They survived a "mission to Mars" that helped us understand the
challenges of long-term isolation. Now the crew who participated
in a mock trip to the Red Planet may have helped overturn a
long-standing assumption of how our body deals with dietary
salt. The Mars 500 mission, which ended in November 2011, was a
dry run for a real Mars mission. It saw six volunteers confined
for 520 days in a mocked-up spacecraft at the State Research
Centre Institute for Biomedical Problems in Moscow, Russia. It
also provided a chance to perform otherwise difficult
experiments on diet. It is known that dietary salt is rapidly
excreted in urine. As it passes through the kidneys it helps
them to eliminate unwanted fluids. But too much salt in the
bloodstream can hamper the ability of kidneys to remove water,
increasing blood pressure and adversely affecting health. It is
a challenge to measure the long-term effects of salt because of
difficulties in regulating dietary intake. However, Mars 500
"mission controllers" were able to