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Explore Uranus

Discover the mysteries of the Sideways Ice Giant, from its tilted cyan clouds and ghostly rings to the frozen moons that circle its frigid skies, and trace humanity’s quest to unveil the secrets of this distant, enigmatic world.

2.9B km
Distance from Sun
50,724 km
Diameter
-224°C
Temperature
30,688 Earth days
Year Length

Physical Characteristics

Bulk Composition

Uranus has no solid surface—its visible “surface” is a frigid cloud deck of hydrogen, helium, and methane. Deeper inside, an “icy” mantle of water, ammonia, and methane surrounds a rocky core.

Hydrogen (H₂)~82%
Helium (He)~15%
Methane (CH₄)~2–3%

Atmosphere

Uranus’ atmosphere is dominated by hydrogen and helium, tinted cyan by trace methane that absorbs red light. High-altitude haze layers and faint cloud bands drift in temperatures near –224 °C.

Hydrogen (H₂)~82%
Helium (He)~15%
Methane (CH₄)~2–3%

Gravity

Despite being four times Earth’s diameter, Uranus’ low density gives it a surface gravity only slightly weaker than Earth’s. A 100 kg person on Earth would weigh about 89 kg on Uranus.

Earth
100 kg
Uranus
89 kg
Gravity ≈ 0.89 g (8.7 m/s²)

Day Length

Uranus spins once every 17 h 14 m—but on its side. Its 98° axial tilt means it essentially rolls around the Sun, producing extreme seasons lasting decades.

24 h 00 m
17 h 14 m
Rapid retrograde rotation with an extreme axial tilt

Atmospheric & Ring Features

Uranus rings and cloud bands
Feature:
Epsilon Ring
Uranus lacks a solid surface—observed landmarks exist in its atmosphere or ring system.

Notable Phenomena

Polar Hoods

Bright methane-ice haze caps appear over each pole during summer, reflecting sunlight and giving the planet a softly glowing crown.

Linked to the planet’s extreme 98° axial tilt

Transient Dark Spots

Voyager 2 discovered a “Great Dark Spot” in 1986; Hubble has since watched similar storm vortices form and fade in Uranus’s upper clouds.

Storm widths can exceed 3,000 km

Narrow Ring System

Thirteen ultra-dark, razor-thin rings—dominated by the dense ε-ring—encircle Uranus, shepherded by tiny moons like Cordelia and Ophelia.

Rings likely formed from moonlet collisions

Uranus’ Moons

Titania

Titania

Diameter
1 578 km (981 mi)
Orbital Period
8.71 days
Distance from Uranus
435 910 km (271 000 mi)
Discovery
W. Herschel, 1787

Largest Uranian moon; scarred by canyons hundreds of kilometers long, hinting at ancient tectonic activity.

Oberon

Oberon

Diameter
1 523 km (947 mi)
Orbital Period
13.46 days
Distance from Uranus
583 520 km (362 000 mi)
Discovery
W. Herschel, 1787

The outermost big moon, heavily cratered with bright ejecta rays that stand out against its dark surface ice.

Ariel

Ariel

Diameter
1 158 km (720 mi)
Orbital Period
2.52 days
Distance from Uranus
191 020 km (119 000 mi)
Discovery
W. Lassell, 1851

Brightest major moon with intricate networks of fault valleys suggesting relatively recent resurfacing.

Miranda

Miranda

Diameter
471 km (293 mi)
Orbital Period
1.41 days
Distance from Uranus
129 390 km (80 400 mi)
Discovery
G. Kuiper, 1948

Features 20-km-high cliffs and patchwork “coronae,” making it one of the most bizarre landscapes in the Solar System.

Orbital Comparison

Origin Theory

The major moons of Uranus likely coalesced from a disk of debris created after a giant impact tilted the planet on its side. Their mixed ice-rock composition supports an origin from Uranus’s own material rather than captured objects.

Future Exploration

The Uranus Orbiter & Probe mission—top priority of NASA’s 2023 Planetary Decadal Survey—aims for a launch in the early 2030s. It would conduct multiple close flybys of Ariel, Miranda, Titania, and Oberon, mapping their geology and searching for subsurface oceans.

Uranus Exploration History

1970s
First Flyby
Voyager 2

Voyager 2

January 24, 1986

Voyager 2 remains the only spacecraft ever to visit Uranus. During its historic fly-by it discovered 11 new moons, imaged dark rings, and revealed a magnetic field tilted 59° from the planet’s rotation axis.

First Flyby 11 New Moons NASA
No missions available for this category.

