Daily life aboard the International Space Station moves fast. Really fast. Traveling at approximately 17,000 miles per hour, 300 miles above the Earth, astronauts watch 16 sunrises and sunsets every “day” while floating around in a box with a handful of people they depend on for survival.
One need look no further than Hollywood blockbusters like “The Martian,” “Gravity” and “Interstellar” for futuristic visions of life beyond Earth as we venture longer and deeper into outer space. But what about the human body’s response to real-life spaceflight – what are the health effects? Will space travelers age at different rates than those of us on Earth? Just how adaptable to the space environment are we?
Certainly these are concerns for NASA. How space travel and long-duration missions might change the human body, and whether those changes are permanent or reversible once astronauts return to Earth, is largely unknown. The opportunity to explore these intriguing questions arose with identical twin astronauts Scott and Mark Kelly.
In November of 2012, NASA selected astronaut Scott Kelly for its first one-year mission. At a press conference not long thereafter, it was Scott who hinted that that this mission might provide the chance to compare the impact of space living on his body with his Earth-dwelling identical twin brother, Mark Kelly, who had also been an astronaut and former Navy test pilot. Remarkably, the Kelly twins were individuals of similar “nature (genetics) and nurture (environment),” and so the perfect space experiment was conceived – featuring “space twin and Earth twin” as the stars. Scott would spend a year in space aboard the International Space Station, while his identical twin brother, Mark, would remain on Earth.
The NASA TWINS Study represents the most comprehensive view of the human body’s response to space flight ever conducted. Results will guide future studies and personalized approaches for evaluating health effects of individual astronauts for years to come.
As a cancer biologist at Colorado State University I study the impact of radiation exposure on human cells. As part of the TWINS Study, I was particularly interested in evaluating how the ends of the chromosomes, called telomeres, were altered by a year in space.
Teasing apart health effects of space living
NASA put out a call and selected 10 peer-reviewed investigations from around the country for the TWINS Study. Studies included molecular, physiological and behavioral measures, and for the first time ever in astronauts, “omics”-based studies. Some teams evaluated the impact of space on the genome – the entire complement of DNA in a cell (genomics). Other teams examined which genes were turned on and producing a molecule called mRNA (transcriptomics). Some studies focused on how chemical modifications – which do not alter the DNA code – affected the regulation of the genes (epigenomics). Some researchers explored the proteins produced in the cells (proteomics), whereas others scrutinized the products of metabolism (metabolomics).
There were also studies examining how the space environment might alter the microbiome – the collection of bacteria, viruses and fungi that live in and on our bodies. One investigation examined the immune response to the flu vaccine. Other teams searched Scott’s biological samples for biomarkers of atherosclerosis and upward fluid shifts in the body due to microgravity, which can affect vision and cause headaches. Cognitive performance was also evaluated using computer-run cognition tests specifically designed for astronauts.
More than 300 biological samples – stool, urine and blood – were collected from the twins at multiple times before, during and after the one year mission.