- The energy required to send objects from the Moon to space is much less than from Earth to space.
- Ease of landing on and launching from the Moon makes it an ideal construction site or fueling station for spacecraft. Some proposals even include using electric acceleration devices (mass drivers) to propel objects off the Moon without building rockets.
- Proximity of Moon to Earth makes it ideal to colonize. The Moon is the closest large body in the solar system to Earth. While some Earth-crosser asteroids occasionally pass closer, the Moon's distance is consistently within a small range close to 384,400 km. This proximity has several benefits:
- Proximity of Moon to Earth makes it ripe for tourism.
- The energy required to send objects from Earth to the Moon is lower than for most other bodies.
- Transit time is short. The Apollo astronauts made the trip in three days. Other chemical rockets such as would be used for any Moon missions in the next one to two decades at least would take a similar length of time to make the trip.
- The short transit time would also allow emergency supplies to quickly reach a Moon colony from Earth, or allow a human crew to evacuate relatively quickly from the Moon to Earth in case of emergency. This could be an important consideration when establishing the first human colony.
- The round trip communication delay to Earth is less than three seconds, allowing near-normal voice and video conversation, and allowing some kinds of remote control of machines from Earth that are not possible from any other celestial body. The delay for other solar system bodies is minutes or hours; for example, round trip communication time between Earth and Mars ranges from about eight minutes to about forty minutes. This again would be of particular value in an early colony, where life-threatening problems requiring Earth's assistance could occur. (See, for example, Apollo 13.)
- Moon colony would feel comforted by site of large Earth. On the lunar near side, the Earth appears large and is always visible as an object 60 times brighter than the Moon appears from Earth, unlike more distant locations where the Earth would be seen merely as a star-like object, much as the planets appear from Earth. As a result, a lunar colony might feel less remote to humans living there.
- The Moon would be ideal site for a space observatory. A lunar base would provide an excellent site for any kind of observatory. Particular advantages arise from building observatory facilities on the Moon from lunar materials. As the Moon's rotation is so slow, visible light observatories could perform observations for days at a time. It is possible to maintain near-constant observations on a specific target with a string of such observatories spanning the circumference of the Moon. The fact that the Moon is geologically inactive along with the lack of widespread human activity results in a remarkable lack of mechanical disturbance, making it far easier to set up interferometric telescopes on the lunar surface, even at relatively high frequencies such as visible light.
- Colonizing the Moon is a good test for colonizing Mars. If the Moon were colonized then it could be tested if humans can survive in microgravity. Those results could be utilized for a viable Mars colony as well.
- The Moon is ideal for launching rockets on mission to Mars. A lunar base could also hold a future site for launching rockets, to distant planets such as Mars. Launching rockets from the Moon would be an easier prospect than on Earth due to the Moon's lower gravity requiring a lower escape velocity.
- The Moon's gravity is too low for human health. "Why the Moon will Never be Colonized." Phil for Humanity: "The Moon will never be colonized for a single reason. Basically, the Moon’s gravity is less than 17% of Earth’s gravity, and people can not survive long periods of time at such low gravity. [...] Even though people could easily survive short time periods in this low gravity, it would be extremely unhealthy for prolonged periods of time especially when returning to Earth. For instance, long stays in low gravity can and will result with significant loss in bone density and muscle atrophy, just to name the two most common issues with low gravity. However, assuming that the colonization of the Moon is a one-way ticket without ever returning back to Earth and Earth’s higher gravity, adults could live relatively long and mostly healthy lives on the Moon."
- The children of Moon colonizers would not be healthy. "Why the Moon will Never be Colonized." Phil for Humanity: "The bigger problem with colonizing the Moon is the effects that low gravity will have on children. The human development process has evolved perfectly with Earth’s high gravity. On the Moon, children would most likely develop severe and possibly fatal deformities under low gravity. For instance, their bones would be extremely brittle and break often. Their hearts would be very weak and never fully develop, as well as possibly all of their other muscles too. Children would literally grow to extreme heights that will cause severe complications on the spinal cord and digestive systems, because these organs have limited stretching capabilities. As a result, colonists on the Moon might not be able to have healthy children capable of living long enough to have children of their own."
- Territorial claims on the Moon will become a source of conflict. Just as humans staked out claims on Earth's North Pole, it is also likely that different countries will begin staking claims to territory on the Moon. This creates the possibility of raising tensions between nations.
- The Moon has extreme temperature extremes. The Moon would has very extreme cold and heat, depending on where the sun shines, which presents many challenges to a lunar colony. The lack of a substantial atmosphere for insulation results in temperature extremes and makes the Moon's surface conditions somewhat like a deep space vacuum. It also leaves the lunar surface exposed to half as much radiation as in interplanetary space (with the other half blocked by the moon itself underneath the colony). Although lunar materials would potentially be useful as a simple radiation shield for living quarters, shielding against solar flares during expeditions outside is more problematic. (See also Proton exposure)
- The Moon lacks materials for self-sufficiency. The Moon lacks light elements (volatiles), such as carbon and nitrogen, although there is some evidence of hydrogen near the north and south poles. Additionally, oxygen, though one of the most common elements in the regolith constituting the Moon's surface, is only found bound up in minerals that would require complex industrial infrastructure using very high energy to isolate. Some or all of these volatiles are needed to generate breathable air, water, food, and rocket fuel, all of which would need to be imported from Earth until other cheaper sources are developed. This would limit the colony's rate of growth and keep it dependent on Earth.
Also, the lack of an atmosphere increases the chances of the colonial site being hit by meteors, which would impact upon the surface directly, as they have done throughout the Moon's history. Even small pebbles and dust (micrometeoroids) have the potential to damage or destroy insufficiently protected structures.
Moon dust is an extremely abrasive glassy substance formed by micrometeorites and unrounded due to the lack of weathering. It sticks to everything, can damage equipment, and it may be toxic.
Growing crops on the moon faces many difficult challenges due to the long lunar night (nearly 15 earth days), extreme variation in surface temperature, exposure to solar flares, and lack of insects for pollination. (Due to the lack of any atmosphere on the Moon, plants would need to be grown in sealed chambers, though experiments have shown that plants can thrive at pressures much lower than those on Earth.) The use of electric lighting to compensate for the 28 day/night might be difficult: a single acre of plants on Earth enjoys a peak 4 megawatts of sunlight power at noon. Experiments conducted by the Soviet space program in the 1970s suggest it is possible to grow conventional crops with the 15 day light, 15 day dark cycle. A variety of concepts for lunar agriculture have been proposed, including the use of minimal artificial light to maintain plants during the night and the use of fast growing crops that might be started as seedlings with artificial light and be harvestable at the end of one lunar day. A farm at the lunar North Pole could provide eight hours of sunlight per day for rotating crops, a beneficial temperature, radiation protection, insects for pollination, and all other plant needs artificially during the local summer for a cost. One estimate suggested a 0.5 hectare space farm could feed 100 people.