Super-Earths with shallower bodies of water, rather than a few large oceans, may be even more suitable for life than our planet, a new study suggests.
Scientists have long focused their search for extraterrestrial life on Earth-like planets - but that may be a mistake, said astrophysicist Rene Heller from McMaster University.
Heller said our planet may not be the most ideal place for life and scientists need to consider non-Earth-like, so-called 'superhabitable' planets which have conditions that are more suitable for life to emerge and evolve.
These planets would probably be two or three times more massive and much less mountainous than Earth. They would probably be older, too.
"The Earth just scrapes the inner edge of the solar system's habitable zone - the area in which temperatures allow Earth-like planets to have liquid surface water," said Heller.
"So from this perspective, Earth is only marginally habitable. That led us to ask: could there be more hospitable environments for life on terrestrial planets?" Heller said.
Heller and co-author John Armstrong of Weber State University described superhabitable planets in the journal Astrobiology.
In it, they outline some of the characteristics such planets might have. These include many, shallower bodies of water (rather than a few large oceans), a more reliable global "thermostat" that impedes ice ages, and a magnetic shield, to protect the planet from cosmic radiation.
Heller said the theory means astronomers should be aiming their telescopes at planets that have so far not garnered much attention in the search for extraterrestrial life.
"We propose a shift in focus. We want to prioritise future searches for inhabited planets. We're saying 'Don't just focus on the most Earth-like planets if you really want to find life," Heller said.