As NASA astronauts Suni Williams and Butch Wilmore reunite with their families this week after spending nine unexpected months in space, we have begun to wonder: what exactly happens to the body in space?
When astronauts leave Earth’s atmosphere, they encounter more than just the complexities of space travel; they also face significant changes to their bodies due to the unique conditions of space.
From muscle atrophy to shifts in vision, here are some of the surprising effects of zero gravity…
Height
Peggy Whitson, known for being the first woman to command the International Space Station twice, and for holding the record for most cumulative days in space by an American astronaut, happily shared that one of the perks of going to space is a growth spurt.
Talking to BBC Global last year, the astronaut and biochemist explained: “Without gravity, when you get into space your spinal cord actually relaxes. You don’t have gravity pushing all your vertebrae together, and then when you go into space you get taller, slightly – I grew about about half an inch/three quarters of an inch.”
However, this effect is only temporary.
“Unfortunately I didn’t get to stay taller, because as soon as I got back within 24 hours you shrink back down, gravity does that to you,” added Whitson.
Bones and muscles
In the weightless environment of space, bones and muscles weaken due to reduced gravity, which can lead to bone density loss and muscle atrophy.
“On orbit, we lose 1% of our bone mass in a month if we don’t do anything about it,” Whitson told the BBC. “So, it’s almost 10 times or a little bit more accelerated in space – and our muscles are the same way.”
Therefore, astronauts have to combat these effects with exercise.
“In order to counteract some of these negative effects, in particular the bone loss, we have what is called a resistance exercise device,” said Whitson. “Normally on earth they would recommend that you lift weights, and of course there is no weight in zero gravity, so you have to work against a resistance.
“If you know you are losing bone mass at 1% per month, you’re very motivated to do the exercise, and it’s about 45 minutes to an hour everyday of resistive exercise.”
Vision
Some astronauts experience changes to their eyes and vision during spaceflight, a phenomenon known as Spaceflight Associated Neuro-Ocular Syndrome (SANS), according to the NASA website.
Although the exact cause is unknown, some researchers suspect the fluid shifting towards the head, caused by microgravity in space, could be an underlying cause of SANS.
“In space there is a headward redistribution of body fluids and that can raise intracranial pressure, the pressure around the brain and the eyeball,” Canadian Space Agency astronaut Dr Robert Thirsk told CBC News. “The eyeball is normally spherical in shape, but for some of us, the increased pressure on the back end of the eye pushes the eye in and can change the focal length of our eyeballs.
“So, I became farsighted during my time in space. Thank goodness for most of us, these vision changes reverse once we get back home after several weeks or months.”
Heart
Spending time in space can negatively impact the heart and circulatory system due to microgravity, leading to changes in heart muscle function, shape and potentially increased risk of cardiovascular issues.
“Since the whole body is exposed to micro-gravity, the heart doesn’t need to pump around as much blood as it used to on Earth, and the cardiovascular system deteriorates,” Angelique Van Ombergen, lead for life sciences at the European Space Agency explained on a YouTube Short.
“There is also radiation that can cause DNA damage, which can increase the risk of cancer and cause cardiovascular degeneration.”
Astronauts counteract these effects through daily physical activity while working and/or through exercising.
Immune system
According to NASA’s website, when in space, many factors such as physiological stress, disrupted circadian rhythms, radiation, microgravity, and other spaceflight factors can alter an astronaut’s immune response.
T-cells, a type of white blood cell, play a vital role in protecting the body from infections. An investigation called T-Cell Act in Ageing by NASA was the first time scientists were able to show that gravity makes a difference in the activation of the T-cell.
Their results revealed that specific genes within T-cells showed down regulation – a decrease in cell response – when exposed to microgravity. This combined down regulation in the genetics of T-cells leads to a reduction in the body’s defence against infections during spaceflight in various ways.
Astronauts also face higher radiation exposure in space than on Earth, which can damage immune cells and disrupt immune function, potentially leading to increased risks of infections and other health problems.
