NASA Astronauts Splash Down in SpaceX Capsule: Watch Live With Updates
For a NASA astronaut, an assignment to the International Space Station means planning for six months in space. That’s long enough to study changes to the human body — research that’s crucial if astronauts make the trip to Mars one day — but not so long that the changes become debilitating for the astronauts after they return home.
Sometimes the stay in orbit can be shorter, a consequence of a change in the travel schedule of the spacecraft coming and going. Sometimes it lasts longer, as with Suni Williams and Butch Wilmore, who spent more than nine months on the space station before heading home on Tuesday.
That is not an unusually long stay, and NASA does not expect them to experience serious long-term health repercussions. Frank Rubio holds the record for the longest stay in space by an American astronaut at 371 days.
Still, the human body is not intended to work well without gravity, and it takes time to adjust.
Last fall, Ms. Williams appeared to look gaunt in some pictures. NASA responded to rebut rumors that she was ill and losing weight.
The biggest change while in orbit is that fluids within an astronaut’s body float upward. Faces swell and sinuses become congested while legs turn scrawnier. About half of astronauts experience space sickness — queasiness, dizziness and vomiting — for the first few days.
Without gravity, bone mass tends to diminish, a space version of osteoporosis. But exercising a couple of hours a day has largely solved that problem for astronauts living on the International Space Station, and astronauts return to Earth without brittle bones.
The weightlessness of space can flatten the shape of eyeballs, causing potentially serious changes to the retina and blood flow to the eyes for some astronauts in addition to changing how well they can see.
Above the atmosphere, more intense bombardment of radiation raises the chances of cancer. Astronauts continuously wear a dosimeter while in space to measure how much radiation their bodies absorb. NASA aims to keep the lifetime risk of an astronaut dying of cancer to no more than 3 percent higher than the general population.
After a while, the bodies of astronauts acclimate to floating. Then the return to Earth and the weight of gravity takes another toll.
Upon landing, the vestibular system — the organs of the inner ear that maintain balance — is confused by gravity, a force it has not experienced for months. Astronauts are often wobbly. Sometimes they need to be carried to the medical examinations that are conducted right after landing.
One NASA astronaut returning on a Crew Dragon in October was hospitalized overnight because of a medical issue. NASA, citing privacy, did not identify the astronaut or the medical issue. All three NASA astronauts on that Crew Dragon participated in a news conference a couple of weeks later and appeared to be in good condition. They declined to identify which of them had become ill or provide any more details about the medical issue.
Recovery can take weeks or months. Matthew Dominick, who served as commander of the SpaceX Crew-8 mission, described the readjustment.
“The big things you expect, right?” he said. “Being disoriented. Being dizzy.”
But he said he was surprised by “little things like just sitting in a hard chair,” which proved painful.
He recalled eating dinner with his family a few days after his return. “I could not sit on that hard chair anymore,” he said. “So I just laid a towel down on the ground outside on our patio, and I lay down so I could be part of the conversation, but I was not going to sit anymore.”
He added, “It’s a very slow progression.”
Sometimes, the changes persist — and not always for the worse.
Jessica Meir, a NASA astronaut, said on a broadcast last week that she experienced changes to her eyes while she was in space.
The worrisome effects went away, she said, “but the one lasting symptom that I have is that I have perfect vision.”
Other lasting changes could be more subtle. In 2015 and 2016, a NASA astronaut, Scott Kelly, spent 340 days at the space station, taking part in a nearly yearlong study of his health. His health reading was then compared those of with Mark Kelly, his identical twin brother and retired NASA astronaut who remained on Earth.
NASA researchers reported that his body experienced a vast number of changes while in orbit. DNA mutated in some of his cells. His immune system responded in new ways. His microbiome gained new species of bacteria.
Still, astronauts recover and do other things. Mark Kelly, for example, is now a United States Senator. Others lead organizations promoting planetary defense from hazardous asteroids, return to NASA as top officials or even go back to orbit working for commercial space companies.
