NASA is preparing a mission that will do one last repair of the Hubble Space Telescope. Afterward, if Hubble malfunctions, it will be allowed to die. Does that trouble you?
I’ve been working with a team planning the next great space observatory, the James Webb Space Telescope, scheduled for launch in 2013. Webb will be able to probe regions of the cosmos that are simply not visible to Hubble. With Webb, we have the potential to answer questions about the origins of just about everything in the universe.

Do you think astronomers are something like detectives—or investigative reporters?
Yes. We are most happy when we find something that doesn’t fit our expectations. In 1989, when Voyager 2 flew by Neptune, we saw, for the first time, a great dark spot in that planet’s southern hemisphere. I went to an Earth-based telescope to look at it in real time and the dark spot wasn’t visible. All I could see were these bright clouds alongside where the dark spot was supposed to be. Then in 1993, all the bright stuff was now in the northern hemisphere. A year later Hubble pictures showed the southern dark spot was gone. So far, it hasn’t come back. We don’t know why. But we did learn something new: that Neptune could change dramatically in just five years.

Neptune and Uranus are thought to be the dullest planets in the solar system. Why did you pick such uncharismatic bodies to study?
They are not dull. They change a lot. But yes, they are the Rodney Dangerfield of the solar system—they don’t get respect. They are called the Icy Giants. They’ve been less studied than nearer planets. So whenever I make an observation, anything I find is brand new. With Uranus, now we’re rewriting the textbooks on it. Uranus’s atmosphere is turning on, bright clouds, great dark spots, all sorts of convective activity, which 20 years ago we didn’t see.

Though it’s not your planet, have you been following the recent news from Mars?
Yes. And it’s very exciting. The soil is good. There’s ice. There may be places where the ice is more accessible. It means that there aren’t physical reasons to stop us from colonising that place, if that’s what the fate of humanity is going to be.

Are we getting any closer to discovering possible life outside the solar system?
That’s become a fun question now that we’re discovering planets around other stars. Over 300 new extra-solar planets have been found. The first step is to locate an Earth-size planet the right distance from its own star for water to have been in liquid form long enough to allow life, as we know it, to develop. Then we will have to look at the chemistry of its atmosphere and look for signs that it has been modified by the presence of life. That will be the clue.
_CLAUDIA DREIFUS, NYT