, maybe older fractures (or facing away from the radar). The darker area is smoother, maybe fine dust.
#venus #venera11
#venus #venera11
These maps show the same thing for Venera 12, but this is a very different site. Most of the context map consists of Tessera terrain - rough uplands cut by dense sets of fractures running in different directions. The closeup view at right shows at least 3 sets of fractures with different azimuths. Tesserae are thought to be areas of older crust which have been around long enough to be disrupted by multiple episodes of faulting. A dangerous place to land!
#venus #venera12
#venus #venera12
Despite the danger of trying to land in a very rugged area like Venera 12's site, the apparent age of tessera areas makes them the most favoured sites for new landing missions. How can you make the landing less dangerous? The best plan seems to be: aim for the ejecta of an impact crater in the tessera. The ejecta is made of the stuff you are interested in, but the ejecta deposit covers over the rough terrain, smoothing the surface.
#venus
#venus
While the Veneras were flying, Earth-based radar continued to probe Venus. Here are some radar results from the 1980s. The top image is radar reflectivity - bright is reflective, and it is rough terrain. The resolution is improving. Look at Myletta Fluctus (fluctus = flow), a vast lava flow, about 750 km end to end. The other bright features are tectonic ridges and fractures. Venus has been a geologically active world, most likely it still is.
The other images? That's a new story.
#venus
A JPL team led by Richard Goldstein made these circular images at Goldstone over 2 decades. The black band masks unresolved north-south ambiguity at the radar equator. These are at the middle of the planet's disk on that date where a very bright specular reflection occurs, and radar behaves differently in it than elsewhere. Slopes facing the radar are bright. Rough areas scatter radar away and are dark in his area. Look at the VERY fine ridges at the top of 'C', never seen before.
#venus #radar
#venus #radar
Goldstein started this in the early 1970s and got a few images at each close approach of Venus. The method also gave rough topography of the area. I was fascinated by the slow unveiling of Venus's surface over this period and attempted some geological analysis, which we will look at tomorrow. Goldstein was very generous with me and sent photo prints of all his images over the years.
#venus #radar
#venus #radar
This link goes to my first Venus mapping abstract at LPSC:
I was still a near-beginner at geological mapping and at interpreting radar images, but I think it still looks reasonable now. The map covers all the Goldstone images available at the time (1988, I was still a grad student). I mis-spelled Eistla in 2 different ways! Oh well...
Here is another abstract from 1991 with a version of the map extended by using other radar images:
This is a more complex argument and I'm going to look at it more closely later. Basically, before this two authors had published a hypothesis about Aphrodite being a spreading ridge like those we see on Earth's ocean floors. It had an axis of symmetry which was offset by faults at right angles to the axis. It looked like a reasonable idea... but...
#venus #radar
The previous hypothesis was that Aphrodite was a spreading ridge like the Mid-Atlantic Ridge, its axis offset by 'cross-strike discontinuities' (CSDs - we used to call them transform faults), but these were all in the hemisphere not seen in Earth-based radar. My idea was that the basic pattern of an axis of symmetry offset by parallel CSDs could be extended from Aphrodite into Eistla Regio where we did have radar images. The images might let us test the hypothesis.
#venus #radar #maps
#venus #radar #maps
After analysis my conclusion in that abstract was that there was no evidence in Earth-based radar images for the spreading hypothesis. I went on to write this up in more detail and submitted it to a journal. The referees rejected it on spurious grounds - I think the people I was saying were wrong were doing the refereeing. I didn't pursue the point, but this plus one other case later - a totally different topic - made me give up on the journal treadmill and start compiling atlases.
#venus
#venus
We now pass to Veneras 13 and 14, which gave us the best images we have of the surface of Venus. Where did they land? This map shows the previous 2 sites (Veneras 11 and 12) and two cryptically labelled boxes - I did not know the final figure numbers when I made this. B is Venera 13, C is Venera 14. The area is a mixture of rough uplands (e.g. Dolya Tessera), smooth plains (e.g. Navka Planitia), volcanic features and associated lava flows. What will this look like on the ground?
