Most NASA astronauts hold advanced degrees in science or engineering, but not every person who goes to space is a scientist in any meaningful sense of the word. Roughly a third of NASA astronauts have earned doctoral-level degrees, while the majority hold master’s degrees in technical fields. The reality is that “astronaut” describes a job that has always blended piloting, engineering, maintenance work, and scientific research in varying proportions, and the commercial spaceflight era is stretching the definition even further.
What NASA Astronauts Actually Study
NASA has never sent someone to space without at least a bachelor’s degree. But the educational profile of the astronaut corps skews much higher than that minimum. Among NASA astronauts, about 15% hold a bachelor’s degree, roughly 53% hold a master’s degree, and about 32% hold a doctoral-level degree such as a PhD or MD.1npj Microgravity. A demographic comparison of NASA astronauts and commercial spaceflight participants Those numbers tell you that the astronaut corps is extraordinarily well-educated, but they don’t tell you whether these people are scientists.
The degrees span a range of disciplines. Many astronauts studied engineering, particularly aerospace or mechanical engineering. Others hold degrees in physics, biology, chemistry, or medicine. A sizable chunk are military officers, often test pilots, whose graduate degrees tend to be in engineering or related fields earned through military programs. Having an advanced STEM degree makes you technically trained, but it doesn’t automatically make you a research scientist. A fighter pilot with a master’s in aeronautical engineering and a marine biologist studying coral reefs are both STEM professionals, but they occupy very different intellectual worlds. NASA’s astronaut corps includes both types and everything in between.
The Roles That Shaped Who Does What in Space
For decades, NASA sorted astronauts into distinct categories that reflected whether their primary job was flying or doing science. During the Space Shuttle era, “pilot astronauts” were responsible for flying the vehicle, and their backgrounds were almost exclusively military aviation. “Mission specialists” handled spacewalks, robotic arm operations, and experiments, and they tended to come from science or engineering backgrounds. Then there were “payload specialists,” a category that tells you the most about the scientist question.
Payload specialists were researchers or engineers from outside NASA’s career astronaut pipeline. They were brought aboard specific missions to operate experiments they had helped design on the ground. Some were university professors. Some worked for international space agencies. A few represented private companies. These were the closest thing to pure scientists in orbit: people who went to space to do their own research, not to fly the spacecraft or maintain station systems. NASA phased out the payload specialist role after the Shuttle program ended, partly because the ISS era demanded longer-term crew members trained across a wider set of tasks.
Today, NASA selects astronaut candidates through a unified pipeline. Everyone goes through the same basic training, which includes spacewalk procedures, robotics, Russian language study, survival training, and systems operations. Individual crew members still tend to lean toward either piloting or science and engineering roles based on their backgrounds, but the formal distinction is less rigid than it used to be. The result is astronauts who are generalists first and specialists second.
What Astronauts Actually Do With Their Time in Space
If you picture astronauts spending their days peering through microscopes and making discoveries, the reality would surprise you. Life aboard the International Space Station involves a large amount of maintenance, exercise, and logistics. Crew members spend roughly two hours a day exercising to counteract bone and muscle loss. They clean air filters, repair equipment, unpack cargo shipments, and deal with the unglamorous plumbing of life support systems. Science is part of the daily schedule, but it competes with everything else.
When astronauts do perform experiments, they are usually executing protocols designed by research teams on the ground. A typical scenario looks like this: a principal investigator at a university designs an experiment studying how protein crystals grow in microgravity. The experiment hardware gets launched to the station. The crew receives detailed step-by-step instructions from mission control. An astronaut activates the hardware, swaps samples at prescribed intervals, photographs results, and stows completed samples for return to Earth. The principal investigator and their lab do the analysis and publish the findings.
This makes astronauts more like skilled laboratory technicians than independent researchers in most cases. They are essential to the science, and the experiments could not happen without their hands, their judgment calls when things go wrong, and their ability to operate in an environment where everything floats. But the intellectual ownership of the research usually belongs to ground-based teams. There are exceptions: astronauts with deep expertise in a relevant field sometimes contribute to experiment design or serve as co-investigators. Don Pettit, a chemical engineer, famously improvised fluid physics experiments using off-the-shelf materials aboard the station. But those cases stand out precisely because they are uncommon.
