Jonathan Lunine on Missions to Saturn & Jupiter

Special Topic of Planetary Exploration Interview, August 2011

Jonathan Lunine According to our Special Topics analysis on Planetary Exploration research over the past decade, the work of Dr. Jonathan Lunine ranks at #3 by total cites and #7 by number of papers, based on 122 papers cited a total of 2,806 times. Four of these papers are ranked among the top 20 papers over the past decade and over the past two years.

In Essential Science IndicatorsSM from Thomson Reuters, Lunine's record includes several Highly Cited Papers in the field of Space Science, Physics, and Geosciences.

Lunine is the David C. Duncan Professor in the Physical Sciences at Cornell University, having just completed two years in Rome, Italy, working on several projects and teaching at the University of Rome Tor Vergata. He is a fellow of the American Association for the Advancement of Science and the American Geophysical Union, and a member of the US National Academy of Sciences.

Below, he talks with about his highly cited work in planetary exploration.

SW: Please tell us about your educational background and research experiences.

My research interests center broadly on planetary origin and evolution, in our solar system and around other stars. I am an interdisciplinary scientist on the Cassini mission to Saturn, and on the James Webb Space Telescope, as well as co-investigator on the Juno mission to be launched to Jupiter in August.

I am the author of over 250 scientific papers and of the books Earth: Evolution of a Habitable World (Cambridge University Press, 1999), and Astrobiology: A Multidisciplinary Approach (Pearson Addison-Wesley, 2005). I earned a B.S. in Physics and Astronomy from the University of Rochester (1980), followed by M.S. (1983) and Ph.D. (1985) degrees in Planetary Science from the California Institute of Technology.

SW: What first drew you to planetary research?

I was interested in astronomy from childhood. Growing up near the world-famous Hayden Planetarium I had ample opportunity to convince my mother and cousin to take me there (and to the dinosaurs at the adjacent American Museum of Natural History). I devoured science fiction, Sky & Telescope magazine, articles about the space program, and Carl Sagan's books.

Spurred on by my mother, I wrote to Sagan as a middle school student, asking him what courses I should pursue to become an astronomer, and he wrote back a detailed, two page letter. His encouragement of many young people who are now working planetary scientists illustrates how important it is to cultivate future scientists as early as possible. I am honored to be the occupant today of the chair that Carl held when he was a professor at Cornell.

Jonathan Lunine
Standing in front of a balloon commissioned by National Geographic for an episode on ballooning on Titan (we rode across part of the Mohave). Credit Julian Nott.

Majoring in astronomy in college, I saw the beautiful Voyager images of Jupiter in my junior year, in 1979, and decided to specialize in planetary science, though I do astrophysics as well.

SW: Your most-cited original article in our analysis is the 2005 Nature paper you coauthored, "The abundances of constituents of Titan's atmosphere from the GCMS instrument on the Huygens probe," (Niemann HB, et al., 438[7069]:779-84, 8 December 2005). Would you tell us a bit about this paper—your expectations going in, your findings, where this work has gone since this publication?

My dissertation completed in 1984, four years after the Voyager 1 flyby of Saturn's moon Titan, centered on models of Titan's surface and the interaction of water ice with other molecule species in the outer solar system (Jupiter and beyond). The best way to test these and many other ideas about Titan—a Mercury-sized moon with an atmosphere denser than Earth's and cryogenic (-179 Celsius) surface temperatures—is to return with an entry probe.

This mission, eventually called Cassini-Huygens, began development in 1989 and I was selected to play several roles, one of which is a co-investigator on the Gas Chromatograph Mass Spectrometer (GCMS) on Huygens. The instrument was designed and built at NASA Goddard Spaceflight Center by Dr. Hasso Niemann and his team.

Fast forward 16 eventful years and GCMS was returning data during the descent to the surface of the European Huygens probe within Titan's atmosphere. As a bonus we got over an hour of data after landing. And this turned out to be crucial, because we measured methane and other carbon-bearing compounds evaporating into the heated inlet of the mass spectrometer from the surface on which we landed. In 1983, I had predicted a global ocean of methane and ethane. We didn't find such an ocean at the equator, but with the Huygens results the hunt was on for surface liquids of methane elsewhere on the body.

In 2005 the Cassini Orbiter's camera found a 200-km long feature near the south pole that turns out to be a lake of ethane and probably methane. And, in 2007, the radar experiment on the Cassini Orbiter—an experiment I was also involved in—found what turned out to be seas of liquid hydrocarbons in the northern latitudes. Vast equatorial dunes appear to be made of solid hydrocarbons. So, Titan truly appears to be an organic-rich world, and our GCMS paper reported the first direct sampling of this material in the atmosphere and on the surface.

