SCIENCE IN SPACE

The International Space Station: The greatest science show in the universe

BY CRAIG COLLINS

Before humans had taken up permanent residence aboard the International Space Station (ISS), science was there. The first space station module entered orbit in 1998 with an experiment payload – an investigation evaluating the growth of protein crystals in microgravity – that has since helped investigators treat diseases and disorders on Earth.

In the 1990s, after all the space station international partnerships had been formalized and the station’s first building blocks were being produced with Congress’ approval, NASA issued a public announcement of the new space station’s missions. First among them:

European Space Agency astronaut Alexander Gerst, Expedition 40 flight engineer, conducts a session with the Capillary Flow Experiment (CFE-2) in the Harmony node of the International Space Station in June 2014. CFE is a suite of fluid physics experiments that investigate how fluids behave in microgravity, which could benefit water and fuel delivery systems on future spacecraft. Scientists designed the CFE-2 to study properties of fluids and bubbles inside containers with a specific 3-D geometry.

“To create a permanent orbiting science institute in space capable of performing long-duration research in the materials and life sciences areas in a nearly gravity-free environment.”

In the 22 years since its first experiment reached orbit, the space station has quietly compiled an exceptionally deep and broad record of scientific research. As of summer 2020, 4,269 researchers from 108 different countries and areas had conducted more than 3,000 investigations.

The Destiny laboratory, partially covered with shadows in the foreground, is seen in this photo taken through a window on space shuttle Endeavour’s aft flight deck in December 2001, while the International Space Station (ISS) was still under construction. The U.S. Orbital Segment of the space station was designated a U.S. National Laboratory in 2005. It includes three ISS laboratory facilities: NASA’s Destiny, the European Space Agency’s Columbus module, and the Japan Aerospace Exploration Agengy’s Kibo module.

NASA’s primary goals for space station research are twofold: first, to answer questions and solve problems related to the agency’s future space exploration goals, and second, to improve life on Earth. To strengthen its Earth focus, NASA’s 2005 authorization designated the U.S. Orbital Segment (USOS) of the space station a National Laboratory. When it selected the nonprofit Center for Advancement of Science in Space (CASIS) to manage the ISS U.S. National Laboratory in 2011, it was with an explicit focus on space research aimed at improving life on Earth.

According to Dr. Kirt Costello, chief scientist for NASA’s ISS Program, these two missions operate in parallel, with procedures and processes to avoid overlap: The selection process for National Laboratory research, he said, “is a combination of the commercial developers’ own efforts within the National Lab to fund and select some research, and then stimulate other governmental agencies and commercial providers to bring forward research to perform on the ISS.” Meanwhile, NASA directorates and divisions identify their own research priorities – all of which are discussed through the ISS Program Science Forum – U.S., a group made up of senior science representatives from across these research sponsors.

NASA’s Destiny, the European Space Agency’s Columbus module, and the Japan Aerospace Exploration Agengy’s Kibo module. Right: NASA flight engineer Serena Auñón-Chancellor floats in the Destiny laboratory module in June 2018 with gear from an investigation into how blood cell production is altered in microgravity, the results of which may improve the health of astronauts on long-term missions and help patients on Earth with mobility and aging issues. Scientific research conducted on the space station not only helps to improve life on Earth, but aids in plans for future long-term space exploration.

While most National Laboratories are focused on a specific scientific area, the space station National Laboratory is uniquely multidisciplinary. The Center for Knowledge Dif- fusion, a U.S. nonprofit, has developed an ISS Map of Science to illustrate the interdisciplinary flow of knowledge stimulated by space station research. The map shows connections among fields as diverse as brain research and social sciences; medical and biological sciences; and engineering, math, chemistry, and physics – a scope unequaled by any research facility, anywhere.

SCIENTIFIC BENEFITS FOR HUMANITY

There are several factors – including the station’s orbital path, the technology required to operate and maintain it, and the considerable amount of its surface area exposed to space – that make the space station valuable as a research platform, but probably its most distinguishing trait is its status as a habitable long-duration microgravity environment. This distinction has contributed to the benefit of humanity – to our knowledge of life both on Earth and in space – in many fields of scientific research, including:

NASA astronaut and Expedition 61 flight engineer Christina Koch works on the Cold Atom Lab (CAL), swapping and cleaning hardware inside the quantum research device, on Jan. 28, 2020. The CAL enables research into the quantum effects of gases chilled to nearly absolute zero, which is colder than the average temperature of the universe.

