Spaceflight Insider

Expedition 43: The time of the Kelly twins

NASA-astronaut-Mark-Scott-Kelly-twin-twins-Expedition-43-NASA-photo-posted-on-SpaceFlight-Insider PHOTO DATE: 16 July 2010, LOCATION: Bldg. 9NW, SVMTF - ISS Mockups, SUBJECT: Joint STS-134, Expedition 25 and Expedition 26 ISS Emergency Scenario training. PHOTOGRAPHER: Mark Sowa

NASA has begun a study to test what the human body encounters from one year expeditions on orbit with the Expedition 43 flight of Scott Kelly (seen here on the left with his brother and fellow astronaut Mark). Photo Credit: Mark Sowa / NASA

On March 27, NASA astronaut Scott Kelly along with Russian cosmonaut Mikhail Kornienko (along with Gennady Padalka, also a Russian cosmonaut) launched to the International Space Station to begin a one year mission in orbit. The particular focus of the mission is to do 12 months’ worth of human research and study the effects of microgravity on the human body. The U.S. Space Agency has hinted that this one year mission is the prelude to its efforts to send crews to the planet Mars – with increasing references being made to this happening sometime in the 2030s. The race to send crews to the surface of the Red Planet – begins with a year on orbit.

As in most experiments, there is a control group where no variables are changed – and an experimental group in which one or more variables is changed to see if there is a different outcome compared to the control group. Previous medical studies involving microgravity (independent variable) has always had the experimental group compared to similar humans on Earth who continue their activities with Earth’s gravity as one of the determining factors.

Expedition 43 Scott Kelly Baikonur Cosmodrone Soyuz NASA photo posted on SpaceFlight Insider

Kelly (seen here) and Mikhail Kornienko will spend one year on orbit. During this period Kelly will be the focus of a special experiment while on orbit. Photo Credit: Bill Ingalls / NASA

Both Kelly and Kornienko will constitute the experimental group in this mission and will be compared to similar humans on Earth for one year. However, in order for the experiments to be as accurate as possible, both groups have to be as similar as possible with the only difference being the independent variable. The fact humans in prior microgravity experiments have different DNA, upbringing, and exercise regimes while in orbit have always brought an uncertainty to the results. Until now that is. Scott Kelly has a twin, one who also happens to be an astronaut (retired) – Mark Kelly.

Twins come in two primary groups: fraternal and identical. Fraternal twins began as two different zygotes who happen to share the same womb, hence the word “fraternal”, but are genetically different. Although they share the same parents, both individuals do not have the exact same genetic makeup. Identical twins are different, however. They begin as one zygote and within a short time separate into two individuals with an identical genetic makeup as they continue to grow and develop.

Identical twins are highly sought after by scientists in various fields that are studying the “nature vs. nurture” aspect of health and development such as medical, psychology, and sociology. Scientists can test the impact of nature (DNA) vs. nurture (environment) on each part separately more accurately with twins who have been separated for a period of time.

In this case, NASA scientists have “struck gold” with the Kelly brothers when it comes to their research on the effects of microgravity on astronauts during long-duration missions. Both men are astronauts with identical DNA and somewhat similar experiences. NASA already has an extensive medical file going back years on the two veteran space flyers. This type of study could give scientists and NASA important data to use for future deep space missions such as an 18 month round-trip journey to Mars.

International Space Station ISS in orbit above Earth NASA photo posted on SpaceFlight Insider

Crew who have conducted prior long-duration stays on orbit have encountered an array of negative physical effects. It is hoped the “twin” study can help provide data on methods to limit the impact of long duration stays in space – as plans to send crews to Mars pick up pace. Photo Credit: NASA

Russian cosmonaut Dr. Valery Polyakov is the current title holder for the longest mission time in microgravity, with 438 continuous days in orbit on the space station Mir from 1994 and 1995. Polyakov is a medical doctor, and was very aware of the detrimental effects of long exposure to the effects of microgravity. His exercise routine while in orbit was extensive owing to his understanding of how long stays in space affect the human body. Because of his regime, he returned to Earth with fewer ill effects.

He exercised faithfully 2 hours per day and his bone loss was lower compared to other astronauts and cosmonauts at only 0.5 percent loss per month for a total of 7 percent during the mission. By comparison, the average astronaut exercises about 45 minutes per day while in space. At least three other cosmonauts have spent a year in space, but no one has come close to Dr. Polyakov’s record since then.

Expedition 43 Soyuz M 16M Expedition 43 Scott Kelly Mikhail Kornienko Gennady Padalka NASA photo posted on SpaceFlight Insider

The Expedition 43 crew launched to the ISS aboard their Russian Soyuz TMA-16M spacecraft on March 27, 2015. Photo Credit: NASA

However, even 438 days is short in terms of what would be required for a mission to the Red Planet. The data supplied by Polyakov’s mission and the other three cosmonauts are all from a small population with different DNA and life experiences, and is considered to be incomplete. At least two other cosmonauts have accumulated more time in space, but always had that time broken up by visits back to Earth between missions granting them an opportunity to recover from microgravity.

