Planetary explorations as for today...

     A major programme in planetary exploration involving microorganisms,known as the Microbial Observatory Programme, is conducted by the International Space Station (ISS) which is a modular space station positioned in a low Earth orbit. Multigenerational research on microbial population dynamics is conducted in this facility. Based on the condition of microgravity, the effect of physical force on microbial life is studied at molecular, cellular and evolutionary stages.

     Liquid water is the most important precursor of life. Hence, the astro-microbiological sites; Mars and the moons of Jupiter and Saturn were selected to scout for microbes in outer space because of the presence of water in recent history. Titan, which is a moon of Saturn, is the only planetary object found in the Solar System which contains hydrocarbons in liquid form on its surface. However, the main astro-microbiological site of interest is Mars, due to its favourable environment and accessibility.

     Up until now the search for microbial life in outer space has been unsuccessful. The very first search took place in the 1970s through the Viking program conducted by NASA. During this attempt, two Mars landers collected soil samples and brought them to Earth in sealed containers. The results did not end the doubt about the existence of life beyond Earth. In the year 2008, sea plankton was found outside the ISS windows by Russian astronauts. However, it was believed that this observation was due to human contamination.

     Experiments have been conducted in space using microorganisms, to estimate the upper boundary of the biosphere and it was concluded that amongst the extreme variables that were investigated, UV radiation caused the most harm to the microbes. Out of the microbes used in this experiment, lichens such as Rhizocarpon sp. and Xanthoria sp., were able to survive 2 weeks under the harsh conditions of outer space.

     In 1967, Biosatellite II was launched by NASA, which contained Salmonella typhimurium and Escherichia coli strains. It was observed that the microbes cultured in space had grown more than the ones grown on the ground level. In fact, it was twice as much. On the Soviet Salyut space station, in 1982, Escherichia coli developed higher resistance to the antibiotics; kanamycin and colistin, and Staphylococcus aureus developed higher resistance to chloramphenicol, erythromycin and oxacillin. However, not all microbes developed such characteristics. In 2011, Mark Ott from NASA discovered that the Staphylococcus aureus cultured under zero gravity was less virulent, increasing the size of its biofilm and appearing as clusters. Rather than becoming a pathogen, the bacteria seemed to display a need to colonize.

     Even though microgravity was believed to be a major reason for the contrasting discoveries of the microbes that were exposed to extraterrestrial conditions, microbiologist Cheryl Nickerson from Arizona State University, formed a new theory that involved a force called “fluid shear”. She carried out a project in 2006, infecting mice with Salmonella grown in outer space. Simultaneously, another batch of mice were infected with Salmonella grown on the ground. Mice infected with Salmonella usually takes around 7 days to die. However, the mice infected with the Salmonella grown in outer space, started to die two days before they were supposed to. Nickerson explained this result using fluid shear. Bacteria that interact with body fluids of other animals sense a physical force applied by the fluid, on their outer membrane. Nickerson’s hypothesis was that the bacteria can decide on their behaviour according to the force that is being applied on its membrane. In space, bacteria experience a low-shear surrounding due to microgravity. The common sites of infection in a human body includes the respiratory system, urogenital system and intestinal tract. These body parts have low fluid shear levels as well. Nickerson’s belief was that the bacteria reprogrammes itself to survive, after sensing the fluid shear levels in its surroundings.

Microbes; to Mars and beyond...

     Ever since the first landing on the moon, Mars became the top priority in the line ups of many planetary exploration programs all around the world. However according to NASA and other commercial organizations like SpaceX, the aim set on Mars is different from that was for the moon. Unlike in the Apollo programs, now the goal is not to visit but to stay, to be specific “Colonize”. The permanent settling on Mars by establishing a self-sustaining system is a long journey to go and still there are some issues without proper solutions. Can we create an oxygenated environment on Mars or do the Mars setters have to wear space suits all the time ? How to create a permanent food supply on Mars ? How to find materials for constructions on Mars ? These are just a few of the many issues that are being addressed by many scientists through different scientific disciplines. Astromicrobiology plays a major role in answering these problems because of the above stated successful experiments carried out with microorganisms not only on Earth but also at the ISSand outer space.

     Amidst all the basic needs in an alien planetary home, breathing comes first even before food . The Martian atmosphere has a gaseous makeup of 95.0% Carbon dioxide, 2.7% Nitrogen, 1.6% Argon and less than 1% oxygen. Scientists, particularly astrobiologists, are constantly involved in a hunt for establishing a steady oxygen supply on Mars. The new hope in this regard is a group of microbes called “cyanobacteria”. Cyanobacteria can absorb carbon dioxide and release oxygen as they perform photosynthesis like plants. One major difference from plants is that cyanobacteria can perform photosynthesis under far less lighting conditions. According to recent research it was figured out that some cyanobacteria possess a special chlorophyll called chlorophyll-f that can utilize Infrared and near infrared waves for photosynthesis. This is how they manage to photosynthesize under low-lit environmental conditions. Another special capability possessed by some cyanobacteria is their ability to survive under harsh environmental conditions. Scientists have already found cyanobacteria on harsh deserted areas, Antarctica and even on the exterior of the International space Station. When all the qualities considered, it enables cyanobacteria to be more suitable in these planetary exploration missions. Therefore, theoretically this group of organisms possess the ability to provide clean air for the humans to breathe on Mars. However, we cannot ensure that cyanobacteria on Earth are entirely applicable to this purpose.

