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Who's Who at NASA: Dr. Jim Green, Director, Planetary Science Division, NASA Headquarters, Washington, DC
Color image of man talking to a group with an comet displayed on a computer screen next to him.
NASA's Planetary Science Chief, James L. Green, at AGU discussing Year of Solar System events, 15 December 2010.

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Dr. Jim Green began his NASA career in 1980 at Marshall Space Flight Center's Magnetospheric Physics Branch where he developed and managed the Space Physics Analysis Network (SPAN), NASA's precursor to the Internet. From 1985 to 1992 he served as Head of the National Space Science Data Center at the Goddard Space Flight Center, followed by a 13-year stint as Chief of the Space Science Data Operations Office. In 2005 he was named Chief of the Science Proposal Support Office, where he served until August 2006 when he was appointed Director of NASA's Planetary Science Division.

NASA Tech Briefs: You began your NASA career in 1980 at Marshall Space Flight Center's Magnetospheric Physics Branch where you developed and managed the Space Physics Analysis Network. What was the Space Physics Analysis Network?

Dr. Jim Green: Yes, SPAN. Those were fantastic days. I was at Marshall Space Flight Center working with a group that was doing some fabulous mass storage technologies, and I had the responsibility to load our spacecraft data into this huge online optical disk systems that provided immediate access to very large quantities of spacecraft data. These were the first online terabyte archives.

I was given the responsibility to work with them and get the data in and then develop the testing and the test plan, and I suddenly realized how inadequate I was to really be able to test the system. It dawned on me, and several others in the group, that the best way to do that was to get the people that we were working with - the co-investigators - to also help me because they wanted to get access to this data too. So that was why I started investigating a variety of network technologies, because all of these groups were at various locations in the United States.

By the end of 1980 we already had several computer links up, and then by 1981 and 1982 I was bringing groups on right and left. The bottom line to that was the technology did not prove to be as useful as we had hoped. It was very cumbersome. It was some of the earliest attempts at using optical disks for online technologies, and that whole field rapidly changed anyway. But the network was an unbelievable success. We literally had NASA's first Internet going. We communicated. We did remote log-ons. Email was every day, of course. The things that we take for granted now we were doing in 1980. We were developing proposals across the Net and it was just doing fantastic. It really developed into quite the capability for NASA.

Then, by 1985, a new wrinkle occurred that turned out to be associated with a spacecraft called the International Cometary Explorer, or ICE. ICE was a spacecraft that's primary mission was really to be a solar wind monitor. It was called ISEE-3 - International Sun Earth Explorer 3 - and it was sitting at the L1 Langrangian point measuring the solar wind. NASA decided to pull it out of that orbit, do a couple of neat swing-bys of the Earth and the moon, and throw it towards a comet called Giacobini-Zinner and fly right through the tail. This was important to do because we'd never had a comet encounter before, and it was a fantastic event, but the really big problem with that was the data system.

The data system for the ISEE-3, when it was sitting at the Lagrangian point, the data was written to magnetic tape. When you filled a tape, you stuck the tape in a box and when you filled the box, you taped it up and sent it to the investigator. So, with that data system everyone got their data a month later - no real time anything - and it was very distributed, meaning it had international investigators and instruments on it from international scientists. Now the press was used to the GPO encounters of Voyager flying by Saturn and Jupiter and Uranus and Neptune, and the press was able to talk to the scientists and have them tell everybody about the new discoveries within hours after the encounter. This really caused a dilemma, and it dawned on a number of us scientists that the best thing we could do was to use the SPAN network in a unique way. We could put the data on the network, send the data to the remote sites where many of the investigators were, have them analyze the data, then bring the data back and have the principal investigators at a central location at Goddard review the analyzed results, make the discoveries, have the press conference, and make it look exactly like the press was used to with the really big encounters from the Voyagers.