With the Kelly twins and their already extensive medical records, NASA and other researchers have been given an opportunity to study the long-term effects with the two most similar humans possible over a set period of time. NASA has made the most of this opportunity, stating: “The Twins Study is ten separate investigations coordinating together and sharing all data and analysis as one large, integrated research team. NASA has selected 10 investigations to conduct with identical twin astronauts Scott and Mark Kelly. These investigations will provide broader insight into the subtle effects and changes that may occur in spaceflight as compared to Earth by studying two individuals who have the same genetics, but in different environments for one year.”

The most common impact on the human body while on orbit – is space sickness. About 40 percent of all astronauts and cosmonauts suffer from a form of motion sickness, but usually recover within 2-3 days. Space sickness can include nausea, vomiting, headaches, malaise, and dizziness. The shifting of fluids within the body is suspected to be the most likely cause of space sickness.

NASA Astronaut Scott Kelly Soyuz M 16M Expedition 43 photo credit Victor Zelentsov NASA posted on SpaceFlight Insider

Scott Kelly training for his one year stay on board the ISS. Photo Credit: Victor Zelentsov / NASA

Along with space sickness, fluid shift causes blood to no longer pool in the legs as it does on Earth; the blood shifts to the torso and brain. The cardiovascular system doesn’t have to work as hard in microgravity and this leads to increased heart rates, increased blood pressure, puffy faces, headaches, nasal congestion, and thinner legs.

Red blood cells also tend to change shape in microgravity. They become more spherical and fewer red blood cells are found in the bone marrow. These cells resume their normal shape once returning to Earth.

Russian Federal Space Agency Roscosmos Soyuz booster

At present NASA is dependent on Russia for access to orbit. Photo Credit: NASA

A weakened immune system also occurs in microgravity, though this may be due to being in an isolated environment. The same phenomenon has been observed in isolated outposts in Antarctica. The T-lymphocyte system is weakened resulting in astronauts and cosmonauts being more susceptible to infection, latent viruses, bacteria, and fungi.

Muscle loss or atrophy, particularly in the legs, can also occur. Without the pull of gravity, muscles tend to waste away and become flabby as would be seen in a sedentary person on Earth. Astronauts and cosmonauts try to counter this with an exercise regime while in space. NASA provides physical therapy upon the crews’ return to help them regain muscle mass and strength.

Balance and orientation are affected. With no “up or down”, crews find they have no reference point to assist them resulting in loss of sense of direction and they feel uncoordinated.

Long term effects, such as would be experienced on a Mars mission, can be more debilitating. Bone loss is probably the most noticed and worrisome. It is estimated that a crew that would travel to Mars would experience bone loss equivalent to what a normal person would experience in one lifetime on Earth. The body excretes calcium and phosphorus and the body experiences symptoms similar to osteoporosis. Dramatic changes occur in the heel, femoral neck, lumbar, and pelvis resulting in a risk of fractures, weakness, and painful kidney stones. Faithful exercise during the mission can slow the bone loss, but not stop it. Many former spaceflight crews spend up to 2 years or more of dedicated training to regain their bone mass after returning to Earth.

Radiation is a significant concern, especially for crews on missions deep into the black of space. The Apollo astronauts reported “light flashes” behind their eyes while traveling to the Moon and back. This was due to cosmic rays traveling through the vitreous humor of the astronauts’ eyes or the visual centers in the brain. Solar flares can produce quite a bit of cosmic rays and could damage the atoms that make up the cells and DNA of a crew. This can cause decreased immunity, an increased risk of cancer, heart disease, brain and central nervous system damage, as well as a higher risk of cataracts.

Astronaut Scott Kelly trains for Expedition 43 Bill Ingalls NASA photo posted on SpaceFlight Insider

As Scott Kelly conducts his one year in space, his brother Mark will serve as the “control” for the twin experiment back on Earth. Photo Credit: Bill Ingalls / NASA

A small group of NASA astronauts have also experienced irregular heart rates. It is unknown at this time if this was a previously undetected condition, or something related to long-term exposure to the microgravity environment.

The Twins Study will involve a team of scientists from NASA and various medical universities from the United States and Germany. They will be testing and studying both twins, giving them identical tests throughout the year. Testing will involve human physiology (fluid shifts and bone loss), behavioral health (cognition), microbiology/microbiome (digestive bacteria), molecular/omics (DNA and RNA), and vision. All data will be shared (once medical privacy concerns are tended to) between the teams. This test could possibly see the largest study ever done in history on a single set of twins.


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Gregory N. Cecil is the only Florida State Certified Educator and Nationally Certified Aerospace Technician in the nation. He holds a Masters in Aeronautical Science: Space Operations Management from Embry-Riddle Aeronautical University and worked on the Space Shuttle Program. He is a science teacher and has taught in both public and private schools. Gregory has written over 50 articles relating to the space program and continues to contribute to the promotion of space.

Reader Comments

Nice article, but please indicate who is who in your pictures.

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