by Curtis C. Ebbesmeyer

Eerie email arrived from Rota Island forty miles north of Guam in the Northern Marianas Islands. Mark Michael, owner of Dive Rota, and fellow divers had recovered two aluminum cylinders from the East Harbor Channel. Mark's messages arrived daily, as if demolition experts radioing hair-raising reports as they defused the bomb.

“They are smaller than a 55-gallon drum, weigh 200+ pounds, and look like they’re filled with concrete. They appeared to have
been made from a single sheet of ½” marine-grade aluminum bent into a cylinder
and heliarc welded at the seam. The bungs in the end are brass and numbered. I removed one of the flanges on the end of
the cylinder. The flange is aluminum and the bolts are brass. There is a tube that runs through the middle of the cylinder for the whole length. In the middle of the tube is a flapper valve of some sort. There are several wires cut and dangling around the flapper valve.”

“I have some possible ID numbers stamped into the aluminum on the top of the cylinder. They are 85 over an 8 and then 85280. The bung markings are ‘ PM ‘in a circle at the top and the number 885307 at the bottom. Both bungs are the same.”

“I have had these cylinders examined by Coast Guard, EOD [Explosive Ordnance Demolition], a private explosive disposal outfit, and SEAL team personnel. All said that they have never seen anything like these, but they were not any type of ordnance they had ever seen or had experience with. I thought maybe they were some type of scientific equipment.”

“That’s fascinating news,” your editor emailed. “Last night, I was watching the History Channel — The Color of
War program — and saw some depth charges go overboard. I had the fleeting impression that some of them resembled your photos. The footage went by so fast that I could not be sure. Please be very careful with your experiments. There is still a lot of nasty stuff left over from wars — bombs, bullets, grenades, depth charges, torpedoes & white phosphorous — who knows what? Perhaps you might check the military history of the island. Troops usually left in place the stuff left over from WWII.”

“I chipped what I thought was cement from the inside, but it isn’t cement. It looks like some kind of brownishclear
resin. Technical personnel suggested I let my sample dry out and then roll it up in a length of newspaper and light it on fire and record the results. The material did not flash, pop or explode. When I examined the remains from the fire, all that I found was brown resin material that had melted like glass. The mystery is still a mystery.”

Mark lived and his email continued.

“I just had a gentleman who is an ordnance & explosives technician come by today as he was on Rota for some other job and showed him my aluminum mystery cylinders. He seems to think that they are some type of depth charges although the aluminum cylinder throws him. He took some measurements and photos and said he would get back to me. He thought it might be some type of experimental thing.”

Finally, on the internet, Mark solved the mystery. Photos and descriptions in the Navy manual OP 1330 (FIRST REVISION; Volume 2), matched perfectly. They are Mark 8, Mod 0 antisubmarine hydrostatic depth charges launched from surface craft. Each held 270 pounds of TNT within an overall device weighing 520 pounds in air. Prior to launching, they could be set to detonate at 50 to 500 feet.

“The depth charges were removed from my premises this morning at my request by our local EMO (Emergency
Management Office), so they no longer represent a danger to anyone around my dive shop. I am still a bit miffed that
the experts years ago informed me that they were not dangerous. There are still some in the area, so if I find any more, they will stay where they are and the EOD people can handle them. I am very glad that this story had a happy ending and nobody got hurt or killed.” 

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by Curtis C. Ebbesmeyer

Next time you see a weather forecast think of balloons falling into the sea. Each day at the same times (00:00& 12:00 Universal Coordinated Time), almost a thousand weather stations scattered worldwide let fly a weather balloon. Buoyed with helium, in a minute the 6-foot spheres ascend a thousand feet lifting miniaturized weather stations known as radiosondes. As they rise, the sondes transmit temperature, pressure, humidity data. In 90 minutes, up where spy aircraft fly, they explode and fall with their sondes to earth and sea.

All totaled in a single year the global weather network launches almost 700,000 sondes. Military and civilian meteorologists send aloft another 200,000 – 300,000, bringing the annual count close to a million. Of the yearly tally, roughly 100,000 probably end up in the ocean.

Do sondes rain much debris on the sea? Like the hockey gloves previously spilled in the North Pacific (Alert Vol. 1,
No. 2 & Vol. 3, No. 1), radiosondes are good floaters, a single one disintegrating into balloon shards, battery, miscellaneous wires and

plastic, and 234 cubic inches of styrofoam, based on the one beachcombed by Cindilla Trent in 1996 at Ocean Shores, Washington. All totaled, the expendable weather apparatus lost annually would fill about six, 40-foot cargo containers (worldwide, about a thousand containers are lost overboard each year).

Sondes signify our throwaway society and the burden weather forecasts place upon the sea. In terms of other expendables, the downed sondes annually rain enough styrofoam to mold 4 million 4-oz. coffee cups. During a decade, sondes contribute a billion bits of styrofoam, enough to litter thousands on each mile of Earth’s 382,000 miles of shoreline.

Inspiration for this article came from beached radiosondes reported by Wim Kruiswijk, Netherlands, and Cindilla Trent, Queen Charlotte Islands.