The real problem was that we also had European investigators, so once we got the approval from the project to use SPAN, I immediately started working with ESA and they were just wonderful to work with. They came up with an international link into Darmstadt, Germany, and then ESA took that link and sent it out to the investigators and voila, we started connecting the European scientists together! And that was 1985. In September of 1985 the ICE encounter [through the comet's tail] occurred, and it worked perfectly. It was just a rousing success. It really was one of the highlights of how we used the network. By 1987 we were in Japan, and by 1992 we were in Russia. So SPAN really was the beginning of NASA's Internet and just a tremendous capability for the science community.

NTB: Since August 2006 you've been the Director of NASA's Planetary Science Division. What is the Planetary Science Division, and how does it contribute to NASA's overall mission?

Dr. Green: NASA's Planetary Science Division is really all about understanding the origins and evolution of the solar system and looking for life beyond Earth. In other words, what are the conditions that could provide a habitat for life, and is there life on other planets or other parts of our solar system, perhaps even moons? And finally, understanding the environment well enough to determine what the hazards are for human habitability as we move into the solar system.

Now, that's our broad objectives and goals. We accomplish that through a variety of spectacular missions. We have missions at many locations in our solar system, and in this next year we're going to have some really unbelievable milestones. In fact, in November 2010 we will have one of our spacecraft named "EPOXI" - it used to be the Deep Impact spacecraft but now we're retargeting it to another comet - fly by Comet Hartley 2.

In [early 2011] we're going to fly by another comet with the Stardust spacecraft that we've renamed "Stardust NExT," and that comet is Temple 1. Now Temple 1 we've already been by with Deep Impact and we've had an impacter on it. But with Stardust we're going to fly by Temple 1 and we're hopefully going to see the impact region. In addition to that we'll be able to see that comet after it's gone by the sun through its sublimation phase and really determine what does a comet do in terms of how it sublimates and how it emits the material that it holds out into the solar wind and, therefore, out into the solar system. So, two fabulous comet encounters are coming up.

In addition to that, in March 2011 is our MESSENGER spacecraft is going to get into orbit around Mercury. Mercury is a fabulous planet! We've flown by it now three times with MESSENGER and several times prior to that in the 1960s and early 70s with one of the Mariners. MESSENGER will get into orbit and be able to study that body like we've never done before. Mercury is a little bit bigger than our moon. It's a small terrestrial planet, but it is extremely dense. In fact, it almost has the same density as Earth, even though it's much, much smaller. The core of Mercury, we now understand, is larger than the core of the Earth. Now these are really puzzling things, and we hope that by getting into orbit and really studying it for two Mercury years or more, we will really be able to understand how that planet formed so close to the sun and why these properties are so unusual about it.

In addition to that, in July of 2011 we have another spacecraft called "Dawn" that is going to get into orbit around a fabulous asteroid called "Vesta." Vesta is an enormous asteroid more than 500 kilometers in diameter, so it is quite a fascinating asteroid. It's in the inner belt, and we will be in orbit for approximately a year before we then break that orbit and go on to the biggest asteroid, called "Ceres." Then we'll have 3 launches: in August (2011) Juno will be launched and going to Jupiter; in September (2011) Grail will be launched going to the moon; in November (2011) MSL - the Mars Science Laboratory - will be launched and going to Mars; and then within nine-or-so months after that it will land on Mars. So we have a litany of some fabulous activities that are going to happen. I believe that after these milestones have been accomplished and the data returned, we'll see some fabulous science discoveries come out of it.

NTB: As you just noted, a large part of the Planetary Science Division's focus is the search for life - or some evidence of life - elsewhere in our solar system, such as Mars, or the moons of Jupiter, and other bodies like these comets and asteroids you've been talking about. In the grand scheme of things, why is the search for life on other planets so important to NASA?

Dr. Green: Well, the search for life is really a fundamental question that we, I believe, as humans are innately drawn towards. We are quite interested to determine how unique this planet is. Obviously there's nothing like Planet Earth in our solar system. But understanding how life might occur beyond Earth is really taking a good look at what the habitable conditions for life are in our own solar system.