#venus
#venus
Here is the Venera 13 landing site in a context map (left) and a closeup (right), using Magellan images. Wen Shu is an impact crater. Muru Tholus is a volcano, and the Fossae are troughs or linear valleys. The closeup (100 km across) is a mixed bag of geology. Bright (rougher) hilly areas and smooth (darker) plains. Smaller dark spots are smoother surfaces, maybe sediment blown into depressions by the wind. Venera 13 can be anywhere in the big circle. What did it see?
#venus #maps
#venus #maps
Venera 13 had 2 cameras and both worked this time, giving 2 panoramas facing in opposite directions. As usual Don Mitchell gives us an excellent treatment of these panoramas:
http://mentallandscape.com/C_CatalogVenus.htm
(about 40% of the way down the page). The scene was scanned through 3 filters plus a clear filter so we have RGB images, nearly complete for one camera, only partial for the other. Here's one of them from that site:
What do these images tell us? The landscape is superficially similar to that of Venera 10, with eroded and broken rock slabs separated by areas of darker gravelly debris. These Soviet versions of the images (from the NSSDCA) show the colour scale on the right side of the images and 2 camera covers which were ejected after landing, plus an arm which gave a reading of the hardness of the surface. This is probably in the dark plains area of the Magellan image.
#venus #venera13
#venus #venera13
Once you have those panoramas you can do some other things with them. Each one sees the horizon at each end and the foreground in the middle, so they can be projected into a sort of cylindrical projection which straightens the horizon. Here are the two Venera 13 panoramas.
Since I didn't do this with Veneras 9 and 10, I will add them here. The processing here shows the distant blocky ridge at the Venera 9 site better than we saw it before.
#venus
#venus
The two Venera 13 panoramas should overlap slightly at their ends so they can be joined as shown here. This shows the actual extent of horizon imaging which is very limited. The overlap is visible at one end but largely obscured by part of the lander at the other end. The bit we see overlapping doesn't match exactly because the view angle is different (it would make a mini-stereo pair). It's too bad the Soviet camera system gave such a limited view, but it's amazing we got anything.
#venus
#venus
Once we have that panorama we can try to project it into a map geometry like this. I know this is not very good geometry, I just did it quickly yesterday. But it gives an idea of what the 'map' coverage is like - not very complete! The odd orientation reinforces the fact that (as I believe) we don't really know the orientation of the scene. Someone with a better grasp of the geometry could make a better version of this.
#venus #venera13
#venus #venera13
Here is a quick closeup of the middle of the previous post at the original scale I worked at.
#venus #venera13
#venus #venera13
Venera 13 didn't just image its surroundings. It analyzed surface composition, recorded sounds including various spacecraft activities, and recorded electrical discharges in the atmosphere. It survived for 127 minutes on the surface - quite remarkable considering the conditions on Venus. A parachute slowed it down but the lander was released from the parachute at 50 km altitude and it just fell to the surface.
#venus #venera13
#venus #venera13
Now we move on to Venera 14, which landed only a few days after Venera 13. I showed a context map of its site and V13's earlier. Here are two closer views. This is a volcanic terrain. Panina Patera is a volcanic eruption site surrounded by vast lava flows (Darago Fluctus). Ingrid is an impact crater. There are many faults and ridges west of the Patera and lava flows mainly to its east, extending at least 300 km.
#venus #maps #venera14
#venus #maps #venera14
What did Venera 14 see in this volcanic landscape? Again we will check in with Don Mitchell:
http://mentallandscape.com/C_CatalogVenus.htm
- look half way down the page. Both cameras worked again, both provided some colour data (most of one pan, a bit of the other). My image is something I scanned in Moscow, showing map-projected versions of the central parts of the two panoramas, on opposite sides of the lander. These are presumably thin lava flows or cemented ash layers.
#venus #venera14
The upper view from yesterday shows the arm which fell onto the surface to test surface hardness - we saw it with Venera 13 too - but here it fell on the camera cover and didn't tell us anything useful. But check the foreground of each view, the lander base ring with its teeth - designed to reduce turbulence during descent, I think. If you view this image:
http://mentallandscape.com/C_Venera14_1.jpg
you see the full set of Venera 14 images (sadly, very low resolution). They tell a story...
