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Planetary science is the scientific study of the planets, moons, rings, asteroids, comets and other bodies of the Solar System, along with the planets orbiting other stars, and of the processes that formed and changed them. It asks how worlds form, why they differ so much from one another, how their surfaces, interiors and atmospheres evolve, and what that implies for the history of the Earth. It is sometimes called planetary sciences, in the plural, because no single method defines it. The field is a meeting point for geology, chemistry, physics, atmospheric science and astronomy, applied to objects that are mostly studied from a distance, by spacecraft, or through the small amount of material that reaches laboratories on Earth.
What planetary science covers
The subject is defined by its targets rather than by a single technique. A planetary scientist might spend a career on one volcanic moon, on the chemistry of a class of meteorites, or on a modeling code for atmospheric circulation. Core questions include:
- Formation: how dust and gas around a young star became planets, moons and small bodies, and how the giant planets and the inner rocky planets came to differ.
- Evolution: how interiors differentiate, how surfaces are reshaped by impacts, volcanism, tectonics, ice and wind, and how atmospheres are gained and lost.
- Diversity: why Earth, Mars, Venus, Mercury and the Moon, and the moons of Jupiter and Saturn, ended up so different.
- Habitability: which environments could have supported liquid water and the other ingredients of life. This is where the field meets astrobiology.
- Extrasolar planets: what planets around other stars are like, increasingly studied with the same physical and chemical tools.
How planetary science relates to neighboring fields
Planetary science overlaps with several established disciplines but is not reducible to any of them. Astronomy and astrophysics find and characterize stars and planets, and many planetary scientists are trained as astronomers. Geology supplies the vocabulary for rocks, landforms and stratigraphy, which planetary geologists apply to other worlds. Geophysics and seismology provide the tools for probing interiors. Mineralogy underpins the analysis of meteorites and returned samples, and remote sensing is the main way surfaces and atmospheres are measured. Astrobiology asks whether other worlds could host life, while planetary science describes the worlds themselves. Engineering fields such as aerospace engineering and robotics build the spacecraft and rovers that make most of the observations possible.
Major subfields
Planetary geology and geophysics
Planetary geology reads the histories of solid bodies from their surfaces. Its evidence includes impact crater populations, which are used to estimate relative surface ages, volcanic and tectonic landforms, the signatures of past water, and the layering of sediments on Mars. Geophysics adds gravity, magnetic and topographic data, and where available seismic data, to constrain interior structure such as core size and crustal thickness. Geologic mapping, done by interpreting images and spectra, is a core craft of the field.
Planetary atmospheres
Atmospheric scientists study composition, structure, dynamics and escape on bodies from Venus and Mars to Titan and the giant planets. Questions include how atmospheres are lost to space over time, how clouds and hazes form, how winds are driven, and how climates have changed. The methods draw on spectroscopy, radio occultation, in situ probes and numerical models, many of them adapted from Earth atmospheric science.
Small bodies: asteroids, comets and the outer Solar System
Asteroids, comets, Kuiper belt objects and dwarf planets preserve material that has changed less than the large planets. Studying them addresses the early Solar System, the delivery of water and organics to the inner planets, and impact hazards. Small-body research combines telescopic surveys, spacecraft encounters, and laboratory work on meteorites, which are fragments of asteroids and a few larger bodies that fall to Earth.
Cosmochemistry and meteoritics
Cosmochemistry applies chemistry and isotope measurements to extraterrestrial material to learn about the composition and timing of Solar System formation. Analyses include elemental and mineral composition, isotopic ratios used for dating, and the survey of tiny presolar grains. It is a laboratory-heavy subfield, and it is closely tied to meteoritics, the study of meteorites. Its instruments, such as mass spectrometers and electron microprobes, are the same ones used in terrestrial geochemistry and mineralogy.
Planetary interiors, rings, moons and magnetospheres
Other subfields model how planets differentiate and generate heat, how tides shape moons, how rings evolve, and how magnetic fields interact with the solar wind. Ocean worlds, meaning icy moons thought to harbor subsurface liquid water, are a major area of current mission planning and overlap strongly with habitability research.
