| Mission type | Long-duration expedition |
|---|---|
| Mission duration | 340d 8h 43m |
| Orbits completed | 5,356[1] |
| Expedition | |
| Space station | International Space Station |
| Began | March 27, 2015, 19:42 (2015-03-27UTC19:42Z) UTC |
| Ended | March 2, 2016, 04:25 (2016-03-02UTC04:26Z) UTC |
| Arrived aboard | Soyuz TMA-16M |
| Departed aboard | Soyuz TMA-18M |
| Crew | |
| Crew size | 2 |
| Members | |
| EVAs | 4 |
| EVA duration | 23h54m |
  Scott Kelly and Mikhail Kornienko | |
TheISS year-long mission , also called theOne-Year Mission, was an 11-month-longscientific research project aboard theInternational Space Station, which studied thehealth effects of long-term spaceflight.[2]
As part of the mission, theNASA Twins Study was conducted. AstronautScott Kelly was selected for the mission with hisidentical twin,Mark Kelly, who stayed on Earth as acontrol. Scott spent 340 days in space for the experiment. The result demonstrated several long-lasting changes, including those related to alterations inDNA andcognition.[3][4]
AstronautScott Kelly and cosmonautMikhail Kornienko spent 340 days in space with scientists performing medical experiments. Kelly and Kornienko launched on 27 March 2015 onSoyuz TMA-16M, along withGennady Padalka.[5][6][7][8] The mission encompassedExpeditions 43,44,45, and46.[9] The pair safely landed inKazakhstan on 2 March 2016, returning aboardSoyuz TMA-18M withSergey Volkov.[10] The mission supported the NASA Twins study, which helps shed light on the health effects oflong-duration spaceflight.[11]
The goal aboard the orbiting laboratory was to understand better how the human body reacts and adapts to the harsh environment of space.[9] Data from the mission was used to improve assessments of crew performance and health. They worked to develop and validate better countermeasures against the risks associated with future missions around theMoon,asteroids and ultimatelyMars.[12]
In November 2012,NASA, theRussian Federal Space Agency (Roscosmos), and their international partners selected two veteran spacefarers for a one-year mission aboard theISS in 2015. AstronautScott Kelly was selected as theidentical twin ofMark Kelly. The mission included collecting scientific data important to futurehuman exploration of the Solar System. Kelly and Korniyenko already had an indirect connection: Kelly was a backup crew for the station'sExpedition 23/24, where Korniyenko served as a flight engineer.[13]
Identical twinsMark Kelly andScott Kelly were studied for changes in the health of a body in space compared to a body on Earth. A variety of mechanisms in the human body were analyzed, notablytelomere length, body mass, eye and bone deformation, and immune response. Ten research teams are assembled to conduct an integrated research on the change on physiological, molecular and cognitive level after exposing to long-duration spaceflight.
The study also required the astronauts to keep a journal, and investigated the psychological effects of living in a confined space for an extended length of time. Kornienko said of his experiences on Expedition 23/24: "The thing you miss there most of all is the Earth itself, I missed smells. I missed trees, I even dreamt of them. I even hallucinated. I thought I smelled a real fire and something being barbecued on it! I ended up putting pictures of trees on the walls to cheer up. You do miss the Earth there."[14] Scott stated that he missed feeling changes in the weather while on the ISS.[15]
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On 12 April 2019, NASA reported medical results, from the NASA Twins study, which demonstrated several surprising changes, including those related to alterations inDNA andcognition, when one twin was compared with the other.[3][4]
The study found:"significant changes in multiple data types were observed in association with the spaceflight period; the majority of these eventually returned to a preflight state within the time period of the study. These included changes in telomere length, gene regulation measured in bothepigenetic andtranscriptional data,gut microbiome composition, body weight,carotid artery dimensions, subfovealchoroidal thickness and peripapillary totalretinal thickness, and serummetabolites. In addition, some factors were significantly affected by the stress of returning to Earth, including inflammation cytokines and immune response gene networks, as well as cognitive performance. For a few measures, persistent changes were observed even after 6 months on Earth, including some genes’ expression levels, increased DNA damage fromchromosomal inversions, increased numbers of short telomeres, and attenuated cognitive function."[16]
During spaceflight, the length oftelomeres increased by 14.5%. During spaceflight, the increase is observed from flight day 14 to flight day 334. The effect is rapidly reversed after returning Earth and ultimately fall back to near preflight level after 6 months (190 days).[4] The other effects of spaceflight, such as reduced body mass and increased serum folate level, are associated with telomeres elongation.
Telomere length is associated with aging and lifespan. Shorter telomeres are related to early deaths, vice versa.[17] However, the exact effect of spaceflight to lifespan is currently not known.
The study found no significant changes inT cell production after the firstvaccination of the study.
The International Space Station developed exercise equipment, includingtreadmills and resistance devices to limitmuscle atrophy in alow gravity environment. Weightlessness causes body fluids in astronauts to accumulate in the upper half of the body, leading to facialedema and unwelcome side effects. One problem may be the low gravity affecting the body in unforeseen ways and it can be hard to detect the cause and effect of gravity on the body. Space seems to cause trouble for a number of body parts including bone, sometimes the eyes, and a classic problem isspace sickness.[citation needed]
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Vladimir Titov andMusa Manarov spent 365 days in space onMir from December 1987 to December 1988.Valeri Polyakov spent 438 days on Mir in 1994-1995 andSergey Avdeyev spent 380 days on Mir in 1998-1999.[18][19]
Prior to the year-long mission, the longest mission on the ISS was 215 days byMikhail Tyurin andMichael López-Alegría.Christina Hammock Koch holds the record for the longest single spaceflight by a woman at 328 days.[20] In March 2022, NASA'sMark T. Vande Hei and the RussianPyotr Dubrov landed, following 355 days in space as part of ISSExpeditions 64/65/66.[21]
