The following questions were answered by astronomer Dr. Cathy Imhoff of the Space Telescope Science Institute.

Is there really extraterrestrial life?
It is very hard to answer your questions because the only life we know of for sure is on Earth! Almost 20 years ago, we landed the Viking spacecraft on Mars. One of its tasks was to search for life. It tested for bacteria or microbes, but it didn't find any. There is a big debate about what life on another planet would be like. Life on Earth is very complicated, so some people argue that it would be very unlikely for life to arise somewhere else that would be like us. But others point out that the chemicals and processes involved in life on Earth are very common in the universe and would be expected to occur anywhere under the right conditions, so life elsewhere might be similar to that on Earth.

Do you believe in UFOs? Do you think there is life on other planets?
UFO means "unidentified flying object," so yes, I believe that there are unidentified flying objects because many people have seen them. But are they spaceships from another planet? I am doubtful. We have been seeing UFOs for the last several decades, yet no one has come forth with any hard evidence, like a piece of a spacecraft or an alien walking up and introducing himself at the White House. As a scientist, I must ask for proof and there doesn't seem to be any.

But I think that there must be life on other planets. So far there doesn't seem to be any on the other planets in our solar system. But it is hard to believe that Earth is the only place in the whole galaxy (which includes BILLIONS of stars) where life has arisen. The organisms on Earth are made up of substances that are pretty common in the universe — hydrogen, oxygen, carbon, nitrogen. We see complex organic molecules like formaldehyde and alcohol in cold, dark clouds in space. Amino acids have been found in meteorites. So I think that there must be other creatures out there somewhere.

But they will be hard to find. The distances in the universe are incredibly vast. We have a hard time finding planets around other stars (see my earlier posting on this) — how will we find other creatures? Just sending a radio signal takes years to get to another star, and it becomes very, very weak. We are still pretty far from the day when we can zoom around in the universe on the U.S.S. Enterprise. I wish we could!