If you’ve heard of Mark Kelly, it may be because his wife, Gabrielle Giffords, a U.S. representative from Arizona, was the victim of an assassination attempt in 2005. Mark Kelly himself is now a candidate for U.S. Senate, having entered politics in the aftermath of his wife’s shooting.

Mark is, however, also an astronaut: one of a set of identical twin astronauts who have been a scientific boon to NASA in their study of how space affects the human body.

Photo: Twitter/ @cenmag

Mark’s identical twin Scott Kelly spent 340 days in space aboard the International Space Station, providing invaluable information to scientists who want to better understand how to maintain a crew’s health during the hoped-for long mission to Mars or an extended stay at a base on the Moon.

Mark and Scott

Both Mark and Scott studied engineering in college, with Mark receiving a bachelor’s degree in marine engineering from the United States Merchant Marine Academy and Scott a degree in electrical engineering from the State University of New York.

Photo: Instagram/ shuttlecdrkelly

After their university education, in the late 1980s, both brothers enlisted in the U.S. Navy with Scott becoming a Navy pilot in 1987 and Mark becoming a pilot in 1989. Both brothers graduated from the Navy test pilot school in 1994. The twins later worked toward and received Masters degrees before embarking on astronaut training in 1996.

The brothers flew on Space Shuttle missions throughout the late 1990s and early 2000s as pilots and later commanders. In addition, both Mark and Scott spent time on the International Space Station (ISS), running experiments on magnetics, antimatter, dark matter, and cosmic rays. At one point in 2011, Mark and Scott became the first twins in space.

The Twins Experiment

Taking advantage of the unique opportunity presented by identical twin astronauts, NASA, in 2015, designed an experiment that would ask Scott to spend an extended time in space, with Mark remaining on earth as a control. The goal was to measure the effects of extended spaceflight on the human body (as evidenced by Scott’s condition) and using Mark’s body and condition as a baseline.

Photo: Twitter/ @carlzimmer

Scott stayed in space through the ISS expeditions 43, 44, 45, and 46, eventually almost completing a full year. During this time, ten separate research teams worked to track, manage, and record the changes in Scott Kelly’s health before his mission, during the mission, and after his return, always comparing to the condition of his brother on the ground. While some preliminary findings have been published before, in the spring of 2019, more findings were released.

Telomeres and Aging

In 2019, an integrated paper from the research team cohort was published, revealing some surprising and reassuring data about the resiliency of the human body in space. These findings related mainly to the human immune system and DNA as it relates to aging and recovery.

Photo: Twitter/ @sciencemagazine

One data point related to chromosomal dynamics had to do with Scott Kelly’s telomeres. Telomeres, a biomarker of aging that appears in white blood cells at the end of chromosomes, can be shorter or longer depending on the age and condition of a person. Scott Kelly’s telomeres were longer than his brother’s during his stay in space, then shorter than his brother’s after his return to earth. The telomeres finally found a balanced length (in comparison with Mark Kelly’s) six months after his return.

Why is this important? Because telomeres tell us a lot about how stable cells are and how long they can last. Telomeres, in brief, are a roadmap to how long a person can live. The older a cell, the shorter a telomere. When your telomeres are eaten away over time, your cells show signs of age and stress.

While this isn’t enough to prove that time in space will lengthen your life, it does point in that direction, and more telomere studies are planned to confirm this hypothesis.

Immune System Response

A second key finding from the study highlighted the resiliency of Scott Kelly’s immune system, which responded appropriately in space. The research team administered a flu vaccine to Scott during his time in space, hoping to see if it would affect him in the same way as it would on earth. And it did!

Photo: Pixabay

This is an important finding, as a fully functioning immune system will be essential for astronauts on long-duration space missions and potentially for protecting astronauts from alien microbes.

Permanent Body Changes

This finding has to do with what scientists call “gene expression”: the way that a human body’s DNA reacts to and changes our appearance or body in connection with the environment.

Photo: Twitter/ @fox12oregon

The twin study showed changes in the expression of Scott’s genes, with most of those changes returning back to the baseline provided by Mark once Scott returned to earth. Some changes, however, remained (to date) permanent. While we don’t know a great deal about what these changes are, NASA reports that the permanent changes have to do with Scott’s immune system and ability to repair his DNA. This seems to have been a positive change, as NASA says that the study “demonstrated how a human body adapts and remains robust and resilient after spending nearly a year aboard the International Space Station.”

We’ve only scratched the surface of what we can learn from this study, and scientists worldwide are anxious to keep working through the data for years to come!