Since the earliest days of human space travel, it's been clear that life in outer space has an impact on our physiology. Now, identical twin astronauts Scott and Mark Kelly, stars of NASA's Twins Study, have yielded a goldmine of new details about the precise effects of spaceflight on the body, right down to the genome. This information will be crucial to understanding how astronauts might react to long-duration space trips to the Moon, Mars, and beyond.
The Kelly brothers were closely studied by ten different research teams at various points, including before, during, and after Scott Kelly's 340-day-stint living on the International Space Station. Mark Kelly, who has flown in space previously, although never for such a long period of time, acted as the control subject on Earth.
Because the Kellys are essentially carbon copies of each other, the influence of genetic variability in the experiments was vastly reduced, which is a well-documented benefit for twin studies on Earth. But on the flip side, a sample size of just two people is fairly meagre, even if they are twins, so there were plenty of factors that could not be fully controlled. The Twins Study research leads plan to include samples from other unrelated astronauts to help compensate for this weak spot in the experiment.
One of the most well-substantiated and surprising findings from the recently released preliminary results are the noticeable differences between the twins' genetic responses to their respective environments, on Earth and in space.
This was especially evident in the brothers' telomeres, which are regions located at the ends of chromosomes, often compared to the tiny plastic caps on the ends of shoelaces. Telomeres have become a hot topic over the past decade: their lengths roughly correlate with signs of stress and aging. Scientists have found that these chromosomal bookends generally shorten as humans grow older, which has stimulated research into reversing the effect to stave off age-related conditions and diseases, and spawned a whole industry of unproven products aimed at activating telomerase, an enzyme that elongates chromosomes.
Susan Bailey, a professor of radiation cancer biology and oncology based at Colorado State University, headed up the team focused on interpreting the twins' telomere activity. Bailey's group expected to see Scott Kelly's telomeres shorten relative to his brother, due to the stressful and unusual conditions of life in space. But in a fascinating twist, the team observed the reverse outcome.
"What we saw was the opposite of what was predicted," Bailey told me over the phone. "We saw increases in the populations of cells with longer telomeres, and that was associated with spaceflight. We also got some samples postflight, after Scott returned, and it was fairly dramatic and obvious that it returned to preflight levels quite rapidly, so it seemed to be something very specific about spaceflight."
Does this mean that spaceflight could be some untapped fountain of youth? Probably not, though it's fun to entertain the idea. "That's exactly what you immediately think—there you go, we've got the answer here," Bailey laughed. "But I don't think it's as simple as that." For instance, she pointed out that telomere-lengthening can also correlate to cancer growth, so it's not as if it's a surefire sign of eternal youth.
To that point, the genetic information sourced by the Kelly twins' bloodwork and samples will have to be meticulously analyzed to assess what specific factors contributed to the results. Everything from radiation exposure, diet, sleep schedules, and exercise routines likely impacted the data. The fact that telomerase activity in both Kelly twins spiked during an emotional family event in November 2015 suggests that psychological stress also leaves an imprint.
"There's some evidence that telomerase does respond to life stresses in animal models," Bailey said. "So for us, that was a great demonstration of it in humans."
One of the Twins Study's other lead investigators is Chris Mason, an associate professor in the department of physiology and biophysics at Weill Cornell Medical College, who headed up a team that conducted genome sequencing on the twins. Like Bailey, Mason found that there was a noticeable deviation between the twins' genetic responses to their environments. For instance, over 200,000 RNA molecules were expressed differently between them over the course of the experiment.
"This is higher than the range we see for a normal person over time, so it does indicate a significant degree of molecular change for a body in space," Mason told me over email. "We are also surprised to see the body's specific response in gene expression and epigenetics to space travel, since this has never been seen before."
Whether this means that specific "space genes" were activated in Scott Kelly cells remains to be seen. Bailey, Mason, and the other teams will spend at least the next year fine-tuning and comparing their results in order to get a firmer understanding of how spaceflight affects gene expression, and the host of behaviors associated with it.
"That's where I think the power is going to come from, once we start putting it all together," Bailey said. "We do have something different going on here. We don't know what it is, but it's very intriguing and fascinating to try to figure it out."
Get six of our favorite Motherboard stories every day by signing up for our newsletter .