Interesting! I think this (and large-scale searches in general) is one area where a drone is probably much more likely to work than a helicopter/pilot, simply because of the sheer area to cover.
Interestingly the data has largely already been acquired globally since the 1950's using fixed wing aircraft, helicopters in places like PNG, and human pilots.
Drones took a bit long to arrive.
Eg. Australia has already been covered with multi instrument surveys (nine channel magnetics, 256 channel radiometrics, microwave radar DTM, etc.) with 27 million line-kilometres of survey data gridding the country.
Australian, South African, Russian, Canadian companies and pilots have been jobbing on this work about the globe for decades, in the USofA the USGS and DoE have been surveying internally during the same 70 year period.
What is the primary purpose of these endeavours? Mineral detection, space safety, radio stability, or just general scientific “because we can (and probably should)”?
Mineral and energy exploration, either broad area (an entire country or significant part) or more detailed closely spaced examination of specific areas.
Such surveys are funded by large companies wanting to extend their exploration data, mid size companies wanting to firm up infomation on a prospect, and national governments | world bank projects that are looking to promote exploration and development in greenfield locations.
You can fly over the same spot in four different directions and get four different readings.
You can fly over the same spot at four different times of day and get four different readings.
You also really want nine magnetometers, one for each X,Y,Z axis and repeated on each wingtip and tail boom.
If you're going to filter like a professional you need a base station to record the diurnal flux and subtract that in post, you also need to fly calibration clover leafs in a magnetically level wide area and develop a Kalman filter to subract heading generated flux.
There's also the active magnetism compensation caused by the aircraft and its components, such as
engine accessories, engine masses, avionics, current generated on the fuselage and other factors. If you're running a small fleet of aircraft to cover a million line kilometers or are otherwise pooling results into a standard magnetic map collection each aircraft will need to have its signature influence removed.
If you're mapping entire countries over decades then, of course, everything needs to be levelled against the changing IGRF (Internatinal Geomagnetic Reference Field), or the other one (there's another standard global magnetic reference field).
Then there's the question of just how small an iron rich rock you could reasonably get a blip from.
I would be somewhat shocked if this was a difficult problem for submarine detection aircraft. It's almost exactly what they're built for. https://en.wikipedia.org/wiki/Lockheed_P-3_Orion is what comes to mind, but that's 1960's tech.
I didn't say difficult, I did layout precisely what is involved at entry level in magnetic surveying.
Sub detection in deep water is different problem to shallow, there's unlikely to be another magnetic source below the sub in deep water ... unlikely, but ...
Small surface magnetic objects can be masked by much much larger and deeper (in the earth or in the ocean) magnetic sources.
It's a field strength fall off with distance thing, and "mapping" is an inversion problem.
Now that we know, how does this help us to hide a submarine?
How would a giant meteor like that have stayed intact? The article explains why there wouldn't be an impact crater, but even then, it would heat up massively during entry and it wouldn't exactly land softly. Then again, it'd land on sand which might be a bit more forgiving I suppose. But yeah, I'd expect it to shatter, and / or there being a lot of debris around it as well.
(I am an armchair internet commenter, I don't know much about these things)
If it matches the piece Sidert brought back, it is an approximately equal mix of iron and silica. It would also be many times larger than the largest intact pieces of meteorites found so far (and the largest are all iron), though this is presumably not enough to rule it out being a meteorite.
I just finished reading The Empty Quarter by St John Philby, which has bit about trying to find the lost city of Wabar, now associated with the Wabar meteor crater. The Bedouin guides talk about a chunk of iron the size of a camel, which some of them had seen personally. At the time of the expedition, they couldn't t find it anymore, presumably because the sand had covered it up. This was 1932. In 1966, the sands had shifted again and the iron was visible to a National Geographic expedition. By 1982, it had nearly disappeared again. I have no trouble believing the remains of a meteor could exist in the sands near Mauritania, and not happen to be locatable at the moment.
Or it’s been harvested - historically, meteoritic iron was a significant source of iron in the Sahara, and the techniques for dismantling a meteorite, and the desirability of the readily accessible metal, were well known to local blacksmiths. The fact that he was shown to it in the dead of night, possibly blindfolded, indicates that it was a valuable resource that they wanted to keep hidden.
They might do well to do a metallurgical analysis of old pots, pans, and other iron objects in nearby towns.
I’d be interested to learn more about pre-power-tool techniques for dismantling a meteorite of that size. Do you have any reading recommendations? I’m having trouble getting much further than https://en.m.wikipedia.org/wiki/Meteoric_iron
This Philby story (father of the infamous double agent Kim Philby) is a key plot point in Tim Powers' book _Declare_. It's a mash up of a John le Carre spy novel with Lovecraft. One of Powers' best novels.
