Mars is out; the moon is in. And this time, we may be going there to stay.

On Tuesday (March 24), NASA administrator Jared Isaacman announced new plans to build a "sustained human presence" on the moon, complete with a permanent lunar base. Construction of humanity's new home away from Earth could begin as soon as 2027, Isaacman said.

It's an exciting prospect — but scientists say lunar colonization won't be as simple as packing up and lifting off. The moon's environment is harsh: think razor-sharp, electrified dust and a constant stream of radioactive particles travelling at light speed. Scientists still aren't sure how this increased dose of cosmic radiation, coupled with the moon's weaker gravitational pull, relative to Earth, will affect the human body in the medium- to long-term.

And then there's technological feasibility: Where will astronauts live, and with what resources? At the moment, these big questions are still awaiting answers that may not arrive in time for NASA and Musk's proposed plans.

"I don't think we're quite ready," Caitlin Ahrens, a researcher at University of Maryland and NASA's Goddard Space Flight Center who studies the lunar environment, told Live Science. "A decade may seem far away to some people. To a scientist, it's the blink of an eye."

Satellite of horrors

Moondust is rather different from what we call dust on Earth. Without wind and liquid water, the moon's dust doesn't soften over time. "We're talking very, very sharp little pollen[-size] shards here," Ahrens said.

It's also easily electrified. Simply walking on the moon kicks up dust clouds, and rovers traversing the lunar landscape shoot up "rooster tails" of electrically charged, levitating dust, which sticks to anything in its path, Ahrens said. Energized dust can clog breathing vents in potential living quarters, scratch up spacesuits and coat solar panels, potentially overheating and breaking them. (Dust clogs have already spelled doom for several Mars rovers).

Without the soft blankets of Earth's atmosphere and magnetic shield, moon inhabitants would also be constantly blasted by radiation. Cosmic radiation is "pretty much omnipresent anywhere you go into space," including on the moon, Dr. Emmanuel Urquieta, an aerospace medicine researcher at the University of Central Florida, told Live Science. "It's incredibly difficult to shield."

Cancer is a potential risk, but because health effects of radiation take time to develop, we wouldn't know for certain if this is a major risk factor until potentially decades after landing human settlers on the moon. "Every person that goes to space… will absolutely be test subjects," Urquieta said.

We're not ready for self-defense

Humans on the moon would need hefty building materials to protect lunar habitats against these hazards. Metal or glass domes, subterranean habitats and housing made of 3D-printed moon soil are all potential options being investigated.

But Ahrens, who also works on lunar risk assessment, doesn't think we're ready to plan construction. For example, if NASA decides to invest in an underground habitat — perhaps the most surefire way to avoid radiation — scientists still have no idea how to dig on the moon, she said.

Even with sufficiently protective living quarters, the moon's weaker gravitational pull — just one-sixth that of Earth — may pose health risks. From previous space travel we know that, without the gravitational force humans evolved with, our bones and muscles need significant amounts of exercise to prevent them from withering away. But it wouldn't be practical to lug heavy treadmills, like those used on the International Space Station, to the moon, Urquieta said.

A lack of gravity may also redistribute the body's natural balance of fluids, with potentially disastrous effects. Normally, due to the downward tug of gravity, up to 80% of our blood is in our legs at any given time, Urquieta said. But on the moon, more fluids would flow to the body's upper half, causing loss of blood as the body attempts to rebalance itself, as well as potential swelling at the back of the eye and jugular vein thrombosis, a condition that causes potentially fatal blood clots in the neck. Compared to zero gravity, lunar partial gravity may or may not pose similar health risks. Urquieta said researchers won't know until people spend some time there.

The future of lunar settlement

Ultimately, Ahrens said, these challenges boil down to the need for more data, which scientists are hoping to gather with missions like NASA's Artemis campaign to return humans to the lunar surface as soon as 2028. But she envisions a much slower timeline than Musk's and Isaacman's plans; scientists haven't even taken a sample of the moon's ice yet — a resource lunar settlement planners are banking on.

Depending on its depth and composition, lunar ice could provide water, rocket fuel and rare earth metals. But until scientists get a physical sample of ice, they can't rely on its usefulness or economic prospects. For now, scientific knowledge of the ice's actual chemical composition is very limited: "We know it's cold, and we kind of know where it is," Ahrens said.

When it comes to the moon and its offerings, "we have to be very careful not to sell something which [we] don't have," said Giuseppe Reibaldi, president of the Moon Village Association, a non-profit group focused on international collaboration in lunar activities.

Reibaldi told Live Science that what we find in the moon's ice could be the difference between the lunar equivalent of California's gold rush boomtowns — where settlements sprang up in response to mining opportunities — and Antarctica, where a small number of scientists come and go for solely research purposes.

But even if permanent settlement doesn't happen as soon as hoped, Ahrens said she is optimistic about the forecast for lunar development. "I think it's not all sunshine and rainbows, but it's also not dark rainy clouds either," she said.

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Georgia Michelman is a freelance science and health journalist based in New York City. She holds a B.S. in physics and history from Yale University and is currently enrolled in NYU's Science, Health, and Environmental Reporting Program. Before going into journalism, she worked across the pond for two years at the U.K.-based Science Media Centre, an independent press office focused on controversial science stories. She has strong interests in writing about physics, astronomy, psychiatry, drugs, and public health.