The Orion spacecraft successfully made it back to Earth Sunday, after nearly a month (25 days) in space.

The splashdown was scheduled 50 years to the day after the last humans landed on the moon during the Apollo 17 mission.

Of course, this is a practice flight in some ways. Next time, they want to put people on it. The long-term plan is to send people to the moon regularly, to set up shop there so to speak, as a sort of last gas station before that long road trip to Mars.

It’s hard to imagine living on another planet, not that people haven’t tried. There’s a whole genre of stories dedicated to the idea of space travel, colonies among the stars and the beloved wars in space franchises.

Life on another planet sounds like a nightmare version of life on Earth. Earth, the only planet where you can step outside and just breathe the air, no special spacesuit necessary. The water you need to exist is here, and food you can eat already grows right out of the ground (not without plenty of effort of course, as gardeners will tell you).

I recently learned about moon dust, which will not be news to you if you know much about the Apollo missions. Apparently, lunar dust is extra unpleasant to breathe in and impossible to escape if you’re hanging out on the moon.

Wind and water erode fine particles on this our one easy-to-live-on-planet Earth. Lunar dust, without the benefit of years and years of erosion, is spiky. The dust has silicate in it, a material that’s apparently not fun to breathe in.

Short-term exposure left the Apollo astronauts with sore throats, watery eyes, sneezing and nasal congestion. It’s unclear how long-term exposure would hurt human health. Breathing in lunar dust sounds like something to avoid if possible.

Science fiction prepared me to expect alien parasites, surprise black holes and long-term isolation as the health risks of space. Dust was not on my list.

Of course, Orion avoided lunar dust this mission, since it didn’t touch down on the surface of the moon. It did make two close passes.

Although the Orion capsule has already traveled 1.4 million miles around the moon—the journey isn’t over. The capsule still has to get from the Pacific Ocean to NASA’s Kennedy Space Center in Florida. Imagine that, you made it all the way to the moon and back, and now you have to drive cross country to Florida. I suppose by comparison the cross-country drive is a blip of a trip.