A week ago, we reported that the European space agency’s Herschel Space Telescope had studied the water signature of a nearby comet and found it to be the same as the water in Earth’s oceans. Then, a few days later, we learned of a discovery by the Spitzer telescope that comets had been found swarming through a distant solar system. And shortly after that, Herschel was back in the news for its discovery of vast reservoirs of water around a young star, still busy forming its planets.
At only ten million years old, TW Hydrae is practically an infant star. It is so young that it is still surrounded by a thick disc of material, the remains of the cocoon which nurtured it before it was born. This disc will eventually coalesce into a sytem of planets, asteroids and comets, but until then we have the opportunity to study it and see what it is made of. And what chemical has shown up in surprising abundance? Vast clouds of water vapour, enough to fill Earth’s oceans a thousand times over. The astronomers who found the signal think that the water is produced by the star’s ultraviolet light striking ice-coated dust particles, knocking off individual water molecules. Some of the steamy haze will eventually condense into icy comets, and these comets could bombard the system’s inner planets. In other words, these three discoveries together give strong evidence that watery worlds like Earth may be quite common throughout the universe. And that in turn makes the odds of finding extra-terrestrial life (or at least, life of a sort that we would recognise) a lot higher!