In a billion years from now, the Earth will be inhabited just by microbes. Not animals, not cockroaches but microbes. This conclusion is a result of a computer model used by researchers to predict the status of life on Earth after a few billion years.
As years pass by, the augmenting luminosity of the Sun will create an unfavourable rather intolerable environment for humans, plants and animals alike on our planet. The increased temperatures of up to 100 degrees Celsius will lead to the evaporation of oceans which in turn will lead to increased salinity of large water bodies, high atmospheric pressure and a drastic reduction in oxygen and carbon dioxide content. The poisonous, high pressure, high salinity and zero-oxygen condition will only be withstood by organisms that already survive under such extreme conditions and are called “extremophiles”.
Desert ants sprinting on scorching sand, spiders in snowy areas and beetles with antifreeze blood are some of the creatures identified as extremophiles. The microbial extremophiles either eukaryotic or prokaryotic like bacteria and archaea. These are further classified based on the harsh conditions they can withstand, for example thermophiles withstand extreme temperatures, piezophiles withstand unfavourable pressure conditions and halophiles withstand high salinity. These microbes possess such distinct capacities since they produce enzymes called 'extremozymes' which are capable of functioning at extreme conditions. After a few billion years these microbes will be found in small pockets of water deep down the surface or in caves. But even these special microbes will perish in about 2.8 million years leaving Mother Earth void of any life form and probably making room for new life to emerge again. Why are we telling you such depressing news?
Well, such studies are not conducted just to prove that life on Earth is finite but instead help in determining signatures of Earth-like planets and exploring possibilities of surviving on them in the future. Simple snapshots of planets taken by probing spacecrafts like the Voyager can be used by scientists to predict presence of life forms, mostly microbial life, on Earth-like planets. Another indicator of presence of microbial life is the methane content in the atmosphere. Microbes have a tendency to slightly alter the surroundings hence if these subtle changes are detected, then Earth-like planets can be found.
Microbes will not only be the final survivors on Earth but will be the beacon for finding a new home for life forms on Earth! Whether we will actually reach there, is a different matter altogether.
Contributed by: Sneha Shenoy