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Scott Kelly flu shot
NASA astronaut Scott Kelly gives himself a flu shot in 2015 during his nearly yearlong stay on the International Space Station. (NASA Photo)

WASHINGTON, D.C. — Almost three years after NASA astronaut Scott Kelly returned from spending nearly a year in orbit, researchers are still poring over the data collected during an unprecedented study comparing his health with that of his earthbound twin brother.

They say the comparison hasn’t raised any red flags about long-term spaceflight on the International Space Station. “On the whole, it’s encouraging,” Craig Kundrot, director of NASA’s Space Life and Physical Sciences Research and Applications Division, said here today at the annual meeting of the American Association for the Advancement of Science.

But the studies have raised questions about the potential impact of exposure to weightlessness and space radiation during longer missions to the moon and Mars.

“It’s mostly green flags, and maybe a handful of things that are roughly like yellow flags, things just to keep an eye on,” said Christopher Mason, a researcher at Weill Cornell Medicine who serves as the principal investigator for the Twins Study.

Those yellow flags include a hyperactive immune system response, a heightened rate of DNA repair in Kelly’s genes and higher levels of mitochondria in his blood. Mason and other researchers reported those health effects more than a year ago, but they still don’t fully understand what’s behind them.

“It could be a good, adaptive response to spaceflight, with no permanent consequences, because you’d expect the body to make some adjustments,” Kundrot said. “Or it could be sending things down a path that would be a concern. We just don’t know yet.”

Mason noted that Kelly’s immune system kicked into overdrive after he gave himself a flu shot on the space station — as part of an experiment to gauge how the immune system would react. “All indications seem to be that the immune system is functioning fine,” Mason said. “It isn’t even necessarily indicative of disregulation … ‘hyperactivation’ would be how I’d describe it.”

Some researchers have wondered whether astronauts should undergo gene therapy to cope with the stresses of long-term spaceflight. “The answer is probably ‘not necessarily,’ because this might be how the body adapts to microgravity,” Mason said. “It’s just something to keep an eye on.”

Once Kelly returned to Earth in March 2016, most of the shifts in how his genes were activated — a phenomenon known as gene expression — quickly reverted to the pattern that existed before his yearlong spaceflight. But 7 percent of the changes noted in gene expression persisted all the way up to the end of the study period, six months after the flight ended. (In some quarters, that gave rise to the false impression that 7 percent of Kelly’s DNA had changed.)

NASA’s Twins Study was designed to compare Scott Kelly’s vital signs and gene expression patterns with those of his identical twin brother, Mark Kelly, who also became an astronaut but had retired from NASA by the time Scott began his yearlong stint on the space station.

It’s long been known that spaceflight can be hazardous to your health: For example, weightlessness can cause loss of bone mass and muscle mass, and hurt eyesight.

And that’s not all, Kundrot said.

“You have the radiation,” he said. “You have an altered atmospheric environment — there’s higher CO2 levels on board. You have maybe more stress associated with the event. From a cognition perspective, you’re in a very limited environment, the size of a house. … There are a multitude of things.”

Radiation could be the biggest cause for concern when astronauts take on long-duration missions to Mars. Previous studies have suggested that the radiation levels encountered during an extended Mars mission could exceed NASA’s current guidelines for lifetime exposure, with the result of raising an astronaut’s cancer risk.

Even in the Twins Study, Mason said researchers saw heightened gene activation along “the normal DNA pathways that you would observe when DNA is damaged in ionizing radiation.”

The detailed findings from the Twins Study will soon come out in a series of peer-reviewed papers. In the meantime, NASA is planning a new set of studies focusing on how organisms adapt to the deep-space environment.

Four biological experiments will be packed aboard NASA’s Orion capsule and sent far beyond the moon’s orbit during a three-week test flight currently scheduled for 2020. The uncrewed test flight, known as Exploration Mission-1 or EM-1, will also mark the first launch of a heavy-lift NASA rocket known as the Space Launch System.

Today NASA said the EM-1 experiments will include:

  • Life Beyond Earth: Effect of Spaceflight on Seeds with Improved Nutritional Value: This study, led by Federica Brandizzi of Michigan State University, will characterize how spaceflight affects nutrients in plant seeds, with the goal of gaining new knowledge that will help increase the nutritional value of plants grown in spaceflight.
  • Fuel to Mars: Timothy Hammond of the Institute for Medical Research is planning a set of studies to identify the genes that contribute to the deep-space survival of a type of photosynthetic algae known as Chlamydomonas reinhardtii.
  • Investigating the Roles of Melanin and DNA Repair on Adaptation and Survivability of Fungi in Deep Space: The Naval Research Laboratory’s Zheng Wang and colleagues will use the fungus Aspergillus nidulans to investigate the radioprotective effects of melanin and the DNA damage response.
  • Multi-Generational Genome-Wide Yeast Fitness Profiling Beyond and Below Earth’s van Allen Belts: This investigation will use yeast as a model organism to identify genes that help organisms adapt to the conditions of deep-space flight on the EM-1 mission, as well as spaceflight in low Earth orbit aboard the International Space Station. The lead researcher is Luis Zea of the University of Colorado at Boulder.
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