PHYSICAL SCIENCE

The force of gravity – along with the processes associated with it, such as sedimentation, buoyancy, and convection (heat rises, cold sinks) – dominates all we know about objects and materials: how water behaves; how fire burns; or how materials such as metal alloys, composites (e.g., concrete), or fibers are formed.

In the microgravity of the space station, different forces and physical properties take precedence. For fluids, surface tension becomes the most important factor. In space, bubbles stubbornly refuse to separate out from liquids. Earthbound methods of controlling flows present challenges for functions such as propellants, thermal control, and waste management. Space station fluid studies have contributed to better models for designing microgravity fluid systems on future spacecraft. In the absence of processes such as sedimentation and buoyancy, space station investigators have produced metal alloys and optical fibers far superior to those produced on Earth.

NASA astronaut Jessica Meir cuts mizuna mustard green leaves grown aboard the International Space Station for the VEG-04B space agriculture study on Oct. 30, 2019. The botany research is helping scientists learn how to provide fresh food to space crews on long-duration missions. The Expedition 61 crewmembers also tasted the leaves for edibility and stowed the leftovers in a science freezer for scientific analysis.

One of the experimental platforms Costello is most excited about is the Cold Atom Laboratory (CAL), an instrument being built and upgraded aboard the station to create extremely cold conditions – near-absolute zero – in microgravity, leading to the formation of a “fifth” state of matter: ultra-cooled atoms known as Bose-Einstein condensates (BECs) that behave not as particles, but as quantum waves that can, over time, overlap with neighboring atoms. The BECs that evolve on Earth are pulled down by gravity and can only be observed for a fraction of a second, but in microgravity, they can be observed for up to 10 seconds.

Expedition 57 flight engineer Serena Auñón-Chancellor is pictured on Nov. 9, 2018, mixing protein crystal samples to help scientists understand how they work. Proteins crystallized in microgravity are often higher in quality than those grown on Earth, and present opportunities for the development of new drugs to treat disease.

“We’re trying to understand how particles behave on the most basic of scales and what new devices or techniques we could learn from this,” Costello said. “Presuming you can get them down to temperature and then carefully interrogate them, you can use the interference patterns of atoms to tell you about very sensitive changes in their position and movement. And these can be used as math measurement devices, gravitational detector devices, and other navigational units that NASA has an interest in, for being able to do interplanetary and maybe someday interstellar navigation, where you don’t have a GPS or other system to help you out.”

BIOLOGY/BIOMEDICINE/ BIOTECHNOLOGY

Space station researchers are studying the effects of spaceflight – of near-weightlessness and of direct exposure to space – on the growth, development, and evolution of plants, animals, and living tissues. Astrobiology experiments have involved direct exposure of dormant life forms to space, including solar UV light, vacuum, and radiation. Some organisms are capable of withstanding up to 18 months of direct exposure.

NASA astronauts Andrew Morganand Jessica Meir conduct research operations insidethe Japanese Kibo Lab Module’s Life SciencesGlovebox. The Expedition 61 flight engineerswere studying mice for the Rodent Research-14investigation, which observes how microgravityaffects the body on a cellular and organ level.

Studies of plant growth aboard the space station are primarily aimed at developing food production systems for the station and long-duration exploration missions. The results have helped investigators learn which processes are earthbound and which aren’t – for example, root growth patterns – and suggested ways future growers can either adapt or genetically modify plants to thrive and produce food in space. Studies have also shown that at least four successive generations of higher plants (complex plants with vascular systems, such as greens and vegetables) can grow in spaceflight conditions, suggesting the possibility that greenhouses are potential human life support systems during long-term exploration missions.

