Four Chinese volunteers have completed a 180-day stay inside a mock-up spacecraft on Earth, as China prepares for deep space missions to the Moon and maybe Mars.

The experiment run by the Astronaut Center of China began on June 17, with three men and one woman taking part. Called “Space 180”, it involved keeping the four people isolated in a 1,340 cubic-meter environment to simulate what a deep space journey might be like. A journey to Mars is estimated to take about 200 days.

"Our team is great,” said Tang Yongkang, volunteer team leader, after they had completed the six-month mission on December 14, local time. “Together we finished the task through hard-work and with encouragement and support for each other. We are the best.”

During their time inside, the team grew vegetables and exercised regularly, both important tasks for a deep space mission. They also performed Tai Chi to cope with the isolation, and carried out a number of biological tests.

Food, water, and oxygen were all used and recycled in a controlled environment, something that will be necessary on missions to the Moon or Mars.

The volunteer “taikonauts” (astronauts) were selected from a pool of 2,110 candidates who applied in May 2015. They cultivated 25 different kinds of plants, including sweet potatoes and peanuts, and tested 635 pieces of equipment, reported Yibida. There were more than 10 Chinese and international institutions involved in the experiment, including Harvard University and the German Aerospace Centre.

The experiment is not too dissimilar to ones performed by ESA and NASA. The former was called Mars-500, when a crew of six was kept isolated for 500 days in 2010 and 2011, with their tasks including a practice “Marswalk”. More recently, the fourth NASA-funded HI-SEAS study took place in Hawaii, with the latest crew of six emerging from their habitat on Mauna Loa in August after a year in isolation.

China has been ramping up its space exploration efforts in recent years, including sending two taikonauts to an experimental space station called Tiangong 2 earlier this year. The Chinese National Space Agency (CNSA) has its eye on sending humans to the Moon in the near future, and tentative plans to send people to Mars.

This latest test further cements their resolve to do so. How useful all these separate ground-based simulations are is up for debate, but maybe in the not too distant future they’ll prove to have been worthwhile.