     Astromicrobiology can be the ideal solution to find materials suitable for construction and manufacturing purposes. Transporting the suitable materials from Earth to future alien colonies using rockets is almost impossible. Some captivating experiments have shown that a microbial group called bio-miners can be of help in this problem. Bio miners are the microbes that can release metals by feeding on minerals. Logical speculations can therefore be made that finding bio-miners that are capable of surviving outside the Earth will help supply manufacturing materials to the future colonies. Furthermore, it can provide rare elements to Earth from other planets. On Earth, biomining techniques are widely used in copper and gold mining. However, in the path of manufacturing modern technological instruments, we may need materials that are rare on earth.Scientists have already found out biominers that can leach these rare metals. The next step is to test whether these bio-miners would still survive and function effectively on Mars as on earth. There are ongoing experiments even at ISS in relation to this. If these experiments display favourable results, microbes would act as the metal miners for future martian people.

     Another gripping aspect when it comes to Astro-microbiology is experimenting up to how much of an extent we can make use of microbes in food production in outer space. This has been an emerging field of discussion due to quite a few reasons. The idea of colonizing mars has been embedded within humans since a very long time, scientists are working assiduously towards that goal in the present day. So with all these efforts if one day humans make it to the red planet one of the major challenges will be to generate a stable supply of food, and it would be completely impractical to constantly supply and relaunch resources from earth due to heavy cost. That can be addressed as one aspect of the need for food production in space. Each year a huge amount of astronauts go to space, so something fresh taken from the earth can only be kept up to 2 days maximum. Scientists believe that space farming with micro-organisms will give the ideal solution.

     One of the most promising planetary colonizers are cyanobacteria, therefore scientists believe that cyanobacteria can be used in food production as well. Scientists have found that the sugars produced by cyanobacteria via photosynthesis can be converted to other food products using a bacteria called Bacillus subtilis. Also experiments are being conducted in outer space using genetically modified photosynthetic cyanobacteria Synechococcus elongatus and Bacillus subtilis for the production of disease resistant grains. These two species are said to be working together in a so-called co-culture where one depends on the other. Now the problem with this implementation is that even though Mars receives approximately half of the sunlight the earth receives, it consists of much higher amounts of harmful ultraviolet (UV) and cosmic rays, therefore we can’t be 100% satisfied about the final product.

     In space research, while working with the tiny single-celled fungi “Yeast” which are important in microbe fermentation, scientists have found out that in space there is an increased fermentation efficiency. So now scientists are on a journey in finding whether they can modify the fermentation process on earth to take advantage of that, because when it comes to increased efficiency even a small percentage can save millions of dollars. Even though the down idea of all is to colonize space , if we could find a more advantageous and sustainable method of producing food, an ideal implementation would be to improve them with more modifications on earth as a solution to the world food crisis.

     The only home we humans ever have had so far is our blue planet, the Earth. However, will our planet Earth be able to ensure the survival of human beings forever on Earth ? In other words, Can the continuity of a species be ensured when they are confined to just one tiny planet in this huge universe ? In fact history provides insights that it cannot, dinosaurs being the best example. The only remnants of dinosaurs today are their fossilized skeletons. Can we allow humans to face this same fate? This is the whole idea behind the space exploration missions including Mars colonization. The aim of Mars colonization is to make humans a multiplanetary species in order to ensure their presence in the universe for a longer period of time. Astromicrobiology addresses this aim arguing that microorganisms should be made the “ primary colonists” of the red planet before humans. With the unique capabilities possessed by microorganisms, it is argued that they could make Mars more habitable for humans. However all of these schemes and proposals have their own pros and cons. In fact Mars Colonization itself has its pros and cons. There are many economical, ethical and social problems that have arisen in relation to these space missions. Any efforts taken to invade Mars with microorganisms from Earth, would be a violation of NASA’ s policies on interplanetary contamination. The aim of the planetary protection policy is to prevent Earth being infected by extraterrestrial life forms, while at the same time protecting other planets from being infected by life from Earth. This is one ethical problem. The huge cost related to all these space missions is an economic problem. Some argue that the current problems on Earth such as climate change, energy crisis, food crisis etc. are the problems that should be addressed first, allocating more money and resources rather than focusing the space missions. This is a social problem. Amidst all these arguments lies still the problem whether we can afford to ‘risk the continuity of human species’ by choosing planet Earth to be our only home. “Per aspera Ad astra” ; through hardships to the stars ! Will this be the future of humans? It is yet to be decided

Image credits:

• Figure 1 : 2021. [image] Available at: https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-the-iss-58.html
• Figure 2 : 2016. Bacteria get dangerously weird in space. [online] Available at:
  https://www.washingtonpost.com/news/to-your-health/wp/2016/10/25/bacteria-get-dangerously-weird-in-space/ [Accessed 13 July 2021].
• Figure 3 : Verseux, C., Baqué, M., Lehto, K., de Vera, J., Rothschild, L. and Billi, D., 2015. Sustainable life support on Mars – the potential roles of cyanobacteria. International Journal of Astrobiology, 15(1), pp.65-92.

References

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