Methods and tools
- Remote sensing: imaging, spectroscopy, radar, laser altimetry and thermal mapping from orbiters and flyby spacecraft, plus ground-based and space telescopes.
- In situ exploration: landers, rovers and atmospheric probes carrying cameras, spectrometers and chemical analyzers.
- Sample analysis: laboratory study of meteorites, lunar samples from the Apollo program, and material returned by robotic missions, using high-precision isotopic and microscopic techniques that cannot be flown.
- Laboratory experiments: measurements of how minerals, ices and gases behave under the temperatures, pressures and radiation of other worlds.
- Numerical modeling: simulations of impacts, interior convection, orbital dynamics, atmospheric circulation and planet formation.
- Terrestrial analogs and fieldwork: studying impact craters, volcanic fields, deserts and polar regions on Earth to interpret features seen elsewhere.
Missions and sample return
Most planetary data come from spacecraft, and mission design is therefore a central part of the field. Missions are usually grouped by how they reach their target: flybys, orbiters, landers and rovers, and sample return. Sample return missions bring material back to Earth so it can be analyzed with laboratory instruments far more capable than anything that can be flown. Examples of completed sample returns include the Apollo missions, which returned lunar rock and soil between 1969 and 1972; JAXA’s Hayabusa2, which returned material from the asteroid Ryugu in December 2020; China’s Chang’e-5, which returned lunar material in December 2020; and NASA’s OSIRIS-REx, whose capsule delivered material from the asteroid Bennu in September 2023. Sample return is expensive and slow, which is why returned samples are curated and distributed to many laboratories over decades. Plans for returning samples from Mars have been repeatedly reworked, so consult NASA’s current announcements rather than any fixed schedule.
Mission results are reported in stages: first data releases, then peer-reviewed papers, and then reanalysis as methods improve. Early press interpretations are often revised, so careful writing about planetary results distinguishes what an instrument measured from what scientists infer from it.
A short history of the discipline
Telescopic study of the planets goes back to the early 17th century, and for centuries it was a branch of astronomy. The modern field took shape with the space age. The first spacecraft flybys and orbiters of the Moon, Venus, Mars and the outer planets in the 1960s and 1970s turned planets from points of light into places with geology. The Apollo program, with human exploration and returned samples, brought rigorous geology and geochemistry into the work, and the Lunar and Planetary Science Conference has been held annually since 1970. Later decades added missions to the outer planets and their moons, Mars rovers and orbiters, small-body encounters and sample returns, and the discovery of thousands of planets around other stars, which widened the field’s scope. National Academies decadal surveys now set the priorities that guide U.S. mission selection every ten years; the most recent one covers 2023 to 2032 and is titled Origins, Worlds, and Life.
Funders and programs
NASA
The principal U.S. funder is NASA’s Planetary Science Division, which sits within the Science Mission Directorate and supports both flight missions and research. Research grants are solicited through ROSES, Research Opportunities in Space and Earth Sciences, an annual omnibus solicitation. Within ROSES, the planetary science programs are collected in Appendix C, which includes the Solar System Science program (C.2). Program element names and numbers change from year to year, so applicants should always check the current ROSES text and each element’s own due date and eligibility rules. For a worked example of a NASA-funded fellowship program, see NASA FINESST.
Other funders
Planetary scientists also draw on the National Science Foundation, particularly for ground-based astronomy and geochemistry, and on international space agencies such as ESA, JAXA and the national agencies of other countries. University startup funds, private foundations and mission-team budgets complete the picture. A grant proposal in this field often has to combine a science case with a data-management and archiving plan, which connects directly to the next section.
Data archiving: the Planetary Data System
NASA requires data from its planetary missions to be archived in the Planetary Data System, known as the PDS. The PDS is a distributed archive organized into discipline-focused science nodes, including atmospheres, geosciences, imaging, planetary plasma interactions, and rings and small bodies, plus a navigation node, with project management at NASA’s Goddard Space Flight Center. Its role is to preserve well-documented, peer-reviewed data so that later researchers can reuse them. Our NASA Planetary Data System guide covers how the archive works. Exoplanet data have their own archive; see the NASA Exoplanet Archive guide.
