BILLERICA -- By day, Billerica resident Mark Petty, 48, is an electronic marketing communications specialist. By night, he searches for answers to the unexplained as assistant state director and a field investigator for the Massachusetts Mutual UFO Network, or MUFON.

He continues to search for leads in a December 2004 Billerica incident in which a man and woman, identified only as Robert and Anne, reported seeing a brilliant white light coming toward their house from the west. Reportedly, the light lifted Anne off of the back deck and left blisters on Robert's hand.

Q: How did you get interested in UFOs and the unexplained?

A: I've always been interested in UFOs, even when I was a young'un, and as I got older, I thought, "Why should I be on the outside reading books or articles in the papers? Why don't I just join the group and be on the inside and get first-hand information on what it is all about?"

Q: Have you ever experienced a sighting?

A: I've had several experiences. When I was a teenager, I was

driving from Lowell back to Billerica, and I saw this light in the sky and it was really all of these different colored lights flashing back and forth, and I said to myself, "That's no airplane. What could it be?" After 20 minutes of driving over hill and dale, I actually tracked it down, and it turned out to be a plane with a message board underneath it. I was looking at the edge, so all I saw were the flashing colors. That was my first case, and I solved it.

Q: What is the most interesting case you've ever investigated?

A: A craft actually landed in the courtyard of a housing-project development in the Boston area. The person was a child at the time, about 4 or 5 years old. She heard her grandmother leave the apartment, she looked out the window, and there she saw this craft out there and people walking to it. When she yelled out to her grandmother, her grandmother slowly looked at her, and that's the last thing she remembers. The next morning, she talked to one of the boys she saw heading out there and asked him what happened. His personality suddenly changed. He said nothing happened and that he had to go inside. This happened in the early 1960s. With a child, you have to wonder how much of this may have been a dream, but supposedly this person had never watched anything about UFOs on TV, and her grandparents and mother didn't talk about them, so where did she get the idea?

Q: Do you believe there are beings from other planets trying to contact or study us?  

A: I haven't made up my mind. There are definitely UFOs, but there are a million different explanations for them. Ninety to 95 percent of the time, we find out what it was. But whether there are any from outer space, I can't say for sure. If there are people from another galaxy, they may be thousands of years ahead of us and to them we are like chimpanzees and they are playing with us.

Q: Have you encountered any resistance from the government in your investigations?

A: No. We do Freedom of Information Act reports. That's our greatest interaction with the government, and they've been very cooperative. I've never had any men in black knocking at my door -- that I can remember.

Q: How do you go about investigating a sighting? Is there an evidence trail to follow?

A: Somebody has to contact us, and that is the hardest part, because of the "giggle factor." Somebody sees something, and they try to tell family, friends, co-workers, and everyone laughs at them. Lots of people keep it inside for 10, 20, 30 years. Lots of our cases are so old, because of that, that there is very little trail to follow. We get as many details as we can, check several databases, do (Freedom of Interaction Act) reports, check newspapers, really do a thorough scientific investigation.

Q: What objects are most often behind UFO sightings?

A: The planet Venus, airplanes, blimps, spotlights in thin clouds. It is seeing something in the sky in an unusual way. A plane may be coming straight at them with the landing lights on, very bright, and then all of a sudden it makes a 90-degree turn into its final approach. We had somebody in Chelmsford report a sighting and plotted out the International Space Station and found out it was right overhead at the time.

Q: Do you believe people have been abducted by aliens?

A: I believe people have experienced things where they feel they've been abducted. Whether they've actually physically been abducted, I'm not sure.

Q: What is your favorite movie or TV show about the unexplained or outer space?

A: Close Encounters of the Third Kind is excellent. I always liked Star Trek when I was younger. It was cowboys in space.

Q: Who would win in a fight, E.T. or ALF?

A: That would be a sissy fight. I'd say Darth Vader would come in and take it all.

For more information about MUFON, visit www.massmufon.com.

Jennifer Amy Myers' e-mail address is jmyers@lowellsun.com.