wunder beta🌗 Moons of the Solar System
Volcanoes on Io, hidden oceans on Europa and Enceladus, methane lakes on Titan — a tour of the strange, active, and maybe-habitable moons circling our Solar System.
What you’ll learn
- Our Moon's Violent BirthUnderstand how the Moon formed, how we know, and why it matters to life on Earth.The giant-impact hypothesis holds that a Mars-sized body called Theia struck the young Earth, and the debris formed the Moon. Apollo rocks support this by matching Earth's composition while lacking volatiles. The airless, cratered Moon drives Earth's tides, stabilizes its tilt, and is slowly drifting away.
- Io: The Volcano MoonLearn why Io is so volcanically active and how tidal heating drives it.Io is the most volcanically active body in the Solar System, its colorful surface constantly repaved by sulfurous eruptions. Tidal heating — Jupiter's gravity flexing the moon as neighboring moons stretch its orbit — melts its interior. Voyager first spotted its erupting plumes in 1979.
- Ocean Worlds: Europa and EnceladusDiscover the hidden oceans of Europa and Enceladus and the evidence they could host life.Europa hides a global saltwater ocean beneath its ice, kept liquid by tidal heating. Enceladus vents plumes of water containing organics and hydrogen, which Cassini flew through and sampled. Both offer water, chemistry, and energy, making them prime targets for missions like Europa Clipper in the search for life.
- Titan: A World Like Early EarthExplore Titan's thick atmosphere, methane cycle, and the Dragonfly mission set to fly across it.Titan is the only moon with a thick, nitrogen-rich atmosphere and the only other world with stable surface liquid — lakes and seas of methane and ethane fed by methane rain. Its organic chemistry resembles the early Earth. NASA's Dragonfly rotorcraft will fly across it in the 2030s to search for life's building blocks.
- Oddball Moons and the CountMeet the oddball moons Triton and Charon and understand how many moons exist and why they matter.Triton orbits Neptune backwards, a captured world that still erupts nitrogen geysers. Charon is so large it makes Pluto a near-double world. Saturn and Jupiter each have over ninety moons, with the total in the hundreds and growing. Moons, once dismissed as dead rocks, are now leading places to search for life.
Questions this course answers
According to the leading theory, how did our Moon form?
The giant-impact hypothesis says a Mars-sized body named Theia struck the young Earth, and the blasted-out debris clumped together to form the Moon.
How does the Moon help stabilize Earth?
The Moon's gravity steadies Earth's tilt at around 23 degrees, preventing chaotic wobbles and giving us reliable seasons, while also driving the tides.
What makes Jupiter's moon Io so unusual?
Io has hundreds of active volcanoes and is the most volcanically active body in the Solar System, constantly repaving itself with fresh lava.
What process powers Io's intense volcanism?
Tidal heating — Jupiter's gravity flexing and squeezing Io as its orbit is stretched by neighboring moons — generates enough internal friction to melt rock.
What did NASA's Voyager spot at Io in 1979?
Voyager caught a volcanic plume erupting from Io — the first active volcano ever observed beyond Earth, which surprised scientists.
What is hidden beneath Europa's icy surface?
Beneath Europa's ice shell lies a global saltwater ocean, kept liquid by tidal heating, possibly holding more water than all of Earth's oceans combined.
Grounded in trusted sources
- NASA Solar System Exploration
- NASA Jet Propulsion Laboratory
- European Space Agency
- The Planetary Society
Every Wunder lesson is built from real, reputable sources — never invented.
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