En route to Mars, astronauts may face big health risks | Science News for Students

En route to Mars, astronauts may face big health risks

NASA and other groups are examining hazards of traveling to the Red Planet
Mar 8, 2018 — 6:45 am EST
Mars astronaut

Going into space brings the thrill of a new frontier and risks that scientists are racing to understand, from radiation to isolation.


This is the second of a two-part series on preparations for upcoming human space missions to the Red Planet.

Frank Borman was probably the first person to barf in space.

Borman was part of NASA’s Apollo 8 mission, which lifted off a launch pad in Florida on December 21, 1968. Over the next six days, the mission made history as it circled the moon and returned home. But Borman, who led the mission, became queasy near the beginning.

“I threw up a couple of times,” he recalled in an interview in 1999. Now 89, Borman is the oldest living U.S. astronaut.

“Nobody likes to throw up,” he said. Still, he insisted, this space sickness “wasn’t a big deal.”

This famous image, called Earthrise, was captured by astronauts on the Apollo 8 mission on Christmas Eve, 1968.

In space, gravity is so weak that it might as well not be there at all. The difference between “up” and “down” becomes meaningless. Astronauts can experience nausea and become disoriented. It happens a lot. 

Space sickness isn’t the only side effect to accompany the thrill of leaving Earth. A 2015 NASA report identified 30 factors that could make astronauts sick and unable to do their jobs. And there may be more, it said. Until people visit Mars it will be difficult to fully predict what could go wrong.

“We want to make sure we can bring people back healthy, and safely,” says astronaut Jessica Meir, who lives in Houston, Texas, and works for NASA. She has helped NASA design programs to train space travelers for the hazards of space.

Some of the known risks are extremely thorny. Along with space sickness, there is radiation — high-energy subatomic particles that will pass through an astronaut’s skin, damaging cells inside and out. Space travelers’ bones and muscles also can weaken as those body parts no longer have to constantly work against gravity. Blood and other fluids from the lower parts of the body can accumulate in upper body parts, including around the brain. One side effect: Astronauts may suffer hearing loss.

Space travel can even mess with the mind and mental health. For instance, astronauts travel in cramped quarters with other people. “If your relationships [with them] aren't going well, you start to isolate yourself from the rest of the crew,” says Steve Kozlowski. He’s a psychologist at Michigan State University, in East Lansing. On long-term space flights, astronauts have to collaborate on many tasks. If they don't work well together, those tasks may not get done correctly or on time. That, he says, can jeopardize the mission and lives of the entire crew.

Double Trouble

Today’s astronauts visit the International Space Station. It orbits Earth 381 kilometers (237 miles) overhead. Getting there takes less than a day, and most crew members stay less than a year. A trip to the moon would take about 3 to 5 days. A future voyage to an asteroid could take many weeks. Missions to Mars might last about 3 years.

As astronauts’ time in space increases, so do their health risks. And the most dangerous one facing those angling for Mars is well known, says Meir: radiation.

Life on Earth is protected from space radiation by a big, invisible, lopsided bubble. It’s called the magnetosphere (Mag-NEE-toe-sfeer). It’s the region around Earth dominated by the planet’s magnetic field. Like a shield, the magnetosphere deflects most of the high-energy particles that stream toward Earth from the sun. Only the highest-energy particles will get through.

ISS aurora
This photo was taken from the International Space Station. Those greenish lines are made of light and form from the interaction of radiation from the sun with Earth's magnetosphere.

Space radiation also comes from galactic cosmic rays. These powerful bursts of energy come from deep space. Scientists are still looking for their source. Like solar radiation, galactic cosmic rays can damage the human body inside and out. Also like solar radiation, these rays are deflected by Earth’s magnetosphere.

But a trip to Mars will take astronauts well beyond that protective magnetosphere.

The magnetosphere includes two so-called Van Allen belts. “Once you traverse the Van Allen belts, which wrap around the Earth, there is no more protection,” says engineer Lisa Carnell.

Carnell studies deep-space radiation at the NASA Langley Research Center in Hampton, Va. Her laboratory studies attempt to simulate deep space. They include firing high-energy lasers at targets, including ordinary objects and samples of human tissue. She also has conducted studies on the risk of space-radiation sickness, which can lead to symptoms ranging from nausea and vomiting to organ damage. (This is different from the regular space sickness due to weightlessness.)

Radiation may damage the cardiovascular system, which includes the heart and lungs. It also can damage the central nervous system, which includes the brain and spinal cord. So radiation may impair someone’s ability to think clearly.