Researchers continue to investigate microgravity’s effects on the unusual protein crystals that can be formed in space. Proteins are responsible for a wide range of biological functions, and understanding their shape is key to understanding how they interact with cellular structures and pharmaceuticals. To study proteins, scientists let them form crystals in their natural state – dissolved in liquid, much as they’re found in living organisms. On Earth, this process is subject to sedimentation, but on the orbiting laboratory, Costello explained, “You remove the buoyancy-driven convection and the settling that occurs, so you have a much slower and much purer crystallization of proteins.” Using space station-grown crystals, for example, scientists have formulated a drug that targets a specific location on a protein involved in Duchenne Muscular Dystrophy (DMD), an incurable genetic disorder. Studies of animal models have suggested this new drug may be able to double the lifespan of people with DMD.

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Animal models – studies of mice and rats in space – have helped investigators evaluate the physiological, muscular, and skeletal effects of microgravity, as precursor research to discovering drugs and other therapies to counteract some of these effects. Additionally, a series of investigations recently launched by the National Institutes of Health is studying microgravity’s effects on the growth of three-dimensional, human-like tissues. Known collectively as Tissue Chips in Space, the investigations will study the effects of microgravity on bio-printed tissue samples that model the structure and function of human organs such as the lungs, bones, and liver.

HUMAN RESEARCH

The most effective way of studying the rapid changes microgravity causes in the human body – many of which resemble the onset and progression of aging-related diseases on Earth – is to study humans themselves. Space station astronauts aren’t just the lab technicians who help conduct experiments; they’re often the subjects. Research on the effects of long-term space exposure on the human body, including bone-density loss, muscle atrophy, and vision impairment, have given investigators an idea of the future risks, such as fractures or difficulties with balance or movement, that might be associated with interplanetary voyages.

Above and below: NASA astronaut Scott Kelly (pictured at above on the space station) and former NASA astronaut Mark Kelly (pictured below on Earth) give themselves flu shots for an ongoing study on the human immune system. The vaccinations, administered in the fall of 2015, were part of NASA’s Twins Study, a compilation of multiple investigations that took advantage of a unique opportunity to study identical twins Scott and Mark Kelly, while Scott spent a year aboard the International Space Station and Mark remained on Earth. A summary of the study’s results was published in 2019.

NASA astronaut Michael Barratt began his NASA career as an aerospace physician in 1991, joined the astronaut corps in 2000, and lived on the space station from spring to fall of 2009 as a flight engineer for Expedition 19/20. “We became aware, in the first few years of station flight, that people were coming back with changes in their retinas and optic nerves, and really in various parts of their brains,” he said. His 2009 mission helped to capture onboard scans of astronauts that revealed more detail: thickening of retinas and optical nerves, and “brain shift,” or the repositioning of a person’s brain inside their skull – all most likely caused by fluids migrating into the head and increasing cranial pressure. Later studies have revealed that these brain changes are more pronounced among those who stay in space the longest.

The subject of probably the most fascinating study of spaceflight’s effect on the human body, the NASA Twins Study, is Scott Kelly, the astronaut who, along with cosmonaut Mikhail Kornienko, spent nearly a year (340 days) aboard the orbiting laboratory from 2015 to 2016. Because Kelly has an identical twin brother – retired NASA astronaut Mark Kelly – who offered a control subject, 10 research teams from around the country studied the physiological, molecular, and cognitive changes associated with Scott’s long-term spaceflight exposure. A summary of Twins Study results was published in the journal Science in April 2019. Some of the findings, particularly those relating to changes in chromosome shape and gene expression, have been surprising, and provided a jumping-off point for new studies.

The Alpha Magnetic Spectrometer (AMS), photographed during a spacewalk by NASA astronauts Shane Kimbrough and Peggy Whitson in January 2017. The AMS, a powerful magnet that has detected particles that support the existence of dark matter, is helping scientists to answer questions about fundamental cosmology and the formation of the universe.

For some of the space-related physiological changes discovered in the early space station years, such as bone-density loss, investigators have already discovered effective countermeasures, such as vitamin D supplements and strenuous resistance exercise, that can counteract them. These discoveries will be important not only for the health of future long-term explorers, Barratt said, but also for the private astronauts now poised to take flight.

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“We’re on the cusp of a new wave of commercial spaceflight,” he said, “where nonprofessional astronauts will be flying. We need to characterize changes like this so that the flying public understands what to expect, how to prepare, how to monitor and manage, and how to maintain optimal health with spaceflight.”

