The Planet Detective

For the past 30 years, Bruce Campbell has patiently sought to solve the mysteries of Venus.

Bruce Campbell is a senior scientist at the National Air and Space Museum’s Center for Earth and Planetary Studies, where he has worked since 1992. He holds a B.S. in geophysics from Texas A&M University and a Ph.D. in geology and geophysics from the University of Hawaii. Using radar observations from orbiting space probes and ground-based telescopes, Campbell studies the surface and subsurface geology of the moon, Mars, Venus, and the icy moons of the outer planets. His research has been published in more than 100 scientific publications. Campbell is a science team member for radar sounder instruments on the Mars Reconnaissance Orbiter, the Jupiter Icy Moons Explorer, and the Europa Clipper missions. He recently spoke with Air & Space Quarterly senior editor Diane Tedeschi.

When did you first become interested in space?

Well, when I was a kid, I always liked space exploration stuff. I remember them bringing a TV into the cafeteria at school so we could watch some of the later Apollo moon landings. And I watched the Apollo-Soyuz mission. But when I did my undergraduate work at Texas A&M, my studies were concentrated in a program that was primarily oil exploration. 

How did your career in planetary science begin?

My interest in planetary science emerged after I left Texas A&M. As an undergraduate, I didn’t really understand that you could have a career in planetary science—that you could get a job in it. I was fortunate that right after my senior year of college, I got an internship at the U.S. Geological Survey’s astrogeology branch in Flagstaff, Arizona. At the time, they were working on Soviet radar images of Venus—part of the first batch of images gathered by Venera 15 and 16. And I was just sold. Learning how to analyze those images of Venus was a great intern experience. After that, I moved on to graduate school in planetary science.

Why is radar such an important technology in studying the planets?

A radar signal will travel much farther into the ground than a normal optical image will let you see. If we go to long enough wavelengths, we can see three kilometers down into the polar caps of Mars. For the moon, we can see up to about 30 meters below the surface. But the really neat part for me, and the part that I saw that summer in Flagstaff, was that radar is the only way to make a detailed map of the surface of Venus—because the atmosphere is just solid clouds. So here was a way for a satellite to make an image of the ground that was completely invisible by other means. And there it was on a big black-and-white printout. At the time of my internship with the U.S. Geological Survey, satellite data was mostly displayed on printed photos. And it was just completely amazing to me that you could do that. 

 

What is the most unexpected thing you’ve discovered about Venus?

We are getting more and more evidence from some of my work and from work by a lot of other people pointing toward relatively recent—and maybe even ongoing—volcanic activity at the surface. As each of the new Venus missions comes along, one of their primary goals is to map out what’s going on today at the surface. Where could volcanos be erupting? How recently has it happened?

If you could safely travel to anywhere in the solar system, where would you go?

Oh, no question—it would be Venus. I mean it was the first thing I saw when I discovered planetary science during my internship in Flagstaff. And for Venus, there are only four photographs of the surface. That’s all there is. Four photographs looking out from the side of a lander. And that’s for a planet the size of the Earth. So, yeah, it would be fascinating to actually see what the surface is like. Some of the landforms on Venus are unlike anything we see elsewhere in the solar system. We don’t understand how they formed.

 

What are these exotic landforms?

They’re called “tesserae,” which are upland plateaus that have very dense tectonic folds, ridges, and valleys. The tesserae valleys and ridges trend in multiple directions, and it’s hard to even understand what the surface was like before it was deformed. Tesserae cover only about seven percent of Venus, but they are the places we are most likely to find older rocks that could hold clues to past water.

If funding was not an issue, what would be your dream planetary exploration mission?

Staying with the same theme, it would be a lander or multiple landers that could go into the mountainous areas on Venus. Because those are the places where there might be geologic evidence of a period when there was water at the surface. That’s a huge question these days: Was there ever a period of time when Venus had an ocean? And if it did have an ocean, is there anything left behind? Is there any geologic evidence that we can use to say, yes, an ocean was there at some point?

How have you contributed to the Europa Clipper mission? 

My major role on Europa Clipper is to be part of the team for the radar sounder, which is called REASON [Radar for Europa Assessment and Sounding: Ocean to Near-surface]. Most of the work I’ve done up to this point is trying to understand what REASON will be seeing by looking at the radar sounder data from the Mars Reconnaissance Orbiter, where we can look at the polar caps of Mars. We’ve been doing that for 15 years or so. We’ve got a long-running Mars database to draw from, which will help us understand what REASON might eventually see when it starts to look through the ice of Europa. And of course, the major finding there would be to hopefully see the base of the ice and its interface with Europa’s ocean. Equally important, though, would be to see rising bodies of water coming up through the ice—those would be great places to land.

Which object in our solar system do you think might have some form of life?

It would have to be Europa. That’s the one place where you’ve got that combination of water and minerals and heat. Hopefully down the road, we could have a lander take a look at that material.

 

How do you make peace with the slow pace of planetary research?

With the radar instrument that I worked on for the Mars Reconnaissance Orbiter, for example, it was quite a few years from the time our team was brought onboard to work with the engineering group until the time that the instrument was eventually launched and put into orbit around Mars. Now that same pre-launch teamwork is going on with REASON, and the VERITAS mission to Venus is just in that phase of starting to build the hardware. To me, that’s a satisfying thing to be working on—to simply enjoy the engineering part of it. But, yeah, these planetary exploration projects have very long stretches of waiting—especially missions to Jupiter and Saturn, where you’re looking at five to seven years of travel time after launch. I’ve found the best thing is to have just enough projects so that the missions all mature at different times. Certainly, for Venus, we waited a very long time between Magellan and now. I came into graduate school as Magellan was beginning its Venus mission, and now VERITAS, DAVINCI, and EnVision are all coming along 35 years later.

Have you ever been wrong? Is planetary science sometimes humbling?

A lot of the findings from Mars have surprised us. Using the very-long-wave-length radar to look down below the Martian surface, we expected to find ice early on in specific places—and we didn’t. Conversely, we’re starting to think there are fairly good-size ice deposits in places that were not high on the list.

Are there any up-and-coming technologies that could facilitate exploration of the outer solar system?

I think at this point we’re still very much propulsion limited. And we’re data-rate limited—by the fact that we use the radio downlink. There are demonstrations of technologies like laser communications that might someday increase the amount of data you could get back from the outer solar system. And solar-electric propulsion—at least for getting around in the inner solar system—has a lot of promise.

Does your job require field research?

Over the years, our team at CEPS [Center for Earth and Planetary Studies] has used the radio telescope in Green Bank, West Virginia, and the Arecibo telescope in Puerto Rico. Most of the time, there would be somebody from CEPS at one telescope and somebody from CEPS at the other. Because for radar experiments, it can still be very hands-on. You’re literally plugging in cables to go from one part of the hardware to the other. And you’re following the radio signal until it goes from where it comes in from the antenna to where it goes in to be sampled by the computer. To me, being at the telescopes during an experiment is a thrilling part of the job. You walk outside at three in the morning, and you look up. You see the telescope pointed at the moon or Mars while it’s doing its observations. The radar is running—transmitting and receiving—while you’re standing there looking up at the sky above the telescope. Yeah, that doesn’t get old.