Galactic cosmic rays can shower astronauts with particles of many sizes. Carnell likens this radiation to invisible bullets fired from deep-space guns. “There are different types of guns and different types of damage they can do,” she notes.

glowing bottles
These plastic bottles glow after being pummeled by ions from the Galactic Ray Simulator at Brookhaven National Laboratory in New York.
U.S. DOE, Brookhaven National Laboratory, NASA

Cosmic rays include small particles, which are parts of an atom. Those particles are like BBs. The simplest may be isolated protons or electrons. Bigger ones may include the cores of atoms of lithium, carbon or iron. Carnell likens these to rifle bullets.

In laboratory studies, she says, exposure to beams of these particles will cause cancer in mice. Scientists haven't seen evidence of higher cancer rates in astronauts. But astronauts have not yet remained in space for very long. And even those who have stayed up for months on the ISS are still protected by the magnetosphere.

Mars is far outside that protective bubble. Data collected by the Curiosity rover, which roams the Red Planet, finds that surface space radiation levels there are high. This suggests astronauts who go to Mars will face a high risk of cancer.

Space missions will have to protect astronauts from that radiation. Carnell says engineers are looking for many ways to do that. Each has pros and cons. One solution includes building space ships and space suits from thick materials that could shield the passengers. However, such a ship might be too heavy and expensive to launch. And those suits would be bulky.

Another solution would be to design and use new materials that deflect more radiation. But scientists need time and money to develop these materials. Organizations such as NASA are planning to send people to Mars in the next 15 years. SpaceX, a private company, wants to get people there by 2020. (In January 2018, the company sent the world's heaviest rocket —  called Falcon Heavy — barreling toward the Martian neighborhood. It carried a sportscar.) A third solution might be to develop a medication that can block the harmful effects of radiation from inside an astronaut’s body. Such a drug does not yet exist.

And, with medicine, there’s another cause for pause. Astronaut urine is recycled for drinking water. Scientists would have to make sure any treatment for radiation is safe no matter where it ended up, every time it passed through a body.

“I don’t think that we’ll ever get to the point that we completely mitigate the risk,” says Carnell. “So the ultimate goal is to reduce the risk as much as possible.”

Brawn and brains

Astronauts face other health risks from space travel. Those include the loss of bone and muscle. Meir, the astronaut, says the International Space Station includes equipment that can help limit that. Onboard the ISS is the ARED. This stands for Advanced Resistive Exercise Device. The machine uses vacuum tubes to provide resistance to movements — as weights do in the gym.

 Advanced Resistance Exercise Device
Koichi Wakata of the Japan Aerospace Exploration Agency works out on the Advanced Resistance Exercise Device on the ISS.

Astronauts on the ISS work out with ARED two hours each day. This should cut muscle or bone mass, Meir says: “That’s one of the big things we have solved.”

The ISS has plenty of room for the ARED. The first spacecraft to Mars won’t be nearly as spacious. So engineers are developing smaller exercise equipment for these craft. Exercise, after all, will remain a critical health issue for people travelling into deep space, Meir says.

Scientists planning for Martian missions also need to think about what goes on in an astronaut’s head. Rachael Seidler is a kinesiologist (Kih-NEES-ee-OL-oh-gizt) at the University of Florida, in Gainesville. (Kinesiology is the study of how bodies move.) She has been investigating how space travel alters the brain.

Seidler and her team studied brain scans from 27 astronauts who had been in space. Fourteen had spent six months on the ISS. The rest had spent about two weeks on a space shuttle.

Living in space led to surprising changes. Seidler’s team identified places in the brain where the amount of gray matter had either decreased or increased. Gray matter includes nerve cell bodies, which are like the control center for these cells. 

Seidler doesn’t think the decreases suggest astronauts are losing brain cells. Instead, she suspects that fluids — including those around the brain — move around freely in the microgravity of space. Those shifts may have caused some of the changes she observed.

“Your brain is kind of floating a little bit higher in the skull than it does on Earth,” she explains. As a result, “There’s a redistribution of fluids.” That’s one reason, she says, “If you look at photos of astronauts when they first go into space, they have this puffy-face look.”

That also may help explain some symptoms seen in returning astronauts. The longer they had spent in space, the more dramatic the changes to their gray matter.

Upon returning to Earth, they often have difficulty with balance and hand-eye coordination. They can’t drive a car for a few weeks, sometimes for months. They must undergo physical therapy to get used to gravity again.

Her team reported its results in December 2016 in Nature Microgravity.

Seidler says she wants to figure out if some of these effects are linked to the brain changes she’s observed. This research could be useful for future missions, since going to Mars means more time in space and possibly more brain changes.

