moons
67 questions tagged moons — spanning every one of the seven Ws.
Which is the largest moon in the solar system?
Ganymede, a moon of Jupiter. At about 5,268 km across, it is even wider than the planet Mercury.
Which Is the Most Volcanically Active Body in the Solar System?
Jupiter's moon Io is the most volcanically active body in the solar system, with more than 400 active volcanoes.
Which moon has a thick atmosphere?
Titan, Saturn's largest moon, is the only moon in the solar system with a thick atmosphere, denser than Earth's.
Which moon sprays water into space?
Saturn's moon Enceladus shoots jets of water vapour and ice grains into space from cracks near its south pole.
Why do Jupiter’s moons Io, Europa, and Ganymede get heated by tidal forces?
Their orbits are squeezed by Jupiter’s gravity and by resonances with one another, which flexes their interiors. That constant flexing turns orbital energy into heat.
What is Titan?
Titan is Saturn’s largest moon and the only moon in the Solar System with a thick atmosphere.
What is Europa?
Europa is a moon of Jupiter that likely has a subsurface ocean beneath its icy crust.
What is Enceladus?
Enceladus is a small icy moon of Saturn that shoots water-rich plumes from its south pole.
Where is Saturn’s moon Titan found?
Titan orbits Saturn, far from the Sun in the outer Solar System. It is Saturn’s largest moon and the second-largest moon in the Solar System.
Where is Europa's subsurface ocean thought to be?
Europa’s ocean is believed to lie beneath its icy crust, which surrounds the moon entirely. The liquid water is not exposed on the surface.
Which volcano is the most volcanically active body in the Solar System?
Io, a moon of Jupiter, is the most volcanically active body in the Solar System. Tidal heating from Jupiter drives constant eruptions and lava flows.
Which moon is the largest in the Solar System?
Ganymede, a moon of Jupiter, is the largest moon in the Solar System, with a diameter of about 5,268 km.
Which moon is volcanically active today?
Io, a moon of Jupiter, is the most volcanically active body in the Solar System. Its surface is covered with hundreds of active volcanoes.
Which planet has the largest moon system in comparison to its size?
Pluto’s moon Charon is unusually large relative to Pluto, with a diameter about half of Pluto’s. The pair is often described as a binary system.
Which planet has the most moons among the inner planets?
Mars has the most moons among the inner planets, with two: Phobos and Deimos.
Which planet has the most confirmed natural satellites among the inner planets?
Mars has the most moons of any inner planet, with 2 known moons: Phobos and Deimos. Earth has 1 and Mercury and Venus have none.
Which moon is the largest moon in the Solar System relative to its planet’s size?
Charon is especially notable because it is unusually large compared with Pluto, but the largest moon overall is Ganymede. Ganymede is bigger than Mercury and has its own magnetic field.
Which planet has the largest known number of moons among the giant planets?
Jupiter has the most known moons among the giant planets, with more than 90 confirmed moons. Saturn has many too, but Jupiter currently leads in confirmed counts.
Which moon has the thickest atmosphere in the Solar System?
Titan, Saturn’s largest moon, has the thickest atmosphere of any moon in the Solar System. Its dense nitrogen-rich air is even thicker at the surface than Earth’s by pressure.
Which moon has the most active volcanoes in the Solar System?
Io, one of Jupiter’s moons, is the most volcanically active world known in the Solar System. Its activity is driven by tidal heating from Jupiter and neighboring moons.
How do astronomers find hidden moons around planets?
They look for small changes in a planet’s motion, rings, or shadow patterns, and sometimes direct images from spacecraft reveal them. Tiny gravitational effects can expose a moon even when it is hard to see.
How do scientists know Io is the most volcanically active world in the Solar System?
Spacecraft images and infrared observations show hundreds of active vents and frequent eruptions. Io’s volcanism is driven by tidal heating from Jupiter and nearby moons.
Why does Jupiter’s moon Io have so many volcanoes?
Io is squeezed by Jupiter’s gravity and the pull of neighboring moons, and that tidal flexing generates enough heat to melt rock inside it.
Why does Europa likely have a subsurface ocean?
Tidal heating from Jupiter keeps Europa’s interior warm enough to maintain a global ocean beneath its icy crust.
Why is Enceladus one of the best places to look for life-supporting chemistry?
Its south polar geysers喷 out water-rich plumes from a subsurface ocean, carrying salts and organic compounds into space.
Why is Titan’s atmosphere so thick compared with most moons?
Titan is cold enough to retain gases, and it may have been supplied with nitrogen and methane over time. Its gravity is strong enough, for its size, to hold a dense atmosphere.
Why does Europa likely hide a global ocean beneath its ice?
Jupiter’s gravity flexes Europa and generates internal heat, which can keep water beneath the surface liquid. Surface features also suggest the ice shell may be floating over a salty ocean.
Why does Enceladus spray water ice into space?
Saturn’s gravity and tidal forces heat Enceladus’s interior, powering geysers that erupt through cracks near the south pole. The plumes likely come from a subsurface ocean.
What is a moon in the Solar System?
A moon is a natural satellite that orbits a planet, dwarf planet, or other body.
When was Saturn’s moon Enceladus discovered?
Enceladus was discovered on 28 August 1789.
When was Jupiter’s moon Ganymede discovered?
Ganymede was discovered on 7 January 1610.
Where is Io’s volcanic activity concentrated?
Io’s volcanism is spread across the moon’s surface, but many of its most active volcanoes cluster near the equator. Io is the most volcanically active body in the Solar System.
Where is Europa’s likely subsurface ocean thought to be located?
Europa’s ocean is believed to lie beneath a thick icy shell on the moon orbiting Jupiter. It may contain more water than all of Earth’s oceans combined.
