John Spencer got interested in astronomy as a teenager in the north of England. He got his undergraduate degree in Geology at the University of Cambridge, England, in 1978, and came to the USA in 1980 to work on a PhD in Planetary Sciences at the University of Arizona, which he obtained in 1987. He then spent 4 years as a postdoc at the University of Hawaii, where he learned observational astronomy on the telescopes of Mauna Kea Observatory. Since 1991 he has been an astronomer at Lowell Observatory in Flagstaff, Arizona.

He is most interested in the satellites and other small bodies in the outer solar system. The moons of Jupiter have been his prime research focus, especially the volcanos of Io. However, has also worked to understand the seasonal migration of frosts that we expect to occur on Triton and Pluto, and the effect this will have on their atmospheres, which are controlled by the distribution of frost.

On New Horizons, John is working to make sure the mission has the capabilities to understand Pluto's frosts, and thus the history and future of its atmosphere. He's also working on plans to find the one or more Kuiper Belt Objects that New Horizons will fly past after its Pluto encounter.

For a recent profile, see
http://www.earthsky.org/edge/profiles/spencer.html

Dr. Spencer answers some questions for us:

The Pluto Portal: What interests you about the exploration of Pluto?
Dr. Spencer: Pluto is the largest object in the solar system still unexplored by spacecraft. We know enough about it to know that it's complex and dynamic place with much to tell us about the outer solar system, but there's much we'll never know till we go there.

The Pluto Portal: What advice would you give to someone interested in a career in space science?
Dr. Spencer: Get a good grounding in the basic sciences, and in math. Keep abreast of the latest developments in space science via the Web, books, and TV, but strength in the basic sciences
is most important. You don't need to specialize in astronomy or space science till graduate school, but look out for the many summer studentships available for undergraduates- these can give you a taste of what space science is like and whether you really want to pursue it.

The Pluto Portal: What do you think the most interesting discovery in space has been, why?
Dr. Spencer: There have been so many! I think the realization, 400 years ago, that the Earth is a planet- that those moving lights in the sky are our siblings- is one of the most revolutionary. The expansion of the universe is a close second.

The Pluto Portal: Do you think Pluto is a planet, if so why or why not?
Dr. Spencer: Pluto is a remarkably interesting and unique place. Whether you call it a planet or not makes no difference to what it is, so I don't get too excited about this "controversy". We've always called it a planet and I don't think there's any compelling reason to change its status, but it's certainly very different from the other eight planets.

The Pluto Portal: What kind of discoveries do you think are waiting to be made in the Kuiper Belt?
Dr. Spencer: We'd love to know what these objects are made of, and whether they have a surface "crust" created by cosmic rays or evaporation, that's different in composition from the interior. New Horizons may be able to answer that question when it flies by one or more Kuiper Belt objects, by looking for places where the crust may have been broken by impacts or even by geological activity. I also want to know what other objects are out there, if any, that are similar in size to Pluto, and what they are like. We'll need telescopes on Earth to answer that one. Of course the most interesting discoveries
will be the ones we can't predict in advance.

The Pluto Portal: Write your own Pluto or Kuiper Belt Question someone from the General Public may be interested in, and answer it!
Dr. Spencer: Why are we concerned that Pluto's atmosphere might disappear before we can get there to study it?
Dr. Spencer: We think Pluto's atmosphere is mostly made of nitrogen gas, like Earth's, but at the extremely cold temperatures on Pluto, nitrogen can freeze solid on the surface. The colder it is, the more of the nitrogen will freeze and the less will be left to form the atmosphere. Pluto reached the closest point to the sun in its orbit in 1989, and will be receding from the sun, and getting colder on average, till 2114- it's already 3% further away than it was in 1989. What we don't know is how quickly the frost will cool and the atmosphere will freeze- there are many uncertainties. But it's a safe bet that the longer we wait, the less atmosphere there will be when we finally get there (unless we wait till the 23rd century, that is).