The Moons of The Moons of Our Solar SystemOur Solar System

How many moons are in our solar system?

1? 9? 61? 159?

159 and counting!

Moons of the Inner Planets

MercuryMercury = 0 = 0

Venus = 0

Earth = 1, The Moon

Mars = 2, Phobos & Deimos

Moons of the Outer Planets

Jupiter = 63, including Callisto, Io, Europa, Ganymede

Saturn = 56, including Titan, Enceladus, Dione, Pan

Uranus = 27, including Ariel, Titania, Puck, Oberon

Neptune = 13, including Triton, Galatea, Larissa

Pluto = 3, Charon, Nix, Hydra

Comparing the Moons with Earth

The Earth’s Moon 384,403 km (238,857 mi) from 384,403 km (238,857 mi) from

Earth & 3,476 km (2,160 mi) in Earth & 3,476 km (2,160 mi) in diameterdiameter

27 days, 7 hours, 43 minutes for 27 days, 7 hours, 43 minutes for rotation and revolution around rotation and revolution around the Earththe Earth

Earth’s gravity keeps the same Earth’s gravity keeps the same face of the moon permanently face of the moon permanently turned toward usturned toward us

The Earth’s Moon It’s the only other place in the Solar System It’s the only other place in the Solar System

that humans have visited.that humans have visited. Recently, water ice was discovered at the Recently, water ice was discovered at the

poles underneath the dusty, cratered surfacepoles underneath the dusty, cratered surface A “blue moon” is a second full moon in 1 A “blue moon” is a second full moon in 1

month, & occurs every few yearsmonth, & occurs every few years

The Earth’s Moon along with Jupiter & 4 of its moons

The Moons of Mars Mars has 2 moons: Phobos & DeimosMars has 2 moons: Phobos & Deimos In Greek, Phobos means “fear” & Deimos means In Greek, Phobos means “fear” & Deimos means

“dread”; they are the sons of Mars, the god of “dread”; they are the sons of Mars, the god of warwar

These moons are heavily cratered & probably These moons are heavily cratered & probably captured objectscaptured objects

The Moons of MarsPhobos is 27 km (17 mi) wide and Phobos is 27 km (17 mi) wide and

completes its orbit of Mars in 8 hours completes its orbit of Mars in 8 hours Deimos, at 14 km (9 mi), is one of the Deimos, at 14 km (9 mi), is one of the

smallest moons in the Solar System smallest moons in the Solar System

Phobos Deimos

The Moons of Jupiter

Jupiter has 63 moons & thousands of small Jupiter has 63 moons & thousands of small objects orbiting itobjects orbiting it

Scientists refer to it as a “mini Solar System”Scientists refer to it as a “mini Solar System”

Jupiter with its moon, Io

The Moons of Jupiter In 1610, Galileo was the first person to In 1610, Galileo was the first person to

discover the largest moons of Jupiter: discover the largest moons of Jupiter: Ganymede, Callisto, Io, and Europa Ganymede, Callisto, Io, and Europa

Since then, several spacecraft have Since then, several spacecraft have examined these “Galilean Satellites” closelyexamined these “Galilean Satellites” closely

Ganymede Callisto Io Europa

The Moons of Saturn

Saturn has 56 moons Saturn has 56 moons The Cassini spacecraft discovered 12 new The Cassini spacecraft discovered 12 new

moons orbiting the planet in 2005 alonemoons orbiting the planet in 2005 alone

Saturn Cassini spacecraft

The Moons of Saturn Saturn’s moons vary greatly in size & shapeSaturn’s moons vary greatly in size & shape Titan, the largest moon, contains ingredients Titan, the largest moon, contains ingredients

that one day may nurture life!that one day may nurture life!

The Moons of Uranus

Uranus has 27 moonsUranus has 27 moons Many of them are icy, without an atmosphere Many of them are icy, without an atmosphere

or magnetosphereor magnetosphere

The rings of Uranus and its many moons

The Moons of Uranus

The 5 largest were discovered in the The 5 largest were discovered in the 1919thth and 20 and 20thth centuries: Titania, Oberon, centuries: Titania, Oberon, Umbriel, Ariel & MirandaUmbriel, Ariel & Miranda

TitaniaOberon

Umbriel

ArielMiranda(images not to scale)

The Moons of Neptune

Neptune has 13 moons, 3 of which were Neptune has 13 moons, 3 of which were discovered in 2002, 2 more in 2003discovered in 2002, 2 more in 2003

In 1989, Voyager 2 discovered 6 moons not In 1989, Voyager 2 discovered 6 moons not visible from Earthvisible from Earth

All of Neptune’s moons are composed of rock & ice, but little else is known about them

The Moons of Neptune

Neptune has 3 larger moons: Triton, Nereid & Neptune has 3 larger moons: Triton, Nereid & ProteusProteus

Triton is the only moon in the solar system with Triton is the only moon in the solar system with a retrograde orbit, and 1 of 3 with an atmospherea retrograde orbit, and 1 of 3 with an atmosphere

Triton

Nereid

Proteus

Images from Voyager 2 in 1989

The Moons of Pluto Pluto has 3 moons: Charon, Nix, and HydraPluto has 3 moons: Charon, Nix, and Hydra Charon and Pluto have a mutually Charon and Pluto have a mutually

synchronous orbit, meaning they always synchronous orbit, meaning they always show the same face to each othershow the same face to each other

For the Greeks, Charon was the boatman For the Greeks, Charon was the boatman who carried dead souls to the underworld, who carried dead souls to the underworld, ruled by Plutoruled by Pluto

Pluto

Charon

The Moons of Pluto At 1,186 km (737 mi), Charon’s diameter is At 1,186 km (737 mi), Charon’s diameter is

little more than half of Pluto’s; no other little more than half of Pluto’s; no other moon in our solar system is so close in moon in our solar system is so close in size to its planetsize to its planet

Charon appears to be covered by water Charon appears to be covered by water ice, differing from Pluto’s surface of ice, differing from Pluto’s surface of frozen nitrogen, methane & carbon frozen nitrogen, methane & carbon dioxidedioxide

Hubble Space Telescope image of Pluto (left) & Charon

The Moons of Pluto

In November 2005, astronomers discovered two new In November 2005, astronomers discovered two new moons of Pluto: Nix and Hydra. Both moons are moons of Pluto: Nix and Hydra. Both moons are much farther away from Pluto than Charon, and much farther away from Pluto than Charon, and many times smaller.many times smaller.

Nix is named after the Greek goddess of night, Nix is named after the Greek goddess of night, Charon’s mother. Hydra is a beast that guarded Charon’s mother. Hydra is a beast that guarded Pluto’s underworld.Pluto’s underworld.

Moons of Our Solar Moons of Our Solar SystemSystem

Earth is not the only planet with a moon. At least Earth is not the only planet with a moon. At least 159 moons with craters, volcanoes & other 159 moons with craters, volcanoes & other spectacular features exist in our solar system.spectacular features exist in our solar system.

Which ones are your favorites?