Oliver Knickel, a captain in the German Army, was part of the six-man team that emerged in front of scientists and journalists at the Russian Institute for Biomedical Problems (IBMP) after being cut off from the outside world for over three months.

The experiment, which began on March 31, aimed to replicate the conditions astronauts would face on a manned mission to Mars, including a simulated landing on the planet's surface.

Scientists monitored the psychological and physical effects of the prolonged isolation on the participants, and are hoping this will bring a better understanding of the problems of long-term space flight. The four men only had contact with scientists playing the part of ground staff, and even these communications were delayed by 20 minutes.

"We do not know how humans react to being in such a state of isolation, how the psychological situation among the participants' functions, what happens to their nutrition and bodies," Johann-Dietrich Woerner of the German Aerospace Center said before the experiment.

German "a little melancholic"

The six lived in the 550 cubic meter (19,500 cubic feet) facility with tiny individual bedrooms, each having a maximum area of 3.2 square meters (34 square feet), and were confronted with artificially created emergency situations to determine the effects from a decrease in work capability, sickness, and failures of the on-board systems and equipment.

"We have of course gone through all daily procedures one last time," Knickel wrote in a final online diary entry about the experiment. "I have to say that all of us even got a little melancholic realizing that next week at the same time we might never fulfill these things again which have become such familiar habits."

The six volunteers will now be subjected to a series of physical and psychological exams to establish a draft guide of what actual astronauts could experience.

"I have absolutely lost the feeling for time on a long-term basis," Knickel wrote. "Although not having seen the sun during the whole isolation period, I still have a sense of when it is morning and when it is evening just by how tired I am. But I absolutely have no idea about the total length of time we have spent inside the module."

Tests not tough enough

Though scientists attempted to recreate the conditions of a flight to Mars, critics have said the test was not stringent enough because the six men knew they could exit the experiment if necessary for medical or other reasons. The men were also not exposed to the weightlessness and added radiation from the sun that would accompany an actual interplanetary flight.

"It's conditional, as if preparing to drift on ice floes in the Arctic held in winter on a pond near Moscow," Valentin Lebedev, a member of the Russian Academy of Sciences and former cosmonaut, wrote in a paper published by the Russian Federal Space Agency.

He said a special module that could be connected to the International Space Station would provide a better simulation of a Mars mission.

"Then it will be possible to create conditions in the module closest to interplanetary flight," Lebedev wrote.

A joint venture between the European Space Agency (ESA) and the IBMP, the experiment, titled Mars 500, served as a forerunner to a longer project set to start in early 2010 when six other volunteers will subject themselves to the same living conditions for 520 days - the amount of time scientists say would be needed for a return trip to Mars - the ESA said in a statement.

The Red Planet's distance from Earth varies between 55 million kilometers (34 million miles) and more than 400 million kilometers.

sms/AFp/dpa/AP

Editor: Mark Mattox