Abstract
This article examines how physicians have helped shape human space exploration, and to articulate, from first-hand experience, why their medical training, scientific mindset and leadership abilities have played a significant role; and continue to offer relevance even as space exploration moves towards deep space and long-duration missions.
Medicine and spaceflight may appear unrelated, yet a distinguished group of physician-astronauts are reshaping both fields. 2025 marked 61 years since the first physician travelled to space and 60 years since NASA first selected physicians as astronauts (physician-astronauts), underscoring the longstanding role medical professionals have played in advancing exploration. Shortly after Yuri Gagarin’s historic flight, physician-cosmonaut Dr Boris Yegorov became the first doctor in space in 1964. NASA’s first physician-astronauts, Drs Joseph Kerwin and Duane Graveline, were selected in 1965. Duane never flew and resigned in under 2 months, citing ‘personal reasons’,1,2 while Kerwin, after waiting several years, finally went on to become the first American physician in space in 1973.
Since then, nearly three dozen NASA physicians went on to become astronauts, advancing not only exploratory science but also biomedical research, mission design, crew operations, public engagement and system-level innovation. Physician-astronauts have been pioneers in their own right; during the early years, representation was limited, with a natural emphasis on selecting pilots as astronauts. Their achievements since have broadened public and scientific expectations, paving the way for future generations of physicians worldwide to contribute to human exploration. These physician-astronauts have also distinguished themselves as leaders in spaceflight, earning notable accolades that set them apart from their peers; and serving as inspirations for future generations. For example, Dr Mae Jemison, the first Black woman and person of colour in space, whose achievements highlight the broader impact of physicians beyond medicine. Dr Andrew Morgan holds the U.S. record for the most spacewalks during a single mission, and Dr Frank Rubio being the current record holder for the longest continuous stay in space in a single spaceflight by an American.
Other countries have also continued to select physicians as astronauts, many of whom have made significant contributions, including Russia’s Dr Valeri Polyakov, who holds the current record for the overall longest continuous stay in space in a single spaceflight with 437 days. Among the nine Canadians who travelled into space, almost half (44%) are physicians, including the first Canadian woman and first neurologist in space, Roberta Bondar who pioneered space medicine research; and Dr David Saint-Jacques, the current Canadian record holder for the longest single spaceflight by a Canadian.
Several physicians are also astronauts with the European Space Agency (ESA) and Japanese Space Agency (JAXA), including Switzerland’s second astronaut Dr Marco Sieber, Austria’s first female astronaut, Dr, Carmen Possnig among ESA'’s reserves; and the first Japanese and Asian woman in space, Dr Chiaki Mukai. ESA recently opened the possibility of sending a person with a physical disability into space, selecting UK physician Dr John McFall to become the world’s first astronaut with a physical disability (parastronaut). 3 Emerging space nations have also selected physicians such as Malaysia’s first astronaut and Saudi Arabia, selecting Dr Mariam Fardous.
Highlighting these achievements is not merely historical annotation; these individuals expanded the range of perspectives, skills and scientific approaches within exploration programmes, helping humanity better understand space, its challenges and the impact of microgravity on the human body.
In addition to their achievements, physician-astronauts have shared in the perils of spaceflight, including the tragic loss of Drs Laurel Clark and David Brown aboard the STS-107 Space Shuttle Columbia. Their legacy endures in the science they advanced and the courage with which they served both medicine and space exploration.
Table 1 provides a list of government-selected physician-astronauts; while extensive, it may not be fully exhaustive due to limits in the public record.
Extensive list of all government space programme physician-astronauts to date. This table is based on publicly available data, acknowledging the limitations in the available information on previous careers for astronauts. No other physician-astronauts from other countries were found in the available data.
Refers to astronauts who are currently active (and may be assigned to future space missions).
Refers to those who became a physician after becoming an astronaut.
STS: Space Transportation System, which refers to the different NASA Space Shuttle missions (from STS-1 to STS-135).
The call to space: why physicians pursue exploration
Choosing to leave a well-established medical career for the intensely competitive world of space is far from conventional. For many physicians, the attraction lies in the ultimate challenge of pushing the boundaries of human physiology and endurance in an extreme environment. The allure of discovery and the opportunity to contribute to advancing humanity deeply resonate with the scientific curiosity that often underpins a medical vocation. The passion towards space is often nurtured by a lifelong fascination with science, engineering and the unknown. For physicians, these factors can be expanded to the frontiers of medical research and technological innovation.
The intellectual rigour, systematic reasoning and adaptability developed through medical training parallel many of the competencies essential for exploration missions, including rapid problem-solving, managing uncertainty and synthesising information in time-critical situations.4 –6
Physicians as explorers: how medical training enhances mission capability
Astronaut selection is famously demanding, testing cognitive, physical, operational and psychological resilience. Physicians are trained to excel in environments characterised by uncertainty, complexity and high stakes, making these skills directly applicable to space missions.
Medical education emphasises structured problem-solving, disciplined reasoning and the ability to make life-or-death decisions with incomplete data. These competencies translate effectively to spacecraft operations, system troubleshooting, habitat management, scientific experimentation and operational decision-making. Physicians also bring expertise in human physiology, behavioural science and health management, informing crew performance, mission planning, risk mitigation and long-duration operations, as well as guiding overall mission design, life-support systems and contingency planning. 5
While physician-astronauts may contribute to space medicine and research, their roles during missions frequently extend far beyond clinical tasks, encompassing leadership, operations, training design, scientific payload development and exploration strategy. For example, Drs Williams, Buckey and colleagues performed the only animal surgery conducted in space during STS-90. Additionally, when a solar array was damaged at the International Space Station (ISS), Dr Scott Parazynski applied his suturing skills to repair it. 7
The continuing legacy of physician-astronauts
Physician-astronauts can offer unique medical and scientific expertise during missions and support crew health, morale and decision-making in challenging conditions. On returning to Earth, astronauts resume or redefine their professional lives. For physicians returning to clinical practice, the experience of spaceflight offers a unique set of perspectives and skills that enhance clinical judgement, adaptability and leadership, with potential benefits for Earth-based healthcare and system innovation. 6
The enhanced capacity for problem-solving under extreme conditions in space would help navigate Earth-based complex clinical cases or healthcare challenges. Astronauts also become very resourceful and accustomed to working with limited supplies, space and improvising solutions; and these qualities would be invaluable in providing medical care in resource-constrained environments such as remote locations or supporting disaster relief.5,6,8 Their unparalleled experience in utilising telemedicine and portable diagnostic devices during their space missions further provides experience and expertise in understanding remote healthcare delivery.5,6,8
Conclusion
Physician-astronauts are STEM champions and accomplished leaders, with many overcoming significant hurdles and barriers to become physicians and astronauts.3,9 This article demonstrates how physicians have played an essential role in advancing human space exploration, and their contributions and influence have spanned science, operations, mission design, leadership, systems thinking, and medical capability. As human spaceflight enters a new era, characterised by public–private partnerships, lunar bases and, eventually, Mars missions, the multidisciplinary strengths of physicians will become increasingly important.5,8 Their combined operational, scientific and medical competencies make them adequately equipped to support the next stage of deep space exploration.
