How Will We Colonize Other Planets?

By: Patrick J. Kiger  | 

SpaceX's Dragon arrived at the International Space Station on May 6, 2019, pictured here over the North Atlantic Ocean. SpaceX

If you think that the idea of colonizing other planets is something out of a particularly far-fetched science fiction movie or book, Elon Musk, founder of private space travel company SpaceX, has a surprise for you.

Musk has said that there's a 70 percent chance that he'll travel on a rocket to Mars in his lifetime, and that he's thinking about eventually moving there to live in a human outpost on the surface of the red planet [source: Allen and VandeHei].


Unlike the protagonist of the science-fiction novel and movie "The Martian," Musk most likely wouldn't be lonely on the red planet. Back in 2012, at a conference of the Royal Aeronautical Society in London, he sketched out a vision for a Mars colony that eventually would grow to the size of a small- to medium-sized city on Earth, with 80,000 inhabitants [source: Coppinger].

While Musk envisions a private-sector Mars colony, NASA has plans to eventually establish a base on Mars as well. The Trump Administration currently is focused upon revisiting the moon by 2024 and building a permanent base there that would provide the opportunity for "developing the technologies to take American astronauts to Mars and beyond," in the words of Vice President Mike Pence [source: Wall]. In anticipation of that day, NASA already is testing technologies such as space habitat modules — basically, spacefaring mobile homes that would provide life support for humans living on the surface of other worlds [source: NASA].

The European Space Agency also has envisioned setting up its own "Moon Village" on the lunar surface [source: Woerner].

Meanwhile, visionaries also are looking toward the eventual colonization of Earth-like exoplanets orbiting around other stars [source: Ceriotti].

What has humans looking to make new homes in the cosmos? The National Space Society, a private-sector organization that promotes a spacefaring future, cites a variety of reasons for building colonies in space. One reason is that other worlds contain vast amounts of metals and other natural resources and potential sources of energy, and provide opportunities for "potentially profit-making industries" [source: National Space Society].

Establishing outposts on other worlds also might be a way to hedge the bet on humanity's survival, in case our existence on our home planet is threatened by a nuclear war, climate change, pandemics and population growth. The late physicist Stephen Hawking believed that humanity needs to colonize another planet within the next century, if it is to avoid the threat of extinction [source: Kharpal].

But before humans venture to distant worlds, they'll most likely be starting with a colony on the moon. In the next section, we'll look at what might be needed to live there.


Lunar Living

Moon base
This artist's concept shows a human landing system and its crew on the lunar surface with Earth near the horizon. NASA

Ever since the Apollo program put the moon within our reach, establishing a lunar outpost has seemed a logical next step. Earth's natural satellite offers several advantages over more distant destinations, such as Mars or Saturn's moon Titan. First, it's relatively close, which means crews could get back and forth from the Earth and moon in just a few days. Additionally, a lunar base would enable use to learn a lot about the effects of low gravity, isolation, high doses of cosmic radiation, and disrupted circadian rhythms on human space colonists — knowledge that would be invaluable when we eventually venture to other worlds [source: Fecht].

Additionally, the moon's low gravity and closeness to Earth would make it an ideal location for a spaceport from which astronauts could embark on missions to Mars and worlds even further away. And in terms of long-term possibilities, the moon is a big place — its surface is roughly the size of Africa — and it has plenty of room for human colonists [source: Gent].


But living on the moon won't be any picnic. With no atmosphere, it experiences huge temperature extremes, swinging from minus 298 degrees Fahrenheit (minus 183 degrees Celsius), at night, to 224 degrees Fahrenheit (106 degrees Celsius) in the daytime at the equator [source: CalTech]. Its surface is also peppered constantly by micrometeorites and cosmic rays [source: Redd].

To survive those hostile environmental conditions, some experts think that colonists will likely have to place their habitats under the lunar soil or at the base of a lava tube [source: Redd]. Others envision domes built by robots equipped with 3D printers, which would provide protection [source: Gent].

Then there's the issue of food and water. In 2018, a team of scientists spotted the first definitive evidence of water ice on the lunar surface, a discovery that suggests that future lunar colonists might be able to extract their own supply, which could provide water for drinking and for irrigating plants in lunar greenhouses, as well as a raw material for rocket fuel [sources: NASA, Grush].

NASA's current plan for returning to the moon involves building a lunar orbital station, the Gateway, which will serve as a staging area for teams of astronauts to make short visits to the lunar surface. The first part of the Gateway is scheduled to be sent into space on a private rocket in 2022 [source: NASA].

Keep reading to find out what the plan is for Mars.