EARTH AND SPACE SCIENCE

An image depicting OCO-3’s first preliminary solar-induced fluorescence (SIF) – the glow plants emit from photosynthesis, in which they capture carbon from the atmosphere – measurements over western Asia, taken in July 2019 while instrument calibration was still being completed after the observatory’s launch in May. Areas with lower photosynthesis activity are shown in light green and areas with higher photosynthesis activity are shown in dark green, which correlate with areas of low and high vegetation, respectively. OCO-3 measurements help quantify carbon dioxide levels on Earth, and, in conjunction with observations from other space station instruments, will provide the fullest picture yet of the interaction between humans and terrestrial ecosystems.

Two hundred and fifty miles above the planet, the space station offers a unique vantage point for collecting space and Earth science data. Its high-resolution imagery and remote-sensing equipment capture details – of agricultural land, glaciers, forests, cities, oceans, and coral reefs – that can be layered with other data sources, on station or gathered by other satellites, to assemble a comprehensive view of Earth systems. For example, measurements from the Orbiting Carbon Observatory (OCO-3), a NASA instrument mounted on the Japanese Experiment Module (JEM) Exposed Facility, help to quantify carbon dioxide levels in terrestrial and ocean ecosystems, as well as from human industrial sources. Combined with near-simultaneous observations from other space station instruments, such as the ECOsystem Spaceborne Thermal Radiometer Experiment (ECOSTRESS), a radiometer that measures plant temperatures in specific locations, and the Global Ecosystem Dynamics Investigation (GEDI), a full-waveform LIDAR (laser scanner) that provides high-resolution observations of the vertical structure of forests, OCO-3 will offer the fullest picture yet of the interaction between humans and their terrestrial ecosystems. Other radiometric sensor data enables scientists to determine changes in soil moisture, vegetation cover, and surface salinity of oceans.

The space station also houses several powerful instruments for studying the universe. X-ray imaging has revealed several new black hole candidates and transient events such as pulsars, stellar flares, and hypernovas. One of the most significant space observation instruments aboard the station, the Alpha Magnetic Spectrometer (AMS), was mounted on the space station in 2011. The AMS, developed by the European Organization for Nuclear Research (CERN), is a powerful magnet that has detected billions of cosmic ray particles, including particles that support the existence of dark matter.

Dark matter is a difficult concept to explain, because even though astrophysicists believe it makes up 85 percent of the matter in the universe, they don’t know what it is, or whether it really exists. It’s been hypothesized since the 1930s, but has never been directly observed because it doesn’t emit heat or reflect light, and it’s not composed of protons and neutrons, like other matter. The AMS has detected many electrons, and their antimatter counterparts, positrons – and it’s detected more positrons than electrons, which confirms the existence of antimatter and supports the idea that positrons are formed by collisions of particles we can’t see: dark matter.

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Many astrophysicists believe this to be the most important physics discovery made aboard the orbiting laboratory – though it’s arguably more of an anti-discovery. “The way theoretical astrophysics works,” said Costello, “is people put out theories, and the bad ones are thrown out until only a few remain.” The AMS is an instrument designed to challenge theories – including the Big Bang Theory, which holds that matter and antimatter exist in equal amounts in the universe. “We don’t see that. We see only a tiny presence of antimatter,” said Costello. “The AMS is really trying to answer some questions about fundamental cosmology and the formation of the universe.”

COMMERCIALIZING SPACE STATION RESEARCH

When the USOS was made a U.S. National Laboratory in 2005, it was with the intent to maximize the use of its research capabilities by other federal agencies and the private sector. Over the past decade or so, space station research has evolved – sometimes slowly – from studies funded almost solely by government into investigations by private-sector partners in a growing number of fields.

Marybeth Edeen manages the ISS Research Integration Office, which oversees the integration of experimental payloads to be delivered to the space station. Much of her recent focus, she said, has been on validating the use of space research for commerce. “As we move more and more toward a commercialized low-Earth orbit ... we want to facilitate relationships with businesses and commercial organizations, and help them take advantage of the station not just to perform research, but to make money.”

