Slice open all eight planets and see what is actually inside - click a planet button, then click a layer in the cutaway to read its composition and how confidently scientists know it.
Every planet is drawn on one shared size scale (Jupiter as the largest reference), so the true size difference between a rocky world's iron core and a gas giant's fuzzy core is visible at a glance. Layers marked MEASURED come from an instrument that directly probed the interior - InSight's seismometer on Mars, decades of seismographs on Earth. Layers marked MODELED ESTIMATE come from gravity-field data (Juno at Jupiter, Cassini's Grand Finale at Saturn) or mass/moment-of-inertia calculations, not a direct probe.
Planet Interior Cutaways 3D Explorer
FreetoolOnline editorial teamPick any of the eight planets and see a half-sphere cutaway of its crust, mantle, and core - click a layer to read what it is made of and whether the boundary was directly measured or modeled.
Drag to orbit the cutaway, scroll or pinch to zoom, and click any layer to open its composition note in the facts panel. Switching planets rebuilds the cutaway on the same shared size scale, so a rocky world's small iron core and a gas giant's huge, fuzzy core are directly comparable.
- All eight planets, each with its own layer stack (2-3 layers depending on how well its interior is known)
- Click-to-inspect layers with a composition note and a MEASURED / MODELED ESTIMATE evidence badge
- Mars and Earth layers trace to real seismometer data - InSight (2021) for Mars, decades of seismographs for Earth
- Jupiter and Saturn's fuzzy cores trace to gravity-field science from the Juno and Cassini Grand Finale missions
- Runs fully in the browser with the vendored three.js engine - no account, no upload
Mercury's core reaches about 83 percent of its total radius - the largest core-to-planet ratio in the solar system - while Earth's solid inner core, radius about 1,220 km, stays solid at temperatures that would melt iron anywhere else because of the crushing pressure. Mars's InSight mission measured a liquid core radius of about 1,830 km in 2021, bigger and lighter than earlier models predicted. Jupiter and Saturn do not have a sharp rocky ball at the center at all - Juno and Cassini gravity data both point to a large, diffuse "fuzzy" core where heavy elements mix gradually into the surrounding metallic hydrogen instead of settling into a hard boundary.
| Planet | Core (or deepest layer) extent | Evidence |
|---|---|---|
| Mercury | ~83% of radius | MESSENGER gravity + moment of inertia |
| Earth | Inner core radius ~1,220 km | Seismology (measured) |
| Mars | Liquid core radius ~1,830 km | InSight seismology, 2021 (measured) |
| Jupiter | Diffuse core ~15% of radius | Juno gravity science, 2017-2021 |
| Saturn | Diffuse core ~15% of radius | Cassini Grand Finale gravity science, 2019 |
Everything renders on your device with WebGL. The 3D engine loads once (about 0.7 MB) and is cached; no scene data is sent to a server.
The scene is an educational approximation, not a physical simulation - layer boundaries are drawn from published missions and interior models, but Venus, Uranus, and Neptune have never had a seismometer or a close gravity-science orbiter, so their layer boundaries are the least certain of the eight and are labeled MODELED ESTIMATE throughout.
For a step-by-step walkthrough, read the Planet Interior Cutaways 3D Explorer step-by-step guide. The Space 3D collection also includes a Planet Size Comparison 3D Explorer for comparing outer sizes and a Sun Structure 3D Explorer for the Sun's own interior layers.
Frequently Asked Questions
What does Planet Interior Cutaways 3D Explorer show?
A half-sphere cutaway of any of the eight planets, layer by layer - crust, mantle, and core. Pick a planet button, then click a layer in the 3D view (or read the table) to see its composition, depth, and how confidently the boundary is known.
How is this different from Planet Size Comparison 3D Explorer?
Planet Size Comparison lines up whole spheres by outer radius. This explorer cuts each planet open to show what is INSIDE - the crust, mantle, and core layers and how deep each one starts.
What does MEASURED vs MODELED ESTIMATE mean?
MEASURED means an instrument directly probed the interior - InSight's seismometer on Mars (2021) or decades of seismographs on Earth. MODELED ESTIMATE means the boundary comes from gravity-field data (Juno at Jupiter, Cassini's Grand Finale at Saturn) or mass and moment-of-inertia calculations, not a direct probe.
Why don't Jupiter and Saturn have a sharp rocky core?
Juno's and Cassini's gravity-science passes both found that heavy elements are diffused into the surrounding metallic hydrogen over a large region instead of settling into a hard boundary - scientists call it a "dilute" or "fuzzy" core.
Which planet has the largest core relative to its size?
Mercury. Its iron-rich core reaches about 83 percent of the planet's total radius, the largest core-to-planet-radius ratio of any planet in the solar system.
Is this a physical simulation?
No. It is an educational approximation built from published mission data and interior models, not a solver. Venus, Uranus, and Neptune have never had a seismometer or close gravity-science orbiter, so their layer boundaries are the least certain of the eight.