Now, as I mentioned, we have some fabulous missions going to locations that will move us closer to understanding the habitability of Mars and other locations, but also whether there might be life there. MSL - the Mars Science Laboratory - is a perfect example of that. MSL is quite the astrobiology laboratory. It has the ability to make a variety of measurements. One measurement that we're quite interested in is following up our new discovery that Mars is emitting methane. Methane can be emitted biologically of course; everyone is well-aware of that. But it can also be generated, as we call it, abiotically; in other words, with non-biological processes. So, by looking at the isotopes of methane, MSL will give us an indication of whether that methane is being generated by life on Mars or not.

We're now doing research in the outer part of our solar system - places like Europa. Europa is just a fabulous, unbelievable moon of Jupiter. Europa is fairly large, about the size of Earth's moon. It has a very hefty ice crust all around it and we now know that it has more water below that ice crust than the Earth has. It looks like it's a potentially habitable environment because of the energies that might be associated with keeping the ice in liquid form below the ice shell and potential sources of food and other organics. It really is a very intriguing environment. We really need to follow up with a future mission to Europa.

So, the life question is of natural interest, and in planetary science it is all about looking at our own planetary systems and bodies to determine their habitability, and I think we're in store for more really fantastic surprises.

NTB: In April 2010, noted British astrophysicist Dr. Stephen Hawking attracted a lot of media attention by commenting that in our search for extraterrestrial life, humans should think very carefully about whether or not we should broadcast our existence to a potentially hostile universe. I don't know if it was in direct response to Dr. Hawking's comments or not, but around that same time you were quoted in the media as saying that NASA is ready to "protect Earth and our species." Exactly what did you mean by that statement?

Dr. Green: Well, indeed, Stephen is a really well-respected, deep-thinking scientist, and when he comments on topics it's something that we should really think about and consider. But we're really a long way away from encountering the kind of intelligent life that I believe Stephen was referring to. As I mentioned earlier, planetary science at NASA is really all about stepping out into our own solar system, and we know that in our own solar system, Earth is the only unique body in this environment that houses life as we know it in terms of human and complex life. However, that doesn't mean that life in other forms - perhaps in microbes and other less complex life - hasn't evolved elsewhere in the solar system, and that's what we're seeking in these new steps.

To be able to do that and do it right, we do, indeed, follow the international rules of planetary protection. Planetary protection is really quite clear and it's really all about if we're going to go somewhere and study life, we have to be careful about contaminating that life with our own life. In other words, we send sterile spacecraft. When Phoenix dug into the dirt on Mars, that arm and the equipment - the tray that was acquiring the material - were all sterilized and very carefully managed such that we didn't contaminate that environment.

In a similar way, we've actually brought back samples from comets. Stardust flew by Wild 2 and brought back some fabulous samples that we've started to study and, in fact, in those samples most recently we found the amino acid glycine. Now glycine is just a fabulous find for us and it's discovery really allows us to start thinking about how comets could've seeded not only the Earth but other planets with some basic materials that are important for life and sustaining life. In that respect we have to be very careful about whatever we bring back so that we don't contaminate the Earth. So there are a variety of policies and procedures - rules if you will - that we follow very closely, that will enable us to manage and carefully analyze any sample that we bring back and protect the Earth.

NTB: One of the backbones of the Planetary Science Division appears to be the Research and Analysis Program. What is the Research and Analysis Program, how does it work, and what are some of the benefits it produces for NASA?

Dr. Green: The Research and Analysis Program is really all about providing a variety of opportunities for the community to move our science forward. For example, we have opportunities in our Research and Analysis Program that allow scientists to propose to do research in the outer planets area, propose to do research in planetary atmospheres, small bodies such as comets and asteroids, study the geology of Mars and other terrestrial planets, just to name a few. Fabulous discoveries have been made from our planetary data, and that data is there to continue to be mined and analyzed.

