Undreamed Shores - Ocean Worlds: The Story of Seas on Earth and Other Planets - page 257

through its atmosphere and travelling to Earth has shown the pres-
ence of water, 169 using NASA's infrared Spitzer telescope, and meth-
ane, as detected by the Hubble telescope. 170
The technique is delicate enough not only to detect what kind of
gas is present, but its motion also. Winds have been detected on the
exoplanet HD 189733 b, which is tidally locked so that one side always
faces its sun (rather like the Moon facing the Earth). When it transits,
it therefore always presents its dark side to us on Earth. The tempera-
tures of that dark side atmosphere signal that heat is being transported
from the daytime side to the night side efficiently. This indicates that
there must be atmospheric circulation—and so implies the presence
of winds on that distant world. 171
The Supercritical Oceans of 55 Cancri e
The planet 55 Cancri e is another strange and hot world, orbiting
so close to its sun that a year lasts just 18 hours. First discovered by
the wobble effect in 2004, the infrared light from this super-Earth
exoplanet was detected for the first time in 2012 using the Spitzer
telescope. 172 Lying 40 light years away from Earth in the constella-
tion of Cancer, 55 Cancri e is a little over twice the radius of Earth
and a little under eight times as massive. To us it is a hellish place,
so close to its sun that it is tidally locked with the same side of the
planet always facing its star, like HD 189733 b. The side facing the sun
may reach as high as 2,000 degrees Celsius, suggesting that the planet
does not have a substantial atmosphere with winds that can effi-
ciently distribute the heat around the planet (or, it may be that the
infrared light that has been detected is from an unexpectedly hot
part of the atmosphere).
One might imagine there should be no water at all at such tem-
peratures, on such a planet. But an Earthbound imagination may not
be the best guide. The mass and radius of 55 Cancri e are consistent