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P.S: This post is part of a series that I’m doing on Space microbiology and hence, the condensed introduction to the subject. My future posts will look at various aspects of this field and how it has been developing 🙂
 
At some point in our lives, maybe during our science classes especially we might have come across the various theories as to how life on Earth began. One of the most unique and highly debated theories is that of life coming to Earth from outer space and the theory collectively is known as Panspermia. It seems almost improbable right considering that man can’t survive a second in space without a spacesuit! But microbes are a special breed of their own aren’t they? We have seen it time and again with their unique abilities to adapt to any environment, it shouldn’t be surprising that they could possibly have the ability to survive space. 
 
Why the particular interest in microbes?
Well, we’re all well aware of the fact that humans didn’t just pop onto the planet and began creating civilizations for the heck of it. Life began from the micro-level and there is the evolution of organisms is definite proof of this (Tree of life, anyone?). The first-ever paper to be published in this sector happened in the year 1903 when Svante Arrhenius, a scientist postulated that there is a possibility that microbial spores have the ability to travel in space when they are driven by radiation but the paper was soon DEBUNKED and the entire hypothesis was thrown out because of our inability to test at the time! The hypothesis was known as ‘radiopanspermia’  and the main issue was that he hypothesized that since the particles are so small (in the micrometer range), they would be propagated by the pressure of radiation that the sun emits. Needless to say, this would not necessarily be possible but maybe, just maybe a part of this theory could be true?
 
The revival of the panspermia theory
In today’s day and age, we are more than capable of testing out various hypotheses and from the time mankind has made space travel a reality, this theory has been to test. What is interesting is that scientists had tested Bacillus subtilis (spore-forming bacteria) spores to see whether the theory held some ground. The tests failed and the spores were killed due to the extreme space environment. 
 
There is rock evidence that suggests that at a time period where the Earth and Sun’s velocity were at their minimum, weak interplanetary transfers could have been possible. If life arose on Earth at a period where water was readily available, it can be possible that it traveled to or from outer space due to the high meteorite activity at the time.
Source: Amaya Moro Martin, Princeton University
 
After experimenting over several years, we do know that it is possible that rocks can get ejected from a planet’s surface in the event that it is hit by a high impact asteroid or any other space junk. This is when the ‘Lithopanspermia’ theory had come about where it was hypothesized that it can be possible that microbes travel through space using these rocks as their vehicles!
 
So, do we have proof that microbes can survive in space?
Yes, we certainly do. Many experiments have been carried out in the past where it has been observed that many species of lichens such as Rhizocarpum geographicum, Xanthoria elegans, and Anabaena cylindrica etc. The special mention would be the cyanobacterial species because it is a well-known fact that they are responsible for the purification of the Earth’s atmosphere which led to the ideal conditions (or less than ideal, thanks to mankind for destroying our atmosphere) that have supported life over time. 
 
Robotic arm that is holding the bacteria that was tested in space
Robotic arm that is holding the bacteria that was tested in space
Source: NASA
 
Recent reports from the infamous SpaceX mission in conjunction with the International Space Station have also shown that a bacterial species Deinococcus radiodurans, a species that is known to survive radiation, hence the name has the ability to survive in space for up to three years. This is one of the longest studies done on microbes and scientists from this study have also indicated that maybe microbial life did travel to Earth on its own, unassisted through rocks by forming clumps. The theory is known as ‘massapanspermia‘ is yet to be verified and accepted by the scientific community but instead of answering our previous questions, it seems like, with more experimentation, we have even more questions to answer!
 
 
References
 
Horneck, G., Klaus, D. M., & Mancinelli, R. L. (2010). Space microbiology. Microbiology and molecular biology reviews : MMBR74(1), 121–156. doi: 10.1128/MMBR.00016-09
 
Levy, M. G. (2020, August 26). Scientists discover exposed bacteria can survive in space for years. Retrieved from https://www.smithsonianmag.com/science-nature/scientists-discover-exposed-bacteria-can-survive-space-years-180975660/
 
 
 

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