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Editor's choice: International Space Station science

Is colonisation of space feasible? The International Space Station (ISS) is the collaborative hub of research which aims to answer this question. Here, Editors from two open-access Nature Research journals, npj Microgravity and Scientific Reports, have brought together more than 30 free-to-access papers describing data generated aboard the ISS. This Collection spans materials science, genetics, plant science, biology of fish and rodents, and human physiology.

Human

  • npj Microgravity | Article | open

    Prolonged exposure to microgravity has a long-term effect on the perception of upright. On earth we use visual, body, and gravity cues to help us determine the orientation of ourselves relative to the world which affects many perceptual tasks including reading, recognizing faces, and navigating. Laurence R. Harris and colleagues at York University assessed how seven astronauts who spent 168 days on average on the International Space Station perceived their orientation before, during and after flight. Although no changes were observed during their missions, astronauts’ judgements in the absence of visual cues were worse upon return to earth compared with ground-based controls. Harris and his team found that the effect persisted for up to four months after the astronauts returned to earth. These findings could help develop countermeasures to avoid perceptual mistakes during space travel, and contribute to facilitating safer, long-duration journeys without gravity.

    • Laurence R. Harris
    • , Michael Jenkin
    • , Heather Jenkin
    • , James E. Zacher
    •  &  Richard T. Dyde
  • npj Microgravity | Article | open

    Long-duration spaceflight increases the reactivation of latent herpes viruses in astronauts and is accompanied by a rise in stress hormone levels. This study shows that the frequency and viral loads of reactivation of Epstein-Barr virus, varicella-zoster virus, and cytomegalovirus were even greater in blood, urine, and saliva samples from astronauts staying 60 to 180 days onboard the International Space Station than has previously been observed for short-duration (10–16 days) missions. Changes in viral reactivation were also found to be associated with changes in the daily trajectory of salivary cortisol during these long-duration missions. These results indicate that the effects of the microgravity environment on the immune system are increased with prolonged exposure and highlight the potential increased risk of infection among crewmembers.

    • Satish K. Mehta
    • , Mark L. Laudenslager
    • , Raymond P. Stowe
    • , Brian E. Crucian
    • , Alan H. Feiveson
    • , Clarence F. Sams
    •  &  Duane L. Pierson

Fish & rodent

  • npj Microgravity | Article | open

    Shuttle-era ‘mousetronaut’ homes tolerate longer space trips than expected, allowing animal experiments on the International Space Station. Eric Moyer at the NASA Ames Research Center in California and colleagues tested whether existing Shuttle-era animal enclosures, which facilitate rat and mouse experiments in space, could accommodate longer stays than their rated 20-day flight window. They found that with minor modifications to feeding hardware, the enclosures handled 35-day rat and mouse experiments, with no ill effects for animal health (e.g, carbon dioxide buildup) or astronauts (e.g, smell confinement). Animals showed slight differences in organ mass compared with controls. This work opens up the possibility of extended animal experiments on International Space Station trips, experiments which examine topics like bone and muscle degradation in astronauts undergoing extended spaceflight.

    • Eric L Moyer
    • , Paula M Dumars
    • , Gwo-Shing Sun
    • , Kara J Martin
    • , David G Heathcote
    • , Richard D Boyle
    •  &  Mike G Skidmore
  • npj Microgravity | Article | open

    An experiment conducted in mice offers support to the claim that long space missions may have adverse effects on the skin. Such effects have been documented by astronauts, who often complain of skin irritation and dryness after spending lengthy periods in zero gravity. Betty Nusgens and co-workers at the University of Liège, Belgium, together with scientists in Italy, sent mice to spend three months on the International Space Station. Upon the animals' return to Earth, the scientists found a 15% reduction in the thickness of the dermis – the layer of skin tissue directly beneath the skin surface – compared with mice kept on the ground. This skin thinning may result from defective collagen synthesis. The “astromice” also exhibited disrupted hair follicle growth and abnormal gene expression in the skin's muscle layer.