When Astronauts Become the Experiment
Here is where the scientist question gets genuinely strange: astronauts are not just people who do science in space. They are also the subjects of science. Every crew member aboard the ISS participates in biomedical studies, sometimes dozens of them simultaneously. Researchers on the ground study how spaceflight affects the human body, and astronauts are the only available test population.
Studies cover everything from bone density loss and cardiovascular changes to cognitive function and psychological resilience. In one study aboard the Life and Microgravity Spacelab, four astronauts completed sessions of cognitive performance tests before, during, and after their flight. Two of the four showed statistically significant changes in orbit: one was degraded on two tests, and the other was degraded on one test while exceeding expectations on another.2PubMed. Cognitive performance aboard the life and microgravity spacelab Small sample sizes like this are a persistent challenge in space research. There are so few astronauts that almost every study involves single-digit participants, which makes broad conclusions difficult to draw.
The dual role of being both the person running experiments and the subject of other experiments raises ethical questions that don’t come up in most research settings. Astronauts face an unusual power dynamic: their employer is also the organization conducting the research, and declining to participate in a study could theoretically affect career prospects or mission assignments. Scholars in bioethics have argued that organizations conducting space exploration research should take steps to minimize the potential for undue influence, ensuring that consent discussions are private and that information about participation is kept confidential.3Bioethics. Informed Consent for Research Participation During Space Exploration: Ethical Issues The concern isn’t that astronauts are being coerced, exactly, but that the environment makes truly voluntary participation harder to guarantee than in a university lab where you can walk out the door.
This creates a paradox worth sitting with: astronauts contribute to science both as operators and as data points. A crew member might spend the morning running someone else’s cell biology experiment and the afternoon providing blood samples, wearing biosensors, and filling out psychological questionnaires for someone else’s human physiology study. Whether that makes them a scientist, a technician, or a research subject depends on which hour of the day you ask.
Commercial Spaceflight Changes Who Goes to Space
The question of whether astronauts are scientists gets even muddier when you include people who fly commercially. Companies like SpaceX, Blue Origin, and Virgin Galactic have sent dozens of people to space or to the edge of it, and their passenger lists look nothing like NASA’s astronaut corps.
Among commercial spaceflight participants, educational backgrounds are far more variable. About 13% had less than a bachelor’s degree, 31% held a bachelor’s degree, 35% held a master’s degree, and 14% held a doctoral degree.4npj Microgravity. A demographic comparison of NASA astronauts and commercial spaceflight participants The occupational mix is striking: the most common background among commercial participants is entrepreneurship, including entrepreneurs, executives, and investors, at about 42%. Engineers made up roughly 21%, and scientists, educators, and physicians together accounted for about 11%.5npj Microgravity. A demographic comparison of NASA astronauts and commercial spaceflight participants
Some of these commercial flights have carried legitimate scientific payloads and participants who trained to operate them. The SpaceX Inspiration4 and Polaris Dawn missions included biomedical research components, and Axiom Space has sent private astronauts to the ISS to conduct experiments. But others have been essentially tourism flights, where the passengers’ primary qualification was the ability to pay for a ticket or win a promotional contest. A few seats on commercial flights have been auctioned off or donated to charities, meaning people from socioeconomic backgrounds far removed from aerospace have flown to space.
This diversity is by design, and it is a genuine shift. For sixty years, going to space meant being selected by a government agency through a brutally competitive process that filtered for military test pilots or PhDs. Now it also means being a billionaire who bought a seat, a cancer survivor who won a charity raffle, or a social media influencer on a sponsored trip. These people are sometimes called “astronauts” in media coverage, which can frustrate career astronauts who spent years in training. The question of whether astronauts are scientists increasingly depends on which astronauts you mean.
How NASA Selects for Science Aptitude Today
NASA’s current astronaut selection criteria explicitly require a background in a STEM field, but the definition is broad. You need at least a master’s degree in engineering, biological science, physical science, computer science, or mathematics, or alternatively a medical degree, or two years of work toward a doctoral program in a related field. Piloting experience can substitute for some educational requirements, reflecting the enduring importance of vehicle operations. The agency also accepts test pilot school graduates, which keeps the door open for applicants whose primary skill set is flying rather than research.
What the selection criteria tell you is that NASA wants people who can understand science and work comfortably in technical environments, not necessarily people who will design and lead their own research programs. The emphasis is on versatility. A candidate who can repair a carbon dioxide scrubber, run a combustion science experiment, operate a robotic arm to grapple a cargo vehicle, and do a spacewalk to replace a solar array panel is more useful than a narrow specialist who is brilliant in one domain but lost in others.
