Eli5: Why is Earth’s moon often the top candidate for the attempted establishment of a human colony in space?


Eli5: Why is Earth’s moon often the top candidate for the attempted establishment of a human colony in space?

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Because it’s small and close, mostly. Being able to reach the moon relatively quickly is an asset given frequent (and expensive) resupply missions that would be needed. The moon’s small size means it would be relatively easy to launch material back off the moon for return journeys.

Honestly, because it’s really close.

The Moon is a great candidated because the cost of transport between Earth and Moon is *relatively* timely and inexpensive.

Colonising the moon would also theoretically make travel to other places easier, as it would be easier to escape the Moon’s gravity than the Earth’s – we could move bigger payloads with less fuel.

Mainly proximity. First off it’s close enough that we’ve sent several probes and people so we’re quite familiar with it’s atmosphere and topography. That allows us to know with more certainty the challenges of living there. Second we can quickly transport supplies and equipment lowering the cost and risk.


We’ve successfully been able to get humans to the Moon multiple times, because we don’t have to worry about months (or potentially years) of travel. Apollo 11 (the first humans on the Moon) took 8 days, round-trip.

It is relatively close therefore relatively easy to resupply and potentially evacuate. It would also provide a convenient place to build and launch ships to further locations. There is also plenty of hydrogen and oxygen available if we develop the tools to extract it.

If you could drive to the Moon it would take you about half a year of non stop driving to get there.

But to get to Mars, the next closest celestial object, would take five hundred years (doing 60mph/90kph).

The moon is comparatively easier than any other option to get to. To get the moon we only need to cross 238,900 miles, Mars for comparison is at closest 33,900,000 miles away or up to 138,120,000 miles away.

The moon takes a few days to get to at any time, it takes a several months to get to Mars during a window every couple years.

Its wayyyy closer

If something goes wrong, you can hop into a ship, blast off, and only need 3 days of oxygen to safely make it back to Earth from the Moon

Launch tables from Mars to Earth aren’t readily available, but from Earth to Mars takes 120-220 days depending on when in the launch window and how strong the rocket is. Mars would basically need to keep a full year’s worth of supplies somewhere super duper safe. If something goes wrong and they need to bail but those supplies were damaged/destroyed there’s no coming home, just dying in the darkness of space

We always do test runs close by. They test out Mars rovers in a desert in Chile because its a close approximation and wayyyy easier to access than Mars itself and if something goes wrong they can just fly a spare part in next week. Prototypes and proof of concept always stay close because the assumption for the first run is that something will go wrong, and if nothing goes wrong then it wasn’t an adequate test

The primary reason is that it’s close and easiest to reach compared to other targets like Mars.

In order to travel to other planets like Mars, for example, we need to wait for the Earth and Mars to be close to each other in their relative orbit positions around the sun in order for it to be practical to reach Mars. This alignment only happens once every 26 months and when it comes up it still takes several months for a vessel to make the trip with today’s technology.

The moon, on the other hand, is orbiting Earth and a mission can be launched practically every day and it only takes about 3 days of travel to reach it. So if help or supplies are needed the colony on the moon can be reached quickly (in relative terms).

So, a colony built anywhere but the moon needs to be self sufficient from day 1 because no help or supplies can be sent for at least 2 years. A moon colony does not need to be self sufficient and can be practically resupplied on a periodic basis.

Furthermore, some ambitious scientists hope to use a base on the moon as a launching point for missions to other planets. The moon’s gravity is a lot less than on Earth so you don’t need as much fuel to get off the surface of the moon. So you can send heavier cargo loads using less fuel to other planets from the moon than launching it from Earth.

I must agree. The moon is 257 thousand miles away from earth its easily reachable with the rocket technology we have today.

The first time you go camping, you’re probably going to go to one of those established sites with showers and toilets and numbered campsites. You learn a lot about camping that way. You get used to setting up camp, cooking on a camping stove or over a fire pit, and sleeping in the great outdoors.

Where do you go from there? Maybe it’s a campground without showers and toilets. Maybe it’s a hike into the woods or up a mountain to the site. The things learned from your early camping experiences carry over and prepare you for a more remote camping experience.

The moon is sort of like the earlier scenario. It’s a stepping stone towards a more remote location. You can get to the moon on a couple days. You can launch at anytime to get there. It’s relatively easy. Mars is months away, and you can only launch when the orbits of the two planets are in the right spot. The moon is car camping, mars is everest camp 3.

Did anybody boil it down to location?

In short, it takes about three days to travel between Earth and the Moon. And we can *more or less* launch a rocket to the Moon at any time. Its distance from us doesn’t change *that* much.

Compare this to the next closest candidate, Mars: Getting there takes 9 months *in the best case*. In addition to this, because Mars is in a separate orbit around the sun, it’s only occasionally close to us. It spends a good chunk of its time at the opposite side of the sun from us. So if we want to get to Mars in *only* 9 months, we have to launch within very specific launch windows. How often do those occur? About once every 26 months.

So with a colony on the Moon we can send supplies fairly quickly if needed. We can react to emergencies. The people on living on the Moon could evacuate at almost any time if needed. Heck, while it would be expensive to do so, a colonist could even head back to Earth for a vacation or to see their family. That’d be basically impossible if they were on Mars. If an accident happens on Mars and they need unscheduled supplies sent, better hope they can hold out a year or two. And if they ever need to evacuate, well, tough luck. They’re not coming back to Earth. It’s just not doable.