Download Unit 7 Planetary Sciences - Comparisons of Moons ppt

Saturn, with two small
moons, as photographed
by Voyager 2.
1979 – Far-out
voyages
The twin Voyagers
begin landmark
observations of the
outer planets that last
until 1989.
The two spacecraft
discover a total of 22
new satellites — three
at Jupiter, three at
Saturn, 10 at Uranus
and six at Neptune —
and send back
stunning space
images and
revelations about the
moons.
Researchers spot more
moons around Jupiter by
tracking the motion of
objects with a highpowered telescope.
Year 2000: More moons
Powerful electronic
imagers integrated into
ground-based telescopes
on Earth in the late 1990s
yield rich returns in the
search for more
extraterrestrial moons.
Researchers find 11 new
moons around Jupiter
and 12 moons circling
Saturn.
The largest moon circling the largest planet in our solar system, icy Ganymede measures
5219 Km across. This moon of Jupiter, in the upper left-hand corner, is slightly larger than
Saturn's giant satellite Titan (5150 Km), and its size overshadows the planets Mercury (4878
Km) and Pluto (~3000 Km). It is shown here with fellow Jovian moons Io, Europa and Callisto.
(Earth’s Moon is 3476 Km in diameter. The Earth is 12,756 Km in diameter. Jupiter is
142,796 Km.)
Speeding around a planet 11 times the size of Earth in less than two days takes its toll on Jupiter's
geologically active moon Io. The gravitational stresses cause so much heat inside Io that volcanoes on
the frozen world spew matter 185 miles into space, shooting more than a mile upward every two
seconds. (Tidal forces, Jupiter’s main radiation belt and Io is strongly influenced by Jupiter’s magnetic
field, wreaking havoc on the Sulfur and Iron in the core.)
At first glance, Jupiter's moon Europa is a relatively simple world. But looks can be
deceiving: Cracks cover the moon's icy surface, signals the possible presence of an
underground liquid ocean. Since water appears to be key to life as we know it, scientists
would not be surprised if Europa harbors some form of microscopic life. The temperature of
the water is measured from 40-60 degrees below the surface.
The Saturn moon Iapetus puzzled
generations of astronomers by
apparently vanishing every time it
moved around to the western side
of its home world. The mystery
remained until Voyager flybys
showed the moon to be almost
perfectly two-toned: half sooty
black, half sparkling white.
Scientists theorize the moon's
leading face was darkened after
flying through a debris cloud
created when a space rock
collided with the neighboring
moon Phoebe.
The gravitational bond between Triton and its mother planet Neptune is so odd that
astronomers believe the satellite's capture was particularly rough, with lots of heat
generated in the process. However, the spacecraft Voyager 2 found Triton to be brutally
cold, with temperatures plunging to minus 391 degrees Fahrenheit — frigid enough to
turn nitrogen, carbon dioxide and methane into ice.
With no atmosphere,
our own moon
experiences
temperature swings
in the extremes,
soaring above 250
degrees Fahrenheit in
full sun and dipping
450 degrees below
zero in darkness.
Besides the moonless
planets of Mercury
and Venus, other hot
spots in the solar
system include the
volcanoes of Io, a
moon circling Jupiter.
Saturn's tiny moon Enceladus — about the width of Arizona — features a surface marked with
craters, fissures, plains, volcanoes, cracks and ridges. Heavily covered in ice, the moon reflects
around 90 percent of the sunlight that strikes its surface, giving it a brightness similar to that of
freshly fallen snow.
A thick atmosphere distinguishes the moon Titan from other satellites in our solar system.
Even though this moon — Saturn's largest — is typically cloaked in a thick fog,
researchers recently uncovered evidence that icy continents and seas of liquid methane,
ethane or other hydrocarbons might cover its surface. They hope that the spacecraft
Cassini, now en route to Saturn, might help reveal more.
The martian moon Deimos, lower left, is so tiny you could walk across it in less
than nine hours. Believed to be a captured asteroid, the satellite may soon lose
its standing as the solar system's smallest moon, however. Powerful telescopes
are finding even smaller shards orbiting Jupiter.
Deimos is shown here with asteroid 951, top, and fellow martian moon Phobos.