There have been Christmas trees in space before, of course. The first was made by the Skylab 4 astronauts Gerald Carr, William Pogue and Edward Gibson in 1973, who improvised a festive centrepiece from leftover food containers. In one ghostly black-and-white photo, it looks surprisingly good, a bit like a plastic tree that's covered in fake snow. Rather appropriately, the team topped it with a cardboard cut-out in the shape of a comet.

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