Where is Enceladus’s water plume source located?
Enceladus’s geyser-like plumes come from fractures near its south pole. They spray water ice and vapor into space.
Which moon is the most volcanically active world in the Solar System?
Io, a moon of Jupiter, is the most volcanically active body in the Solar System. Hundreds of volcanoes are active there because of intense tidal heating.
Which moon has the thickest atmosphere?
Titan, Saturn's largest moon, has the thickest atmosphere of any moon. Its nitrogen-rich atmosphere is denser than Earth's at the surface.
Which moon is the most volcanically active body in the Solar System?
Jupiter’s moon Io is the most volcanically active world in the Solar System. Its surface is continually reshaped by hundreds of volcanoes.
Whose mission first confirmed the presence of methane lakes on Titan?
NASA’s Cassini mission. It detected large liquid hydrocarbon lakes and seas on Titan in the 2000s.
Whose spacecraft first discovered active volcanoes on Io?
NASA’s Voyager 1. In 1979 it found active volcanism on Jupiter’s moon Io.
How do astronomers discover moons around distant planets?
They look for small changes in a planet’s light, motion, or the shadows and transits caused by a moon. In some cases, moons are discovered by imaging, but many are found indirectly.
How do Jupiter's moon Io's volcanoes erupt so intensely?
Io’s volcanoes are driven by tidal heating: Jupiter and the nearby moons constantly flex Io, generating enough friction to melt rock inside it.
How do scientists know Europa may have a global ocean under its ice?
They use gravity measurements, magnetic data, and surface cracking patterns to infer a salty ocean beneath Europa’s icy shell.
How does Saturn's moon Titan have rivers and lakes without liquid water on the surface?
Titan is cold enough for methane and ethane to be liquids, so it has hydrocarbon rain, rivers, and lakes instead of water-based ones.
Why do the Galilean moons of Jupiter have such different surfaces?
Each moon experiences a different mix of heating, geology and radiation. Io is volcanic, Europa is icy, Ganymede is cratered and Callisto is ancient and heavily battered.
Why does Io have so many volcanoes?
Io is heated by tidal flexing from Jupiter and orbital resonances with Europa and Ganymede. That constant squeezing melts rock and fuels hundreds of volcanoes.
Why is Europa considered one of the best places to search for alien life?
Europa likely has a global subsurface ocean beneath its ice shell, kept liquid by tidal heating. Liquid water, chemical energy and rock-interaction make it a prime target.
Why does Titan have lakes and rain, even though it is so cold?
Titan's temperature is low enough for methane and ethane to behave like water does on Earth. That lets it have clouds, rain, rivers and lakes of liquid hydrocarbons.
Why does Triton orbit Neptune backward?
Triton is likely a captured object from the Kuiper Belt, not a moon that formed with Neptune. Its retrograde orbit suggests it was pulled in later.
Why does the Solar System have so many moons around the giant planets?
The giant planets formed with large disks of material around them and had enough gravity to capture many objects. Their strong gravity also helped keep those moons in place.
What is a hydrocarbon lake?
A hydrocarbon lake is a lake of liquid methane and ethane rather than water. Titan, Saturn’s largest moon, is the best-known world with them.
What is cryovolcanism?
Cryovolcanism is the eruption of icy or slushy material instead of molten rock. It is seen or suspected on bodies such as Enceladus and Triton.
What is a galilean moon?
A Galilean moon is one of the four large moons of Jupiter discovered by Galileo in 1610. They are Io, Europa, Ganymede and Callisto.
Where is Europa’s likely subsurface ocean located?
Europa’s ocean is believed to lie beneath its icy crust. It surrounds the moon of Jupiter and may contain more water than all of Earth’s oceans combined.
Where on Ganymede is the Galileo Regio region found?
Galileo Regio is a dark region on Ganymede, Jupiter’s largest moon. It is one of the moon’s oldest and most heavily cratered areas.
Where is Io’s most active volcanic region located?
Io’s intense volcanic activity is spread across its surface, but the moon’s most famous active hotspots are in its equatorial and mid-latitude regions. Io orbits Jupiter and is the most volcanically active body in the Solar System.
Where is Titan’s methane lake region found?
Titan’s methane lakes are mainly near its north pole, with many also in the south polar region. Titan is Saturn’s largest moon.
Where is Triton’s geyser activity located?
Triton’s geysers were observed near its south polar region. Triton is Neptune’s largest moon.
Which moon is the most volcanically active in the solar system?
Io, one of Jupiter’s moons, is the most volcanically active body in the solar system. Tidal heating from Jupiter drives constant eruptions.
Which moon has the thickest atmosphere among the moons in the solar system?
Titan, Saturn’s largest moon, has the thickest atmosphere of any moon. Its atmosphere is mostly nitrogen and is denser than Earth’s atmosphere at the surface.
Which moon is the most volcanically active?
Io, one of Jupiter’s moons, is the most volcanically active body in the Solar System. It has hundreds of active volcanoes driven by tidal heating.
Which moon is the only one known to have stable surface liquid methane lakes and seas?
Titan is the only moon known to have stable lakes and seas on its surface, and they are made of liquid methane and ethane. These bodies of liquid are concentrated near its poles.
Which moon is the most volcanically active object in the Solar System?
Io, one of Jupiter’s moons, is the most volcanically active body in the Solar System. It has hundreds of active volcanic centers driven by tidal heating.
Whose observations first revealed that Jupiter has four large moons?
Galileo Galilei discovered Io, Europa, Ganymede and Callisto in January 1610. They were the first moons found orbiting another planet.
How do moons help reveal whether a planet has oceans under its surface?
A moon's gravity can create tides and flexing that generate heat, which may keep a hidden ocean liquid.