Four volunteers attend an oath-taking ceremony before they enter the simulated space "cabin" Yuegong-1 at Beihang University in Beijing, capital of China, July 9, 2017. The second volunteer group, two men and two women, replaced the first group and stepped into Yuegong-1 on Sunday. They will stay there for 200 days. The experiment, code-named "Yuegong-365," is Beihang's second attempt to see how the Bioregenerative Life Support System (BLSS) works in a moon-like environment. (Xinhua/Zhang Chenlin)