There's another comment in this thread that mentions the book Declare by Tim Powers. St John Philby is an important (offscreen) character in that book, and certain details from The Empty Quarter are cast in a different light by the plot of the Powers book. I also just love reading travel narratives, so it wasn't too much of a stretch.
What are the odds some entrepreneurs quietly chopped up and sold it as ore - either all at once or over several forays- at some point in the last 100 years? It was likely worth something, and even an expedition into the desert seems likely to be cheaper than mining.
Cutting a large chunk of iron/nickel alloy is really hard. It would require bringing serious power tools, a large source of energy to power them (not solar), and a crew of people who could operate and fix all of these in the harsh environment of the desert.
Not impossible, but likely won't be cost-effective for several tons of plain "iron ore" or "scrap metal". But if that thing contained gold and platinum, maybe! :)
> One detail in particular is strikingly credible: Ripert described finding "metallic needles" in one area of the meteorite that he tried to break off by hitting it with the fragment. The needles proved too ductile. In 2003, scientists discovered that iron meteorites often do indeed contain nickel-rich spikes that are similarly ductile. There is no way Ripert (or any contemporary scientist) would have known about that in 1916.
There doesn't seem to be any other explanation, other than him having actually seen such odd 'needles'. It's not something one would just make up out of the blue.
Peary took an iron meteorite from Greenland to the chagrin of the local Inuit who had been using it for knives. Whacking it with a rock in -40 temperatures might have been the mechanism.
43 comments
[ 1.9 ms ] story [ 123 ms ] threadDrones took a bit long to arrive.
Eg. Australia has already been covered with multi instrument surveys (nine channel magnetics, 256 channel radiometrics, microwave radar DTM, etc.) with 27 million line-kilometres of survey data gridding the country.
https://ecat.ga.gov.au/geonetwork/srv/eng/catalog.search#/me...
https://www.ga.gov.au/about/projects/resources/awags
Australian, South African, Russian, Canadian companies and pilots have been jobbing on this work about the globe for decades, in the USofA the USGS and DoE have been surveying internally during the same 70 year period.
Such surveys are funded by large companies wanting to extend their exploration data, mid size companies wanting to firm up infomation on a prospect, and national governments | world bank projects that are looking to promote exploration and development in greenfield locations.
You can fly over the same spot at four different times of day and get four different readings.
You also really want nine magnetometers, one for each X,Y,Z axis and repeated on each wingtip and tail boom.
If you're going to filter like a professional you need a base station to record the diurnal flux and subtract that in post, you also need to fly calibration clover leafs in a magnetically level wide area and develop a Kalman filter to subract heading generated flux.
There's also the active magnetism compensation caused by the aircraft and its components, such as engine accessories, engine masses, avionics, current generated on the fuselage and other factors. If you're running a small fleet of aircraft to cover a million line kilometers or are otherwise pooling results into a standard magnetic map collection each aircraft will need to have its signature influence removed.
If you're mapping entire countries over decades then, of course, everything needs to be levelled against the changing IGRF (Internatinal Geomagnetic Reference Field), or the other one (there's another standard global magnetic reference field).
Then there's the question of just how small an iron rich rock you could reasonably get a blip from.
Add on a few days for calibration, sorting out airstrips and fuel supplies and you're sorted.
Next contract please.
Of course that leaves the post processing . . .
Sub detection in deep water is different problem to shallow, there's unlikely to be another magnetic source below the sub in deep water ... unlikely, but ...
Small surface magnetic objects can be masked by much much larger and deeper (in the earth or in the ocean) magnetic sources.
It's a field strength fall off with distance thing, and "mapping" is an inversion problem.
Now that we know, how does this help us to hide a submarine?
(I am an armchair internet commenter, I don't know much about these things)
They might do well to do a metallurgical analysis of old pots, pans, and other iron objects in nearby towns.
Actually, here’s a source - that does indeed seem to be the case.
https://www.tf.uni-kiel.de/matwis/amat/iss/kap_a/advanced/aa...
This was especially true before iron smelting was perfected. The perhaps most famous ancient artifact of this kind is Tutankhamun's meteoric iron dagger from around 1330 BC. -- https://en.wikipedia.org/wiki/Tutankhamun%27s_meteoric_iron_...
Not impossible, but likely won't be cost-effective for several tons of plain "iron ore" or "scrap metal". But if that thing contained gold and platinum, maybe! :)
There doesn't seem to be any other explanation, other than him having actually seen such odd 'needles'. It's not something one would just make up out of the blue.
The meteorite is now in a New York museum.