All things must come to an end - except microbes. These microscopic organisms are set to inherit the Earth after everything, humans most especially included, perishes in a billion years. They won't last long, though, because they are predicted to become extinct as well in another billion years.

A new study has set the lifespan of our home planet to two billion years. According to Jack O'Malley-James, an astrobiologist at the University of St. Andrews in Edinburgh, in less than a billion years from now the Earth will become too hot for living things to endure, thanks to the overzealous Sun.

Using a computer model presentation at the Royal Astronomical Society (RAS) in Britain, Mr O'Malley-James explained on Monday that as our Sun ages, it will become hotter and more luminous, which will raise the heat level on Earth by more than 220 degrees.

This will cause increased evaporation rates and chemical reactions with rainwater, which will therefore cause a dramatic level decrease in atmospheric carbon dioxide (CO2). And when that happens, the plants (which depend on CO2 for photosynthesis) and the herbivorous animals (which depend on plants for food), as well as carnivorous animals (which, in turn, depend on herbivores), will all die out.

A group of microbes called extremophiles will still be around at that time, though.

"There won't be very much oxygen present, so they need to be able to survive in low or zero oxygen environments, high pressures, and high salinities because of evaporating oceans," Mr O'Malley-James said, adding that he believes that microbial life will be clustered around the last drops of water deep underground or at cooler, higher altitudes.

In another billion plus years (about 2.8 billion years from now), even extremophiles won't be able to withstand Earth anymore. The conditions will continue to worsen that they will eventually vanish as well.

In studying how our planet will expire, the researcher and his team said that it can give us insight on how life might survive elsewhere in the universe.

"If you were to find an Earth-like planet and to take a snapshot in time of the life living on the surface, it's more likely that you would find microbial life than you would the more complex life like we see on Earth today," Mr O'Malley-James told BBC.

Microbes cause subtle changes to the ratios of gases in the atmosphere, which could enable astronomers to detect their presence on other planets similar to Earth some day.

"One of the best candidates is methane. This could be used to indicate the presence of life, although it depends on how much is produced and whether it builds up to a detectable level in the atmosphere," he continued.

"If we can pick up all these subtle levels of gasses on remote planets, maybe we could detect it."

The RAS annual meeting, which is attended by more than 600 astronomers, is scheduled for five days, and will end on Friday.