The Artemis plan: Why NASA sees the moon as a stepping stone to Mars

An illustration of the Earth, the moon and Mars (not to scale). Future crewed space missions will use the lunar surface as a stepping stone to the Red Planet.
An illustration showing Earth, the moon and Mars (not to scale). Future crewed space missions will use the lunar surface as a stepping stone to the Red Planet. (Image credit: NASA/Robert Lea)

The next era of crewed space exploration is about to dawn, with NASA's Artemis program gearing up to send humans back to the moon for the first time in over half a century. And this milestone will eventually lead to the first human setting foot on the surface of Mars, if all goes according to plan.

On Aug. 29, the Space Launch System (SLS)  —  the most powerful rocket ever built by humanity  —  is scheduled to blast off from Launch Pad 39B at NASA's Kennedy Space Center in Florida, kicking off the Artemis 1 mission.

The main payload of the SLS will be the Orion spacecraft, which will be sent farther into space than any vehicle intended for humans has ever traveled before. This will serve as a crucial test for future Artemis missions that will see Orion carry a woman and a person of color to the surface of the moon for the first time.

Related: NASA's Artemis 1 moon mission: Live updates

That will be a stunning achievement in its own right. But putting astronauts on the moon for the first time since the final Apollo mission in 1972 has a bigger goal: establishing a sustainable human presence on and around the moon and developing infrastructure that will allow humans to go even deeper into the solar system.

Indeed, NASA sees the moon as a "proving ground" for the human exploration of Mars, as then-agency chief Jim Bridenstine said in 2018.

Earlier this year, NASA released its "moon to Mars" objectives, which identified 50 key points that fall under the broad categories of exploration, transportation and habitation, moon and Mars infrastructure, operations and science. 

"These objectives will move us toward our first analog Mars mission with crew in space and prepare us for the first human mission to the surface of the Red Planet," Jim Free, associate administrator for NASA's Exploration Systems Development Mission Directorate, said in a statement in May.

Stepping stone and testing ground

The advantage of using the moon as a stepping stone to Mars is its proximity to Earth. A crewed mission can get to or from the moon in just three days, whereas a mission straight from Earth to Mars or vice versa would take at least seven months, with a round-trip mission estimated to last approximately 500 days.

NASA will be paying close attention to the effects of limited gravity  —  or microgravity  —  on the human body during crewed flights to the moon to assess the effects of long journeys to Mars.

With the concept of sustainability in mind, the Artemis 1 mission will also carry 10 tiny cubesats to space. Several of these little satellites have the explicit mission of mapping the distribution of water on the moon. This includes searching for hydrogen reserves locked up in ice in the shadowy and frigid craters of the lunar polar regions.

Water found across the lunar surface may not just be used to sustain astronauts. Methods are currently being developed that could see lunar water converted into rocket fuel. This could mean that craft leaving Earth for Mars wouldn’t have to blast off with all the fuel needed to traverse the long gulf to the Red Planet.

Hauling less fuel would make interplanetary missions much more cost-effective or allow spacecraft to carry more cargo and scientific instruments.

Forthcoming Artemis missions to the moon's surface, the first of which should be Artemis 3 no sooner than 2025, will also allow new technologies to be tested off Earth that could eventually also be deployed on Mars. 

According to NASA, early discussions of such technology have included roving instrument kits to search for resources across alien vistas and a habitable mobility platform that would allow humans to operate on the lunar surface for up to 45 days. 

Other proposed systems that could be tested on the lunar surface before being included on a journey to Mars are human habitats and life support systems that allow astronauts to operate for long periods at distances from Earth as great as 1,000 times the distance between our planet and the International Space Station. (The ISS orbits Earth at an average altitude of 250 miles, or 400 kilometers.)

Related: Water on the moon is more common than we thought, studies reveal 

The gateway to Mars

While Artemis 1 will serve as an important test of much of the technology needed for prolonged space travel, one important aspect of NASA's crewed moon plans remains unestablished  —  the Gateway space station

Gateway will be the first space station placed into orbit around the moon. Equipped with docking points for various spacecraft, a module called the Habitation and Logistics Outpost (HALO)  —  serving as the station’s living and work areas  —  and scientific equipment, Gateway will add sustainability to operations on the moon and for crewed deep-space journeys, NASA officials say. It will also allow refueling for extended trips into space.

But, even before such journeys are underway, Gateway — for which key components are expected to launch no sooner than November 2024  —  will help NASA and other space agencies investigate the effect of long-term deep space missions on the human body.

Gateway will also play an important role in the delivery of materials to the moon that will help develop infrastructure on the lunar surface. 

This infrastructure will eventually include a transportation system that can deliver large payloads from Earth to Mars via the moon, if all goes according to plan. This capability, in turn, will lead to the development of power systems on the Martian surface that could enable long stays on the Red Planet for humans.

These are not short-term goals. NASA currently estimates that humans won’t be ready to set foot on Mars until at least the late 2030s or the early 2040s. It’s clear, however, that Artemis 1 represents an important first step on the long road to Mars.

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Robert Lea
Senior Writer

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.