You’re looking at the night sky. Maybe you see that steady, non-twinkling orange dot and realize it’s Mars. You start wondering what it’s actually like down there on the surface—the dust, the ancient volcanoes, the dry lakebeds. If you want to know what the study of the planets is called, you might reflexively say "astronomy." You aren't wrong, but you aren't exactly right either.
Honestly, it’s more specific than that.
While astronomy is the big, sweeping umbrella that covers everything from black holes to the Big Bang, the gritty, boots-on-the-ground (or rover-on-the-ground) research of worlds is known as planetary science or planetology. It’s a messy, beautiful hybrid of geology, atmospheric physics, and chemistry. It’s less about staring through a telescope to find a point of light and more about figuring out why Venus has a "runaway greenhouse effect" or why Saturn’s moon Enceladus is shooting saltwater geysers into space.
Planetary Science is basically Geology with a Passport
Most people don't realize that planetary science didn't really take off as its own distinct beast until the Space Age. Before the 1960s, planets were just fuzzy discs in a viewfinder. Then, we started crashing probes into them. Suddenly, we weren't just observing; we were analyzing soil.
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Take planetary geology, for example. It’s also called exogeology. If you’re studying the rock formations on the Moon or the tectonic shifts on Mercury, you’re basically a geologist who just happens to work on a different zip code. You’re looking at impact craters and trying to date them based on how many other craters have landed on top of them. It’s forensic work on a galactic scale.
Dr. Sarah Stewart, a professor at UC Davis, famously researches how giant impacts shape planets. Her work on "synestias"—huge, donut-shaped masses of vaporized rock—shows that the study of planets isn't just about looking at cold rocks; it's about understanding violent, molten history. This isn't just "looking at stars." It’s physics in the dirt.
Why the Atmosphere Matters More Than You Think
It isn't all rocks. If you’re looking at Jupiter or Neptune, there isn't even a "surface" to stand on in the traditional sense. This is where planetary atmospheres come in.
Scientists in this niche are obsessed with fluid dynamics. They want to know why Jupiter’s Great Red Spot has been spinning for centuries or how Titan (Saturn’s moon) can have clouds, rain, and lakes made of liquid methane. Imagine being a meteorologist, but instead of predicting rain in Seattle, you’re trying to model 1,000-mph winds on Neptune. It’s wild.
The Chemistry of Other Worlds
Then you have cosmochemistry. This is the study of the "stuff" the universe is made of. By analyzing meteorites—which are basically leftover construction scraps from the formation of the solar system—cosmochemists can tell us exactly what was happening 4.5 billion years ago. They look at isotopes. They find amino acids on space rocks. They’re hunting for the chemical precursors to life itself.
Is it Astronomy or Astrophysics?
People get these terms tangled up constantly. Look, astronomy is the oldest science. It’s the broad mapping of the heavens. Astrophysics is the "how" and "why"—the math behind the gravity and the nuclear fusion inside stars.
Planetary science sits right in the middle, but it leans heavily into the "Earth sciences." If you study Earth, you’re a geoscientist. If you apply those same rules to Mars, you’re a planetary scientist. The crossover is so tight that NASA often uses Earth’s own extreme environments—like the Dry Valleys of Antarctica or the acidic Rio Tinto in Spain—as "analog sites" to test how life might survive on other planets.
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The Search for Life (Astrobiology)
We can't talk about the study of planets without mentioning astrobiology. This is the "Is anyone out there?" wing of the field. It’s highly interdisciplinary. You need a biologist to understand the limits of life, a chemist to find the organic molecules, and a planetary scientist to tell you if the planet’s environment is actually habitable.
Think about Europa, Jupiter's moon. We’re almost certain there’s a liquid water ocean under its ice crust. The study of that moon involves planetary science (the ice shell), geophysics (the tidal heating from Jupiter), and astrobiology (the potential for hydrothermal vent life). It’s all connected.
Why This Field is Exploding Right Now
We used to just have eight planets to look at (sorry, Pluto, we still love you). But since the launch of missions like Kepler and now the James Webb Space Telescope (JWST), we’ve discovered thousands of exoplanets—planets orbiting other stars.
This has shifted the study of the planets from a "local neighborhood" hobby to a "galactic census." We are now seeing "Hot Jupiters" that orbit their stars in just a few days and "Super-Earths" that are bigger than our world but smaller than Neptune. Each one of these requires planetary science to understand. We’re literally looking at the light passing through the atmospheres of planets trillions of miles away to see if they have oxygen or water vapor.
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Practical Insights for the Aspiring Space Nerd
If you're actually interested in getting into this, or just want to sound smarter at a dinner party, keep these distinctions in mind:
- Don't call a planetary scientist an "astrologer." Just... don't. That’s horoscopes. They will be annoyed.
- Think in systems. Planetary science is about how a core, a crust, and an atmosphere interact. It’s "Systems Science" on a planetary scale.
- Follow the missions. If you want to see the science in action, follow the Mars Perseverance Rover or the Juno mission at Jupiter. These are the primary tools of modern planetology.
- Look at the moons. Often, the moons are more interesting than the planets they orbit. From the volcanic hellscape of Io to the potential life-harboring oceans of Enceladus, "planetary" science includes any large body that isn't a star.
Real-World Applications
Why spend billions of dollars studying the clouds on Venus or the dust on Mars? It’s not just for fun. Understanding the "runaway greenhouse effect" on Venus helped climate scientists on Earth understand our own atmosphere better. By seeing what happened to a "twin" planet that went wrong, we get a roadmap for preserving our own.
Similarly, studying the history of water on Mars tells us about the long-term evolution of planetary climates. This isn't just abstract trivia. It’s a survival manual for humanity.
Next Steps for Your Journey into the Stars
To dive deeper into planetary science, start by exploring the NASA Planetary Data System (PDS). It is a public archive of data from every NASA mission. You can look at raw images from the surface of Mars or the rings of Saturn.
If you prefer a more structured approach, look into "Comparative Planetology." This is the specific method of comparing different worlds to find universal truths. Reading books like The Planets by Andrew Cohen or following the work of the Planetary Society (founded by Carl Sagan and now led by Bill Nye) will give you a solid foundation in how we explore these distant worlds.
The study of the planets isn't just a niche academic pursuit; it’s the story of where we came from and where we might end up. Whether you call it planetary science, planetology, or exogeology, it remains our best shot at understanding our place in the cosmos.