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Seabed telescopes to look into our planet to see cosmos

"Instead of studying signals from the Crab Nebula, we may start to pick up light from real crabs -- or lobsters or bacteria and think these are coming from outer space. That would rather spoil things."

Monty Priede, a professor with Aberdeen University's Oceanlab

Scientists are finalizing plans for a ?140 million (US$264.7 million) telescope that will sit on the seabed in the deepest part of the Mediterranean -- and be pointed downwards.

The aim is to study the universe's most elusive particle, the neutrino, and through that to understand more about the complexity of space and how it develops. Billions of these ghostly entities zip through our planet every second on their journeys across space from distant black holes, galaxies and exploding stars. The telescope will track them as they pass through the Earth.

"Neutrinos are the closest thing to nothing you can study," said Lee Thompson, a professor at Sheffield University in England and one of the project's leaders.

"Unlike light -- which is often blocked or obscured as it travels through space -- neutrinos pass through everything: stars, planets, people, you name it. That makes them an amazingly rich source of information about the distant universe. The only problem is that they tend to pass through telescopes and detectors as well," he said.

However, scientists have found that neutrinos occasionally strike atoms in such a way that they emit brief, faint pulses of light. The seabed telescope, which is being designed by a consortium of European scientists, including groups at Aberdeen, Liverpool and Sheffield universities, will exploit this effect.

The observatory -- known as Kilometer Cubed -- will consist of rows of light detectors that will fill a cubic kilometer of the Mediterranean and rest on the seabed, 2km or 3km below the surface. Robot submersibles will be used to build and service it.

An identical device is to be built by the US in the Antarctic. Buried under several kilometers of ice, it is known as IceCube.

"The two machines will be able to study, simultaneously, the skies over both the northern and southern hemispheres," said the European project leader, Uli Katz, a professor at Erlangen-Nuremberg University in Germany. "It will give us enormous power to study the cosmos."

The neutrinos will be detected after they have passed on their straight course through the Earth and emerge into the sea, before heading back into space again.

Scientists have selected a seabed site to build their observatory for several reasons, Thompson said.

"Down there, we can use the Earth as a huge shield. Only these particles can pass straight through the planet so we can be sure that what emerges is a neutrino," he said.

At these depths on the seabed there is no light and in the pitch black the odd flash of light produced by a passing particle hitting a water molecule will be easy to detect. The scientists will also be able to trace the sources of the neutrinos.

There is one drawback to this design, however: glowing crustaceans. Marine biologists at Aberdeen University, Scotland, have discovered that even at these depths, life thrives on the seabed and many creatures provide their own illumination.

"Some of these are very tiny, like ostracods, which are really just a form of glowing goo," said Monty Priede, a professor with Aberdeen's Oceanlab.

"They still provide pretty intense illumination, however. And that is a real problem. Instead of studying signals from the Crab Nebula, we may start to pick up light from real crabs -- or lobsters or bacteria and think these are coming from outer space. That would rather spoil things," he said.

Finding a site for Kilometer Cubed which is free from bioluminescence is therefore of critical importance for the project.
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