SW: Actually, quite a bit of your work in our analysis deals with explorations of Titan. Can you give us some of the highlights of what you have learned about Titan over the years? What is the value of all these discoveries at the end of the day?

There are now books written on Titan, and even an extended paragraph would not do Titan justice. Think of a world with a hydrologic cycle somewhat akin to Earth's, with clouds, rain and surface liquids, but of methane and other hydrocarbons, not of water. And there's no global ocean—in its place these are polar lakes and seas, with river valleys scattered over the surface. A prodigious organic chemistry is underway in the atmosphere, converting methane and nitrogen to other organics, and these settle onto the surface.

We see on Titan many if not most of the geologic and atmospheric processes observed on Earth, but under very different conditions and hence with different materials—water ice in place of rock, methane in place of liquid water. There's a whole exotic world to explore in our cosmic neighborhood, one on which the organic chemistry that occurred on Earth prior to life may be underway today.

SW: Obviously, these missions are the result of great team effort. Can you give us some insight into how these mission teams work?

"To be one of the first to gaze on images of a landscape shaped by Earth-like processes yet under totally alien conditions, to sample the chemistry of that world...those are truly amazing experiences."

Well, they work like any scientific team—in diverse ways, with varying degrees of success. Large missions tend to have individual instrument teams, with different group personalities driven by the people involved and the demands of the instrument and the mission. Small missions led by individual Principal Investigators (PI's) tend to be more cohesive because the outcome of an entire mission is resting on the shoulders of a smaller group of engineers and scientists.

The Huygens Probe, which carried our Goddard mass spectrometer, was like a small mission embedded within the larger overall Cassini-Huygens mission, and so I felt a strong camaraderie with my fellow Huygens investigators that lasts even today, six years after Huygens fulfilled its mission. To be one of the first to gaze on images of a landscape shaped by Earth-like processes yet under totally alien conditions, to sample the chemistry of that world...those are truly amazing experiences.

SW: You're also involved in a pending launch to Jupiter. What is the Juno team seeking with this mission?

Juno to Jupiter, led by Dr. Scott Bolton of the Southwest Research Institute, is a great NASA mission that will probe deep into the solar system's largest planet through a variety of remote sensing techniques. We'll dive through the deadly radiation belts to fly close over Jupiter multiple times, determining whether the planet has a dense core made of elements we associated with rock and ice, study the aurora and magnetic field, the stormy weather of the turbulent atmosphere, and measure the deep abundance of water—a key to understanding the formation of this touchstone for the hundreds of Jovian-sized planets known to orbit other stars.

SW: You've just spent two years at the University of Rome. What was the nature of your work in Rome?

Both Cassini-Huygens and Juno have strong involvement from Italy, both in terms of scientists and of hardware for the missions, so I worked with a number of Italian colleagues on interpreting Cassini data and getting ready for Juno's launch to Jupiter. Italy has made outstanding contributions to astronomy and planetary science, extending from the time of Galileo Galilei to the space missions of the present day. I was privileged to teach at one of the Italian universities—University of Rome Tor Vergata—which has outstanding masters and doctoral students.

SW: How has the field as a whole changed over the years?

I see two dramatic changes in planetary science. First, it is now recognized as a legitimate field of science unto itself and not the "filius nullius" of astronomy and geology. Indeed, our biggest problem is trying to balance the number of talented graduates who want to pursue a doctoral degree in planetary science with the number of jobs available.

Second, the explosive progress in detecting and characterizing planets around other stars has led to the demand for modeling of planetary processes in all sorts of strange planets, some similar to and others very different from those in our own solar system. And there is the prospect that another Earth-like planet will be found in our local corner of the Galaxy in the coming decade or two. a discovery that would be a fitting climax to four centuries of telescopic observations since Galileo.

SW: Where do you hope to see this research go in the next decade?

I hope to be going sailing on Titan. NASA recently selected three missions in its Discovery program of mid-scale planetary missions, to be competed against each other for a final selection sometime next year. One of these, the "Titan Mare Explorer," or TiME, would float a long-lived probe on one of the large methane-ethane seas in the high northern latitudes of Titan. Dr. Ellen Stofan is PI, I am her deputy, and our Cassini colleague Dr. Ralph Lorenz is the Project Scientist. A bit less than two decades after Huygens put the first mass spectrometer on the surface of Titan, another one could be sampling the organic chemistry in an extraterrestrial sea.End

Jonathan Lunine, Ph.D.
Department of Astronomy
Cornell University
Ithaca, NY, USA


Niemann HB, et al., "The abundances of constituents of Titan’s atmosphere from the GCMS instrument on the Huygens probe," Nature 438(7069): 779-84, 8 December 2005 with 300 cites. Source: Essential Science Indicators from Clarivate Analytics.




   |   BACK TO TOP