Mark on Mauna Kea with (from left): the Subaru and Keck telescopes, and NASA's Infrared Telescope Facility (IRTF).

Where are you from?

I was born in Montebello, Calif. It's a small town east of Los Angeles, part of the urban sprawl that is the Los Angeles Basin. When I was very young, there were still some large fig groves in the area, but by the late1960s they were all turned into housing developments. Other than one summer in Boston, I've always lived in California, most of it in the Los Angeles area.

Describe the first time you made a personal connection with outer space.

I was born in 1962; the year after the first humans went into space, so I grew up with the space program. I remember my dad and older brother watching the launches of Gemini and Apollo, and everyone being excited by the Apollo 11 moon landing. Since they were excited and interested about it, I paid attention too.

My brother was also always building model airplanes and spacecraft, and I imitated him. So my getting interested in space was a gentle, slow process, based mostly on imitating my brother. There were two or three "Gee Whiz!" moments though, that qualified as times where I stepped back and really became aware of a personal connection. The first was the day of the Apollo 11 landing. During the first moonwalk, I remember going outside and looking up at the moon, and thinking that there were people up there, right then. It was an exciting, but also creepy feeling that stuck with me for some time.

Another memorable moment was the Viking 1 landing on Mars in 1976. I was 13 years old. I don't remember the landing itself, but I do remember seeing the first images of the rock-strewn landscape. It was an amazing combination of the familiar (ground, sky, rocks), and alien (the red colors and the total lack of vegetation... I've seen similar places on Earth since then, but at the time it was totally bizarre to me). I could picture myself walking around on this other planet, and I wanted to try it!

A third connection, and the one that was probably my first entirely self-directed one, happened during the1980 and 1981 flybys of Saturn by the Voyager 1 and Voyager 2 spacecraft. By that time I was old enough to be choosing things on my own, as my brother had gone off to college. I remember discovering that a local PBS TV channel had extensive real-time coverage of the missions during the planetary encounters. I chose to spend a lot of time watching that coverage and learning about the planets. From that point on I was always on the lookout for planetary science-related books, news and events.

To me, being a scientist means seeing something in nature and wanting to figure out how it works or why it is the way it is.
- Mark Hofstadter

How did you end up working in the space program?

I was always interested in space as a hobby: building model rockets, reading about the space program, stuff like that. I didn't really think about it as a career until I was graduating from college with my bachelor's degree in physics and didn't know what to do next. I did not want an advanced degree in physics, so looking for a job seemed like the thing I had to do. That's when I realized that, since I always liked planes and space, I might as well try to work in the aerospace industry. I ended up getting a job at the Jet Propulsion Laboratory (JPL) as a contractor. This job was not very interesting, but I was impressed by what the scientists around me were doing. That made me decide to go to graduate school in astronomy, and I applied to a few astronomy departments. Then I saw that some schools offered a degree in planetary science. I didn't know what the difference between planetary science and astronomy was, so I did a little research. I found that most planetary scientists studied objects to which we could actually fly a spacecraft, or on which a human might someday walk. To me, studying something that I might one day get to touch sounded a lot more exciting than looking at things so far away that I'd never see them clearly, so I switched and ended up going to graduate school for planetary science. From that point on, working in the space program was obviously where I wanted to be. It combined my interest in objects that are out there, but not so far away that I (or my robot) couldn't get there.

Who inspired you?

My older brother was probably my biggest inspiration. I saw that he was interested in space, and he convinced my parents to buy a small telescope. Then he built his own six-inch reflector and hosted star parties. I started out just by tagging along, but soon decided that it was fun!

What is a Planetary Scientist?

Every scientist does things a little differently than his or her peers, but to me, being a scientist means seeing something in nature and wanting to figure out how it works or why it is the way it is. Why is the sky blue? Why does Jupiter have a giant storm on it (bigger than the entire Earth!) that has lasted for more than 400 years? These are the kinds of things I like to think about. One of my colleagues describes it as, "A scientist likes to figure things out."

Some of the day-to-day details of my job are:
1) Planning new observations of planets that will answer interesting questions about them.
2) Looking at measurements I've already made to figure out what they mean.
3) Talking to colleagues for new ideas and help in figuring things out.
4) Writing requests (we call them proposals) to either use a particular telescope, or to get the money needed to build a spacecraft or to conduct research.
5) Writing reports on things I've learned, so that other scientists can build upon what I've done.

Tell us about a favorite moment in your career.

One of my favorite moments is the first observing run I had completely on my own. I had just received my Ph.D., and I requested two days of time on a radio telescope (the Very Large Array (VLA) in New Mexico) to look at Neptune. I chose the project, I was awarded the telescope time, and it was up to me to make it all happen. My observations started in the early morning (something like 4 a.m.), and I remember waking up and walking from the dorm area to the control room. It was a cold, dark, beautiful night, with some patches of snow on the ground. Out by the dorms I stopped, looked out at nature, and took deep breaths of the crisp air. I felt connected to the world around me, like what often happens on a camping trip when you get far away from everything man-made. Then, as I walked to the control room, I began seeing all the big radio dishes (there are 27 of them at the VLA), and heard the hum of equipment and the whir of motors. I was struck by the contrast between a nature-filled winter's night far from any city, and the high-tech equipment all around me. And I began thinking about how all 27 of those antennas were about to swing around and stare at a little patch of the sky that I selected, and I was going to see things on a planet that nobody else had ever seen. It was a fabulous feeling of being excited about what I was doing, and being a little scared that I might mess something up. And the best thing about that experience is it pretty much feels the same way every time I go observing!

What advice would you give someone who wants to follow the same career path as you?

The first thing I always tell people is that they should do something that interests them and is fun. I also point out that fun does not mean easy. I think facing challenges is part of what makes my job exciting. If you want to work in a scientific or engineering field, you will almost certainly need a bachelor's degree, and probably a Ph.D. if you wish to do research. Taking a lot of math in school is likely to be useful. (For me, math is one of the challenges I deal with... I really don't like it, but it's a powerful tool that lets me do exciting things.) I also think that having a wide breadth of knowledge is important. While scientists tend to focus on a particular topic -- mine is the atmospheres of planets -- it helps to know things about other technical areas, such as geology, oceanography or chemistry.

What do you do for fun?

Beach volleyball. As much of it as possible.