On Monday, President Trump signed the Space Policy Directive 1, the broad-brush outline of a plan to return American astronauts to the moon. The signing coincides with the 45th anniversary of the last time humans set foot on the moon: the 12-day mission of Apollo 17 in 1972.

Standing behind President Trump as he signed the directive — see him at 0:37 of this video — was surviving Apollo 17 astronaut, geologist and former U.S. senator Harrison “Jack” Schmitt (R-N.M.).

As you’ll see in the video, Schmitt practically rolled in Moon dirt in the course of his three-day geological field trip to the lunar Taurus-Littrow Valley. While mission commander Capt. Eugene Cernan’s suit stands on display at the National Air and Space Museum here in Washington, Schmitt’s suit has been put to work behind the scenes, providing test samples to determine how badly Moon dust damaged these suits. NASA’s official conclusions, though they make for some dry reading, describe cloth worn out and metal seals and joints pitted and scored by the hard, sharp lunar regolith — dust, basically, but dust that's much more dangerous than the Earth kind.

This was after only three days on the Moon. Plans are sketchy and have seen many revisions over the years, but all of them call for much longer stays on the Moon as a rehearsal for eventual extended stays on Mars. There are many technical hurdles to be overcome before any of this can be realized — but getting a handle on Moon dust will have to be a first step.

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