    • Thibaut Neutelings
    • , Betty V Nusgens
    • , Yi Liu
    • , Sara Tavella
    • , Alessandra Ruggiu
    • , Ranieri Cancedda
    • , Maude Gabriel
    • , Alain Colige
    •  &  Charles Lambert
  • Scientific Reports | Article | open

    • Cora S. Thiel
    • , Diane de Zélicourt
    • , Svantje Tauber
    • , Astrid Adrian
    • , Markus Franz
    • , Dana M. Simmet
    • , Kathrin Schoppmann
    • , Swantje Hauschild
    • , Sonja Krammer
    • , Miriam Christen
    • , Gesine Bradacs
    • , Katrin Paulsen
    • , Susanne A. Wolf
    • , Markus Braun
    • , Jason Hatton
    • , Vartan Kurtcuoglu
    • , Stefanie Franke
    • , Samuel Tanner
    • , Samantha Cristoforetti
    • , Beate Sick
    • , Bertold Hock
    •  &  Oliver Ullrich

Other biology

  • npj Microgravity | Brief Communication | open

    • Anna-Sophia Boguraev
    • , Holly C. Christensen
    • , Ashley R. Bonneau
    • , John A. Pezza
    • , Nicole M. Nichols
    • , Antonio J. Giraldez
    • , Michelle M. Gray
    • , Brandon M. Wagner
    • , Jordan T. Aken
    • , Kevin D. Foley
    • , D. Scott Copeland
    • , Sebastian Kraves
    •  &  Ezequiel Alvarez Saavedra
  • Scientific Reports | Article | open

    • Sarah L. Castro-Wallace
    • , Charles Y. Chiu
    • , Kristen K. John
    • , Sarah E. Stahl
    • , Kathleen H. Rubins
    • , Alexa B. R. McIntyre
    • , Jason P. Dworkin
    • , Mark L. Lupisella
    • , David J. Smith
    • , Douglas J. Botkin
    • , Timothy A. Stephenson
    • , Sissel Juul
    • , Daniel J. Turner
    • , Fernando Izquierdo
    • , Scot Federman
    • , Doug Stryke
    • , Sneha Somasekar
    • , Noah Alexander
    • , Guixia Yu
    • , Christopher E. Mason
    •  &  Aaron S. Burton
  • npj Microgravity | Article | open

    A four-year study that monitored bacteria aboard the International Space Station (ISS) has discovered multiple species, mostly of human origin, living aboard. The research, by Masao Nasu and colleagues from Osaka University and the Japan Aerospace Exploration Agency, will help space agencies assess risks to astronauts during long-term spaceflight. The team found multiple types of bacteria lived on the Japanese Experiment Module of the ISS, named Kibo, despite it being disinfected weekly. Most bacteria were of human origin (e.g. gut microbes), which were likely transferred by the astronauts. A small proportion of bacteria was of non-human origin, such as Legionella, which the authors speculate arrived on resupply materials. Since microgravity can affect bacteria in unpredictable ways, such as increasing their virulence, tracking bacterial habitation in the ISS will provide insights for future space travel.

    • Tomoaki Ichijo
    • , Nobuyasu Yamaguchi
    • , Fumiaki Tanigaki
    • , Masaki Shirakawa
    •  &  Masao Nasu
  • npj Microgravity | Article | open

    Researchers in Japan have uncovered the molecular genetic changes that lead to the loss of muscle mass after lengthy periods in space. Atsushi Higashitani at Tohoku University and colleagues in Japan and the UK sent nematode worms into orbit on the International Space Station and observed changes in their gene and protein expression. Compared with worms grown in a centrifuge in space that kept them at normal Earth gravity, worms grown in microgravity showed down-regulation of genes coding for proteins that make up internal cell scaffolding and attach muscle cells to the cuticle. In addition, genes controlling mitochondrial metabolism were switched to “energysaving” mode. Both changes likely contribute to the loss of muscle mass in orbit, and the same proteins are believed to be associated with muscle atrophy in human astronauts.

