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Astronauts undertaking missions to lunar bases or exploring deep space encounter numerous health hazards. Some of these pose severe threats to their survival, and at least one could put the future of deep space missions at risk.
10. Heart-Related Issues
A 2014 study involving 12 astronauts revealed that prolonged exposure to microgravity can cause the heart to become 9.4 percent more spherical, which may lead to cardiovascular complications, particularly during long-duration missions like a trip to Mars.
“The heart doesn’t have to work as hard in space, which leads to a reduction in muscle mass,” explained Dr. James Thomas from NASA. “This could lead to serious issues once astronauts return to Earth, so we are exploring possible strategies to prevent or reverse this muscle loss.”
Currently, the shape change in the heart reverses when astronauts return to Earth, but the long-term consequences remain unknown. It’s already known that astronauts often experience dizziness upon re-entry. A sudden drop in blood pressure can cause them to faint when standing. Some astronauts also suffer from arrhythmia while in space.
Researchers are working on creating exercise programs to protect astronauts on deep space missions from these effects. Similar regimens may also benefit individuals on Earth, such as those on bed rest or those with heart conditions.
A new five-year study has been launched to examine whether space travel accelerates the development of atherosclerosis in astronauts.
9. Alcohol Consumption and Psychological Issues
Despite NASA conducting a confidential health survey of its astronauts, which ultimately downplayed concerns about excessive drinking, allegations surfaced in 2007 that intoxicated NASA astronauts were allowed to fly on both the space shuttle and a Russian Soyuz spacecraft during separate incidents. These incidents occurred even though flight surgeons and fellow astronauts reportedly raised safety concerns with local managers.
At the time, NASA’s policy banned alcohol consumption within 12 hours of astronauts flying training jets. This rule was intended to apply to spaceflights as well. To clear up any ambiguity, NASA officially implemented the 'bottle to throttle' rule after an independent review panel examined the situation.
Mike Mullane, a retired astronaut, revealed that some astronauts would drink alcohol before a flight in order to dehydrate themselves, thus making the countdown to launch more bearable for their bladders.
Psychological challenges have also been experienced in space. During the Skylab 4 mission, astronauts became so frustrated with mission control that they turned off their radios and ignored NASA for an entire day. Researchers are now studying the potential psychological effects of prolonged and stressful deep space missions, such as a journey to Mars.
8. Sleep Shortages and the Use of Sleep Aids
A decade-long sleep study revealed that astronauts consistently struggle with inadequate sleep for weeks leading up to and during their space missions. Three out of four astronauts use sleep medications, which may be hazardous when operating spacecraft or other essential equipment. This becomes particularly worrisome if all astronauts on a mission take the same medication simultaneously, especially if they need to awaken for an emergency situation.
NASA allocates 8.5 hours of sleep each night for astronauts, but in practice, they typically only get around six hours during their missions. In the three months of pre-flight training, astronauts also average less than 6.5 hours of sleep per night.
“Future missions to the Moon, Mars, or beyond will require the creation of more effective countermeasures to enhance sleep during spaceflight in order to optimize human performance,” explained Dr. Charles Czeisler, the senior study author. “These strategies may involve modifying schedules, strategically timed exposure to specific wavelengths of light, and behavioral approaches to ensure sufficient sleep, which is crucial for maintaining health, performance, and safety.”
7. Hearing Impairment
Research indicates that even a single shuttle mission can lead to significant temporary hearing loss, along with a smaller, permanent hearing loss, typically in the higher frequencies crucial for understanding speech. Crews aboard the Soviet Salyut 7 and Russian Mir space stations also experienced both temporary and permanent hearing impairments upon their return, with higher frequencies being the most affected.
Initially, astronauts aboard the International Space Station had to wear earplugs throughout the day. However, NASA found ways to reduce noise levels by installing acoustic padding on the walls and using quieter fans, among other solutions.
Apart from noise, other factors that could contribute to hearing loss in space include atmospheric contaminants, increased intracranial pressure, and elevated carbon dioxide levels.
In 2015, NASA plans to research ways to prevent hearing loss during a year-long mission to the International Space Station with two crew members. The goal is to assess how much hearing they can preserve in these astronauts and establish an acceptable level of hearing loss risk. Ultimately, they aim to find methods to minimize hearing loss over an astronaut's lifetime, not just for a single mission.
6. Kidney Stones
Around 1 in 10 people develop kidney stones during their lifetime on Earth. However, astronauts face an even higher risk in space because the lack of gravity causes bones to lose minerals, releasing salts such as calcium phosphate into the bloodstream. These salts can then accumulate in the kidneys, potentially forming stones of varying sizes, from microscopic particles to as large as a walnut. Kidney stones can cause excruciating pain, and in severe cases, the kidney may stop functioning if a stone blocks the drainage tube.
For astronauts, the risk is amplified by the fact that microgravity leads to reduced blood volume. Additionally, many astronauts fail to drink the required 2 liters (0.5 gallons) of water daily, which is essential for staying fully hydrated and passing the stones through urine.
At least 14 American astronauts developed kidney stones shortly after their missions concluded. In 1982, one Soviet cosmonaut experienced intense pain for two days aboard the Salyut 7 space station, while his crewmate was powerless to help. Before the Soviets could launch a rescue operation, which they initially thought was needed for appendicitis, the cosmonaut passed a small stone in his urine.
