Transcript Medium and Large Icy Worlds - Moon-Edu

Moons of our Solar System
by Mr. McKinsey, November, 2007
A Moon for Every Planet?
• Most planets have moons. Even dwarf
planets have moons. Only Mercury and
Venus do not have moons.
• Moons vary in size, in composition, and in
many other ways.
Gravity
• The sun’s gravity keeps planets, moons, comets
and asteroids in our solar system.
• Each planet’s gravity keeps its moon or moons
in orbit around the planet.
• The pull of gravity depends on the size of the
objects and their distance from each other.
• Close objects pull harder than distant ones.
Moon Characteristics
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Atmosphere
Moon diameter
Surface appearance
Distance from host planet
Size compared to host planet
Amount of reflected light (albedo)
Comparing
Moons
Moons of our
Solar System are
large and small,
smooth and rough,
near and far.
Moon Atmospheres
Moon
Atmosphere?
Earth’s Moon
No
Phobos
No
Io
Yes!
Ganymede
No
Triton
Yes!
Jupiter’s Galilean moons
Io has an atmosphere.
Moon Diameters
Moon
Diameter in Kilometers
Earth’s Moon
3,476.2
Phobos
22.4 (average)
Io
3,643.2
Ganymede
5,262.4
Triton
2,706.8
Earth’s Moon and
Neptune’s Triton to the
same scale.
Ganymede -8th largest world
• Largest
moon in
the solar
system
Io
12th
largest
world
Surface Appearance
Moon
Surface Appearance
Earth’s Moon
Rocky, cratered
Mars’ Phobos
Rocky, smooth
Jupiter’s Io
Rocky, volcanic
Jupiter’s Ganymede
Cratered, icy, grooved
Triton
Icy, volcanic
Phobos photographed from Mars
Phobos, moon of Mars
Io has active
volcanoes.
Io’s Volcanoes
• Volcanic eruptions change Io’s surface
Ganymede
Ganymede’s complex
surface has grooves,
craters, lava flows,
mountains, and water
ice.
Neptune's Triton from a distance of 530,000
kilometers (330,000 miles).
Distance from Moon to Planet
Moon
Moon
Phobos
Io
Ganymede
Triton
Distance from Moon to
Planet in Kilometers
384,467
6,000
421,600
1,070,400
354,760
Neptune (top) and its moon, Triton (bottom)
Ratio of Moon Diameter to
Planet Diameter, as % of Planet Diameter
Moon
Ratio Expressed as a %
Earth’s Moon
27.37%
Mars’ Phobos
0.33%
Jupiter’s Io
2.60%
Jupiter’s Ganymede
3.76%
Triton
5.52%
Jupiter seen below its moon, Io
Reflected Sunlight (Albedo)
Moon
Earth’s Moon
Percent of Sunlight
Reflected by Moon
Surface (Albedo)
7% (0.07)
Phobos
6% (0.06)
Io
61% (0.61)
Ganymede
42% (0.42)
Triton
7% (0.07)