#venus #venera14
The full set of images contains views through filters to produce colour images, taken one after the other and therefore taken at different times. Here I have cropped out a bit of the foreground in 3 views - greatly enlarged and so fuzzy. They differ a bit - soil particles are moving in the wind, especially between the top and middle images. They could be animated. There is a paper about this somewhere.
#venus #venera14
#venus #venera14
Yesterday's image was not the only one like this. Here is a set of five views from Camera 2 on Venera 13, made the same way - from the full image set which, alas, we only have at low resolution:
http://mentallandscape.com/C_Venera13_2.jpg
The changes are small but they are real. There is a messy 6th image but I didn't include it.
Before we continue with Venera 14, I feel I must step aside and look at another line of Venus research... well, we all need a bit of levity in our lives these days, don't we? Veteran Soviet space scientist Leonid V. Ksanfomality of IKI-RAN (the Space Research Institute in Moscow) has published some provocative work - check this out:
https://pdfs.semanticscholar.org/4d92/4dad539e46138cdac33114eeca3da088dbc9.pdf
and this brief item:
https://meetingorganizer.copernicus.org/EGU2012/EGU2012-3487.pdf
Yes - life on Venus seen in Venera images.
#venus
If you are not entirely convinced by this argument, enter the following titles in Google Scholar (other Google-Scholar-like search tools are available):
Hypothetical signs of life on Venus: revising results of 1975 ± 1982 TV experiments
Possible Detection of Life on the Planet Venus
Hypothetic life detected on the planet Venus
(the actual URLs are ridiculously long, this is easier)
Currently, life on Venus is more often assumed to be in the upper atmosphere (if anywhere).
#venus
Busy yesterday with my LPSC abstract - I'll post it here when I submit. Back to Venera 14: here are the two panoramas projected into a sort of cylindrical projection, making the horizons at each end horizontal. Look at the rock layers in the lower right: erosion has cut a hole through one layer to show another underneath. Those layers can only be a few cm thick - an inch if you prefer. could they be lava flows? They would have to be very low viscosity. maybe welded ash flows?
#venus #venera14
#venus #venera14
Here I have fitted the two Venera 14 panoramas together. The join isn't perfect - one join has a visible overlap but the two views from different cameras don't match perfectly. The other join is hidden by part of the lander. This is the best I can do. I have also stretched these vertically a bit to better match what I think the cylindrical geometry should look like. But many aspects of this reprojection geometry are speculative so don't trust me.
#venus #venera14
#venus #venera14
As we saw with Venera 13, once we have that 360 degree panorama we can project it into something resembling a map geometry. I make no claims for accuracy, but I want to show what is possible, and others have done the same (but not, I think, out to the horizon). Here we see a pattern similar to the Venera 13 version with the lander at the centre. As I have said before, we don't know the orientation of the panoramas on the surface so my orientation is arbitrary.
#venus #venera14
#venus #venera14
These Venus landers did more than take pictures. The composition of the surface was measured: it resembled a low potassium basalt at Venera 14. V13 and V14 had seismometers. Typically you want to monitor for long periods to get good seismic data. V13 operated for 127 minutes, the record for Venus, and V14 only for an hour, so you would not expect very much. V13 detected nothing but V14 had two possible detections of motion. Where they caused by wind?
#venus #venera14
#venus #venera14
Well, the Veneras also measured wind, and Venera 14's site was less windy. Here is a paper by our old pal Leonid Ksanfomality:
Ksanfomaliti, L.V. et al., 1982. Microseisms at the VENERA-13 and VENERA-14 Landing Sites. Soviet Astronomy Letters, vol. 8, July-Aug. 1982, p. 241-242.
See it here:
https://adsabs.harvard.edu/full/1982SvAL....8..241K
But much longer-lived instruments will be needed. Sensors in the atmosphere (on balloons) are being looked at, they might detect seismic waves.
