This post is part of a series discussing the recent NASA Discovery Program mission selections for further refinement. From the 27 proposals submitted in November of 2014, NASA has selected 5 missions for further refinement in the next year. Part 1 of the series focused on the overview of the Discovery refinement selections and an interview with the Lead Program Scientist for the Discovery Program, Dr. Michael New. Part II will focus on the Psyche Mission (PI: Linda Elkins-Tanton, Arizona State University, Managed by JPL).
Mission Overview: Psyche
How did the Earth’s core and the cores of the other terrestrial planets come to be? We cannot observe them directly, but there is one place in the solar system where we can find answers: The metal asteroid Psyche. Every world explored so far has a surface of ice, rock, or gas. Orbiting in the outer main belt at 3 AU, Psyche is large (240 x 185 x 145 km), dense (as high as 7,000 kg/m^3), and made almost entirely of Fe-Ni metal.
New meteorite data reveals that metal cores formed within the solar system’s first half million years, and even in very small bodies. Meteorites also reveal that iron meteorite parent bodies produced magnetic dynamos. And high-energy impacts were ubiquitous in the early solar system, so planetary cores likely formed and reformed repeatedly.
Models show that some impacts were accretionary, and others were destructive “hit-and-run” collisions that would strip the silicate mantles from the metal cores. This is the leading hypothesis for Psyche’s formation: it is a bare planetesimal core. While we expect it to be representative of cores everywhere, it is singular by being the only one we can access directly (other metallic asteroids are irregular and far smaller).
Our solar system offers few types of target bodies that await first-time exploration. The metal body Psyche is one of them.
The Psyche investigation has three broad goals:
1. Understand a previously unexplored building block of planet formation: iron cores.
2. Look inside the terrestrial planets, including Earth, by directly examining the interior of a differentiated body, which otherwise could not be seen.
3. Explore a new type of world. For the first time, examine a world made not of rock or ice, but of metal.
If we confirm that Psyche is a planetesimal core, the epoch of formation of its surface will put a new constraint on the dynamic activity of the solar system. The existence of Psyche shows that there were sufficient impactors to strip planetesimals at that time, which provides a new constraint on the evolution of planet-forming populations.
If we discover that Psyche has a magnetic field, then we’ll have dissected a magnetic dynamo for the first time. The increasing evidence that some planetesimals had magnetic dynamos requires that they had convecting cores, but our pale understanding of the ways they solidify makes modeling their dynamos difficult. If we measure a magnetic field at Psyche we will have the first ground truth about the compositions and processes of a planetesimal core. Our understanding of magnetic dynamos, a difficult and ill-constrained field, will be greatly advanced.
If Psyche is a core and solidified from the outside inward, it is an analog for Mercury’s core in the present day, which appears to be solidifying this way. This unexpected process will be observed on Psyche as we never can on Mercury. Solidification inside out, in contrast, parallels the Earth’s core.
Perhaps the most exciting discovery of all would be that Psyche is not a core at all, but primordial, unmelted metal. This material most likely formed close to the Sun in the early disk, where temperatures were high and light elements were volatilized away. Such bodies were likely later injected into the asteroid belt. Further, a primordial Psyche supports the hypothesis that Mercury was formed from material with a larger fraction of metal to begin with, and came by its large core that way, rather than by later stripping. A primordial Psyche introduces a new kind of material that was never known to exist in the early solar system.
Psyche provides a unique window into the formation of the planetary cores that lie deep inside all planets. This investigation is a mission of discovery that gives humankind its first opportunity to explore a metal world while investigating planetary formation dynamics and the origin of the cores of all planets, including our own.
This mission is a partnership between ASU, JPL, and Space Systems Loral.
About the Mission PI (Linda Elkins-Tanton):
Lindy Elkins-Tanton is the Director of the School of Earth and Space Exploration at Arizona State University. She received her B.S., M.S., and Ph.D. from MIT. She spent five years as a researcher at Brown University, followed by five years on MIT faculty, culminating as Associate Professor of Geology, before accepting the directorship of the Department of Terrestrial Magnetism at the Carnegie Institution for Science. In 2014 she moved to the directorship at Arizona State University.
Her research is on the formation of terrestrial planets, and the relationships between Earth and life on Earth. Her work addresses the physical and chemical processes on planetesimals and growing terrestrial planets, and the effects these processes have on the habitability of the resulting body. She has also lead four field expeditions in Siberia, and conducted field work in Iceland, the Sierra Nevada, and the Cascades. She is i
Elkins-Tanton is a two-time National Academy of Sciences Kavli Frontiers of Science Fellow. She won a National Science Foundation CAREER award and the Explorers Club Lowell Thomas prize. She has written a six-book reference series, The Solar System. In 2013 she was named the Astor Fellow at Oxford University, and in 2015 Cambridge University Press published a volume she co-edited, titled Volcanism and Global Environmental Change.
