Scientists have dived into an aquarium to test a new probe that might one day look for life in oceans that may exist beneath the ice crust of Jupiter's icy moon Europa.

Researchers from Nasa's Jet Propulsion Laboratory are conducting the engineering tests in the California aquarium as a warm-up for an experiment that will place a scientific probe in an underwater Hawaiian volcanic vent later this year.

The Lo'ihi Underwater Volcanic Vent Mission Probe will investigate an undersea volcano located 27 kilometres (20 miles) east of the Big Island of Hawaii at a depth of about 1,300 metres (4,250 feet).

"The purpose of using the Monterey Bay Aquarium kelp tank is to begin testing the instruments in an aquatic environment that contains some biological material that will stimulate and test the hardware," said the principal investigator Dr Lonne Lane.

Europa - an ice-covered world

"The information to be gathered from these experiments at the aquarium and later in Hawaii will prepare us for future missions to difficult places like Antarctica's Lake Vostok (under 4 kilometres/2.5 miles of ice), and below the surface of Jupiter's ice-encrusted moon Europa."

The search for life and organisms in extreme environments has prompted scientists to examine the thin, gelatinous veils of material that have been previously observed at underwater volcanic hot water vents.

Although there have been only a few observations of this material, on at least one occasion the white material has appeared to come from the vent throat.

Measurements of thermal conditions inside the vents have produced a range of temperatures from near 80 C (176 F) to almost 350 C (662 F).

The presence of life forms inside these vents would challenge what scientists believe is the accepted temperature range for life to exist.

Is there an ocean beneath the ice-sheets?

Currently the accepted temperature range is about -5 C to 110 C (23 F to 230 F), according to Lane.

"The goal of the Lo'ihi mission in Hawaii is to develop an instrumented underwater probe that can be placed inside these deep, hot water vents," said Dr Lane.

Europa has become one of the most facinating objects in the solar system. The Galileo spacecraft, currently in orbit around Jupiter, has sent back some remarkable pictures of it.

It has a surface of ice that may be only a mile thick. Underneath there may be an ocean of water warmed by volcanic vents.