These experiments also may help scientists understand brain changes in the elderly. As people age, they may show symptoms similar to what astronauts experience upon returning to Earth: problems with balance and vision, for example.

bedrest study
Participants in bed-rest studies have to remain lying down during all activities, even using a computer. Bed rest affects people in ways similar to weightlessness, making these studies an easy, and cheaper, way to study what happens to humans in space.
German Space Agency (DLR)

In the lab, Seidler has been leading bed-rest studies. Her volunteers lie down on a bed for months at a time. During and afterward, the researchers record brain scans of each volunteer.

These show that bed-rest changes the brain in ways similar to what is seen in astronauts. No longer pulled toward the feet by gravity, the fluids in the bodies of bed-rest volunteers move around. Their brains may rise up in their bodies a bit, says Seidler. Bed-rest volunteers also can get the same face puffiness.

These results offer clues to how the brain changes as the brain and body experience the world differently than when just standing up.

Of course, the studies are tricky. They require finding people willing to lie around for months. Seidler is about to launch a study that will require people to lie down for 60 days. She is the first to admit it doesn’t sound like fun. “The idea of maybe lying around in bed for a weekend sounds okay,” she says. “But anything more than that sounds awful.”

Space on Earth

Getting people to lie down isn’t the only way to simulate space. Researchers do it right on Earth in specialized environments.

In January, Ryan Kobrick began a two-week stay at a two-story building in the Utah desert to see how much dust from the outside leaks to the inside as people come and go. Those studies could help scientists predict how dust on the moon or Mars might affect life away from Earth.

Kobrick is a former astronaut. Now he works as an engineer at Embry-Riddle Aeronautical University in Daytona Beach, Fla.

Jessica Meir
Jessica Meir, featured in the PBS special Beyond a Year in Space, trains for interplanetary travel.
PBS/Beyond a Year in Space

Meir, the astronaut, has participated in a NASA program called NEEMO. (NEEMO stands for NASA Extreme Environment Mission Operations.) In this project, a small group of researchers live and work together in Aquarius. It’s an underwater research station in the Atlantic Ocean, some 5.6 kilometers (3.5 miles) off the Florida island of Key Largo. Experiences there are designed to mimic spaceflight. Crew members have to work together to complete tasks and solve problems.

Meir also participated in a simulation program with the European Space Agency. It’s called CAVES (an acronym for Cooperative Adventure for Valuing and Exercising human behavior and performance Skills). Six crew members — including ones from Russia, China, Spain and Italy — spent two weeks together in a deep cave in Italy. They wore space suits and had to rely on each other as they performed various tasks. This included exploring and mapping unknown sections of the cave. Such exploration required working in teams to climb steep cliffs or rappel down. The team also observed and documented the organisms that found alive in the deep.

“It was the coolest experience of my life,” Meir recalls. The caves looked like another planet and the views were extraordinary, she says. She saw spectacular formations made out of rock, never before seen by human eyes. “We were like characters in science fiction — like The Hobbit or Lord of The Rings,” she says.

The CAVES experience, Meir notes, showed the importance of building a crew for outer space that’s made of people who get along.

Experience has shown that getting along is important for astronauts. “Persistent danger and stress can take a toll,” says Kozlowski, the psychologist. “People can irritate you. If you dislike somebody, they can impede effectiveness.”

Kozlowski has been studying participants in a NASA program called HI-SEAS (short for Hawaii Space Exploration Analog and Simulation). Participants live together in a small, dome-shaped habitat on the side of a Hawaiian volcano. The living conditions have been designed to mimic a mission to Mars.

Teamwork is key

In February 2018, the sixth HI-SEAS crew began its eight-month stay. Recruits will be isolated in the habitat for the entire time. While there, they will have to work together, cooking meals or exploring the barren terrain outside the habitat. When they leave the dome, they will don space suits. They will work, eat and sleep as if they’re living on the Red Planet.

By day, crewmembers will answer surveys on how things are going. “They report on whether they’ve had conflicts with other people, or problems with their work,” notes Kozlowski. His team will study these surveys to look at the mission from beginning to end. They want to identify the earliest signs of any conflicts. Reducing those tensions is essential to making Mars missions a reality.

ISS crew
Space travel requires that a diverse group of people get along and work together for periods of time. This image was taken on board the International Space Station in 2010, when a Space Shuttle crew visited.

Conflict was less of an issue during the 1960s, the era of the Apollo missions. Why? Those missions were short. The pioneers of space flight spent a week or less in orbit. Still, on missions short and long, astronauts have to cooperate to succeed.

