The major theme at the present time is trying to understand where we came from.
(December 5,2006) – Ithaca, NY
Keri Kukral of Raw Science TV taped this conversation with Dr. Joseph Burns in 2006 at Cornell University – the year the New Horizons mission launched. It is being republished today (September 28, 2015) with the announcement of flowing water on Mars.
Dr. Joseph Burns is the Irving Porter Church Professor of Engineering and Professor of Astronomy at Cornell University. He received his Ph.D. from Cornell in 1966. He was Cornell’s Vice Provost of Physical Sciences and Engineering between 2003-2007. At Cornell, Joe has taught undergraduate courses in mechanics, applied mathematics, astronomy and physics; on the graduate level, his teaching includes celestial mechanics, mechanics of the solar system, classical mechanics and applied mathematics. His B.S. in naval architecture was obtained from Webb Institute in 1962. In addition to his activities in Ithaca, Burns was an NRC post-doc at NASA’s Goddard Space Flight Center in 1967-68, was a Senior Investigator during 1975-76 and again in 1982-83 at NASA’s Ames Research Center, was also Visiting Professor of Astronomy during 1982-83 at the University of California-Berkeley, and visited the Lunar and Planetary Laboratory of the University of Arizona in 1989-90. He attended the Kavli Institute (UCSB) in Spring 2008 and was at the Isaac Newton Institute (U. Cambridge) in Fall 2009. Burns has also spent extended leaves in Moscow (1973), Prague (1973), and Paris (1979, 1984).
Below is a modified transcript of their discussion. Edits and changes have been made by the participants to clarify spoken comments recorded.
Burns: We are living at a very special time. We have an opportunity to be able to understand where we came from and how common are living beings. Are we alone out there? How do other planets form? Is there life elsewhere and are we threatened? We have an opportunity to explore areas that we’ve never seen and by looking at other planets we have a chance to better understand how Earth operates.
Kukral: What are the major themes in solar system exploration in the next decade?
Burns: In the next decade we want to be able to work on really two separate themes. One is how planets work. What are the processes in planetary atmospheres and planetary interiors? How does geophysics work in other situations? The major theme at the present time is trying to understand where we came from. We need to look at materials that still retain the history of the early solar system. We’d like to look at disks of material to see how planets grow within a disk of material such as the nebulae that form around other stars. We have an analogue of that in the case of Saturn’s rings in our own solar system. We’re trying to understand the constituents and components of the Earth. Where did they come from? We’re interested in where the volatiles – water for instance – came from that we are endowed with in our oceans. Where did the organics out of which life was born come from? How common are the processes that brought that material here? Finally, what exactly makes a planet habitable? In the last decade, more than 200 planets in other solar systems have been found. Right now we’re trying to explore which of those might be habitable and what are the characteristics. How close do you have to be to the central source of heat? How do you have to spin? What chemicals must you be endowed with? Questions like that.
Kukral: What importance does the Pluto-Kuiper Belt mission have on our understanding of the evolution of the solar system and of human life?
Burns: The Kuiper Belt and the mission to explore Pluto are important because they allow us to look at the very distant reaches of our own solar system. This is the region from which we think most of the volatiles will be formed in the coldest reaches of the solar system. We have an opportunity to see that region. Also, material coming from that area is material that has not been processed very much because it is so extraordinarily cold, maybe 30 degrees above absolute zero. Processes are slowed down extraordinarily long. In addition, that is a region that we see many other stars possess. If we look at stars, they have disks of material around them. With current telescopes, we can only see those disks of material when they are at great distances from their stars. The sort of analogues that we have to the growth of the solar system are in fact areas that are way out at 30 or 40 times as far from their respective suns as the Earth is, and that’s exactly where the Kuiper Belt is for us so we probably have an analogue for many of the systems that we’re seeing through our telescopes.
Kukral: What is the transfer of biomaterials within our solar system?
Burns: It’s something that you don’t often think about. Material comes from other planets to us, and we, that is the Earth, probably send materially inadvertently out to other planets, satellites, and areas that might possibly be habitable. If we go to the Museum of Natural History in New York City, it has lots of meteorites. A small fraction of those meteorites comes from Mars and a small fraction come from the Moon. It’s quite evident that material is able to be transported from one celestial body to another. Earth is also losing material in a similar way. An impact events throws out debris at very high speeds and some debris can escape the Earth, for example. In the case of Mars we’ve done numerical experiments to confirm the presence of the meteorites that we see here. The numerical experiments we’ve done show some small fraction, maybe a few percent of the material launched from Mars end up on the Earth.
One might think, “how can you possibly get that much here?” but when you think about it, there are not too many other destinations that this debris can go. Some of it will re-collide with Mars but then Mars’s gravity starts to kick this material around in the solar system. Some of it goes out towards Jupiter. There are regions between Mars and Jupiter especially where Jupiter has a periodic influence, sort of a beat phenomenon, that will throw material into the inner solar system. Sometimes that stuff will strike the Earth. If it doesn’t actually hit the Earth, it will bounce of the Earth’s gravity field. It might go into Venus and perhaps Venus might throw it back to Earth which can send it out further into the solar system.
It diffuses throughout the solar system. Maybe 2 – 4% of the material lost from Mars hits the Earth. Another fraction like that hits Venus. A large fraction goes headway into the sun. Another fraction, perhaps 30 or 40% of it, gets tossed out as far as Jupiter and is then launched into interstellar space. When there is a big impact event on the Earth, the same thing happens. It’s got to escape not only the Earth’s gravity but pass through the Earth’s atmosphere so a smaller fraction make it out. It is quite likely some fraction of our material has struck say Mars. If there are life forms embedded in this rocks, those rocks will carry life to Mars. Whether Mars is habitable or hospitable to those organisms is yet to be determined.
There are of course other hospitable places in the solar system, we think. There is the second satellite of Jupiter, Europa. We see very strong circumstantial evidence that it has a liquid ocean very close to its surface. If that’s true, it means we have liquid water. We have energy because there are tides that pump that liquid water and heat it up. We also have the presence of organic compounds, things that contain carbon, hydrogen, nitrogen, and oxygen, just like that from which we are made. There is a possibility that life could form on this satellite Europa. In the Saturnian system, we have now with the Cassini mission found a similar satellite Titan. It is tiny, only a few hundred miles across. We see liquid water being sprayed out of its surface so there is that combination of heat, liquid water in which chemical and biological interactions can occur, and organic materials. It is a possibility as a habitat for life. In addition, Saturn has a very remarkable satellite Titan, one of the largest in the solar system. It has a very complex array of hydrocarbons that have developed over the course of time. Once more, it is a possibility of being able to see life being born. A smaller and smaller fraction of the material which is thrown of the Earth will reach those various places including Europa and Titan. Some of it may survive. To give you a sense of how much material is being launched this way, we get probably on Earth over 40 kilograms (100 pounds) of material from Mars every year. A lot!
“Solar system exploration is that grand human endeavor which reaches out through interplanetary space to discover the nature and origins of the system of planets in which we live and to learn whether life exists beyond Earth… It has a proud past, a productive present, and an auspicious future.” – Dr. Joseph Burns in a statement to the Sub-committe on Space and Aeronatutics Committee on Science, US House of Representatives (October 3, 2003).
Photo: NASA (Mars)