Space

24 "super-habitable" exoplanets potentially better than Earth identified

24 "super-habitable" exoplanet...
Artist's concept of the first validated Earth-sized exoplanet found by the Kepler Space Telescope
Artist's concept of the first validated Earth-sized exoplanet found by the Kepler Space Telescope
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Artist's concept of the first validated Earth-sized exoplanet found by the Kepler Space Telescope
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Artist's concept of the first validated Earth-sized exoplanet found by the Kepler Space Telescope

A team of scientists led by Washington State University (WSU) geobiologist Dirk Schulze-Makuch has identified two dozen exoplanets that could be more favorable to life than the Earth. Based on data from the Kepler mission, these super-habitable worlds may have conditions more suitable for sustaining life for a longer period of time than our planet.

One of the major questions vexing modern science is whether there is life elsewhere in the universe. While no direct evidence of such life has been discovered, exoplanet-hunting missions like Kepler have changed many of our ideas about how planetary systems are formed and have provided scientists with the means to think about life beyond our solar system without leaning so heavily on conjecture and speculation.

Out of the more than 4,000 exoplanets found so far, a number have been deemed to be habitable, though this is a somewhat misleading term. It doesn't mean a planet where one could land and start homesteading. It means a rocky planet that is in the right orbital region around its star where the temperature is moderate enough for liquid water to exist on its surface without freezing or boiling away. To give an idea of how generous this is, Earth is habitable under these criteria, but so are Venus and Mars, which are scarcely garden spots.

Now, WSU has refined the search a bit and have come up with 24 candidate exoplanets that are not only habitable, but potentially more habitable than the Earth. Situated more than 100 light years from the Sun, these exoplanets culled from the Kepler Object of Interest Exoplanet Archive of transiting exoplanets were selected because they have some properties that might make them better able to sustain life.

One thing that the researchers suggest could make a planet more habitable would be its sun. The usual assumption is that an orbit around a G-type star like the Sun would be the best place to find a habitable planet. However, such stars only have a lifespan of about eight to 10 billion years, and it took four billion for anything other than the simplest of life to evolve on the Earth. A K-type dwarf star, on the other hand, would be cooler and less massive than the Sun, but it would have a lifespan of up to 70 billion years – allowing for a much longer time for life to emerge and develop.

Another pair of factors would be size and mass. Part of the reason the Earth is habitable is because it's large enough to be geologically active, giving it a protective magnetic field, and has enough gravity to retain an atmosphere. According to the team, if a planet was 10 percent larger, it would have more surface area to live on. If it was 1.5 times as massive as the Earth, its interior would retain more heat from radioactive decay, would remain active longer, and hold onto its atmosphere for a longer time.

In addition, if a world was 5° C (8° F) warmer than the Earth and had more water, it would enjoy the biodiversity of a rainforest over much of the planet.

The team says that none of the 24 planets found have all of these characteristics, but one has four of the critical factors. At any rate, all 24 could be the focus for later telescopic studies.

"It’s sometimes difficult to convey this principle of super-habitable planets because we think we have the best planet," says Schulze-Makuch. "We have a great number of complex and diverse lifeforms, and many that can survive in extreme environments. It is good to have adaptable life, but that doesn’t mean that we have the best of everything."

The research was published in Astrobiology.

Source: Washington State University

26 comments
mhenriday
«It [i e, «habitable»] means a rocky planet that is in the right orbital region around its star where the temperature is moderate enough for liquid water to exist on its surface without freezing or boiling away. To give an idea of how generous this is, Earth is habitable under these criteria, but so are Venus and Mars, which are scarcely garden spots.» The average surface temperature on Mars is 227 K, max 268 K, the average surface temperature on Venus 735 K. On neither of these planets is water liquid on the surface....

Henri
sidmehta
"Chart a course, Commander Sulu... warp 5"
Brian M
"if a world was 5° C (8° F) warmer than the Earth and had more water, it would enjoy the biodiversity of a rainforest over much of the planet."

Interesting comment given the worry about the earth's global warming and melting ice caps (read more water)!
Nobody
Whoa. Lots of speculation going on here. There are thousands of reasons the earth is habitable for us not just four. Being closer to a cooler star would lead to more radiation. Being larger would mean greater gravity so space travel would be more difficult. Having different oxygen levels would mean that fire would be impossible or out of control. 20% OXYGEN IS IDEAL with just 5% more or less limiting any industrial processes needed for progress. Not having fossil fuels would make metal refinement unlikely. Not having a moon and tides would mean nutrient transfer would be difficult and limited. Being all rain forest would reduce the abundance of life. Cold oceans and climate lead to greater schools of fish and wildlife. Ocean currents lead to greater regions that are thermally stable. Rotational velocity contributes to prevailing winds and storm intensity along with temperature extremes between night and day. Even mountain ranges add to climate and life diversity. The list goes on and on why we were made for our earth and for us it is the Garden of Eden. This research shows a lack of thought about what is habitable. If we can't thrive there, it is not habitable and sustainable for us.
piperTom
"if a world was 5° C (8° F) warmer than the Earth..." more biodiversity. But, NO, when it got just 2° warmer, its people would panic, try to make a sudden switch in energy use, and go extinct. ... AND, that's how you get biodiversity.
c2cam
@piperTom - LOL, that was a good one.
DavidB
There are planets that are “better than Earth” and “more suitable for sustaining life for a longer period of time than our planet”?

Well, yeah, and it’s because there are no humans on them. How ‘bout we leave these planets—and, more important, any life forms that may have developed there—the heck alone?

It’s our own grimy, greedy, clutching, covetous, self-serving, war-mongering hands that have all but ruined the one we already live on.
fredricwilliams
Your article says: "It means a rocky planet that is in the right orbital region around its star where the temperature is moderate enough for liquid water to exist on its surface without freezing or boiling away. To give an idea of how generous this is, Earth is habitable under these criteria, but so are Venus and Mars, which are scarcely garden spots."

However this is wildly inaccurate. The average temperature on Venus is 864 degrees Fahrenheit (462 degrees Celsius). Water boils at 212 degrees Fahrenheit (100 degrees Celsius). Venus, by the reported definition is not habitable.
RobWoods
Yes, I agree with Brian M and piperTom and have thought about the 5 degree increase in the earth's temperature too. So much for all the hulabaloo about global warming and such, according to this article it can't be a bad situation for earth either than.
michael_dowling
So what if they are suitable for life? Being light years from here,we will never visit them. Best we can hope for is finding they have an advanced civilization we could trade notes with,but that would take 100 years one way.