DID YOU KNOW? Recent evidence suggests Earth’s water was delivered by asteroids, rather than comets as was once thought
EXOPLANETS
The worlds beyond our Solar System that may have water
Kepler-62 system Could this far-off celestial body harbour life? The mysterious red dwarf star system known as Kepler-62 is located 1,200 light years from Earth, and two of its orbiting planets show signs of having large amounts of water. The first is Kepler-62e, which orbits its star at the equivalent distance of Mercury from the Sun in our Solar System. Owing to its size and distance, scientists think it may have a cloudy sky
and water on the surface, possibly even encased in a global ocean – a water world. The same may also be true of Kepler-62f, which is also 1.6-times the size of Earth. Both worlds are thought to be in the habitable region (also known as the Goldilocks zone) of their star, where liquid water can exist due to the fact that the temperatures are neither too hot nor too cold.
Cold
The Kepler system
At the outer reaches of a planetary system, temperatures are too low for liquid water to exist.
How these alien worlds may be able to hold water
Star Kepler-62 is about 69 per cent the mass, and 64 per cent the size, of our Sun.
Hot
Gliese 1214b Parent star: Gliese 1214 Ocean world status: Unknown
This world, located 42 light years away from us, is 2.7-times the size of Earth. A huge fraction of its mass is thought to be water, but being so close to its star, where the temperature and pressure are both extremely high, its water may be in an exotic form.
Just right The temperatures in the habitable zone, where Kepler-62e and -62f reside, could support liquid water.
Close to a star, liquid water boils away as temperatures rise.
Goldilocks zone The habitable – or ‘Goldilocks’ – zone of Kepler-62 is closer to the star than that of our Sun’s.
Proxima b Parent star: Proxima Centauri Ocean world status: Unknown
Proxima b is the closest Earth-like planet to us, located just 4.2 light years away around Proxima Centauri. It orbits in the habitable zone, and some models say it has a good chance of having a significant amount of water.
KEPLER-62 SYSTEM
“Proxima b is the closest Earth-like planet to us”
Parent star:
KEPLER-62 Ocean world status:
UNKNOWN
Depending on how salty the ocean on a world is, it could have a major effect on its climate – and therefore its ability to host life. On Earth, the salinity levels cause warm water to move to the poles, where it is cooled. But for a world with a saltier ocean, water from the poles could flow to the equator, creating a circulation pattern that dramatically warms the polar regions, possibly increasing the planet’s habitability. A low salinity – close to that of fresh water – could have the same effect. So salt may be key in the hunt for life outside the Solar System.
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The salinity of an ocean may play a key role in a planet’s habitability
© ASA; ESO
Salty oceans