An upcoming study has revealed that if Mars first samples come back to Earth, scientists should be looking for old sleeping bacteria.
In a groundbreaking study, researchers comprising Northwestern’s Brian Hoffman and Ajay Sharma have discovered that ancient bacteria can live near the surface of Mars longer than believed. In addition, when bacteria are in a deep slumber and therefore protected from cosmic radiation and solar protons, they can live for a longer time.
In addition, since scientists have demonstrated that specific strains of bacteria can survive despite Mars harsh conditions, future astronauts and space tourists may accidentally infect Mars by bringing bacteria.
Simulating Mars
The climate on Mars is brutal and harsh. The harsh and frigid conditions, averaging temperatures of -80°F (-63 degree Celsius) at mid-latitudes, make Mars, Red Planet seem inhospitable to living things. But, more disturbingly, Mars is also continuously bombarded by intense cosmic galactic radiation and solar protons.
To determine if life can survive under these conditions, Daly, Hoffman, and others first decided the limits of ionizing radiation that could sustain the microbial world’s life. They then exposed six species of Earthling bacteria and fungi on the simulation of a Martian surface that is dry and frozen; they then destroyed them using protons or gamma rays (to mimic radiation from space).
In the end, the researchers concluded that certain terrestrial microorganisms might survive on Mars on many millions of years of geologic timescales. Moreover, the researchers discovered that a robust microbe, Deinococcus radiodurans (affectionately called “Conan the Bacterium”), is especially well-suited for being able to withstand Mars in the harsh environment. In the new experiments, Conan the Bacterium survived astronomical amounts of radiation in a cold, dry environment much longer than Bacillus spores which could live on Earth for thousands of years.
Radiation
To determine the effect of radiation, the researchers exposed their samples to massive doses of gamma radiation and protons, typical of the radiation that Mars experiences in the near subsurface. However, they also revealed them to lower doses, possibly if a microorganism is submerged.
Hoffman’s team at Northwestern employed the latest spectroscopy technology to assess the level of manganese antioxidants inside the cells of microorganisms that have been radiated. According to Hoffman, the magnitude of radiation dose the organisms or their spores can endure is related to the number of manganese antioxidants it has. Thus, having more manganese antioxidants will confer more radiation resistance and a greater chance of survival.
In previous studies, researchers discovered that Conan, the Bacterium placed in liquid, could withstand 25,000 units of radiation (or “grays”), which is equivalent to 1.2 million years right below Mars surface. However, the latest study has discovered that when the hearty bacteria is frozen, dried, and deep buried– as is typical of the typical Martian climate — it may endure 140,000 shades of radiation. This is twice what could cause death to humans.
While Conan, the Bacterium, could only endure for a few hours at the surface, surrounded by ultraviolet light, its lifespan is significantly increased when it is shaded or placed just below the surface. For example, if it is buried just 10 centimeters beneath the Martian, the surface of Conan the Bacterium’s lifespan is extended by 1.5 million years. When placed 10 meters below the surface, the Bacterium’s color could last for a staggering 228 million years.
