Back in February, I wrote how two planets around other stars didn't seem to have any water. Since that time, two other studies, including one announced yesterday in the prestigious journal Nature, have contradicted this claim, saying there are "clear signs of water." Who is right?
I haven't read the papers in detail, though it wouldn't surprise me if there is lots of water in these planets. Water is very common in the Universe, as are its constituent parts -- hydrogen and oxygen. But it is possible to hide the signatures of water. Indeed, the reason water was not seen in the first studies of these planets seems to be that the atmospheres of these planets are very different from atmospheres in our solar system. Unlike on Earth, where the temperature of the atmosphere gets colder as you go higher, in these planets, the temperature seems to be fairly constant.
When astronomers look at the spectrum of light from a star or planet to figure out what it is made of, we rely on physics that requires the lower parts of the atmosphere to be warmer than the upper parts. If the temperature stays the same, then the physics we rely on doesn't hold, and other techniques are needed.
This goes to show that studying planets around other stars is very hard. Many claims are going to be made that end up being wrong. This is how science is done -- observations are made, hypotheses (educated guesses) are created to explain those observations and make predictions, and then the new predictions are tested. It's quite okay for scientists to be wrong at first, because the scientific method allows us to zero in on the truth. And in new fields, like planets around other stars, there is often little evidence to base these hypotheses on. So, we are bound to be wrong, and probably quite spectacularly wrong, and probably quite often wrong.
The only thing that worries me is that a lot of science is announced these days by press releases as well as through traditional journals. Often, press releases are meant to show off flashy research that, if right, is pretty important. Unfortunately, this flashy work is often wrong. Again, this is normal -- it's part of science to be wrong, as long as the right answers are found -- but the corrected analysis rarely turns into a press release. And so the public wonders why, a few years later, what they thought was true about astronomy is completely wrong. Press releases bring prestige to researchers and universities, but although they are also intended to keep you all informed of what we are learning about the Universe, I think it does a disservice when these releases are dramatically wrong.