    • Akira Higashibata
    • , Toko Hashizume
    • , Kanako Nemoto
    • , Nahoko Higashitani
    • , Timothy Etheridge
    • , Chihiro Mori
    • , Shunsuke Harada
    • , Tomoko Sugimoto
    • , Nathaniel J Szewczyk
    • , Shoji A Baba
    • , Yoshihiro Mogami
    • , Keiji Fukui
    •  &  Atsushi Higashitani

Physical science

  • npj Microgravity | Article | open

    Recent International Space Station (ISS) chemistry experiments may improve the reliability of satellites recording Earth's climate data. Orbital monitoring of infrared radiance requires probes with extraordinarily low drift rates of less than 0.1 kelvin per decade. To achieve such precision, materials such as gallium (Ga) that undergo liquid/solid phase changes at precise temperatures are included onboard the satellite and then calibrated against ground-based standards. Shane Topham from the Space Dynamics Laboratory in Utah and co-workers have now resolved uncertainty surrounding the effects of microgravity on the temperature of Ga phase transitions. Experiments on the ISS tested how hermetically sealed Ga samples melted and froze during repeated 6 hour cycles. Only single millikelvin differences were detected between orbiting samples and those on Earth — an accuracy well-suited for remote sensing thermal reference standards.

    • T Shane Topham
    • , Gail E Bingham
    • , Harri Latvakoski
    • , Igor Podolski
    • , Vladimir S Sychev
    •  &  Andre Burdakin
  • npj Microgravity | Article | open

    New research conducted aboard the International Space Station highlights the possibilities of materials processing in space. A team led by Yasuhiro Hayakawa at Shizuoka University in Japan sought a new way to process indium–gallium–antimonide (InGaSb) alloys, which are gaining attention as heat-to-electricity convertors and infrared sensors but can be impractically brittle when made using conventional methods. In a series of long-term crystal growth experiments performed under low-gravity conditions, Hayakawa's team was able to predictably control InGaSb composition. This is because, in outer space, GaSb starting materials dissolve at rates that depend on crystal orientations, producing concentration gradients. These gradients, in combination with favorable interfaces for uniform distributions of indium, offer ways to tune and manipulate InGaSb materials that are quite convoluted on Earth.

    • Velu Nirmal Kumar
    • , Mukannan Arivanandhan
    • , Govindasamy Rajesh
    • , Tadanobu Koyama
    • , Yoshimi Momose
    • , Kaoruho Sakata
    • , Tetsuo Ozawa
    • , Yasunori Okano
    • , Yuko Inatomi
    •  &  Yasuhiro Hayakawa
  • npj Microgravity | Article | open

    New research shows that minimizing the effects of gravity can improve the fabrication of high-tech semiconductors. Yuko Inatomi from the Japan Aerospace Exploration Agency and co-workers investigated the growth of indium gallium antimonide (InGaSb) alloys on the International Space Station (ISS) and under standard terrestrial conditions. The team placed ‘sandwich’ samples, where a thin InSb layer sits between thicker chunks of GaSb, into a high-temperature furnace and characterized the alloy crystals formed in the mixing zone. The researchers found significant differences in crystal qualities and growth rates. Whereas samples grown on Earth had mostly curved growth interfaces, those formed on the ISS were nearly flat-a change that produced smoother distributions of atoms with a higher growth rate than typical conditions. The authors attribute the improved kinetics in microgravity to a reduction in convection forces at growth interfaces.

    • Y Inatomi
    • , K Sakata
    • , M Arivanandhan
    • , G Rajesh
    • , V Nirmal Kumar
    • , T Koyama
    • , Y Momose
    • , T Ozawa
    • , Y Okano
    •  &  Y Hayakawa