Successful Settlement of Mars

Sketch of manned Martian outpost
Artist's sketch of what the first Martian outpost might look like. How would you like this to be your front yard?

Some space experts have argued that NASA should focus on going to Mars instead of returning to the moon. But President Trump's appointee as NASA chief, Jim Bridenstine, has reassured Mars proponents that despite Trump's switch to prioritizing a lunar mission, the space agency still intends to go to the red planet. Bridenstine has said that returning to the moon will enable the agency to develop technologies for an eventual Mars mission, including "precision landing systems, methane engines, orbital habitation, surface habitation, surface mobility, long duration life support operations and much more" [source: Smith].

Since NASA's December 2017 shift to focusing upon returning to the moon, it hasn't put out any updated plans for making a manned landing on Mars and establishing a human colony. But in a plan that the agency published in 2015, the initial mission would be complex. Astronauts would make the 180-day trip to Mars in a crew habitat module, a two-level container that would double as a habitat on the Martian surface. By the time the astronauts landed, a separate laboratory module, a rover vehicle and other equipment — including a nuclear reactor — and supplies already would be waiting for them on the Martian surface, after being transported there by robotic spacecraft. Another spacecraft, fueled for a return to Earth, would be positioned in orbit to enable the initial crew to eventually return to Earth [source: NASA]. Subsequent missions might expand that original base or set up others to form a Mars colony.


On Mars, human colonists would have to grow their own food. NASA has been experimenting with growing vegetables on the International Space Station, and also has developed simulated Martian soil, which contains nutrients that plants would need to survive, to better understand how it could be used to grow crops [source: NASA].

Over the years, science fiction writers and futurists have speculated about the possibility of terraforming Mars, to transform its environment to something closer to Earth's. One approach would involve releasing carbon dioxide trapped within the Martian surface to make the atmosphere thicker, which also would help to trap solar radiation and warm the surface. However, a NASA study published in 2018 concluded that the Martian surface doesn't contain enough CO2 to be put back into the atmosphere to create a greenhouse effect, and it wouldn't be possible to extract much of what is there with present technology [source: NASA].

In the next section, we'll talk about the possibility of colonizing an asteroid or dwarf planet.


Establishing Colonies Beyond Mars

Do you think you could live on this rock?
Riser/Getty Images

Asteroids — those rocky objects that orbit the sun in a wide band between Mars and Jupiter — could serve as stepping-stones to the outer planets. There are only 100 asteroids larger than 125 miles (200 kilometers) across, but a billion or more may exist, making them one of the solar system's greatest resources [source: Rees].

But colonizing an asteroid would be even more challenging than building a base on Mars or the moon. Asteroids don't have much gravity, so astronauts would face serious health problems from living in that environment unless they created artificial gravity inside the base, possibly by continually spinning the entire habitat.


Because the asteroid belt is so far from the sun, solar arrays that powered such machinery would have to be gigantic. There also would be the problem of shielding the colonists from cosmic radiation. You might think that tunneling into the surface might provide some protection, but doing that would be tricky, because a lot of the objects that we call asteroids aren't actually solid rock, but basically bunches of space junk without much structural integrity [source: Allison].

But if we were going to colonize a smaller distant object, the dwarf planet Ceres, the largest object in the asteroid belt and the only dwarf planet in the inner solar system, might have some possibilities. NASA's Dawn probe discovered that the asteroid has an outer shell that's rich in water, in the form of ice and hydrates [source: NASA].

The Obama administration had an ambitious plan, the Asteroid Redirect Mission, which called for capturing part of an asteroid and bringing it back to the vicinity of the moon, so that astronauts could land on it and retrieve samples. But the project was cancelled in 2017 by the Trump Administration [source: Malik].

Are you ready to head beyond the solar system?


Heading for a Planet in Another Star System

the Dawn spacecraft blasting off
The Dawn spacecraft began its 1.7 billion-mile journey in 2007 to study asteroids, thanks to a trio of solar electric ion propulsion engines.

If we're going to colonize a planet in another star system, we have to answer two questions. First, do any Earth-like planets even exist outside of our solar system? Thanks to NASA's Kepler telescope, the answer to this question is yes. Kepler, which was decommissioned in 2018, located nearly 2,700 planets — what astronomers call exoplanets — orbiting stars anywhere from a few hundred to a few thousand light-years away. Many of the exoplanets are gas giants similar to Jupiter and Saturn. But others are "super Earths," rocky planets slightly bigger than ours [source: Howell]. Some of those might possibly have the right conditions to be hospitable to human colonists.

The second question is purely logistical: How do we get to a planet located trillions of miles from our own? To answer this question, scientists will have to rethink space travel. For example, the idea that a single crew will fly to a remote planet is highly unlikely. Instead, spacecraft might need to carry family groups capable of living in space for generations [source: Feltman].


