Twins in Space

Twins in Space: An Unlikely Cosmic Experiment

NASA's Kelly brothers offer science a rare chance to study how space affects the body

No one ever pretended outer space is a hospitable place. There’s the hard vacuum, the lethal cold and the ever-present risk of even a small meteor hit. And then there’s the way the human body seems to revolt at the very idea of being there.

No sooner do astronauts arrive in space than up to 40% of them begin throwing up. Most of them adjust soon enough, but they may continue to feel dizzy and fatigued all the same. There’s also back pain, calcium loss, muscle atrophy, nasal congestion, accelerated heart rate and increased blood pressure—all a result of the skeletal and circulatory systems trying to adjust to zero gravity. Longer term damage may include distorted cell growth—also a result of zero-g—and DNA changes caused by cosmic radiation, leading to an increased risk of cancer and other diseases.

But how much of all that can you blame exclusively on space? Some people just have weaker bones than others; some are predisposed to hypertension or cancer. Separating heredity from environment isn’t easy even when the environment you’re talking abo ut is a decidedly extreme one. Serendipity, however, has now provided a perfect way to begin investigating the mystery, in the form of Scott and Mark Kelly, identical twins who just happen to be astronauts.

The Kellys have already achieved national and even global renown—Mark for his four shuttle missions and his cumulative 54 days in space, not to mention his high-profile devotion to his wife, former Congresswoman Gabrielle Giffords, as she continues to recover from the 2011 assassination attempt that nearly took her life; and Scott for his two shuttle flights, including a six-month stay aboard the International Space Station (ISS). Mark has since retired from NASA, but Scott is still flying, set for a full-year aboard the ISS, beginning in March 2015. And that has provided NASA with an unprecedented opportunity to run a nifty experiment.

In anticipation of the time Scott will spend aloft, NASA’s Human Research Program—a division of the space agency that studies space biology and safety—has begun requesting ideas from biologists and other researchers for comparison tests that can be conducted on the two men, both during and after the year-long mission. The name of the project—Differential Effects on Homozygous Twin Astronauts Associated with Differences in Exposure to Spaceflight Factors—is just the kind of scientific mouthful you’d expect, but it also frames perfectly just how valuable twins can be to scientists trying to understand the human body. The genetic software of identical twins matches perfectly, which means that most differences in how they age and the illnesses they do or don’t develop are attributable to environmental factors or life experiences. That makes the Kellys priceless lab subjects. “This is a once-in-a-space-program opportunity,” said John Ch arles, chief of the Human Research Program’s International Science Office, in a statement that accompanied the announcement of the project. “The mission of the HRP is to reduce the risk to astronauts during long-duration space flight. In typical investigations, we usually have a specific outcome in mind and are goal-oriented. In this case, the slate is essentially blank. I am anxious to see what proposals we receive from the scientific community.”