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Comment by rmason | Hacker News Reader

I'm reading this and wondering why you couldn't build a waterproof beacon? At least by tracking it you could prove that it didn't exit into Lake Superior.

https://en.wikipedia.org/wiki/Underwater_locator_beacon

http://www.rjeint.com/aviation-underwater-locator-beacons

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You should drop synthetic DNA in it and then sample all nearby lakes and do PCR. Even aftera trillion-fold dilution it should be detectable. Would be cheap, easy and very likely to work. A cool weekend project for your kids!

> You should drop synthetic DNA in it and then sample all nearby lakes

Sounds like the backstory for a Lake Placid or Piranha-style movie...

In a typically-HN thread full of armchair experts brainstorming obvious "why don't they try" ideas [1], this is a truly interesting idea that I bet the experts haven't considered. Also some good potential in the area of espionage, if it already isn't being done.

1. See also the Malaysian Airlines disappearance thread.

Having seen this crop up on reddit before, with no novel or technically plausible ideas suggested, I have to say, Hacker News delivers :)

This would not be permitted for any NIH funded lab, there are pretty strict rules about handling recombinant DNA. There might also be laws preventing this, I'm not sure.

Why is this so if the DNA isn't part of an organism?

I guess there is some risk in some circumstances that the DNA will affect organisms just by being present in their environment, without having been actively introduced into their cells?

https://en.wikipedia.org/wiki/Transformation_%28genetics%29

Pardon my ignorance on this - but wouldn't dropping Synthetic DNA into the water be polluting it in some form?

The article mentioned locals claiming to have pushed down a car one night ... No idea what volume of synthetic DNA would be sensible here, but I can imagine it'd mass less than a car.

Almost every living thing contains DNA (the possible exception being some viruses if you consider them living).

I imagine leaves / fish / spit / what have you fall into the water all the time.

The only synthetic part of it is the sequence - on a molecular level it's exactly the same as naturally-occurring DNA.

There's a good chance a beacon would get stuck or lodged somewhere, even though the water itself would continue to pass through (think sand or very narrow fractures). Hydrogeologists use a variety of dyes or other water additives that are better suited for this, and it doesn't seem to have worked yet.

>> Hydrogeologists use a variety of dyes or other water additives that are better suited for this, and it doesn't seem to have worked yet.

The one thing the article failed to mentioned is the possibility they have no idea where to look for the dye to be coming out. It's easy to do this on an island (such as the famous Oak Island), not so easy at Kettle Falls where this waterfall is quite a ways inland and the only logical outlet would either be the Brule River, or a deep cavern that leads to the coastline of Lake Superior.

Add in the fact in some areas the lake can be as deep as 1,300 feet, and you've got one hell of a hard time trying to find out where the water goes.

I'd place beacons in live fish. They are well suited to navigating underwater hazards.

Acoustically ping a serial number for a couple of days. Place an array of sonobuoys in the likely outlet area, scan with boats further afield. If there is a fish sized outlet, then they should be able to get out. If you start finding your fish you can start refining the resolution of the search and plopping more fish in the falls.

At the same time, lower teathered hydrophones into the falls at various distances. If the pingers accumulate somewhere there, then you have a suggesting of fish impermeable structure.

I might need to add lights to the fish so they can see.

Plus you'd get some great YouTube footage a fisherman who catches a fish with headlights.

Use something with as close to exactly the density of water as you can manage.

Put a 1 week timer on it that releases some air inside it (a chemical reaction would be easier than compressed air) to make it surface.

Make a bunch of them, in case one gets stuck anyway.

Find an organism that passes through the passage and a way to track that.

Hitch your wagon to something living that will be able to find a way.

A fish with a GPS tracker perhaps? If they attach them to ground animals, why not water?

They also/already attach them to whales, sharks and dolphins, at the least. I bet someone, somewhere, have done it to a fish...

The limit is probably the size of the tracker. The ones I saw look about as big as a standard river fish..

Try otters. They'll eat the zebra mussels when they're done.

You'd need something super specialized, because water and rocks/earth block radio waves exquisitely well, and the churning water would be difficult to survive regardless. So perhaps some sort of camera + high sensitivity inertial measurement unit in an extremely rugged housing along with an ultrasonic data transmission system or something. All of which would be extremely custom and would likely require several iterations and vast expenditures of money and effort just to collect a little data.

Not that you'd find it again unless you attached it to a piece of string.

I'm just assuming it'd be gone forever, which is why you'd need some sort of wireless data transfer system (ultrasonic sound, for example).

Small GPS receiver card (chip?), GSM module with prepaid SIM, a bit of flash storage to record GPS data and a battery - all sealed in a rugged ball. This shouldn't be that costly, no? Or will it be hard to make the battery last beyond few days?

At the very least this should give the first surface point for that undergraund stream.

Water is essentially non permeable by radio waves at the frequencies you would use for GSM and GPS, which is why communicating with submarines is extremely tricky. I've always assumed (but never been able to find information on) convicts with GPS tracking anklets taking baths and unknowingly getting in trouble for breaking the recorded path.

Both the GPS and the phone module is going to be useless while underground, so perhaps it will be better to turn them off altogether and use a separate timer to reconnect them after a few days. A disconnected battery can last quite a long time.

Even an energized battery, on a low duty cycle, (Transmitting once a day at low power), can last upwards of 20 years.

You'd probably need to make it very slightly more dense than water, or it may get trapped at the surface in an underground cave. This means it won't surface by itself once it leaves the cave system, and as water blocks RF pretty effectively, you'd not get a signal. To make it work, you'd need to add some additional mechanism to allow it to become more buoyant over time - perhaps a slow chemical reaction creating gas?

The earth is really good at blocking radio waves; the beacon is only going to be good when it shows up again in water open to the sky.

Similarly, it may be that the water is getting to Lake Superior just fine, but that the path it takes has plenty of opportunity to get debris caught up or lost in a side-channel.

A ping pong ball or dye isn't going to work if it is surfacing in Lake Superior. That lake is so vast that the kind of a tracker they use in airplane black boxes is a good bet. Short of mapping the lake bottom, which is unrealistic, we may never solve the mystery.

The US Navy has been quietly mapping ocean bottoms for decades, since nuclear submarines started going all over the oceans.[1] The resolution isn't all that great, but by now they know where most of the seamounts are. It's a boring job. Cruise across ocean in a straight line towing a sonar array, return along a parallel track, repeat.

But maybe nobody has bothered to do the Great Lakes in detail yet. Not much submarine traffic.

[1] http://oceanexplorer.noaa.gov/explorations/lewis_clark01/bac...

> Short of mapping the lake bottom, which is unrealistic

Is it? http://www.telegraph.co.uk/news/earth/environment/archaeolog...

Granted, these guys seem to be piggybacking on massive work done by oil companies, but the North Sea is roughly 3x Lake Superior, so you only need 1/3 of the effort. You just have to find an excuse...

A radioisotope might work, though good luck convincing people to dump tonnes of radioactive marker into a hole that nobody knows where it goes. A pinger from an aeroplane would do an alright job, but they are usually specified to work for a week which might be far longer than the period underwater.

Exactly, something with intermittent GPS pinging so that should it ever resurface we get a signal.

I'm pretty sure you're not going to get a GPS signal from satellites wherever that water is going.

And what happens if somewhere down below the temperature suddenly rises and all those plastic beacons with some soldered electronics inside simply melt or break?

It there was a lot of heat down there we would know - there would be hot springs somewhere nearby.

For plastic to melt it would be hot enough to make steam, and we would see that.

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