Presence of microbial life in our stratosphere teaches us about the possibility of life on other worlds

Wednesday, September 12, 2018 by

Scientists are of the opinion that stratospheric microbes may provide clues on extraterrestrial life. The understanding of how these microbes tolerate such extreme conditions could lead to improved scouting and space exploration missions.

The assumption is that alien planets would have similar environments to those found in the stratosphere. This has always been an area of fascination for biologists: How do high-altitude microorganisms survive in such stressful conditions?

Co-author of the study, Shiladitya DasSarma, a microbiologist at the University of Maryland School of Medicine explains that despite popular opinion, microbes thrive in all sorts of conditions, even those that humans would find inhospitable.

Yet studying these microorganisms would require a lot of time and energy. Remember that the space being considered is vast. The stratosphere is an atmospheric level right above the troposphere. It is around 22 miles (or 35 kilometers) thick and is the layer that protects the planet from ultraviolet radiation. In order for the examination to be thorough, scientists would have to collect data from all parts of the stratosphere. But according to Priya DasSarma, the study’s lead author, such an endeavor would prove to be priceless.

The community exercise would eventually result in what she calls an “Atlas of Stratospheric Microbes.” The compendium would provide useful information on how cells adapt and survive in harsh environments.

“[This] has implications when it comes to planetary protection (not exposing other planets to terrestrial germs), and to astrobiology more generally,” she said.

Studying harsh environments

Conditions in the stratosphere are extreme. The air there is dry, as it contains very little water vapor. This is why there are hardly any clouds found in this layer. It also explains why cold, heavier air “sinks” to the bottom while warm, lighter air remains at the top (almost integrating with the mesosphere, the level above the stratosphere). This is completely the opposite of conditions in the troposphere, the area where humans live.

Imagine yourself climbing a mountain in the stratosphere. The absence of water vapor would mean that as you get closer and closer to the top, you would need to take off your warm clothes rather than putting them on as you normally would.

The air in the stratosphere is also a thousand times thinner than it is at sea level. It is because of this that aircraft and weather balloons reach their maximum altitudes within the stratosphere.

The lack of vertical convection likewise implies that materials can remain in the stratosphere for a very long time. Large volcanic eruptions or meteorite impacts, for example, can fling aerosols into the stratosphere. These particles linger there for months or even years, causing uncertain effects.

Space is a spectacularly hostile place

Experts believe that lifeforms do exist outside the planet — but that they are most likely microorganisms that have adapted to survive in harsh environments. It is necessary, then, to understand how these extremophiles (microbes that are capable of living in hostile places) are able to thrive.

Quite recently, five teams of researchers set out to study the Danakil Depression in Ethiopia. One of the parts of the Depression, the Dallol hydrothermal outcrop, is considered to be one of the hottest places on Earth. It is a uniquely hostile place for life thanks to its extreme salinity and acidity. Dallol is also enveloped in toxic gases including chlorine and sulfur vapors. With their research, the scientists hope to gain a better understanding of conditions that may be found on Mars and Titan.

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