As long as nuclear holocaust, an errant asteroid or some other disaster does not intervene, the Earth could continue to host life for at least another 1.75bn years, a new study shows.
According to the research, astronomical forces will eventually render the planet uninhabitable. Somewhere between 1.75bn and 3.25bn years from now, Earth will travel out of the solar system's habitable zone and into the "hot zone."
These zones are defined by water. In the habitable zone, a planet (whether in this solar system or an alien one) is just the right distance from its star to have liquid water, Fox News reports. In the "hot zone" closer to the sun, the Earth's oceans would evaporate. Of course conditions for complex life including humans would become untenable before the planet even enters the hot zone.
But the researchers' main concern was the search for life on other planets, not predicting a timeline for the end of life on this one.
The evolution of complex life on Earth suggests the process requires a lot of time.
Simple cells first appeared on Earth nearly 4bn years ago. "We had insects 400m years ago, dinosaurs 300m years ago and flowering plants 130m years ago," lead researcher Andrew Rushby, of the University of East Anglia in the United Kingdom, said in a statement. "Anatomically modern humans have only been around for the last 200,000 years so you can see it takes a really long time for intelligent life to develop."
Rushby and his colleagues developed a new tool to help evaluate the amount of time available for the evolution of life on other planets, a model that predicts the time a planet would spend in its habitable zone. In the research, published on September 18 in the journal Astrobiology, they applied the model to Earth and eight other planets currently in the habitable zone, including Mars.
They calculated that Earth's habitable-zone lifetime is as long as 7.79bn years. (Earth is estimated to be about 4.5bn years old.) Meanwhile, the other planets had habitable-zone lifetimes ranging from 1bn years to 54.72bn years.
"If we ever needed to move to another planet, Mars is probably our best bet," Rushby said in a statement. "It's very close and will remain in the habitable zone until the end of the sun's lifetime 6bn years from now."
While other models have been developed for Earth, they are not suitable for other planets, he added.
