Jovian planets composition: Jupiter and Neptune have more rock and hydrogen than Jupiter and Saturn

Uranus and Neptune have higher densities than Saturn because they have a higher proportion of hydrogen compounds and rock

If two planets have the same composition, the more massive one will be more dense

formation of Jovian planets: Accretion built solid planetesimals of rock and ice with about ten times the mass of Earth, and the gravity of these planetesimals then pulled in hydrogen and helium gas from the surrounding nebula.

Jovian Moons

Ganymede and Titan are around the same size as Mercury but are geologically active

Jupiter’s moon Io is the most active volcanically in the solar system and Europa has a global subsurface ocean

Saturn’s moon Titan has higher atmospheric pressure than Earth, and imaging says its surface has rivers of liquid methane and ethane. it doesn’t have liquid water because it is too far from the sun

Some Jovian moons have tidal heating which makes their interiors hotter

Since they formed in the colder solar system they are usually icy in composition

All 4 Jovian planets have rings

Mercury isn’t geologically active because its small size allowed it to cool too quickly

The moon Io doesn’t have a cool interior because it probably has some sort of internal heat (tidal heating)

Tidal heating - source of internal heat created by tidal friction

Io has strong tidal heating because gravity has a much larger effect on Io than on the moon and also because its orbit is slightly elliptical

The tidal force is strongest when Io is closest to Jupiter and weakest when Io is farthest from Jupiter

Most Jovian moons have circular orbits

Io orbits Jupiter 2x for each orbit of Europa and 4x for each orbit of Ganymede

2 orbiting objects are required for orbital resonance

Saturns rings are bright because the sun reflects light off of the icy particles

Enceladus has fountains of ice spraying into space

A comet forms a coma when it gets close to the sun (heat from the sun causes the ice to turn into gas forming a cloud)

Comets look like fuzzy patches of light

Asteroids orbit the sun at about 3AU

The length of a comet’s tail is determined primarily by the comet’s distance from the Sun; its tail is the longest when it is closest to the Sun

Pressure from sunlight and the solar wind create comet tails, but the comet must already have material released from its surface and interior before the tails can form.

A comet plasma tail consists of ionized gas

The tail always faces away from the sun because of the pressure exerted by the fast-moving charged particles in the solar wind

Oort cloud comets probably formed in the same region as Jovian planets

Pluto

Known prior the New Horizons mission: pluto is lighter than any other terrestrial planet, it has a comet-like composition, it is a member of the Kuiper belt, ht is sometimes nearer to the Sun than Neptune

Learned from the New Horizons mission: pluto has an atmosphere, it has smooth plains of nitrogen ice, it has tall mountains built of ice, Charon has deep canyons

Possible but not proven: pluto has active volcanoes and a subsurface of liquid ocean water has been geologically active within the past 100M years because pluto has large regions have few impact craters

Pluto’s geological activity involves nitrogen ice, so Pluto doesn’t need so much heat

The comet that killed dinosaurs occurred about 66 Million years ago

Kpg/K-T layer boundary: dinosaur fossils are only found below the kpg boundary, not above

kpg layer formed about 66M years ago and was found by radiometric dating

other proof: the surface is rich in iridium, which is common in meteorites, and the surface contains shocked quartz and rock droplets (tektites), and the presence of soot

meteorites are pieces of asteroids which are made of rock that contain metals

The impact crater is thought to be in Mexico’s Yucatan Peninsula

The impact created forest fires all around the world, which created smoke so thick that there was no sunlight for several months, killing off other species in the food chain, which led to other creatures existence (such as humans)

planets didn’t form in the region occupied by the asteroid belt because orbital resonances with Jupiter disrupted orbits