Conan The Bacterium

Martian surface may have been home to microbes for millions of years.

Researchers created a Mars simulation in a laboratory to test whether bacteria and fungi can survive on Mars, even though there is no evidence of life. Scientists were shocked to find that bacteria can survive for up to 280 million years if it is buried and protected against the solar radiation and particles that bombard Mars’ surface.

These findings suggest that, if there was ever life on Mars, it could still be found in its subsurface. Future missions could then explore this area as they drill into the Martian soil.

Although Mars may have been a more welcoming environment for life billions of years ago with an atmosphere and water on its surfaces, the red planet today is more like a desert. Mars’s deserted midlatitudes average a temperature of minus 80° Fahrenheit (minus 62% Celsius). The thin atmosphere on Mars means that radiation is a constant threat.

In a statement, Brian Hoffman, Charles E., and Emma H. Morrison Professor of Chemistry and professor of molecular biology at Northwestern University’s Weinberg College of Arts and Sciences said that there is no water or significant water in Mars’ atmosphere. “So cells and spores would die.” It is also known that Mars’ surface temperature is approximately the same as dry ice.

Researchers determined the survival limits for microbial life exposed to ionizing radiation, similar to what it would experience on Mars. Next, six species of bacteria and fungi from Earth were introduced to a Martian environment. The team then zapped them with protons and gamma radiations to simulate space radiation.

Deinococcus radiodurans emerged as the clear winner. Due to its tough nature, the microbe was nicknamed “Conan the Bacterium”. It seemed well suited for life on Mars.

Polyextremophiles are bacteria that can withstand extreme conditions like acidity, dehydration, and cold temperatures. This hardy microbe is among the most resistant to radiation known to science.

Research has shown that bacteria can survive for 1.2 million years below the surface of Mars in harsh radiation and dry environments. This is more than any microorganisms that have survived on Earth for millions.

Conan the Bacterium can survive radiation exposures up to 140,000 units if it is frozen, dried, and buried under the Martian surface. This is 28,000 times more than the radiation that could cause death for a human.

Under a microscope, the bacteria look like a pumpkin. It would survive for only a few hours on Mars’ surface if it was exposed to constant ultraviolet light. Conan the Bacterium’s survival rate increased to 1.5 million years, just four inches (10 cm) below the surface. It would have a life expectancy of about 280,000,000 years if the bacteria were 33 feet (10 m) below the surface.

Astrobiology published Tuesday a study detailing these findings.

Researchers were able to determine how many manganese antioxidants were in the microorganisms’ cells after they had been exposed to radiation. The team discovered that the microbes were more likely to survive radiation than the ones with fewer manganese antioxidants.

The genomic structure of Conan the Bacterium links chromosomes to plasmids, ensuring that cells remain aligned and can heal themselves after radiation exposure. Conan the Bacterium might have evolved on Mars billions of years ago when water was still available on Mars’ surface. The bacteria’s dormant remains could be hiding deep beneath the planet’s surface.

“D. radiodurans, which are buried beneath the Martian surface, could not survive dormant over the 2 to 2.5 billion year period since Mars’ disappearance of water,” stated Michael Daly, a professor at Uniformed Services University of the Health Sciences, and member of the National Academies Committee on Planetary Protection.

“We believe periodic melting could enable intermittent repopulation or dispersal. It is possible that Martian life existed even if they aren’t currently present on Mars. However, their macromolecules would and viruses could survive for much longer. This increases the likelihood that future missions will reveal if there was ever life on Mars.

These findings will have implications both for returning Martian samples to Earth and landing crewed missions on Mars.

NASA and the European Space Agency will jointly steer the Mars Sample Return program. This ambitious program will launch multiple missions on Mars to return the samples collected by the Perseverance Rover.

The Mars Rover Team hopes that rock and soil samples taken from an ancient lake and river delta in Mars’ Jezero Crater could help determine if there was ever life on Mars. These samples could even contain microfossils containing ancient microbial life.

In addition, astronauts could accidentally transmit hitchhiking bacteria to Mars from Earth.

Hoffman stated that “We concluded terrestrial contamination on Mars would be essentially permanent” over some time of thousands of years. This could hinder scientific efforts to find Martian life. If microbes were to have evolved on Mars, they might be capable of living up to the present day. This means that returning Mars samples could potentially contaminate Earth.

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