We also use this program to do some development on planetary instruments, whether for astrobiology purposes or in situ measurements, or imaging and remote sensing purposes. We do want to fund some really critical new technologies and developments to see how those might be applied to planetary instruments for our future. So the program is really quite broad. We spend well over $200 million a year on that and it's really reaping enormous benefits. I think it's the heart of the science discoveries that you've seen coming out of NASA on a regular basis in planetary science.

NTB: Throughout your career you've been involved with data collection, management, and dissemination technology. The amount of scientific data being generated has increased exponentially over the last three decades. Has the technology required to manage and archive it kept pace, and how does NASA deal with that problem?

Dr. Green: That's a good question. I would say with respect to the planetary science data, the answer would be yes. The reason I say that is, we don't bring in as much data as, say, Earth Science, because Earth is right here and those satellites orbit this planet and can beam directly down to the Earth huge amounts of data. It's much harder to do that with our spacecraft that are so far away. Consequently, what is called the bit rate, or the rate of the data that comes from planetary spacecraft, is much less. Therefore, the volume of data that we have in our archive is much less. That means we have several hundred terabytes of data that we've acquired over the last four years. That's an enormous amount of data. However, Earth Science sometimes has terabytes in a few days, so consequently the technologies for storage and dissemination of Earth science data can easily be applied to planetary science since we don't have quite that data volume.

Now, with that said, the best thing to do with data that comes into our archive is to provide it online and provide it in a way where the information about the data is available for scientists to make decisions about using it or not using it, and even more importantly, how to use the data correctly. That we call metadata, and we generate metadata along with the archive data. We've developed a system called the Planetary Data System - it's one of NASA's oldest distributed data systems. We have quite a few nodes stretched all across the country and data is constantly pouring into these nodes at NASA centers and other universities. The Planetary Data System is doing an outstanding job. We're going to continue on with that structure, and continue to improve it with time.

You have also become one of the world's foremost authorities on magnetospheres. What are magnetospheres, and what is it about them that captured your interest?

Dr. Green: Some solar system bodies generate their own magnetic field. The extent and shape of that magnetic field into the space around a body is called a magnetosphere. My interest in magnetospheres started when I was at the University of Iowa. I really enjoyed anything to do with the electromagnetic spectrum and, in particular, the radio end of the spectrum. Radio waves are actually generated by magnetospheres. We've known that one of the brightest radio objects - and the first planetary object - discovered at radio frequencies was Jupiter. Jupiter generates decametric radio emissions that we are observing from Earth even today, and that's actually a magnetospheric phenomenon. So, my interest in planetary science actually started with my interest in understanding how emissions in the radio end of the spectrum are generated by magnetospheres.

Now that we have spacecraft that actually make radio frequency measurements in magnetospheres, we see a tremendous host of other in situ radio and extremely low frequency and ultra-low frequency radio waves. It's fascinating to me to understand the physics of how these waves are generated and what they tell us about the space environments of these magnetospheres.

NTB: While we're on the subject of magnetospheres, when you were at the Goddard Space Flight Center you were a co-investigator and deputy project scientist on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission. Tell us about that mission and what it accomplished.

Dr. Green: IMAGE was a real delight to be involved with. My actual start in IMAGE really occurred in the late 1980s. I wrote a proposal to study the use of electromagnetic waves to measure various aspects of magnetospheres just like a cop uses a radar wave to understand your speed. Same principle, but I was taking it into the magnetosphere. I did get approved to do that research. I began in the 1990s to pull a team together, and we eventually ended up developing an instrument called the Radio Plasma Imager - RPI - and we were able to get it on the IMAGE mission, which had another group of fabulous remote sensing instruments. RPI was just an unbelievable instrument in the sense that it would not only measure electromagnetic waves that are intrinsic to a magnetosphere, but it would generate waves, bounce them off magnetospheric structures, and it enabled us to really visualize what these plasmas look like and how they moved in time. The instrument was so successful that we generated almost a peer-reviewed publication a month from a team of 8 - 10 of us.

