The International Space Station is the longest-running continuously inhabited human outpost in space, and this year it celebrated its 15th anniversary.
As the ISS orbits the Earth it is essentially in a state of free fall, counteracting the Earth’s gravity and providing an ideal platform for science in space.
Science aboard the ISS is decidedly cross-disciplinary, including fields as diverse as microbiology, space science, fundamental physics, human biology, astronomy, meteorology and Earth observation to name a few.
But let’s take a look at some of the biggest findings:
1. The fragility of the human body
The effects of the space environment on the human body during long duration spaceflight are of significant interest if we want to one day venture far beyond the Earth. A crewed journey to Mars, for example, may take a year, and the same time again for the return leg.
Microgravity research on the ISS has demonstrated that the human body would lose considerable bone and muscle mass on such a mission. Mitigation technology, involving the use of resistive exercise devices, has shown that it is possible to substantially alleviate bone and muscle loss. Coupled with other studies into appropriate nutrition and drug use, these investigations may lead to improvements in the treatment of osteoporosis, a condition affecting millions of people across the globe.
2. Interplanetary contamination
A long-term goal of many space agencies is to fly humans to Mars. The red planet is of particular interest because it is one of the most accessible locations in which past or present extraterrestrial life may exist. It is imperative, therefore, that we do not inadvertently contaminate Mars with terrestrial organisms. Likewise, we must be careful not to back-contaminate Earth with any possible Martian life forms during a sample return mission.
Certain hardy bacterial spores, such as the Bacillus subtilis in the picture were exposed to space aboard the ISS, but shielded from solar UV-radiation, and demonstrated a high survival rate. The space vacuum and temperature extremes alone were not enough to kill them off. These remarkable bugs could be capable of surviving an interplanetary space flight to Mars and live there, under a thin layer of soil, were they to be accidentally deposited by a spacecraft.
This finding has huge implications; if microorganisms, or their DNA, can survive interplanetary spaceflight, albeit by natural means, it leaves open the possibility that life on Earth may originally have arrived from Mars, or elsewhere.
3. Growing crystals for medicine
A key challenge in developing effective medicines is understanding the shape of protein molecules in the human body. Proteins are responsible for a huge range of biological functions, including DNA replication and digestion – and protein crystallography is an essential tool for understanding protein structure. Crystal growth within a fluid on Earth is somewhat inhibited by gravity-driven convection and the settling out of denser particles at the bottom of the fluid vessel.
Crystals in a microgravity environment may be grown to much larger sizes than on Earth, enabling easier analysis of their micro-structure. Protein crystals grown on the ISS are being used in the development of new drugs for diseases such as muscular dystrophy and cancer.
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