Miranda: The Jigsaw Puzzle Moon
Miranda is the smallest and innermost of Uranus's five major moons, but it has the most extreme and varied topography in the solar system. The moon's surface is a chaotic jumble of different terrain types—ancient, heavily cratered regions mixed with young, smooth areas, massive canyons, and unique features called "coronae" that are found nowhere else. Verona Rupes, a cliff 20 km high, is the tallest known cliff in the solar system. Miranda's bizarre appearance suggests it may have been shattered by a massive impact and then reassembled, or it may have experienced extreme geological activity. The moon's small size makes such extreme topography even more remarkable. This article explores Miranda's extreme topography, unique geology, possible formation history, and the mysteries that make it one of the most unusual worlds in the solar system.
In Simple Terms
Imagine if you took a jigsaw puzzle, shook it up, and then put it back together in a random way—that's what Miranda looks like. It's the smallest of Uranus's major moons, but it has some of the most dramatic features in the entire solar system. There's a cliff called Verona Rupes that's 20 kilometers tall—that's taller than Mount Everest! If you fell off the top, it would take you 12 minutes to hit the bottom because Miranda's gravity is so weak. Miranda also has strange features called "coronae" that look like giant ovals with ridges and grooves inside them—these don't exist anywhere else in the solar system. Scientists think Miranda might have been completely shattered by a giant collision and then pulled itself back together, which would explain why it looks like a cosmic jigsaw puzzle. Or maybe it had extreme geological activity that reshaped its surface in weird ways. Either way, Miranda is a reminder that even small moons can have incredibly dramatic and mysterious histories.
Abstract
Miranda is the smallest of Uranus's five major moons, with a radius of 236 km and a mass of 6.59 × 10¹⁹ kg. The moon orbits Uranus at 129,390 km, completing an orbit in 1.41 days. Miranda is famous for having the most extreme and varied topography in the solar system, with a chaotic jumble of different terrain types including ancient, heavily cratered regions, young smooth areas, massive canyons, and unique "coronae"—ovoid features with concentric ridges and grooves found nowhere else in the solar system. Verona Rupes, a cliff 20 km high, is the tallest known cliff in the solar system. Miranda's bizarre appearance suggests it may have been shattered by a massive impact and then reassembled, creating the jumbled terrain, or it may have experienced extreme geological activity driven by tidal heating or other processes. The moon's small size makes such extreme topography even more remarkable—features that would be impressive on a large moon are extraordinary on such a small body. Miranda is composed primarily of water ice with a small amount of rock. This article reviews Miranda's extreme topography, unique geology, possible formation history, and exploration by Voyager 2.
Miranda as seen by Voyager 2, showing its chaotic, jumbled surface with extreme topography. Credit: NASA/JPL (Public Domain)
Introduction
Miranda, named after a character in Shakespeare's "The Tempest," was discovered by Gerard Kuiper in 1948. The moon remained a small point of light until Voyager 2's 1986 flyby, which revealed its bizarre, jumbled surface. Miranda's extreme topography immediately captured attention—how could such a small moon have such dramatic features?
Miranda's unique appearance makes it one of the most fascinating worlds in the solar system. Understanding Miranda is important for understanding the processes that can shape small moons, the effects of massive impacts, and the diversity of geological features possible on icy worlds.
Physical Characteristics
Basic Properties
Miranda is a small icy moon:
- Radius: 236 km
- Mass: 6.59 × 10¹⁹ kg
- Density: 1.20 g/cm³ (low, indicating mostly ice)
- Surface gravity: 0.079 m/s² (extremely weak)
- Escape velocity: 0.19 km/s
Miranda's density suggests it's composed of roughly 60% water ice and 40% rock by mass.
Orbit
Miranda orbits close to Uranus:
- Semi-major axis: 129,390 km
- Orbital period: 1.41 Earth days
- Rotation: Synchronous (same face always toward Uranus)
- Eccentricity: 0.0013 (nearly circular)
Extreme Topography
Verona Rupes
Verona Rupes is the tallest known cliff in the solar system:
- Height: 20 km (taller than Mount Everest)
- Type: Fault scarp
- Formation: Created by tectonic activity
- Significance: Extraordinary for such a small moon
A person falling from the top would take 12 minutes to reach the bottom due to Miranda's low gravity.
Coronae
Miranda has three unique "coronae":
- Inverness Corona: Trapezoidal, with concentric ridges
- Arden Corona: Ovoid, with parallel grooves
- Elsinore Corona: Ovoid, with complex patterns
These features are found nowhere else in the solar system and their origin is unknown.
Canyons
Miranda has massive canyons:
- Depth: Up to 20 km
- Width: Tens of kilometers
- Formation: Possibly from extension or impacts
- Age: Relatively young
The canyons are among the deepest in the solar system relative to body size.