Frank Borman’s barfing experience on Apollo 8 is a perfect example. On that December day in 1968, fellow astronaut Jim Lovell came to Borman’s aid. He helped clean up. “Lovell, as I recall, squirted it out the urine dump system or something,” Borman recalled.

In 1985, astronaut Jake Garn also became nauseous on a space flight. (Garn, a senator from 1974 until 1993, was the first member of the U.S. Congress to go into space.) His queasiness didn't last long: He soon felt better and was able to do his job. But for a while it had been touch and go. After he returned from space, NASA jokingly established the “Garn scale” as a way to measure space sickness. (A comic strip from the time called him “Barfin’ Jake Garn,” but he never actually threw up.) The sicker you got, the higher your score on the Garn scale.

In an interview from 2005, Garn reflected on his famous bout of nausea in space. He said he had no regrets. Even with all its hazards and risks, Garn said no experience on Earth was comparable to getting away from it all in space. 

“Believe me,” he said, “I’d throw up every day just to go into space again.”

See part 1: Preparing for that trip to Mars.

On the Mauna Loa volcano in Hawai'i, the HI-SEAS research team has partnered with scientists from NASA Goddard to do planetary fieldwork experiments with the Miniaturized Laser Heterodyne Radiometer (mini-LHR).
NASA Goddard

Power Words

(more about Power Words)

Apollo missions     NASA’s third human spaceflight program eventually took humans to the lunar surface. Along the way, this program sought to develop the technologies needed for long-distance space travel. It got a big kick-start after President John F. Kennedy proposed in 1961 creating the national goal of “landing a man on the Moon and returning him safely to the Earth.”

asteroid     A rocky object in orbit around the sun. Most asteroids orbit in a region that falls between the orbits of Mars and Jupiter. Astronomers refer to this region as the asteroid belt.

astronaut     Someone trained to travel into space for research and exploration.

barf     Slang for vomit.

BBs     A type of small pellets, usually made from steel, which are fired by shotguns and air rifles. They can ricochet off of hard surfaces, making their use dangerous in confined spaces.

behavior     The way something, often a person or other organism, acts towards others, or conducts itself.

brain scan     A technique to view structures inside the brain, typically with X-rays or a magnetic resonance imaging (or MRI) machine. With MRI technology — especially the type known as functional MRI (or fMRI) — the activity of different brain regions can be viewed during an event, such as viewing pictures, computing sums or listening to music.

cancer     Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.

cardiovascular     An adjective that refers to things that affect or are part of the heart and the system of vessels and arteries that move blood through the heart and tissues of the body.

cell     The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells.

component     Something that is part of something else (such as pieces that go on an electronic circuit board or ingredients that go into a cookie recipe).

Congress     The part of the U.S. federal government charged with writing laws, setting the U.S. budget, and confirming many presidential appointments to the courts, to represent the U.S. government interests overseas and to run administrative agencies. The U.S. Congress is made of two parts: the Senate, consisting of two members from each state, and the House of Representatives, which consists of a total of 435 members, with at least one from each state (and dozens more for the states with the biggest populations).

cosmic rays     Very high-energy particles, mostly protons, that bombard Earth from all directions. These particles originate outside our solar system. They are equivalent to the nucleus of an atom. They travel through space at high rates of speed (often close to the speed of light).

element     (in chemistry) Each of more than one hundred substances for which the smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.

engineer     A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.

fiction     (adj. fictional) An idea or a story that is made-up, not a depiction of real events.

gravity     The force that attracts anything with mass, or bulk, toward any other thing with mass. The more mass that something has, the greater its gravity.

gray matter     One of two main types of tissue found in the brain and spinal cord. It consists mainly of nerve cell bodies.

habitat     The area or natural environment in which an animal or plant normally lives, such as a desert, coral reef or freshwater lake. A habitat can be home to thousands of different species.

International Space Station     An artificial satellite that orbits Earth. Run by the United States and Russia, this station provides a research laboratory from which scientists can conduct experiments in biology, physics and astronomy — and make observations of Earth.

iron     A metallic element that is common within minerals in Earth’s crust and in its hot core. This metal also is found in cosmic dust and in many meteorites.

journal     (in science) A publication in which scientists share their research findings with experts (and sometimes even the public). Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject. The best journals are peer-reviewed: They send all submitted articles to outside experts to be read and critiqued. The goal, here, is to prevent the publication of mistakes, fraud or sloppy work.

laser     A device that generates an intense beam of coherent light of a single color. Lasers are used in drilling and cutting, alignment and guidance, in data storage and in surgery.

liquid     A material that flows freely but keeps a constant volume, like water or oil.

lithium     A soft, silvery metallic element. It’s the lightest of all metals and very reactive. It is used in batteries and ceramics.

magnetosphere     The region surrounding Earth (or another astronomical body) in which its magnetic field protects the planet from the solar wind.