It was just a tremendous opportunity that allowed us to really understand magnetosphere-solar wind dynamics, how things change, and really bring that to a visual perspective through imaging techniques. We could see the plasmasphere, which is the evaporated ionosphere. We could see its structure and how it changed with time. RPI could also observe intense electromagnetic waves that are generated above auroras, called auroral kilometric radiation. With IMAGE we could simultaneously observe the aurora and the auroral kilometric radiation, and understand a lot more about their relationship and dynamics and how the magnetosphere was generating these radio waves. By making these measurements at the Earth, we were then developing an understanding of how these processes could also work in other locations in our solar system, such as Jupiter. Jupiter does the same kind of stuff, but it does it in a bigger way because it is a much more intense magnetic field. And a much higher intensity set of energetic particles.

So, IMAGE was a spacecraft launched in 2000, it lasted for about five years, and it was highly successful and a very exciting time in my career to be associated with it.

NTB: Looking ahead, what would you say is the Planetary Science Division's top priority over the next five years?

Dr. Green: Well, I would go back to our key goals - understanding the origin and evolution of the solar system and looking for the potential of life elsewhere in the solar system. I believe the Planetary Science Decadal that comes out early next year and will chart our course for the next ten years will keep these same priorities going. These are just fundamental areas for us to continue to explore. We have made some astounding discoveries, but many more are on the way. In the next few years I believe we will make major progress on understanding the potential for life or habitability. I think we're on track to make some fabulous measurements at Mars that will take us one giant step closer to answering that question, at least for that particular planet.

In addition, we are just now seeing a scientific revolution that is going on in that field and we have much more to learn about it. I'll give you a perfect example. Is Pluto a planet or not? That is a topic that even kids can resonate with. And the reason why we now think of Pluto as part of a different class of objects shows an evolution in our thinking. If I can take a minute, perhaps I can give you a little understanding of how that goes.

If we go back in time, let's say 1850, and you went into a library, pulled out the physics book, and looked at the chapter on solar system because you wanted to memorize the names of all the planets, how many planets would you need to know? You would probably be very surprised if I told you 23. The reason why there were 23 is because in the early 1800s telescopes were getting much better at observing fainter objects. Many people in the general public were starting to use them. Amateurs were finding all sorts of objects and it was quite an exciting time to be a ground-based astronomer. New objects were found like Vesta, Ceres, Eros... In other words, you were observing bodies in the asteroid belt.

NTB: And you had no technology to figure out whether they were planets or not, right?

Dr. Green: Correct!

NTB: So you assumed they were planets.

Dr. Green: That's right! You called them planets. But by 1852, when the astronomers got together and really began to noodle on "What's going on here?" you recognized that this was really a different class of objects, and that class was defined as asteroids. We now know there are probably a million or more asteroids in the asteroid belt, which exists between Mars and Jupiter.

We are right now in the same part in our history - in exactly an analogous way - by thinking about Pluto as a planet or other type of solar system body. Pluto turns out to be what we call a Kuiper Belt object. Another class of objects. This is fantastic! How did this occur? Well, around 1990, because telescopes on Earth were getting quite outstanding and they continue to improve with time, a series of astronomers were observing and finding what were objects - they could be planets - but they were objects at distances greater than Pluto. Since 1990 we've found about 1300 of these objects, one of which is bigger than Pluto. That object is called Eris, and it's about twice as far as Pluto is from us right now.

So this whole new set of objects that we're finding, we now call the Kuiper Belt, after astronomer Gerard Kuiper. He suggested that comet-like debris left over from the formation of the solar system should exist just beyond Neptune, and now we want to study them. So, our mission called New Horizon, which will fly by Pluto in 2015, will be our first fabulous glimpse of a completely new type of object - once again, a Kuiper Belt object - and it will be quite fascinating to understand a lot more about its structure, its shape, and see how these objects are really part of the origin and evolution of our solar system.

This next decade in planetary science is going to be incredibly rich with fabulous amounts of data, and I think we'll continue to make some really outstanding and astounding discoveries as we move into the future.

Last Updated: 9 February 2011

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Last Updated: 9 Feb 2011