NASA is trying to solve the mystery of why some astronauts suffer from vision loss after returning from space – and the solution might be a new type of sleeping bag.

More than half of the astronauts aboard the International Space Station have had their eyesight degrade – which NASA believes is due to fluid buildup in the head caused by zero-gravity conditions.

The solution?  A special sleeping bag that uses a “vacuum cleaner-like suction device” to draw fluid towards the feet instead of the head.

The sleeping bags are still being tested and haven’t been used on the ISS yet.  But NASA hopes to solve the vision-loss problem before attempting a manned flight to Mars.