It’s what the show “Big Brother” would look like if a space agency produced it. An international crew is counting down the days until they enter a mock spacecraft in Moscow where they will live for more than a year -and-a-half to study the toll isolation and cramped spaces would take on the mind and body on a trip to Mars. The six-man crew — made up of volunteers from Russia, China, Italy and France — will enter their “ship” on June 3 for a 520-day stay during which they’ll conduct nearly 100 experiments. Their days will be strictly divided into three eight-hour segments for work, leisure (they recently bought a Wii) and sleep.