Ancient bacteria may be sleeping beneath the surface of Mars, where it has been shielded from harsh space radiation for millions of years, new research suggests.
Researchers simulated conditions on Mars in a lab to see how bacteria and fungi could survive even though no evidence of life was found on the red planet.
To their surprise, the scientists discovered that the bacteria could probably survive for 280 million years if they were buried and protected from the ionizing radiation and solar particles that bombard the Martian surface.
The findings suggest that if life ever existed on Mars, its dormant evidence could still be located underground, a place future missions could explore by drilling into Martian soil.
The surface of Mars looks like a frozen desert
Today, the Red Planet looks more like a frozen desert, although Mars was probably a more hospitable environment for life with an atmosphere and water on its surface billions of years ago.
The planet’s arid mid-latitudes have an average temperature of minus eighty degrees Fahrenheit (minus 62 degrees Celsius). There is also the constant threat of radiation because Mars has such a thin atmosphere.
“There is no running water or significant water in the Martian atmosphere, so the cells and spores dry out,” said study co-author Brian Hoffman, professor of chemistry. Charles E. and Emma H. Morrison and Weinberg Professor of Molecular Biosciences at Northwestern University. College of Arts and Sciences, in a statement.
“The surface temperature on Mars is also known to be roughly similar to dry ice, so it is indeed deeply frozen,” he said.
A study has determined the survival limits of ancient bacteria
A research team has determined the survival limits of microbial life when exposed to ionizing radiation as it might be on Mars.
The team then introduced six types of bacteria and fungi found on Earth into a simulated Martian surface environment while zapping them with protons or gamma rays to mimic space radiation.
A microbe called Deinococcus radiodurans and nicknamed “Conan the Bacteria” seemed perfectly suited to life on Mars due to its tough nature.
The hardy microbe is one of the most radiation resistant organisms known to science. This is because it is a polyextremophile, which means it can survive harsh conditions such as dehydration, acid, and cold temperatures.
Previous research found that the bacterium could survive for up to about 1.2 million years just below the surface of Mars amid harsh radiation and the dry, frozen environment. It could therefore survive certain microorganisms on Earth.
Ancient bacteria can survive intense levels of radiation
The new study determined that when Conan the bacterium is dried, frozen and buried deep below the Martian surface, it can survive 140,000 units of radiation, which is 28,000 times more than the level of radiation exposure that could kill a human. .
The bacterium, which looks like a pumpkin seen under a microscope, would likely only survive a few hours on the Martian surface after relentless exposure to ultraviolet light.
The predicted survival of Conan the bacterium has increased to 1.5 million years just four inches (ten centimeters) below the surface and about 280 million years when buried thirty-three feet (ten meters) beneath the surface.
Review study Astrobiology bacteria survival details
The researchers were able to measure the number of manganese antioxidants that accumulated in the cells of microorganisms when exposed to radiation.
The more manganese-based antioxidants the team found, the more likely the microbe was to resist radiation and survive.
The cells of Conan the bacterium remained aligned and were able to repair themselves after exposure to radiation since its genomic structure connects chromosomes and plasmids.
The dormant remnants of the bacterium might just be sleeping deep in the planet’s subsoil if a Conan-like microbe had evolved on Mars billions of years ago when water still existed on Mars’ surface.
Information about ancient bacteria on Mars
Study author Michael Daly, a professor of pathology at the Uniformed Services University of the Health Sciences and a member of the National Academies Committee on Planetary Protection, said in a statement:
Although D. radiodurans buried in the Martian subsoil could not survive dormancy for the estimated 2 to 2.5 billion years since the disappearance of running water on Mars, these Martian environments are regularly altered and melted by meteorite impacts.
We suggest that periodic melting could allow intermittent repopulation and dispersal. Moreover, if Martian life existed, even if viable life forms are not present on Mars, their macromolecules and viruses would survive much, much longer.
This reinforces the likelihood that, if life ever evolved on Mars, it would reveal itself in future missions.
Samples of ancient bacteria taken from Mars
An ambitious program, called The Mars Sample Return Program, piloted jointly by NASA and the European Space Agency will launch several missions to Mars to collect and return samples that have been collected by the Perseverance rover.
The rover team hopes the rock and soil samples can determine if life ever existed on the Red Planet.
The samples, which will be taken from the site of an ancient lake and river delta in Mars’ Jezero Crater, may even contain microfossils of ancient microbial life.
Rovers rather than astronauts to take samples from Mars
Additionally, astronauts have the potential to accidentally deliver bacteria hitchhiking from Earth when they land on Mars.
“We concluded that terrestrial contamination on Mars would be essentially permanent — over periods of thousands of years,” Hoffman said.
“This could complicate scientific efforts to search for Martian life,” he said. “Similarly, if microbes evolved on Mars, they might be able to survive to the present day. This means that returning samples from Mars could contaminate Earth.
#Ancient #bacteria #sleep #surface #Mars