#venus #venera14
Veneras 13 and 14 were followed by Veneras 15 and 16. But here we step out of the sequence of landers. These were orbiters with synthetic aperture radar instruments, the only thing which can really give us high resolution imaging of the surface. And they are unique in Soviet space exploration, the only Soviet missions which undertook systematic mapping of another world. There was no Soviet systematic imaging of the Moon and Mars, only the US did that.
#venus
#venus
Veneras 15 and 16 together mapped maybe 25% of the planet around the north pole - not global but enough to get to grips with Venus geology at last. USGS worked with them to make maps:
geology:
https://www.lpi.usra.edu/resources/venus_maps/2059/
topography:
https://www.lpi.usra.edu/resources/venus_maps/2041_1/
shaded relief:
https://www.lpi.usra.edu/resources/venus_maps/2041_2/
radar mosaic:
https://www.lpi.usra.edu/resources/venus_maps/2041_3/
The Soviets published a large format atlas too. You can see it in our library at Western.
#venus #maps
We were looking at Veneras 15 & 16, the Soviet radar mapping missions. A good place to go for images is Don Mitchell's page:
http://mentallandscape.com/C_CatalogVenus.htm
(just below half way down the page).
The mapped area was portrayed in 27 map quadrangles. A nice (but very rare) atlas was compiled from the mission data.
Here is a comparison of Venera and Magellan resolutions:
https://science.nasa.gov/photojournal/venus-comparison-of-venera-and-magellan-resolutions/
Now the Soviet images look mediocre but they were our first good view of surface geology.
#venus #venera15
There's a bit more information here:
https://petermasek.tripod.com/venera15.html
- I can't vouch for the viewing software, I am just pointing out the details on this page... and if you look further down there are a lot of other interesting links to play with.
Here:
https://rgcps.asu.edu/venera-15-16/
are links to high resolution versions of the map quads shown by Don Mitchell.
I will look at a few interesting features tomorrow.
#venus #maps #venera15
I should point out another set of maps of Venus, the ones USGS produces as a record of Venus feature names:
https://planetarynames.wr.usgs.gov/Page/venus1to5m_Radar
The index would be clearer if it had a radar image base. Click on a quad and it will appear... let's look at the Lakshmi Planum sheet:
https://asc-planetarynames-data.s3.us-west-2.amazonaws.com/v7_comp.pdf
and the Russian version from yesterday's link:
https://rgcps.asu.edu/venera-mapsheets/V04_M60N295.png
Lakshmi Planum is the dark area seen earlier in Earth-based radar images.
#maps #venus #venera15
Lakshmi is surrounded by mountain belts. We can see how gaps in Magellan radar data are filled by the Venera data. At far right in the Russian map is Maxwell Montes, a very high plateau crowned by Cleopatra, a large impact crater which is on the Fortuna Tessera Magellan map. Here is Cleopatra in Venera data. Maxwell Montes is very rugged, a tricky place to land. The image shows smoother areas around the big crater, where ejecta fills depressions to smooth the surface.
#maps #venus #venera15
#maps #venus #venera15
Mark McCaughrean@PhilStooke Excellent work, Phil, and far more honest than the dubious versions that have been circulating for of the Venera images that have full & made up horizons.
@markmccaughrean Thank you. I have commented on those 'artistic' views earlier in this thread.
@PhilStooke @markmccaughrean Thanks, Phil. For some reason, the rest of the thread didn’t show up when I looked earlier, but it’s there now – there’s a lot of excellent material there & many new insights for me.
As for Don’s images, I guess the thing that’s always confused me is how & why he added in those wide horizons, as they don’t exist in the original Venera data AFAIK. I mean, his website & work are excellent in general, but that aspect has always baffled me somewhat.
@markmccaughrean Agreed. I suppose it's OK to try to show what the surface might look like in a more conventional geometry, but it is very confusing to the public. Most people will think it is real data.
Dźwiedziu@PhilStooke
Mastodon, if not ActivityPub in general, counts each link as 23 characters.
Unfortunately I can't find a good source for this.
@PhilStooke
Is there a good source of the sound recordings?
Also the 50km fall is impressive.