With increased awareness of the future challenges of climate change, some people may wonder - wouldn't it just be easier to start all over again somewhere else?
Setting up a human colony on another planet may sound appealing, but in reality it would prove exceptionally challenging.
In an article published this week in the Nature Astronomy journal, scientists announced the discovery of an exoplanet called K2-18b that contains water vapour in its atmosphere. This is the first time water has been discovered in the atmosphere of an exoplanet with temperatures that could support life as we know it, the scientists said.
All the planets in our solar system orbit the Sun. Those circling other stars are called exoplanets.
Dr Cindy Ng, senior lecturer at the National University of Singapore's Department of Physics, said: "It is never easy to start somewhere else. Humans came from billions of years of biological evolution to adapt ourselves to Earth's conditions."
But she noted that Earth will one day run out of resources. "We do not rule out the possibility that future humans will migrate to another planet in order to survive."
K2-18b sits in the "habitable zone" of its host star. The zone is defined by a planet's ability to sustain liquid water on its surface, given sufficient atmospheric pressure.
Although some exoplanets reside in a habitable zone, it does not mean they have the conditions suitable for human life. Here are some planets that scientists have considered to be in the habitable zone:
Often referred to as Earth's "sister" planet, Mars is touted as a possible second home for humans. But the average temperature there is around minus 63 deg C and can go as low as minus 125 deg C at the poles. Also, the atmosphere is around 95 per cent carbon dioxide and only 0.174 per cent oxygen. The soil has a relatively high concentration of toxic salts, and no liquid bodies of water have been confirmed on the planet.
It means that if humans were to ever try to make Mars home, significant effort would have to be put into terraforming it so that it can sustain human life. Solutions include detonating nuclear weapons to melt ice caps and pumping greenhouse gases into its atmosphere to raise the average temperature.
It was once known as the most habitable exoplanet. Discovered in 2015, it orbits an active red dwarf star. Although Earth is protected from solar flares by its magnetic field, created by a rotating molten iron core, scientists do not know if Kepler 438b has a magnetic field. If it does not, its surface would suffer a heavy dose of radiation every time there is a solar flare, making it a wasteland.
Though scientists have not confirmed this exoplanet's size, it has a mass roughly 4.5 times that of Earth. It is about 22 light years away and has an average surface temperature of 30 deg C. But it is tidally locked - one hemisphere permanently faces the star it orbits, while the other is in perpetual darkness.
Every time scientists uncover a potentially habitable planet, we are reminded of just how perfect our own home is. Small changes would make a planet completely hostile to human existence, and Earth is a lonely ball that straddles this delicate balance to sustain life.
• Source: Nasa, Space.com