We tend to think Earth is the gold standard. It is the only planet we know that has life, so naturally we use it as the yardstick when we hunt for life elsewhere. But a growing number of scientists are asking an awkward question: what if Earth is just average?

In a latest study conducted among scientists underlines that many scientists believe there are planets outside our solar system “where life is even more abundant and sustainable.” The full article was not accessible to us, so what follows is the background on the idea, taken from published research and other coverage.

What “superhabitable” means

Astronomers call such a place a “superhabitable” world, meaning a planet or moon that could suit life better than Earth does. The term goes back to a 2014 paper by astronomers René Heller and John Armstrong. Their complaint was that the usual search looks for Earth twins in the “habitable zone”, the band around a star where water can stay liquid, and that this is a narrow, Earth-centred way of looking at things.

What would make a planet better than ours

The researchers’ list, as summarised by Wikipedia and Space.com, goes roughly like this:

• A different star. Orange K-type dwarfs are cooler and dimmer than our Sun. They give off less harmful ultraviolet light and live far longer, 20 to 70 billion years, compared with under 10 billion for the Sun.
• An older planet. Somewhere around 5 to 8 billion years old, against Earth’s 4.5 billion, giving life more time to settle in.
• A bit more size. Perhaps up to about 1.5 to 2 times Earth’s mass, which means more surface area and a core that stays hot and keeps the magnetic field going for longer.
• A warmer, wetter climate. Space.com puts it at around 5 °C warmer than Earth, with shallow oceans and land broken into smaller continents.

Not every scientist is equally convinced by each item. The Wikipedia entry notes the criteria are hypothetical, since nobody knows the best temperature or atmosphere for life.

Do any actual candidates exist?

Some. In 2020, Dirk Schulze-Makuch, Heller and Edward Guinan went through data on about 4,500 planetary systems and picked out 24 possible candidates. According to Space.com’s 2022 report, none ticked every box, and all are more than 100 light-years away. Schulze-Makuch’s favourite, KOI 5554.01, is about 700 light-years away.

He was careful about what that means. “We caution that while we search for superhabitable planets, that doesn’t mean that they necessarily contain life,” he said. He also put it plainly: “We are so over-focused on finding a mirror image of Earth.”

There’s also a lab angle. NewsBytes, in a report dated October 14, says astrobiologist Iva Vilovic found garden cress grew better under light from K-dwarf stars. We could not check that experiment ourselves, so treat it as a single reported result.

Why you shouldn’t pack your bags

“Better for life” is a prediction, not a discovery. These planets are too far and too faint to study in detail with today’s instruments. Telescopes such as the James Webb Space Telescope and ESA’s upcoming PLATO mission are expected to help, but nobody has found a confirmed superhabitable planet, and nobody has found life on one.

Still, the idea changes the question. The search for life may not need a copy of Earth. It may just need a planet that gives life a good enough chance.