Damn, this is just a tragedy:

One of the world's 'best robots ever' lost off Chile
He was one of the first successful, unmanned, free-swimming ocean robots. But now, the 15-year-old autonomous benthic explorer – beloved ABE to those that designed, built and operated him at the Woods Hole Oceanographic Institution – is gone, lost off the coast of Chile in the early hours of last Friday.

On its 222nd dive, researchers on the vessel Melville lost all contact with the autonomous vehicle. Best guess what happened? A catastrophic implosion of one of the glass spheres used to keep ABE buoyant. If that happened, the pressure at 1.86 miles down - two tons per square inch - would have caused all of ABE's other spheres to implode, leaving it unable to surface and destined to remain forever at sea.

ABE was brought out of retirement (its replacement, Sentry, was on another expedition) for the trip to the Chile Triple Junction, the only place on Earth where a mid-ocean ridge is being pushed beneath a continent in a deep ocean trench. On ABE's first dive, it detected evidence of hydrothermal vents and was journeying to it again on its second dive.

The loss had nothing to do with earthquake activity off Chile, researchers said.

ABE, launched in 1995, ushered in a new era of deep sea vehicles that could operate without a tether to the surface, according to researchers. It "revolutionized deep-sea exploration by expanding scientists' abilities to reach into the deep," said Chris German, National Deep-Submergence facility chief scientist and a co-chief scientist for the Chile Triple Junction expedition.

ABE could stay under water for up to a day and ventured into some of the remote and risky places on earth, making detailed maps of mid-ocean ridges and was the first autonomous vehicle to locate hydrothermal vents.

So beloved was ABE, the editors of Wired magazine in 2006 called it one of their 50 best robots ever, a mix of real and fictional robots...

Source: Boston Globe

...goodbye, Faithful Servant...