A home away from home

Saturday. November 28, 2020

I

On February 14, 1990, the Voyager 1 space probe captured a photograph of the Earth from a distance of about 3.7 billion miles away. In his 1994 book 'Pale Blue Dot', Carl Sagan, referring to that photograph, famously wrote

From this distant vantage point, the Earth might not seem of any particular interest. But for us, it's different. Look again at that dot. That's here. That's home. That's us. On it, everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives... The Earth is a very small stage in a vast cosmic arena... In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves. The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

Carl Sagan, Pale Blue Dot

Soon enough the idea of a permanently manned modular space station in low Earth orbit was materialized with the help of five international space agencies in the form of the International Space Station (ISS). Since November 2, 2002, the ISS has seen continuous human habitation. This year marks the 20th anniversary since the first residents arrived at the ISS. During these two decades, it has housed 242 visitors from 19 countries. Over the years, the station has served as a laboratory for scientific research. Scientists have tried to uncover questions pertaining to biology, medicine, earth science, material science, physics and astronomy.

II

Yuri Gagarin's 1961 voyage around the earth proved that humans could survive in space. However, missions to the Moon and Mars for habitation requires a better understanding of the human physiology, and adaptation and survival of living organisms in space. The microgravity laboratory on the ISS has hosted more than 3000 research investigations which enable us to understand the changes in various biological functions in the absence of gravity. Recently, an initiative called SPOCS has been started for citizen science research including studies on bacteria resistance and sustainability. Such studies are helpful in exploiting benefits from microbes in food and nutrient production, which would further assist in long-duration exploration missions like Mars. In addition to conducting research, the crew members of the ISS themselves serve as human subjects, contributing to studies on the effects of microgravity on human health and wellbeing.

In order to study the physiological, molecular and cognitive changes that could take place in a human body from exposure to spaceflight hazards, NASA in 2015 undertook the twin study on astronauts Mark and Scott Kelly. This study was designed to compare physiological, molecular and cognitive profiles of the identical twins. It was found that Scott, who spent a year in the ISS, showed changes in only a few gene expressions compared to Mark, who stayed on Earth. Findings from the Twins Study may be used to develop new treatments and preventative measures for a multitude of health risks. 

Apart from understanding the unfamiliar microbial composition of a spaceship atmosphere, long-duration missions would require food availability for the crew. In 2014, the Vegetable Production System also known as Veggie, was installed as a space garden on the ISS. Veggie’s purpose is to help study plant growth in microgravity while adding fresh food to the astronauts’ diet. BRIC (Biological Research in Canisters) and APH (Advanced Plant Habitat) are additional installations which help in understanding how to keep plants flourishing in space and better enable long-duration missions.

The microgravity conditions at ISS enable researchers to perform experiments for vaccine development. Studies have been done on several infectious disease causing microbial cells including Salmonella bacteria, Streptococcus pneumonia bacteria and Methicillin-resistant Staphylococcus aureus (also known as MRSA) among others. Even a novel cancer therapy that targets both tumor cells and the endothelial cells of tumor blood vessels, has been tested onboard the ISS. Research on diseases like Parkinson’s, Alzheimer's, multiple sclerosis etc. has also been carried out in the station.

III

The ISS houses the Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) instrument, which records the temperature of plants on the Earth’s surface by measuring the heat they give off. This enables ECOSTRESS to address questions regarding the response of the terrestrial biosphere to changes in water availability, impact on the global carbon cycle due to changes in diurnal vegetation water stress and improved drought estimation by advanced monitoring of agricultural water consumption.

High resolution laser ranging observations of the 3D structure of the Earth is made possible through another instrument called the Global Ecosystem Dynamics Investigation (GEDI). Data from the instrument can help determine how much carbon storage is lost from deforestation or gained from growing forests, water resource management, carbon cycle science, and weather prediction. Clear high-definition images taken from the ISS aids in responding to disasters such as storms and fires.

IV

In the field of material research, microgravity is of immense help because it alters processes ranging from crystal growth to fluid mixing, separation between gases and liquids, heat transfer, solidification and combustion. Researchers at ISS were able to grow crystals which are larger and more well-ordered than crystals grown on Earth. This increase in ordering in organic molecules such as proteins can lead to improvements in drug development, formulation, manufacturing, and storage as well as agricultural solutions that better protect crops and enhance plant growth. For inorganic molecules, high-quality crystals can lead to advances in electronics, radiation detection, and metal manufacturing.

More than 30 experiments have been conducted on colloidal dispersions onboard the ISS. Colloids are found almost everywhere - in butter, milk, aerosols and paints. Colloidal particles are typically nanometers in size, which makes them buoyant but hard to image. So, researchers model colloids using systems having larger, micrometre-sized particles. Studying these larger particles require gravity to be taken into account. In the microgravity environment, it becomes easier to study such systems as it takes gravity out of the equation. Studies on fluid flows in microgravity have allowed engineers to design better urine-processing equipment, heat exchangers, and even coffee cups. 

The primary focus of microgravity combustion experiments has been related to either fire safety in space or a better understanding of practical combustion on Earth and in space. In microgravity, flames burn differently, forming little spheres - which turn out to be wonderful mini-labs for combustion research. Researchers on the ISS found, rather accidentally, that droplets of heptane continued burning as cool flames, after flame extinction under certain conditions. These cool flames could potentially be useful in designing less polluting vehicles on Earth.

V

The first physics experiment on the ISS involved a dusty plasma - an ionized gas enriched with dust particles. Of the many physics experiments since then, the cool-est one (pun intended) is probably the production of Bose-Einstein condensate (BEC) from atoms of rubidium-87 using the Cold Atom Lab (CAL). BEC's serve as a valuable tool for quantum physicists. All atoms in a BEC occupy the same quantum state and have the same energy level. Below a critical temperature, the dilute gas of atoms begin to act in unison as a superfluid, thus, magnifying quantum behaviour to macroscopic scales. At the CAL facility, temperatures as low as one picokelvin (one trillionth of one Kelvin) are expected to be achievable. Additionally, microgravity environment results in longer observation time, providing opportunities for deeper insights into the behaviors of atoms and BEC's. The CAL is now equipped with an atom interferometer for subtle measurements of changes in gravity across a planet's surface.

Fundamental physics experiments for detecting dark matter and antimatter, and performing precision measurements on cosmic rays have been carried out with the Alpha Magnetic Spectrometer (AMS). Dedicated to the study of neutron star environments is the Neutron star Interior Composition Explorer (NICER) X-ray telescope. Apart from observing x-ray pulsars, magnetars and x-ray bursts, the telescope is also capable of providing a direct spectral view of the inner accretion disk of Black Hole binaries and black hole-type transients.

VI

These are a few of the many interesting studies taking place at the ISS. All these scientific achievements prove that human curiosity and imagination is bound by none. As we now look forward to send people to Mars, we need to realize that this is not merely a civilization which is venturing out for habitation. We are looking for a deeper understanding of our existence and that of the universe and in doing so, the ISS is the closest home away from home. In the words of Carl Sagan:

Exploration is in our nature. We began as wanderers, and we are wanderers still. We have lingered long enough on the shores of the cosmic ocean. We are ready at last to set sail for the stars.

Carl Sagan, Cosmos

Uddeepta Deka

A wanderer on the landscape of physics problems.

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