If being locked up in a cramped capsule for 17 months with five strangers is your idea of a good time, the European Space Agency (ESA) may have a job for you.

ESA is looking for a few good men and women -- four, to be exact -- with the right qualities for an Earth-bound simulation of a Mars mission that may (or may not) happen a couple of decades from now.

For candidates under 185 centimetres (six feet one inch), aged 20 to 50, who speak Russian or English and think prolonged confinement in a tiny space is an interesting challenge, the agency is now accepting applications.

Having a PhD in medicine, biology or engineering is a big plus, the ESA said in a press release on Tuesday.

The 520-day dry run will start next year and follows a similar experiment with a different crew of six at the same Moscow facility earlier this year that lasted only 105 days.

The 550-cubic-metre (19,500-cubic-foot) module aims to replicate the conditions of a manned space voyage to Mars, including a simulated landing on the Martian surface, communication delays of up to 20 minutes and emergencies.

More than 5,600 people applied more than two years ago for the six spots.

The "help wanted" announcement on Tuesday said ESA still needed to fill two places, along with two replacements, in case of illness or accident.

"Selection will be based on education, professional experience, medical fitness and social habits," ESA said in a statement.

"Potential candidates... will be screened in a process similar to that used in astronaut selection."

Depending on the conjunction of Earth and Mars, the real mission would consist of around 490 days of travel time there and back, plus a month on the Red Planet.