Microbes may have survived for millions of years beneath the surface of Mars | CNN

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A new study shows that ancient bacteria may have been dormant beneath the surface of Mars, where they have been shielded from the harsh radiation of space for millions of years.

While no evidence of life has been found on the Red Planet, the researchers simulated conditions on Mars in the lab to see how bacteria and fungi might survive. Scientists were surprised to discover that bacteria could likely live for 280 million years if they were buried and protected from ionizing radiation and sun particles that bombard the surface of Mars.

The results indicated that if life has ever existed on Mars, lurking evidence of its existence likely lies deep within the planet’s surface – a place that future missions could explore while drilling into Martian soil.

While Mars was probably a hospitable environment for life billions of years ago, including the atmosphere and water on its surface, today the Red Planet is like a frozen desert. The average temperature of the planet’s arid mid-latitudes is minus 80 degrees Fahrenheit (minus 62 degrees Celsius). Then there is the constant radiation hazard because Mars has a thin atmosphere.

Study co-author Brian Hoffman, Charles E. Arts and Sciences, in a statement. “It is also known that the surface temperature of Mars is almost similar to dry ice, so it is already very frozen.”

A research team has identified the limits to surviving microbial life when exposed to ionizing radiation as it might on Mars. Next, the team introduced six species of bacteria and fungi found on Earth to simulate the Martian surface environment — all while using protons or gamma rays to mimic space radiation.

A clear winner has emerged called Deinococcus radiodurans. The microbe, nicknamed “Conan the Bacterium” due to its ruthless nature, seemed perfectly suited to life on Mars.

Bacteria are polystreptomycetes, which means they can withstand extreme conditions such as drought, acidic temperatures, and cold. The powerful microbe is one of the most radio-resistant organisms known to science.

Previous research has found that bacteria can live 1.2 million years below the surface of Mars amidst harsh radiation and a dry, frozen environment – and some microorganisms known to live on Earth for millions of years.

The new study finds that when Konan’s bacteria are dried, frozen and buried deep in the surface of Mars, they can survive 140,000 units of radiation – 28,000 times greater than the level of radiation exposure that could kill a human.

The bacteria, which looks like a pumpkin when viewed under a microscope, likely only lived for a few hours on Mars after constant exposure to ultraviolet light. The expected survival rate of Conan the Bacterium has increased to 1.5 million years just 4 inches (10 cm) below the surface, and about 280 million years if the bacteria were 33 feet (10 meters) deep.

Astrobiology published a study detailing the findings on Tuesday.

The researchers were able to measure the number of manganese antioxidants that accumulated in the cells of microorganisms while exposed to radiation. The more manganese antioxidants the team found, the more likely the microbe could resist radiation and survive.

The genetic makeup of Conan the Bacterium binds chromosomes and plasmids together, which means that cells remain balanced and can repair themselves after exposure to radiation. And if a microbe similar to Conan evolved on Mars billions of years ago, when water was still present on Mars, the remnants of dormant bacteria may have lain dormant deep in the Earth’s interior.

Study author Michael Daley, associate professor of pathology at the Uniformed Services University of the Health Sciences and a member of the National Academies Committee for Planetary Protection, said in a statement.

We suggest that periodic dissolution can allow for intermittent re-relocation and dispersal. Also, if life on Mars existed at all, even if no viable life forms now exist on Mars, their large particles and viruses would survive much longer. This raises the possibility that if life evolved on Mars, it would be revealed on future missions.”

The findings have implications for returning Mars samples to Earth as well as landing missions on Mars.

The Mars Sample Return Program, an ambitious program run by NASA and the European Space Agency, will launch multiple missions to Mars to collect and return samples collected by the probe.

The rover team hopes that rock and soil samples taken from the site of an ancient lake and river delta in Mars’ Jezero Crater will be able to determine if life exists on the Red Planet. Specimens may even contain microfossils of ancient microbial life.

In addition, astronauts have the ability to deliver bacteria that are accidentally transmitted from Earth when they land on Mars.

“We figured that terrestrial pollution on Mars would be permanent — over thousands of years,” Hoffman said. This could complicate scientific efforts to search for Martian life. Likewise, if microbes evolved on Mars, they could survive to this day. This means that returning Martian samples could contaminate Earth.”

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