Mars     The fourth planet from the sun, just one planet out from Earth. Like Earth, it has seasons and moisture. But its diameter is only about half as big as Earth’s.

mass     A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from.

matter     Something that occupies space and has mass. Anything on Earth with matter will have a property described as "weight."

microgravity     Gravity that is a fraction of the force experienced at sea level on Earth.

molecule     An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).

moon     The natural satellite of any planet.

muscle     A type of tissue used to produce movement by contracting its cells, known as muscle fibers. Muscle is rich in protein, which is why predatory species seek prey containing lots of this tissue.

NASA     Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.

nausea     Feeling sick to one's stomach, as though one could vomit.

nerve     A long, delicate fiber that transmits signals across the body of an animal. An animal’s backbone contains many nerves, some of which control the movement of its legs or fins, and some of which convey sensations such as hot, cold or pain.

nervous system     The network of nerve cells and fibers that transmits signals between parts of the body.

neuroscientist     Someone who studies the structure or function of the brain and other parts of the nervous system.

orbit     The curved path of a celestial object or spacecraft around a star, planet or moon. One complete circuit around a celestial body.

organ     (in biology) Various parts of an organism that perform one or more particular functions. For instance, an ovary is an organ that makes eggs, the brain is an organ that makes sense of nerve signals and a plant’s roots are organs that take in nutrients and moisture.

particle     A minute amount of something.

persistent     An adjective for something that is long-lasting.

physical     (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).

planet     A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and has cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, the object must be big enough to have pulled neighboring objects into the planet itself or to have slung them around the planet and off into outer space.

psychological     An adjective that refers to how the human mind works, especially in relation to guiding actions and behavior. 

psychologist     A scientist or mental-health professional who studies the human mind, especially in relation to actions and behaviors. 

radiation     (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.

rappel     To travel down a cliff or other near-vertical rock face by sliding along a rope while periodically kicking off against the surface with your legs.

Red Planet     A nickname for Mars.

risk     The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

science fiction     A field of literary or filmed stories that take place against a backdrop of fantasy, usually based on speculations about how science and engineering will direct developments in the distant future. The plots in many of these stories focus on space travel, exaggerated changes attributed to evolution or life in (or on) alien worlds.

sea     An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

silicon     A nonmetal, semiconducting element used in making electronic circuits. Pure silicon exists in a shiny, dark-gray crystalline form and as a shapeless powder.

simulation     (v. simulate) An analysis, often made using a computer, of some conditions, functions or appearance of a physical system. A computer program would do this by using mathematical operations that can describe the system and how it might change over time or in response to different anticipated situations.

stress     (in biology) A factor — such as unusual temperatures, movements, moisture or pollution — that affects the health of a species or ecosystem. (in psychology) A mental, physical, emotional or behavioral reaction to an event or circumstance (stressor) that disturbs a person or animal’s usual state of being or places increased demands on a person or animal; psychological stress can be either positive or negative.

survey     (v.) To ask questions that glean data on the opinions, practices (such as dining or sleeping habits), knowledge or skills of a broad range of people. Researchers select the number and types of people questioned in hopes that the answers these individuals give will be representative of others who are their age, belong to the same ethnic group or live in the same region. (n.) The list of questions that will be offered to glean those data.

symptom     A physical or mental indicator generally regarded to be characteristic of a disease. Sometimes a single symptom — especially a general one, such as fever or pain — can be a sign of any of many different types of injury or disease.

terrain     The land in a particular area and whatever covers it. The term might refer to anything from a smooth, flat and dry landscape to a mountainous region covered with boulders, bogs and forest cover.

therapy     (adj. therapeutic) Treatment intended to relieve or heal a disorder.

tissue     Made of cells, any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.

van Allen belts     Two belts, an inner and outer one, surrounding Earth. They consist of cosmic rays — charged particles (electrons and protons). The belts extend from about 13,000 to 60,000 kilometers (8,100 to 37,300 miles) above the planet’s surface. The high-energy particles, a type of radiation, vary over time and altitude and pose a health risk to exposed space travelers.


Journal:​ ​​V. Koppelmans et al. Brain structural plasticity with spaceflight. Nature Microgravity. Vol. 2, December 19, 2016. doi:10.1038/s41526-016-0001-9.

Report: Lisa Carnell et al. Evidence Report: Risk of acute radiation syndromes due to solar particle events. NASA report. April 6, 2016.