Rethinking extreme environments, from human spaceflight to heat in Philadelphia

Mallika Sarma lives life to the extreme.

From a personal life that includes rigorous training in the Indian classical dance of Bharatanatyam as a child and Olympic weightlifting as an adult to a professional life of research at high altitudes in Nepal and among foragers in a remote Congo village, Sarma has always sought challenges.

“I’m a cliche,” she says with a laugh amid a fast-talking interview, sitting in her Penn Museum office between the walls she had painted bubblegum pink when she arrived at Penn last summer as an assistant professor of anthropology. Across the room is a whiteboard that bears the question driving her work: “When the going gets tough, how do we stay going?”

With a background in human biology—an interdisciplinary field focused on human variation in evolutionary, environmental, and social contexts—Sarma studies how humans adapt to extreme and novel environments. Core to her research is understanding the hypothalamic-pituitary-adrenal axis, which regulates the body’s response to stress, and the stress hormone, cortisol.

As a postdoctoral researcher in the Human Spaceflight Lab at Johns Hopkins University from 2020 to 2024, she examined how vestibular function—balance and ability to visually focus, two important abilities in space—changes depending on a person’s stress level. She also studied whether interacting with a team member would increase or decrease stress. Initial analyses showed that stress impacts vestibular function, Sarma says, but that team dynamics complicate matters, leading to different physiological and performance outcomes.

As part of her research, she contributed to a Nature paper on molecular and physiological changes in the three-day SpaceX Inspiration4 mission in 2021, the first all-civilian flight. Using new in-flight technologies such as handheld ultrasound imaging and smartwatch wearables, the researchers reported physiological, neurovestibular, and neurocognitive responses, which suggested that short missions don’t pose a significant health risk.

In a piece on the human biology of spaceflight and a new article in Wilderness & Environmental Medicine that she co-wrote, Sarma stressed that as space missions become longer and farther, we need frameworks that extend beyond the current emphasis on acute physiological and behavioral outcomes.

She and collaborators highlight case studies from Mexico, Samoa, and the backcountry of the American Rockies—where Sarma conducted research—to show how mixed methodologies and technologies such as lipid and glucose measuring devices, heart rate monitors, semistructured interviews, and 24-hour dietary recalls used on Earth could inform health systems research in space.

Bringing research closer to home

When she moved to Center City last June with a 7-month-old in tow, Sarma thought, “I can’t even think; it’s so hot.” She realized that the questions she had about human spaceflight—about how human bodies acclimatize, how behavior shifts, and how we build our environments—were questions she could be asking in Philly about extreme heat.

Exploring the idea that extremes might need to be redefined using a wider lens, together with fellow human biologist Alexandra Niclou, Sarma co-wrote the introduction to a special issue of the American Journal of Human Biology.

“The term ‘extreme environments’ conjures up images of rugged terrains, limited access to necessary daily resources, and quixotic climatic conditions,” they write. But they argue that “our definitions of extremes should change with our changing world” and advocate for a more holistic perspective, highlighting papers in the issue that deal with precarity, obesity, climate change, and the COVID pandemic.

Sarma is also applying the skills she learned translating academic research into real-world outcomes. She previously had to show how her work could impact day-to-day operations on the International Space Station, the moon, or Mars. Now, she is thinking about how extreme heat research on public health infrastructure and social supports can be implemented in the community.

Another takeaway from her spaceflight research is the importance of taking a systems approach. For example, if one is only thinking about cortisol changes in space without the context of behavior, downstream physiology, and immune function, “you’re going to end up with a dead person,” she says.

In Philadelphia, Sarma is in the early stages of a project that she says will involve conducting surveys, taking pictures with thermal imaging cameras, and collecting data on physical activity, cortisol shifts, testosterone levels, and more.

“There is a huge range of variation in how people are responding to an environment, and it’s important to understand what exactly is driving it,” she says. Is the variation due to differences in hormones or diet or exercise or social relationships? How do you separate out sex differences from gender roles? Parsing these questions requires a wide subject pool.

Sarma says when it comes to extreme heat, there is “such amazing work being done at Penn looking at sustainability and design,” and she wanted to add a psychophysiological lens, looking at how heat changes people’s hormones and behavior. She was recently named an Environmental Innovations Initiative Faculty Fellow and is part of EII’s Extreme Heat Working Group.

“Part of the reason why I was so excited to come to somewhere like Penn was because it has the resources and the brainpower to do the kind of interdisciplinary research that everyone wants to do,” says Sarma.