According to a recent study, researchers should be on the lookout for ancient bacteria on Mars when the first samples from Mars reach Earth.
In a groundbreaking investigation, a research team led by Brian Hoffman and Ajay Sharma of Northwestern University discovered that ancient microorganisms might survive far longer than previously thought near to the surface of Mars. Also, germs may live a lot longer when they are buried because they are protected from radiation from the sun and the galaxy.
These results make it more likely that future missions like ExoMars (the Rosalind Franklin rover) and the Mars Life Explorer, which will have drills to get materials from 2 meters below the surface, will find signs of life on Mars if it ever existed there.
Further concern is that future astronauts and space travelers could unintentionally infect Mars with their own hitchhiking bacteria because researchers have demonstrated that some kinds of bacteria can live despite the hostile environment of Mars.
The article will be released in the journal Astrobiology on Tuesday, October 25.
The study’s principal investigator, Michael Daly, a professor of pathology at Uniformed Services University of the Health Sciences (USU) and a member of the National Academies’ Committee on Planetary Protection, said: “Our model organisms serve as proxies for both forward contamination of Mars and backward contamination of Earth, both of which should be avoided.” Importantly, these findings have ramifications for biodefense as well, because the danger from biological agents like anthrax continues to worry the military and homeland security.
Hoffman, a senior co-author of the study, said, “We found that terrestrial contamination on Mars would essentially be persistent—spanning timescales of thousands of years.” “This might make it more difficult for scientists to search for life on Mars. Similarly, if bacteria developed on Mars, they might have persisted up to the present. Therefore, bringing back Martian material could contaminate the Earth. ”
Hoffman teaches molecular biosciences and is the Charles E. and Emma H. Morrison Professor of Chemistry at Northwestern’s Weinberg College of Arts and Sciences. He belongs to the Chemistry of Life Processes Institute as well.
Simulating Mars
Mars has a harsh and merciless climate. The dry and icy temperatures on Mars appear to be uninhabitable to life, averaging -80 degrees Fahrenheit (-63 degrees Celsius) at mid-latitudes.Even worse, solar protons and powerful galactic cosmic radiation are continuously bombarding Mars.
The ionizing radiation survival limits of microbial life were first established by Daly, Hoffman, and their collaborators in order to investigate if life could endure in these circumstances. Then, they put six different kinds of bacteria and fungi from Earth on a dry, frozen surface that was meant to look like Mars’ surface and hit them with protons or gamma rays to make it look like radiation in space.
Cells and spores would dry out because there is no flowing water or much water in the Martian atmosphere, according to Hoffman. Also, everyone knows that Mars is very cold because the temperature of its surface is almost the same as that of dry ice.
In the end, the scientists came to the conclusion that some terrestrial microorganisms would be able to endure on Mars for geologic epochs of hundreds of millions of years. In fact, the scientists found that one hardy microbe, Deinococcus radiodurans, or “Conan the Bacterium,” is especially well-suited to surviving the severe conditions on Mars. Conan the Bacterium outlasted Bacillus spores, which may have lived on Earth for millions of years, by surviving huge quantities of radiation in the frigid, arid environment.
Radical radiation
The scientists exposed samples to high doses of gamma radiation and protons, which are typical of what Mars experiences in the immediate subsurface, as well as much lower amounts, which would happen if a microbe was deeply underground, in order to assess the impacts of radiation.
The concentration of manganese antioxidants in the cells of the exposed bacteria was then measured by Hoffman’s team at Northwestern using a sophisticated spectroscopic technique. Hoffman discovered a link between the amount of manganese antioxidants a microbe or its spores contain and the amount of radiation dosage it can withstand.Therefore, having more manganese antioxidants increases radiation resistance and improves lifespan.
In prior research, scientists discovered that Conan the Bacterium can withstand 25,000 units of radiation (or “grays”), or around 1.2 million years just below Mars’ surface, while held in liquid. However, the latest study discovered that the resilient bacterium could withstand 140,000 grays of radiation when it was dry, frozen, and deeply buried, which would be characteristic of a Martian environment. The human lethal dose is 28,000 times higher than this one.
The lifespan of Conan the Bacterium increases noticeably whether it is shaded or situated directly beneath Mars’ surface, despite the fact that it could only endure a few hours at the surface while drenched in ultraviolet light. Conan the Bacterium has a 1.5 million year lifespan when buried 10 cm below the Martian surface. Additionally, the orange-colored bacterium might live for 280 million years if buried 10 meters below the surface.
Considering upcoming assignments
The researchers discovered that the bacterium’s genomic structure is partially responsible for this astounding survival achievement. Long thought to be true, the researchers found that Conan the Bacterium’s chromosomes and plasmids are linked together. This keeps them in perfect alignment and gets them ready for repair after strong radiation.
This means that any microorganisms like Conan the Bacterium that lived when water last flowed on Mars could still be sleeping in the deep subsurface.
However, Daly noted that such Martian ecosystems are frequently changed and destroyed by meteorite impacts. Although D. radiodurans buried in the Martian subsurface could not live dormant for the estimated 2 to 2.5 billion years since flowing water left on Mars, “Daly stated. “We propose that intermittent dispersal and repopulation might be possible under periodic melting. Additionally, even though there are no current viable lifeforms on Mars, if Martian life ever arose, its macromolecules and viruses would last for a considerably longer period of time. This increases the likelihood that future missions will find evidence of the existence of life on Mars. “