Scientists will also have to come up with better propulsion systems to cut the travel time. Nuclear fission- and fusion-based engines might be feasible, but more likely candidates include solar sails, ion-propulsion systems or antimatter rockets [source: Stromberg].

Light sails work by directing laser light onto a huge aluminum-foil sail. As photons strike the sail, they transfer momentum and push the sail forward. Ion-propulsion systems use solar panels to generate electric fields that accelerate charged atoms of xenon. Such an engine powered the Dawn mission, which hurled an unmanned spacecraft to two asteroids, Vesta and Ceres, before its mission was completed in November 2018. Antimatter rockets are the most efficient and achieve the highest speeds, but the technology is relatively untested. Such a rocket mixes equal amounts of antihydrogen and hydrogen, which annihilate each other in a combustion chamber to release enormous amounts of energy [source: Stromberg].

In the end, a combination of technologies may be the solution, proving once again that conquering deep space will require cooperation and collaboration among scientists of different disciplines and nationalities.


ScienceAstronomy TermsFloating PlanetScienceAstronomyHow Nomad Planets WorkScienceSpace ExplorationHow Planet Hunting WorksScienceThe Solar SystemWhy is Pluto no longer considered a planet?ScienceFuture SpaceHow Will We Colonize Other Planets?ScienceGeophysicsHow much does planet Earth weigh?ScienceThe Solar SystemWhy Did It Take So Long to 'Discover' Planet Nine?ScienceThe Solar SystemWhat's the Order of the Planets in the Solar System?ScienceThe Solar SystemDoes it rain on other planets?ScienceThe Solar SystemJupiter: Yokozuna of Gas Giants, Banisher of PlanetsScienceThe Solar SystemHow do planets form?ScienceStarsWhite Dwarfs Can Shred Planets to PiecesScienceThe Solar SystemWho Named Planet Earth?ScienceSpace ExplorationDoes a planet need continents to support life?ScienceThe Solar SystemIs Planet Nine Actually a Primordial Black Hole?ScienceSpace ExplorationHow many planets in our universe could support life?ScienceStarsCould a planet exist without a host star?ScienceThe Solar SystemWhy Are Planets Almost Spherical?ScienceThe Solar SystemNASA Announces New Solar System Packed With Seven PlanetsScienceThe Solar SystemPluto: Is It a Planet After All?ScienceThe Solar SystemHaumea, a Dwarf Planet in the Kuiper Belt, Has Its Own RingScienceSpace ExplorationNew NASA Satellite Is Hunting for Distant PlanetsScienceThe Solar SystemAncient Obliteration of Dwarf Planets May Have Created Saturn's RingsScienceThe Solar SystemIs Earth the Only Planet With Tectonic Plates?ScienceStarsHow do astronomers detect that a star has a planet orbiting it?ScienceSpace ExplorationCan we detect water on exoplanets?ScienceThe Solar SystemThe Truth Behind the Rogue Planet NibiruScienceThe Solar SystemUranus: The Planet on a Very Tilted AxisScienceThe Solar SystemPloonets: When Moons Become PlanetsScienceAstronomy TermsPlanetariumScienceSpace Exploration10 Remarkable ExoplanetsScienceSpace ExplorationClosest Exoplanet Yet Confirmed By European Southern ObservatoryScienceStarsSpotted: Early Planetary Formation Around a Binary Star SystemScienceStarsThis Is How We'll Detect Life on Distant ExoplanetsScienceSpace ExplorationNASA's Kepler Mission Adds 100 Alien Worlds to Exoplanet TallyScienceSpace ExplorationCan amateur astronomers spot exoplanets?ScienceFuture Space10 Best Ideas for Interplanetary CommunicationScienceSpace ExplorationLISA: Detecting Exoplanets Using Gravitational WavesScienceThe Solar SystemHow NASA Planetary Protection WorksScienceAstronomy TermsPlanetesimal Hypothesis

