Earth's highest lake explored

The lake is in the Chilean Andes

Scientists are to explore the Earth's highest freshwater lake, found in a dormant volcano in the Chilean Andes, to find out how the organisms that live there can survive in such a hostile environment.

They will ascend nearly four miles to the summit of the Licancabur volcano to explore the 'extremophiles' that live in the lake.

The group, which includes scientists from Nasa and the SETI Institute, will also dive to the bottom of the lake, which is covered with almost two feet of ice during much of the year.

It will give us clues about which planets are good candidates to search for life

Dr Nathalie Cabrol

The information they gather will help astrobiologists devise strategies and technologies to search for life on planets like Mars during future missions.

The expedition's principal investigator, Dr Nathalie Cabrol of the SETI Institute and NASA Ames Research Center, said: "If there was life on Mars 3.5 billion years ago, it could have used defence mechanisms similar to those used by the organisms at Licancabur volcano to survive.

"This expedition and the follow-up mission in 2003 will provide critical astrobiological information about the limits of life on our planet.

"It also will give us clues about which planets are good candidates to search for life and help in the design of future mission strategies and technologies for exploring ancient Martian paleolakes or oceans on Europa."

A moon of Jupiter, Europa is believed by some scientists to contain a subsurface ocean of water.

'Space exploration'

Although the lake at Licancabur volcano is covered with almost two feet of ice during much of the year, the expedition will take place in the southern hemisphere's spring, when the lake is not completely frozen.

The scientists will dive to the lake's bottom as part of the study.

The researchers theorise that the lake's water temperature may remain warm at the bottom because of heat transferred from the volcano.

"Only by going there will we find out," said Ms Cabrol.

The researcher-divers will not use oxygen during their dives, but will have oxygen cylinders onboard a nearby dive boat as a backup precaution.

The site research will answer three questions critical to astrobiology and space exploration, Ms Cabrol said. These are:

How do the organisms there survive in such a low-oxygen, high-ultraviolet radiation environment?

What are the limits of life on Earth?

Why does the water at the bottom of the volcano's lake remain liquid when most of the lake's surface is frozen much of the year?

To find answers to these questions, the scientists plan to study the life forms that live in the lake, such as microrganisms and plankton.

These 'extremophiles' thrive at Licancabur, one of the most Mars-like analogs on Earth.

Another stressor on the life forms at the volcano is low atmospheric pressure, said Ms Cabrol.

Testing

Researchers also hope to learn how the lake itself survives, given that the volcano is in the Atacama desert, one of the driest places on Earth.

Research during the 25-day mission, which began on 16 Oct, will include mapping the crater's geology and topography, surveying the depth, topography and temperature of the lake bottom, characterising the lake's organisms and testing a two-wheeled Mars mini-rover concept.

Samples returned from the lake during the mission will be transferred to a support team of scientists who will begin preliminary analysis in the nearby town of Antofagasta.

Most samples, however, will be flown to the United States for testing.