This is one reason why the astronaut corps has always had more engineers and physicians than, say, particle physicists or ecologists. Engineering and medicine reward the kind of procedural thinking, manual dexterity, and calm under pressure that spaceflight demands. Pure research scientists can thrive in the astronaut corps, but they are often competing against candidates whose broader skill sets make them more attractive for the operational realities of living on a space station.
Directing Robots as a Scientist in Orbit
One vision of astronauts doing science doesn’t involve running experiments inside a pressurized cabin at all. Instead, it involves astronauts in orbit remotely controlling robots on a planetary surface to do geological fieldwork. In the Analog-1 experiment, an astronaut aboard the ISS used a haptic input device with force-feedback to control a mobile robot with a manipulator arm on Earth, directing it to collect rock samples.6PubMed. Exploring planet geology through force-feedback telemanipulation from orbit The idea is that for future missions to the Moon or Mars, astronauts orbiting overhead could teleoperate surface robots in near-real-time, performing tasks like geological sampling that require human judgment and fine motor control but don’t justify the risk and expense of landing a person.
This model would make astronauts something closer to remote field geologists: interpreting terrain, making decisions about where to sample, and responding to unexpected findings as they happen. It requires scientific training, not just technical skill. You would want the person at the controls to understand stratigraphy, minerology, and the geological questions the mission is trying to answer, not just how to move a joystick. If this approach becomes standard for deep-space exploration, it could shift the astronaut role substantially toward science and away from the maintenance-heavy work that dominates ISS operations.
The Gap Between Public Perception and Daily Reality
Popular culture tends to present astronauts as either steely-eyed pilots or brilliant scientists, and the truth is less cinematic than either version. Most astronauts spend more time on housekeeping than on headline-making discoveries. The science they do is real and valuable, but it looks less like a eureka moment and more like following a checklist while floating in a noisy metal tube. The romance of space exploration sometimes obscures the fact that running an experiment in microgravity involves the same tedious sample prep, data logging, and troubleshooting that lab work involves on Earth, just with the added challenge that your tools drift away if you let go.
The perception gap matters because it shapes who aspires to become an astronaut and what the public expects from space agencies. If people believe astronauts are all scientists, they may undervalue the engineering and operational expertise that keeps crews alive. If they believe astronauts are all pilots, they may undervalue the genuine research contributions that justify the enormous expense of human spaceflight. The honest answer is that the astronaut profession sits at the intersection of science, engineering, piloting, and something harder to name: the ability to function as a competent generalist in an environment that punishes mistakes and offers no easy exit.
What Happens When Deep-Space Missions Get Longer
The balance between science and operations may shift again as human missions venture beyond low Earth orbit. A crew heading to Mars will be months away from Earth, with communication delays that make real-time ground support impossible. If something breaks, they fix it themselves. If an experiment produces unexpected results, they can’t phone home for immediate guidance. This isolation could push future astronauts toward deeper scientific training than current ISS crew members receive, because they will need to make independent judgments about research priorities rather than simply executing ground-based instructions.
At the same time, the sheer difficulty of keeping humans alive on a Mars transit and surface mission means that engineering and medical skills may dominate crew selection even more than they do now. Life-support maintenance, radiation shielding management, habitat repair, and emergency medical care are all survival-critical tasks that a crew of six or eight people needs to cover. If two or three of those crew members are also trained geologists or biologists who can do meaningful fieldwork on the Martian surface, that is the ideal. But when push comes to shove, the person who can fix the water recycler probably gets the seat over the person who can identify Martian sedimentary structures, at least until the basic engineering challenges of interplanetary travel are more mature.
The tension between operational competence and scientific expertise has been part of the astronaut profession since its earliest days. The original Mercury astronauts were exclusively test pilots, and the scientists who built the experiments for those missions never left the ground. Apollo eventually sent a geologist, Harrison Schmitt, to the Moon on Apollo 17, but only on the final mission, after years of lobbying by the scientific community. The pattern repeats: operational needs come first, and scientific roles expand as the program matures and the operational basics become routine. If human Mars missions follow the same trajectory, the earliest crews may look more like expedition engineers than research scientists, with the science-heavy crews coming later.