Current Uranus Missions

No Active or En-Route Missions

As of 2025, no spacecraft are operating at Uranus or heading there. The planet’s only close visit was Voyager 2 on 24 January 1986.

NASA’s proposed Uranus Orbiter & Probe flagship—endorsed by the 2023 Planetary Decadal Survey—is still in formulation, targeting a mid-2030s launch but not yet approved. Until then, Uranus awaits its next explorer.

Future Uranus Exploration

Upcoming Missions

Uranus Orbiter & Probe (UOP)

Launch mid-2030s → Arrival ~2044

Top flagship priority of the 2023 Planetary Decadal Survey: a long-lived orbiter paired with an atmospheric entry probe to study Uranus’ interior, rings, moons and extreme magnetosphere.

NASA Flagship mission under formulation

Uranus Pathfinder

Concept: 2030s launch

An ESA medium-class mission concept to orbit Uranus for three years, mapping the magnetic field, sampling the plasma environment and conducting close fly-bys of the major moons.

ESA–NASA M-class study

Ice-Giant Atmospheric Probe

2030s Proposal

A joint NASA-ESA concept for a one-hour descent through Uranus’ cloud tops to directly measure noble gases, isotopes and cloud chemistry—key to constraining planet-formation models.

Stand-alone entry probe with relay carrier

Long-Term Visions

Looking toward the 2040s–2050s, scientists are sketching out bold concepts that could push Uranus exploration even further:

  • Ariel & Miranda Landers to investigate youthful tectonics and search for potential cryovolcanic activity.
  • Ring-Plane Skimmer spacecraft flying within thousands of kilometres of the faint rings to map their composition and micro-structure.
  • Upper-Atmosphere Balloon drifting with the 300 km-h zonal winds to profile temperature, aerosols and trace-gas chemistry over seasons.
  • CubeSat Swarm released during orbital tour for multipoint magnetosphere and auroral studies.

Challenges & Solutions

Cryogenic Temperatures

Uranus’ cloud-top temperatures hover near –220 °C, stressing batteries, lubricants and structural materials.

Potential Solutions:
  • MMRTGs & RHUs for constant heat
  • Low-temperature electronics & aerogels
  • Active thermal cycling during cruise

Ring & Debris Hazards

Uranus has narrow, dark rings and abundant moonlet debris that orbiters must traverse during insertion and tour phases.

Potential Solutions:
  • High-inclination approach trajectories
  • Dust-shield Whipple panels on spacecraft noses
  • Real-time stellar-occultation mapping of ring density

Low Solar Power

At 19.8 AU the Sun’s intensity is just 0.25 % of Earth’s, making solar panels largely impractical for primary power.

Potential Solutions:
  • Next-generation MMRTGs for continuous watt-level output
  • Very-large-area, high-efficiency solar arrays for secondary systems
  • Hybrid power with advanced Li-S batteries

Mars Image Gallery

Voyager 2 Global Portrait

Voyager 2 Global Portrait

The only close-range, true-colour view of Uranus, taken ~81,000 km away during the 1986 fly-by. The faint rings were brightened here to show their structure.

JWST 2023 Rings & Polar Cap

JWST 2023 Rings & Polar Cap

Perseverance Rover, Jezero Crater

Hubble 2014 Storm Belts

Hubble 2014 Storm Belts

A string of giant methane-ice storms stripped across the planet’s mid-latitudes; Hubble caught the outbursts glowing cyan.

Keck Infra-Red Aurora

Keck Infra-Red Aurora

Adaptive-optics on the Keck II telescope picked up a southern auroral oval (false-colour green), pinpointing Uranus’ wildly tilted magnetic axis.

Ariel’s Fractured Ice

Ariel’s Fractured Ice

Voyager 2’s high-res mosaic of moon Ariel shows fresh tectonic canyons cutting through older impact scars—evidence of internal activity.

Voyager 2 Infra-Red Composite

Voyager 2 Infra-Red Composite

A processed three-filter view exaggerates high-altitude hazes (pink) and a warmer equator—one of the earliest multi-spectral looks inside the frigid atmosphere.

Hubble Rings & Moons Composite

Hubble Rings & Moons Composite

By stacking long exposures, Hubble revealed two new outer rings and faint shepherd moons—proof the Uranian system is more dynamic than once thought.

Keck 2011 Storm Cluster

Keck 2011 Storm Cluster

Earth-based near-IR images resolved multiple bright storm cells and traced winds exceeding 360 km h-¹, confirming powerful seasonal convection.