Research themes in Planetary Science
Planetary expertise across Stanford University spans a wide range of integrated scientific themes.
In the past 25 years, the discovery of extrasolar planets – planets orbiting stars other than our sun – has revolutionized our perspective on the Earth, our solar system, and our place in the universe. Astronomers have discovered an enormous variety of such planets, systems incredibly different from our own solar system. Scientists at Stanford study these observationally and theoretically. We use advanced optical technology to find and characterize giant planets that are a million times fainter than the stars they orbit, studying their orbits and atmospheric composition. Theorists develop models of the evolution of planetary atmospheres and surfaces, trying to understand what makes a habitable or even life-bearing world. This lays the groundwork for the day when scientists may find a world, orbiting a distant star, bearing the signatures of life.
From the impenetrable atmospheres of gas giants to rarefied exospheres, planetary atmospheres come in all sizes and compositions. Atmospheres shield the surfaces of terrestrial planets, regulate climate and geochemical cycles, and play a critical role in making a planet hospitable to life. At Stanford, we study the dynamics, structure, and chemistry of planetary atmospheres, and what they can tell us about planetary formation, evolution, and habitability.
Planets form in a disk of dust and gas around a young, growing star. In recent years, new capabilities in astronomy, from detection of exoplanetary systems to detailed observations of the disks around young stars, have radically improved our understanding of the physics and chemistry of planet formation. Remnants of planetary formation in our own Solar System are delivered to the Earth as meteorites; these objects shed light on the provenance of materials that make up the planets, and can help to constrain the timing of early planetary processes. Studying the processes occurring on young planets will help scientists better understand the early environments on the Earth that existed during the time that life first arose. Theorists and experimentalists at Stanford work on these and other questions around planet formation.
From the clouds of Venus to Mars’ subsurface and Europa’s deep subsurface ocean, a multitude of environments are thought to have been or to be habitable in our solar system today. Beyond our own star, even more planets have now been identified as orbiting within the so-called habitable zone of their host star system. At Stanford, we strive to assess the habitability of various planetary environments, in our own solar system and beyond, and to understand how the frontiers of life vary with space, time, and chemistry in the universe.
Churning of liquid metal driven by the cooling of planetary cores has produced magnetic fields on the Earth, Moon, Mars, and other bodies at various points in time over Solar System history. Studying magnetic histories preserved in extraterrestrial samples can be used to constrain how magnetic fields were generated within different planetary bodies and constrain how they thermally evolved over time. Because processes such as heating, exposure to high pressures, and hydrothermal activity can reset magnetization within rocks, magnetic methods can also be used to investigate impact cratering processes. At Stanford, we explore planetary magnetism using a combination of paleomagnetic experiments, measurement of rock magnetic properties, and modeling.
Related Faculty: Sonia Tikoo-Schantz
A planet like the Earth is made of more than just the typical materials we see and interact with every day. Deep within the Earth's interior, rocks and metal exist at extraordinarily high temperatures and pressures, which changes their structure and their material properties. New minerals that cannot exist at surface conditions may exist deep within the planet's interior. Knowing the properties of these materials is important to understanding processes like magnetic field generation, plate tectonics, and melting deep within the Earth and other planets. In addition to materials forming in these extreme conditions, crustal rocks help us to decipher the differentiation and surface histories of planetary bodies. At Stanford and SLAC, scientists learn about these materials through extremely high-pressure experiments, numerical modeling, lab analyses of meteorites and moon rocks, and spectral data from planetary orbiters.
Planetary surfaces are shaped by a multitude of processes, both intrinsic to the planet’s workings (e.g., lithospheric, atmospheric, hydrologic, and biologic) and external (e.g., space weathering and impact cratering), over geologic timescales. From ancient river deltas on Mars to the alien hydrocarbon dunes of Titan, planetary landscapes and rocks offer records of the geologic, climate, and habitability history of bodies within our solar system. At Stanford, we seek to decipher those records through planetary exploration, remote sensing, analog field work, and theoretical, numerical, and lab modeling.
Although landed spacecraft provide the most detailed, in situ observations of the planetary bodies within our solar system, the study of global phenomena requires observations to be made over much larger spatial scales than can be achieved with landed assets. Furthermore, remote sensing is the only suitable approach to study planets outside of the Solar System. Remote-sensing instruments, whether ground-based, orbiting, or flying by, permit to bridge these gaps. At Stanford, we explore the surface and subsurface of icy moons with radar, the mineralogy of planetary surfaces using visible-shortwave infrared spectroscopy, and push the boundaries of imaging and spectroscopy of extrasolar planets.
Answering fundamental questions in Earth and planetary science requires advances in space technology in numerous directions. We investigate how to use multiple satellites to build instruments of unprecedented capability such as large virtual telescopes for high-resolution high-contrast imaging or swarms for environmental sampling at various spatial and temporal scales. We conceive and design future space robotic missions and the required algorithms to target active, dynamic, and uncertain environments. Our research addresses safer, more reliable, cheaper alternatives to conventional solid or liquid rockets. Finally, we seek engineering solutions to cope with the exponential proliferation of space objects in Earth’s orbit and with the risks posed by space debris. It is our mission to help answering those questions and thereof help humanity reach new frontiers.