Earth 2.0? Not Quite

by Saints and Sceptics

NASA’s discovery of Kepler-452b has caused quite a stir in the media, with numerous columnists referring to it as a “Twin Earth” and Twitter dubbing the planet “Earth 2.0”. When scientists at SETI remark that this is evidence that planets like Earth are common, the general impression is given that we will be making contact with ‘Little Green Men’ any day now. This is rather unfortunate. Scientists have not discovered the slightest evidence of life on Kepler-452b. Indeed, in some ways it is highly misleading to suggest that we have discovered another Earth.

Kepler-452b is 1,400 light-years away in the constellation Cygnus. It is is about 60% larger in diameter than Earth and its surface gravity is roughly twice as strong. Kepler’s mass could be five times that of Earth’s. In some ways, Venus is a closer match to Earth – and Venus is not the most hospitable of worlds. However, while we can only speculate about what the planet’s surface looks like, scientists are excited because we know that Kepler-452b could have water.

Water is essential for life – or at least, for life as we know it on Earth. So naturally, when astronomers are searching for life on other worlds, they search for worlds which are in their solar system’s “Goldilocks zone”; a region which is not too hot, nor too cold, for water. Possibly, as many as 1 in 5 Sun-like stars in our galaxy will turn out to have a ‘Goldilocks’ planet (although Sun like planets are relatively rare in the universe).

Unfortunately, merely being in the Goldilocks zone does not guarantee that a planet will have enough water to sustain life – or any water at all. Examination of the light reflected “hot Jupiter” planets has revealed water in their atmospheres. However, we have not yet isolated the light reflected from Earth-like planets; we simply do not know if they any have water…


Why Earth 2.0 May Not Be Like Earth At All