Societies, conferences and journals
The two largest U.S. meetings serve slightly different communities. The Lunar and Planetary Science Conference (LPSC) is held every March near Houston, Texas, jointly sponsored by the Lunar and Planetary Institute and NASA Johnson Space Center, and it draws many geologists, geochemists and geophysicists who study solid surfaces. The Division for Planetary Sciences (DPS) of the American Astronomical Society meets each October; its 58th meeting is scheduled for October 25 to 30, 2026 in Spokane, Washington, and its membership leans toward astronomers and atmospheric scientists. The Meteoritical Society serves the meteorite and cosmochemistry community, and the Planetary Geology Division of the Geological Society of America serves geologists. Leading journals include Icarus, the Journal of Geophysical Research: Planets, Meteoritics and Planetary Science, and The Planetary Science Journal. Many planetary results also appear first as abstracts at LPSC and DPS, which are citable but not peer reviewed in the same way as journal articles.
Training and careers
There is no single undergraduate route. Most planetary scientists hold a degree in geology, physics, astronomy, chemistry or atmospheric science and specialize at the graduate level; a few universities offer dedicated planetary science programs, and many more offer it as a concentration within earth or physics departments. Typical stages are a doctoral degree, one or more postdoctoral appointments, often on a funded mission team or through a fellowship, and then a faculty, research scientist, or government laboratory position. Employers include universities, NASA centers, the Jet Propulsion Laboratory, the Johns Hopkins Applied Physics Laboratory, the Lunar and Planetary Institute, the Planetary Science Institute and other research institutes, and industry partners that build instruments and spacecraft. Skills in programming, data analysis, geospatial software and instrument development are valued across all of these.
Planetary science and research administration
For research administrators, the field has several recognizable features. Funding flows through large, recurring federal solicitations with many program elements, strict page limits and fixed deadlines. Mission-based work involves teams spread across many institutions, so subawards, effort reporting and authorship questions are common. Data-sharing obligations are built into mission and grant terms, with archiving to the PDS as a standard expectation. Export control and international collaboration rules can apply to instrument hardware and some technical data. Returned samples add curation and loan procedures that sit outside the ordinary grant lifecycle. Offices that support these proposals benefit from knowing the ROSES calendar and the archive requirements before a proposal is drafted.
Frequently asked questions
What is planetary science in simple terms?
It is the study of planets, moons, asteroids, comets and the other objects in the Solar System and around other stars, including how they formed, what they are made of, and how they change.
Is planetary science the same as astronomy?
No. Astronomy is the broader study of everything beyond Earth, including stars and galaxies. Planetary science focuses on planets and smaller bodies and draws as much on geology and chemistry as on astronomy.
What is cosmochemistry?
Cosmochemistry is the chemical analysis of extraterrestrial materials, mainly meteorites and returned samples, to learn about the composition and age of the Solar System.
What is the difference between LPSC and DPS?
LPSC is a March conference near Houston that leans toward geology and geochemistry. DPS is the October meeting of the American Astronomical Society’s Division for Planetary Sciences and leans toward astronomy and atmospheres. Many researchers attend both.
Where are planetary mission data stored?
NASA mission data are archived in the Planetary Data System. See the PDS guide for details.
How is planetary science funded in the United States?
Mainly by NASA’s Planetary Science Division, through mission funding and research grants solicited in ROSES Appendix C, with additional support from the National Science Foundation and other sources.
How do I become a planetary scientist?
Study geology, physics, astronomy, chemistry or a related field, get research experience early, and pursue a PhD with a planetary focus, followed by postdoctoral work.
Does planetary science search for life?
Assessing habitability is part of the field, but searching for life and its chemical traces is the focus of astrobiology. No life beyond Earth has been confirmed.