Lots More Information

Related Articles

More Great Links

  • Allen, Mike and VandeHei, Jim. "Elon Musk: There's a 70% chance that I personally go to Mars." Axios. Nov. 25, 2018. (April 14, 2019)
  • Allison, Peter Ray. "How We Could Survive on an Asteroid." June 13, 2018. (April 14, 2019)
  • Associated Press. "Optimism That Earth-Like Planets Exist." CBS News. Jan. 7, 2010. (April 14, 2019)
  • Beardsley, Tim. "The Way to Go in Space." Scientific American Presents: The Future of Space Exploration. 1999.
  • Cool Cosmos. "What is the temperature on the Moon?" (April 14, 2019)
  • Ceriotti, Matteo. "Here's how we could build a colony on an alien world." The Conversation. Feb. 26, 2017. (April 14, 2019)
  • Chang, Kenneth. "Senate Panel Near Agreement on Bill to Roll Back NASA Changes." New York Times. July 8, 2010. (July 31, 2010)
  • Coppinger, Rob. "Huge Mars Colony Eyed by SpaceX Founder Elon Musk." Nov. 23, 2012. (April 14, 2019)
  • European Space Agency.
  • Fecht, Sarah. "Six Reasons NASA Should Build a Research Base on the Moon." National Geographic. Dec. 21, 2013. (April 14, 2019)
  • Feltman, Rachel. "We could move to another planet with a spaceship like this." Popular Science. May 4, 2018. (April 14, 2019)
  • Gallant, Roy A. "National Geographic Picture Atlas of Our Universe." National Geographic Society. 1994.
  • Gent. Edd. "Moon bases being planned now may show us how to live off-planet." NBC News. March 13, 2018. (April 14, 2019)
  • Grush, Loren. "Why mining the water on the Moon could open up space exploration." Aug. 23, 2018. (April 14, 2019)
  • Howell, Elizabeth. "Kepler Space Telescope: The Original Exoplanet Hunter." Dec. 7, 2018. (April 14, 2019)
  • Kharpal, Arjun. "Stephen Hawking says humans must colonize another planet in 100 years or face extinction." CNBC. May 5, 2017. (April 14, 2019)
  • Kushner, David. "Dream Chasers." Discover Magazine. September 2010.
  • Malik, Tariq. "Trump's NASA Budget Eliminates Crewed Mission to Asteroid." Scientific American. March 16, 2017. (April 14, 2019)
  • McKay, Christopher P. "Bringing Life to Mars." Scientific American Presents: The Future of Space Exploration. 1999.
  • NASA. "Can Plants Grow with Mars Soil?" NASA. Aug. 7, 2017. (April 14, 2019)
  • NASA. "Constructing Next-Generation Space Habitat Demonstrators." July 16, 2012. (April 14, 2019)
  • NASA. "Ice Confirmed at the Moon's Poles." Aug. 20, 2018. (April 14, 2019)
  • NASA. "Journey to Mars." NASA. (April 14, 2019) html
  • NASA. "Landing on the Surface." NASA. Aug. 27, 2015. (April 14, 2019)
  • NASA. "Mars Terraforming Not Possible Using Present-Day Technology."
  • NASA. "Moon to Mars Overview." April 5, 2019. (April 14, 2019)
  • NASA. "NASA Begins Testing Habitation Prototypes." March 27, 2019. (April 14, 2019)
  • NASA. "What We Learned from Dawn." NASA. Oct. 31, 2018. (April 14, 2019)
  • National Space Society. "NSS Space Settlement Nexus." (April 14, 2019)
  • National Space Society "Space Settlements." June 17, 2010. (April 14, 2019)
  • Piper, Kelsey. "The case against colonizing space to save humanity." Vox Oct. 22, 2018. (April 14, 2019)
  • Redd, Nola Taylor. "Lunar Shelter: Moon Caves Could Protect Astronauts." May 5, 2016. (April 14, 2019)
  • Rees, Martin. "Universe: The Definitive Visual Guide." DK Publishing. 2012. (April 14, 2019)
  • Rieland, Randy. "If Humans Want To Colonize Other Planets, We Need To Perfect Space Cuisine." March 28, 2018. (April 14, 2019)
  • ScienceDaily. "Suspended Animation Induced in Mice with Sewer Gas: Effects are Reversible." March 25, 2008. (April 14, 2019)
  • Smith, David. "New moon mission will not distract from effort to reach Mars, Nasa boss says." Guardian. May 9, 2018. (April 14, 2019)
  • Sparrow, Giles. "Spaceflight: The Complete Story from Sputnik to Shuttle — and Beyond." Dorling Kindersley Limited. 2007.
  • Stromberg, Joseph. "Can We Power a Space Mission To An Exoplanet?" Smithsonian. June 28, 2013. (April 14, 2019)
  • Weed, William Speed. "Star Trek." Discover Magazine. August 2003. (April 14, 2019
  • Wall, Mike. "US to Return Astronauts to the Moon by 2024, VP Pence Says." March 26, 2019. (April 14, 2019)
  • Woerner, Jan. "Moon Village." 2016. (April 14, 2019)
  • Zubrin, Robert. "Sending Humans to Mars." Scientific American Presents: The Future of Space Exploration. 1999.