There’s a difference in these types of research, Edeen said: “Government research tends to be more fundamental, first principles: How do flames burn in space? How do solids, liquids, and gases behave? If we look at mixtures of liquids and particles, colloids, how do they separate? The research done by commercial companies is what I’ll call ‘applied.’ It’s more focused on improving a product or a process.” One of the station’s oldest private-sector research partners, Procter & Gamble, has spent the last 15 years improving its soft-matter products, such as detergents, fabric softeners, and deodorants, by studying fluid separation in microgravity and formulating better stabilizers.

A growing number of companies are exploring the space station’s potential as a platform for developing or improving products, such as high-quality optical fibers and high-speed turbine blades made of strong metal alloys. Several pharmaceutical companies are paying the Japan Aerospace Exploration Agency (JAXA) to conduct protein crystal research. Through a CASIS-organized initiative, the Cotton Sustainability Challenge, Target Corporation is funding a study known as TIC-TOC (Targeting Improved Cotton Through Orbital Cultivation). TIC-TOC’s orbital studies of cotton growth will be aimed at developing more stress resistant, water efficient, and sustainable cotton.

A new field of materials research – three-dimensional bioprinting of human tissues or organs – is opening up on the space station as the technology matures. It’s harder to print these materials on Earth, Edeen said, because gravity tends to put strain on their structures as they’re being made. In March 2020, the commercial space company Techshot, Inc., manufactured test prints of a partial human meniscus – knee cartilage – for evaluation by their customer, the Uniformed Services University of the Health Sciences. The company’s bioprinter, the Bio-Fabrication Facility, was the first of its kind aboard the orbiting laboratory, launched to the station in July 2019.

NASA astronaut Nick Hague with Techshot, Inc.'s Bio-Fabrication Facility (BFF) aboard the International Space Station. In March 2020, the bioprinter was used to create test prints of human tissue - knee cartilage - on the orbiting laboratory. Research projects in the microgravity of the space station funded by private-sector partners harness the facility's potential as a platform for developing or improving products or processes.

The focus of the Research Integration Office, Edeen said, is on these kinds of applications – things that can’t be made anywhere else. “It’s never going to be cheaper to make products in space that you can make on the ground,” she said. “We’re trying to develop what we call sustainable, scalable demand for microgravity.”

“A LOT OF DISCOVERIES LEFT”

Meanwhile, there are still plenty of questions remaining to be answered for NASA and its space station partners. Last fall, NASA’s inspector general released a report identifying technology gaps and human health risks that need to be more fully researched – and that will take years to complete, meaning that even minor scheduling setbacks could push their completion beyond the station’s retirement date. Fortunately, the agency’s Commercial Crew Program is on the brink of greatly expanding the ability to conduct research aboard the USOS: The SpaceX capsule that launched to the station on May 30, 2020, delivering astronauts to the orbital outpost from U.S. soil for the first time since 2011, will carry four passengers on NASA-contracted missions.

Increasing the available lab technicians from three to four, Edeen said, will have an outsized effect on the amount of research time available, increasing from about 40 hours of total crew time a week to at least 68. The prospect of sending private astronauts to the station, also, will continue a trend toward using crewmembers less as lab technicians and more as research partners. “If a company has very specific objectives, and they want to put their expert on board to run some sort of experiment, they could do that,” she said. “We do foresee that, more and more, we’ll see commercial activity – maybe several companies will get together and fly one super researcher aboard, and he’ll perform a bunch of different investigations.”

It’s likely that decades will pass, long after it has been de-orbited, before we’re able to fully comprehend the impact of the orbiting laboratory’s thousands of scientific studies. Costello thinks we’re not even close to a glimmer of that realization. “We may have finished 20 years of performing investigations on ISS, but we’re really just getting started,” he said. “We’re eagerly awaiting the Commercial Crew Program to get us up to four-crew status, and to be able to do all of the research that we have built up and cued up and ready to go. We’ve got a lot of discoveries left in this program.”

To learn more, visit: www.nasa.gov/iss-science go.nasa.gov/researchexplorer www.nasa.gov/stationresultsresourcelibrary www.nasa.gov/stationnationallab