Surface Geology
Chaotic Terrain
Miranda's surface is a chaotic jumble:
- Mixed ages: Ancient and young terrain side by side
- No pattern: Terrain types appear randomly distributed
- Extreme contrast: Smooth areas next to heavily cratered regions
- Unique features: Coronae found nowhere else
The chaotic appearance suggests a violent history.
Terrain Types
Miranda shows several distinct terrain types:
- Heavily cratered: Ancient, unchanged for billions of years
- Smooth: Young, possibly resurfaced
- Coronae: Unique ovoid features
- Canyons: Deep, linear features
- Ridges: Linear raised features
The diversity is extraordinary for such a small moon.
Formation Theories
Shattered and Reassembled
Theory: Miranda was shattered by a massive impact and then reassembled.
Evidence:
- Chaotic terrain suggests jumbled pieces
- Different terrain types could be from different parts
- Extreme topography could result from reassembly
Challenges:
- Would expect more mixing
- Reassembly mechanism unclear
Extreme Geological Activity
Theory: Miranda experienced extreme geological activity.
Evidence:
- Young, smooth terrain suggests recent activity
- Canyons and ridges suggest tectonic activity
- Coronae may be from upwelling or other processes
Challenges:
- Small size makes significant activity unlikely
- Energy source unclear
Combination
Theory: Both impact and geological activity occurred.
Evidence:
- Impact could have triggered activity
- Activity could have modified impact effects
- Explains both ancient and young features
This theory is most widely accepted.
Composition
Ice and Rock
Miranda's composition:
- Water ice: Primary component (~60% by mass)
- Rock: Silicate material (~40%)
- Structure: Possibly differentiated (ice shell over rocky core)
The density indicates significant rock content.
Exploration History
Discovery
- 1948: Discovered by Gerard Kuiper
- 1986: Voyager 2 provided only close-up images
Voyager 2 (1986)
Voyager 2's brief encounter revealed:
- Extreme topography
- Chaotic terrain
- Unique coronae
- Verona Rupes
- Complex geology
Voyager 2's data is still being analyzed today.
Scientific Importance
Understanding Small Moons
Miranda provides insights into:
- Small body geology: What processes can occur on small moons
- Impact effects: How massive impacts affect small bodies
- Tectonic activity: How tectonics work on icy moons
- Diversity: Wide range of possible moon properties
Unique Features
Miranda demonstrates:
- Extreme topography: What's possible on small bodies
- Chaotic formation: How bodies can be disrupted and reassembled
- Geological diversity: Wide range of features possible
- Formation processes: Different ways moons can form and evolve
Open Questions
Many mysteries remain about Miranda:
- Formation: How did Miranda acquire its extreme topography?
- Coronae: What created these unique features?
- Chaotic terrain: Why is the terrain so jumbled?
- Past activity: Was Miranda once more active?
- Impact history: Did a massive impact shatter it?
- Future: How will Miranda evolve?
A dedicated mission to Uranus would help answer these questions.
Conclusion
Miranda is one of the most unusual moons in the solar system—a small world with extreme topography that defies easy explanation. Its chaotic, jumbled surface tells a story of violent impacts, possible reassembly, and extreme geological activity. Understanding Miranda is essential for understanding the full range of processes that can shape small moons, the effects of massive impacts, and the diversity of geological features possible on icy worlds. As we plan future missions to Uranus, Miranda stands as a high-priority target that will reveal new insights into one of the most fascinating worlds in the solar system.
For related topics:
- Ariel - Another Uranus moon with interesting geology
- Umbriel - Uranus moon with a dark surface
- Titania - Uranus's largest moon
- Uranus - The ice giant and Miranda's parent world
- Planetary Science & Space - Overview of planetary science topics
^[NASA Solar System Exploration - Miranda] NASA. (2024). Miranda: In Depth. NASA Solar System Exploration. https://solarsystem.nasa.gov/moons/uranus-moons/miranda/in-depth/
^[Miranda Topography] Plescia, J. B. (1987). Cratering history of Miranda: Implications for geologic processes. Icarus, 73(3), 442-461.
^[Miranda Coronae] Croft, S. K., & Soderblom, L. A. (1991). Geology of the Uranian satellites. In Uranus (pp. 561-628). University of Arizona Press.
^[Voyager 2 Miranda] Smith, B. A., et al. (1986). Voyager 2 in the Uranian system: Imaging science results. Science, 233(4759), 43-64.
^[Miranda Formation] Tittemore, W. C., & Wisdom, J. (1990). Tidal evolution of the Uranian satellites: III. Evolution through the Miranda-Umbriel 3:1, Miranda-Ariel 5:3, and Ariel-Umbriel 2:1 mean-motion commensurabilities. Icarus, 85(2), 394-443.