About the Mission Deputy PI (Jim Bell)
Jim Bell is a Professor in the School of Earth and Space Exploration at Arizona State University in Tempe, Arizona, an Adjunct Professor in the Department of Astronomy at Cornell University in Ithaca, New York, and a Distinguished Visiting Scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. He received his B.S. in Planetary Science and Aeronautics from Caltech, his M.S. and Ph.D. in Geology & Geophysics from the University of Hawaii, and served as a National Research Council postdoctoral research fellow at NASA's Ames Research Center.
Jim's research group primarily focuses on the geology, geochemistry, and mineralogy of planets, moons, asteroids, and comets using data obtained from telescopes and spacecraft missions. Jim is an active planetary scientist and has been heavily involved in many NASA robotic space exploration missions, including the Near Earth Asteroid Rendezvous (NEAR), Mars Pathfinder, Comet Nucleus Tour, Mars Exploration Rovers Spirit and Opportunity, Mars Odyssey Orbiter, Mars Reconnaissance Orbiter, Lunar Reconnaissance Orbiter, and the Mars Science Laboratory Curiosity rover mission. Jim is the lead scientist in charge of the Panoramic camera (Pancam) color, stereoscopic imaging system on the Spirit and Opportunity rovers, is the Deputy Principal Investigator of the Mastcam camera system on the Curiosity rover, and is the Principal Investigator for the Mastcam-Z cameras on NASA's upcoming Mars-2020 rover. He has been an active user of the Hubble Space Telescope, and of a number of ground based telescopes, including several at Mauna Kea Observatory in Hawaii.
Interview with PI: Dr. Linda Elkins-Taton
What previous mission experience do you have?
I have served on the science teams for two Discovery proposals and a New Frontiers proposal, and I was on the Mars 2020 Rover science definition team as well as the International Lunar Network science definition team. Because I don’t have deep mission experience, I have packed our Psyche team with people who do. What I have along from science is critical experience managing large teams of scientists.
What has been your career steps to this point? Had you always wanted to be a mission scientist?
My career has taken some detours from the traditional straight-and-narrow trajectory through grad school and into a faculty position. For eight years after my Master’s I worked in business, as a management consultant and in several companies, and then I spent two years as a lecturer in mathematics at St. Mary’s College of Maryland. I went back to get my Ph.D. when I was 31. I knew I wanted to stay in science and in academia, but I did not then imagine I would have the opportunity to be a mission scientist. The experience I gained in the business world has been invaluable, and I’m hugely fortunate to be where I am now. I’d start thanking the people who made this possible — we don’t do anything alone in this world — but I’m afraid a big hook will come out and pull me off! Let me just thank Bruce Bills and Daniel Wenkert at JPL for bringing us all together to conceive of this mission.
What are your next steps and main challenges moving forward?
We’re in pretty good shape going into the concept study year. We’ll take all the advice we get during the NASA debrief on our proposal, and we’ll set up a schedule to address all the concerns and get them squared away. There’s nothing on the list right now that we think is going to cause inordinate trouble. We’ll do our best, and hand in the strongest case we can. The Psyche team is a great group of people and we really enjoy working together, and we surely are going in intending to win!
What advice would you give to a new comer in the field looking to go into mission work?
If you have not begun your Ph.D., find an advisor who is involved in missions, and find a project that connects you as well. That way you meet people in the NASA community and you learn what is needed on missions, and you can steer your studies to make you a needed expert. You can do the same kind of thing if you are already finished with your Ph.D., by meeting people and learning what missions need and making connections. It’s inspiring work, scientifically and also socially, both because you can show kids the thrill of exploration, and because you are working in a big team of bright, motivated people.
Why should governments continue sending space missions, when there are so many challenges at home?
For so many reasons. Space missions don’t shoot currency out into space: it’s all paid for here on Earth, supporting the salaries of talented people, supporting their families, supporting communities. The education and technology development that leads to our astonishing ability to produce robotic and manned space missions also benefits people at home, in every way. School curricula are more inspiring. Technologies for everyday life are enhanced. Corporations are supported and new products are produced. And perhaps most importantly, space exploration fills a deep need in humans, the need to explore, to strive, and to overcome great challenges. Space exploration distracts us from local squabbles and aligns humankind together, looking out. This can only be good for our future.