Scientists have been developing an ultrasound machine about the size of a desktop computer, designed to detect kidney stones and use short bursts of sound waves to help expel them from the kidney.
5. Lungs and Dust
Although the effects of dust from other planets or asteroids on astronauts remain unknown, we do know that moon dust caused some health issues during the lunar missions.
The most hazardous effect may be on the lungs if astronauts inhale the fine particulates of moon dust. The dust, with its extremely sharp edges, can damage both the heart and lungs, causing everything from inflammation to an increased risk of cancer. It's somewhat akin to inhaling asbestos.
This sharp-edged moon dust can also irritate and abrade the skin. It's even been known to wear through multiple layers of a Kevlar-like boot. Lunar dust can also scratch the cornea of an astronaut's eye, creating a serious emergency situation in space.
However, researchers acknowledge that they cannot replicate the Moon’s conditions in their tests. For instance, on Earth, the dust particles are no longer in a vacuum or exposed to radiation. Only additional studies on the Moon itself, rather than in a lab, will provide scientists with the full information needed to understand lunar dust toxicity.
4. Immune System Confusion
On Earth, our immune systems can change if we experience insufficient sleep, poor nutrition, or excessive stress. For astronauts on long missions, their immune systems also undergo changes in space, transforming what would be a minor cold or flu into a much more serious health threat.
While the distribution of immune cells doesn’t change drastically, their function can fluctuate, either increasing or decreasing, which confuses the immune system. When cell function weakens, dormant viruses in the body may reactivate, although without noticeable symptoms. When the immune system is overactive, it can lead to allergies and rashes.
“Factors such as radiation, microbes, stress, microgravity, disrupted sleep cycles, and isolation can all impact crew members' immune systems,” explained NASA immunologist Brian Crucian. “If these conditions persist over longer deep space missions, they could heighten the risk of infection, hypersensitivity, or autoimmune problems for astronauts on exploratory missions.”
If needed, NASA plans to implement advanced radiation shielding, nutritional supplements, and medications to mitigate these immune system changes.
3. Loss of Vision
Some astronauts have experienced significant, long-lasting vision issues due to their time spent in space. The duration of the mission correlates with the likelihood of these problems. Among the 300 US astronauts studied since 1989, 29 percent of those on two-week missions developed vision issues, while an alarming 60 percent of astronauts who spent several months aboard the International Space Station faced similar problems.
Researchers at the University of Texas conducted brain scans on 27 astronauts who had been in space for over a month. In more than 25 percent of the subjects, the back of one or both eyes had flattened, causing the eyeballs to shrink and making them more farsighted. The longer the space mission, the more severe and frequent the issue became.
Scientists hypothesize that this may be another consequence of fluid redistribution in a microgravity environment. The increased cerebrospinal fluid flow into the head creates pressure within the skull, but since the bone can’t expand, the pressure leads to the flattening of the eyeballs. It remains unclear if this effect will lessen or worsen for astronauts in space beyond six months. However, this is crucial to understand before embarking on a Mars mission that may last at least a year.
If intracranial pressure is the cause of the problem, one possible solution being explored is generating artificial gravity by rotating the spacecraft for eight hours daily while astronauts sleep. However, it is still uncertain whether this approach will be effective. “This is one issue we don't fully understand yet, and it could be a showstopper for long-duration missions,” said NASA scientist Mark Shelhamer.
2. Cognitive Problems
In experiments simulating deep space conditions, researchers found that exposure to high-energy particles, even in small amounts, led to rats becoming slower in their reactions and more easily distracted. Additionally, changes in the protein composition of their brains were observed.
However, not all rats were affected equally. If this holds true for astronauts, the scientists believe they could create a biological marker to predict which astronauts may experience these cognitive effects. This could potentially help reduce the impact of radiation on these individuals.
A more concerning possibility is the development of Alzheimer’s disease. “Radiation exposure similar to that experienced during a Mars mission might lead to cognitive impairments and accelerate brain changes linked to Alzheimer’s,” stated neuroscientist Kerry O’Banion. The longer astronauts spend in space, the higher their risk becomes.
The silver lining is that scientists conducted a worst-case scenario experiment. They exposed the rats to the entire radiation dose of a full mission all at once. In comparison, astronauts would be exposed to this level of radiation over a span of three years. The human body may be able to adjust to smaller doses over time.
Additionally, materials like plastics and other lightweight substances might offer astronauts better radiation protection than the aluminum currently used in spacecraft.
1. Radiation Hazards
An extremely rare and prolonged absence of solar activity is leading to dangerously high radiation levels in space, an occurrence not seen in nearly a century. “While these conditions might not entirely prevent long-term missions to the Moon, an asteroid, or even Mars, galactic cosmic radiation in particular continues to be a significant and growing threat that limits the duration of space missions,” explained Nathan Schwadron from the UNH Institute for the Study of Earth, Oceans, and Space.
Exposure to this kind of radiation can lead to a range of harmful effects, from radiation sickness to cancer and organ damage. Moreover, these high radiation levels will cut down the number of days astronauts can safely spend behind the spacecraft's shielding by 20 percent.
A single mission to Mars could subject an astronaut to two-thirds of their safe lifetime radiation exposure limit. This radiation has the potential to damage human DNA and increase the risk of cancer. “In terms of the accumulated dose, it’s comparable to undergoing a full-body CT scan every five or six days,” explained scientist Cary Zeitlin.
