Can Bacteria Survive In Space

Can Bacteria Survive In Space

For years, the scientific community has held the belief that investigating whether bacteria can survive in open space could provide crucial insights into various significant issues. This inquiry has practical implications, potentially influencing the approaches of space agencies worldwide in future Mars missions.

On a more theoretical and philosophical level, such research could offer valuable perspectives on the origin of life on Earth. In 2018, a clever experiment involving resilient bacteria, astronauts on the International Space Station (ISS), and microbiologists on Earth validated this notion.


Exploring Bacterial Existence in Space

The experiment was prompted by a theory suggesting that life on Earth might have originated through the transport of microscopic organisms from other regions of space—a concept known as “panspermia,” derived from the Ancient Greek words “pan” (meaning all) and “sperma” (meaning seed).

This theory has ancient roots, first mentioned in the writings of Anaxagoras, a pre-Socratic Greek philosopher from the 5th century BCE. However, panspermia gained scientific credibility much later, aligning with advancements in astrophysics and biology in the 19th, 20th, and 21st centuries.

Scientists have hypothesized that bacteria could have served as the primal seed around which this theory revolves, initiating the infusion of DNA into our planet billions of years ago. Until recently, validating this idea was challenging. Testing it required the development of space flight for accessing the necessary lab conditions. Additionally, because panspermia suggests that extraterrestrial microbes may have traversed great distances over extended periods before reaching Earth, a meaningful experiment needed the capability to observe microbial specimens for an extended timeframe. The establishment of the International Space Station in 1998 and the placement of its first long-term residents in 2000 finally created the conditions essential for a substantial experiment.


The Tanpopo Mission Proposal Equipment for the JAXA Tanpopo-4 investigation aboard the International Space Station


In the mid-2010s, a team of Japanese scientists presented an approach to investigate a key aspect of the panspermia theory: the viability of microbial life surviving in open space without protection. The proposed research suggested collecting resilient bacterial strains and transporting them to the International Space Station (ISS). Once there, astronauts would affix the specimens to the exterior of the station and observe their development over a three-year period.

Upon acceptance of the proposal by JAXA (Japan Aerospace Exploration Agency) and the 26 other participating universities and institutions, the mission was officially named Tanpopo. This designation, meaning dandelion in Japanese, paid homage to the idea of seed dispersal central to the panspermia hypothesis. The Tanpopo mission held the distinction of being the inaugural Japanese-led astrobiology initiative conducted aboard the International Space Station.

The chosen bacteria for the experiment was Deinococcus Radiodurans.

Endowed with the unanimous approval of the nations overseeing the International Space Station (ISS), a dedicated team of scientists, led by Akihiko Yamagishi, a microbiologist from the Tokyo University of Pharmacy and Life Sciences, embarked on their mission with determination. They swiftly pinpointed Deinococcus radiodurans, a resilient bacterium renowned for its radioresistance, as the ideal candidate for their experiment. This bacterium possessed remarkable physical attributes, including a distinctive capability to internally fuse and repair both single- and double-strand DNA.

Deinococcus radiodurans, existing solely in Earth’s atmosphere, prompted Yamagishi and his team to orchestrate a specimen collection endeavor using high-altitude aircraft and scientific balloons situated approximately 7.5 miles above the planet’s surface.

Known as the “strange berry that withstands radiation,” Deinococcus radiodurans can endure radiation levels 3,000 times higher than those fatal to adult humans. As an extremophile, it thrives in conditions that would prove inhospitable for other life forms, including various bacteria. Its resilience extends beyond radiation, demonstrating the ability to endure severe dehydration, vacuum exposure, extreme cold, and even immersion in acid. Aptly nicknamed “Conan the Bacterium” in a playful nod to its formidable nature, this strain became the focus of the experiment: Bacteria In Space.


On April 14, 2015, the collected Deinococcus radiodurans samples underwent division onto three aluminum panels, which were then loaded onto the Space-X rocket CRS-6 and launched into an orbit approximately 250 miles above Earth. Upon safely reaching the International Space Station (ISS), a robotic arm carefully positioned the panels onto a secure handrail outside the Kibo laboratory—a cutting-edge experimental research module generously provided to the ISS by the Japanese government. In this exposed location, the bacteria samples occupied a small groove on the panels, vulnerable to the unfiltered barrage of ultraviolet rays, gamma rays, x-rays, as well as the extreme conditions of open space, including a temperature plummet to minus 484.81 degrees Fahrenheit and exposure to the natural vacuum.

The initial panel underwent retrieval after one year of orbital exposure, subsequently returning to Earth for comprehensive analysis. The second panel was removed after two years, while the last panel, housing Deinococcus radiodurans samples, concluded its three-year residence on the exterior of the ISS in February 2018.

To adhere to rigorous scientific standards, two additional control groups of the bacteria were established—one left on Earth and another placed inside the International Space Station. These control groups underwent parallel monitoring for the same duration as the panels containing bacteria on the outer surface of the ISS.

Upon examination, segments of each Deinococcus radiodurans sample exposed to open space demonstrated resilience, remaining viable even after one, two, and three years of exposure. Despite the outer layer of each colony containing a mass of deceased cells, these dead cells served as a protective shield for the inner layers of bacteria, enhancing their ability to withstand the extreme conditions. The thickness of the colony proved to be a determining factor, with thicker colonies exhibiting greater resistance.

Contrastingly, the bacteria in the two control groups exhibited poorer survival rates than their open-space-exposed counterparts. Factors such as the presence of oxygen and moisture are presumed to have weakened these samples, or some other unidentified factor may have negatively influenced them.

As a result of the Tanpopo mission data, scientists now estimate that Deinococcus radiodurans colonies with a diameter thickness of 0.5 millimeters can endure between 15 and 45 years of exposure to space at low Earth orbit. Moreover, colonies with a thickness exceeding 1 millimeter may survive for up to eight years in outer space—a duration sufficient for a journey between Earth and Mars.

The implications of these findings are profound. The robust survivability of Deinococcus radiodurans under harsh space conditions highlights the need for meticulous precautions in Martian exploration. This extends to thorough cleaning and sterilization of unmanned surveillance equipment sent from Earth to Mars, as well as considerations for potential contamination and false positives in the search for native Martian microbial life during future manned missions.

More significantly, the Tanpopo mission findings advance the panspermia hypothesis. The concept that free-floating bacteria can endure space travel for up to eight years, potentially seeding life on a receptive but previously lifeless planet (known as “Massapanspermia”), inches closer to scientific validation. This raises the possibility that life on Earth originated from a spacefaring microbial infusion from Mars—an idea supported by evidence suggesting Mars had conditions conducive to life between 4.1 billion and 3.5 billion years ago.

Furthermore, the Tanpopo mission findings open up the prospect of “Lithopanspermia,” where a bacterium with properties similar to Deinococcus radiodurans from a distant part of the galaxy could endure much longer when encased in the rocks and minerals of an interstellar comet or asteroid. This implies that life on Earth might have been seeded by microbes evolving beyond our solar system, possibly in a more remote cosmic region.

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