The United States wants to send American astronauts to the surface of the Moon in five years and establish a permanent human presence there.

The plan involves constructing a "lunar gateway," an orbiting laboratory that will serve as a jumping-off point where astronauts can stay before exploring Earth's natural satellite. Eventually, NASA wants to send astronauts to a manned mission toward Mars and further into the solar system.

Humans In Space

These all sound so exciting but the problem is that space is not welcoming to humans. Astronauts who will be sent to space face numerous risks, including cosmic radiation.

The International Space Station, where currently six people live and work, is just 254 miles or about 408 kilometers above the planet. Its crew is largely protected from cosmic radiation by the Earth's magnetosphere, allowing them to stay well under the limits set in place by NASA.

However, the Moon is nearly 240,000 miles away from where the magnetosphere can no longer offer an umbrella against harmful cosmic rays. Mars is even further away.

When the Curiosity rover traveled from Earth to the Red Planet, it discovered that a one-way trip would subject astronauts to an additional 0.3 sieverts of radiation. Going to Mars would expose astronauts to radiation that is equivalent to 15 times the annual radiation limit for workers at nuclear power plants.

It is not deadly, but it can cause serious harm. Exposure to radiation has been linked to an increased risk of cancer.

Scientists still do not fully understand how long-term exposure to radiation in deep space would affect the human body. The only people who have spent time outside of the protective bubble of Earth where the Apollo astronauts who stepped on the Moon decades ago.

More recently, NASA tried to understand the effects of spaceflight on the human body through the "Twin Study." Astronaut Scott Kelly was sent to the ISS for a year, which is double the length of a typical mission.

When Kelly returned to Earth, he scored lower in cognitive tests and his doctors could not figure out why it was taking him a long time to recover.

Mathias Basner, a psychiatrist who led the cognitive testing, suggested that exposure to higher radiation might have contributed to the changes in the astronaut's cognitive capabilities. Living in an isolated environment for a long period of time might have also done some damage. He also noted that going back to Earth's full gravity can be pretty taxing.

"It takes some time for the brain to adapt to the [space] environment, and apparently it also takes some time to adapt back to the gravity environment," Basner explained to Vox. "There are 20 things going on at the same time" that could affect cognition.

What NASA Is Doing To Ensure Safety Of Astronauts In Space

Space is a hostile place, but NASA continues to study how long-haul spaceflight would affect the human body and figure out how they can protect astronauts who venture further into the solar system. The U.S. space agency mainstains a Human Research Roadmap that highlights the known and the unknown risks of going to space.

One of the things that NASA is trying to figure out as part of the road map is how much radiation a human can take before falling seriously ill.

"Ultimately, the solution to radiation will have to be a combination of things," said Jonathan Pellish, a space radiation engineer. "Some of the solutions are technology we have already, like hydrogen-rich materials, but some of it will necessarily be cutting edge concepts that we haven't even thought of yet."

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