Moons of the solar system: 3 categories: 7 large (each is distinctive) 12 medium-size many small (most are captured)

Jupiter and Ganymede

Galilean Moons of Jupiter, shown in relative size

Galilean Moon Orbits

Galilean Moon interiors are quite distinct from each other

Io, the most volcanic object in the solar system, due to tidal forces between Io, Europa, and Jupiter

Io Notice the large ring of volcanic ejecta around a volcano

Io A volcanic plume is seen on top. The hot spot below that is the volcano.

Io A volcanic eruption is seen in a caldera.

Europa

Europa, with an enhanced image on the right

Ganymede

Ganymede has an icy surface with cracks similar to those seen on Europa and other moons.

Callisto

Saturn Cassini is currently in orbit around Saturn and is continually sending back more data about Saturn and its moons.

Saturn’s Atmosphere

Saturn winds and bands

Uranus and Neptune Just one spacecraft (Voyager II) has visited Uranus and Neptune Both planets get their bluish color from methane in their atmospheres.

Uranus’s Seasons are extreme due to its tilt

Neptune’s Dark Spot was temporary, and has now disappeared

Jovian Interiors

Jovian Magnetic Fields Uranus’ and Neptune’s magnetic fields have strange orientations, and are not at all aligned with the rotation of the planet. Saturn’s magnetic field is perfectly aligned.

These are Saturn’s rings, but the other three Jovian planets also have rings, much smaller and difficult to see except by visiting spacecraft.

Large moons of the solar system: Titan This next slide compares the terrestrial planets with the Earth’s Moon, the four Galilean moons of Jupiter, and Titan, the largest moon of Saturn. Titan is the only moon in the solar system which has an atmosphere. The atmosphere is mostly nitrogen and thicker than even Earth’s atmosphere.

Titan, as seen by the Cassini spacecraft false color on the left, infrared on the right

Titan’s atmosphere has a high altitude haze, seen by the Cassini spacecraft on the left is a purplish haze, on the right is a view near the terminator between day and night (Sun to the right)

Titan’s surface features are difficult to see in visible light from the Cassini spacecraft.

Infrared pictures of Titan are not much clearer, but emphasize different details.

A Titan crater, as seen by the Cassini spacecraft with visible light on the left, infrared on the right, and radar images in the middle. A radar shows the details of the topographic (altitude-related) features.

The surface of Titan was imaged by the probe “Huygens” This is taken from about 8 km altitude as it was descending.

Rivers are seen on the surface of Titan as the probe “Huygens” descended to the surface. It landed and took pictures (right).

A possible volcano (a cryovolcano) on Titan, seen by the Cassini spacecraft. This may be a major source of methane for Titan’s atmosphere.

Radar sweeps of the North pole of Titan, taken by the Cassini spacecraft, showing lakes of methane and ethane. Flat areas in radar images are probably liquid surfaces, and are colored blue to resemble features on Earth. The radar image has no color in reality. (late 2007)

A lake (or sea) near the North pole of Titan, taken by Cassini, compared to Lake Superior on Earth.

Titan’s Atmosphere.

EXAM on Thursday Covers Ch. 3, 4, and 5 40 question plus some extra credit Next Tuesday, Oct. 12, we will watch a movie and take notes, then, Write a 2 pp. paper, due a week later. I will give a handout during the exam, describing the writing requirement.