astr (all)

The rotation periods for the Jovian planets Jupiter, Saturn, Uranus, and Neptune are

somewhat shorter than that of the Earth, between 10 to 20 hours.

The mass of Jupiter compared with that of the Earth is

about 300 times larger.

What characteristic features are seen on the visible surface of Jupiter?

light and dark bands parallel to the equator

The existence of the Great Red Spot of Jupiter has been known since

the time of Hooke and Cassini in the 1600s.

The lifetime of the Great Red Spot of Jupiter appears to be

at least 300 years, from visual records.

The rotation period of Jupiter is

relatively short, on the order of 10 hours.

One interesting feature of Jupiter’s rotation is the fact that

regions of Jupiter at different latitudes appear to rotate at different rates.

The composition of the clouds we see on Jupiter is

similar to the composition of the Earth’s clouds (water droplets and crystals of frozen water) in the lower levels but very different (ammonia crystals and other chemicals) in the higher levels.

How thick are the cloud layers on Jupiter’s visible “surface”?

about 60 km

The overall interior structure of the Jovian planets is expected to be

four-layered: a rocky core, a semifluid ice layer, a liquid mantle of hydrogen, and a gaseous hydrogen and helium atmosphere.

The temperature in the core of Jupiter is

hotter than the temperature of the Sun’s surface but cooler than the temperature of the Sun’s core, so nuclear fusion cannot take place.

Jupiter has a magnetic field that is

much more powerful than that of the Earth.

The material in the interior of Jupiter that is thought to be responsible for its powerful magnetic field is

liquid metallic hydrogen.

If we could see the full extent of the magnetosphere of Jupiter from the Earth, how big would it appear in the sky?

16 times larger than the full Moon

The general shape of each of the Galilean moons of Jupiter is

almost perfectly spherical.

Which characteristic of Jupiter’s satellite Io makes it different from any other known satellite in the solar system?

Io is volcanically active, with gas plumes and lava flows.

The surface of Europa, one of the Galilean moons of Jupiter, appears to be covered with

a smooth layer of ice crossed by many cracks.

What features dominate the surface of Ganymede, one of Jupiter’s satellites?

old, dark, highly cratered polygons separated by younger, lighter, grooved terrain

The structure of Callisto, the outer Galilean satellite of Jupiter, is thought to be

a mixed ice-rock interior surrounded by a liquid ocean and then a solid icy crust.

The material that composes the rings of Jupiter

is continually being ejected from the rings and being replenished from material from the Jovian moons.

What kind of ring or rings does Jupiter have?

several thin dark rings made up of very fine dust particles

Saturn, like Jupiter, is composed primarily of

liquids.

Saturn’s atmosphere does not show the same colorful contrast that we see in Jupiter’s atmosphere because

Saturn has a similar circulation pattern to Jupiter’s, but it is obscured by a thick hazy atmosphere

What is the interior structure of Saturn?

rocky core, thick mantle of liquid metallic hydrogen and helium, relatively thin gaseous atmosphere

The rings of Saturn are in which plane with respect to the planetary system?

equatorial plane of Saturn

The physical structure of Saturn’s rings is

a sequence of many thousands of separate ringlets consisting of ice blocks and ice-coated rock.

What is perhaps the most striking feature of the dimensions of the rings of Saturn?

The rings are extremely thin compared to their lateral extent.

The rings of Saturn are seen by

reflected and scattered sunlight.

The particles in Saturn’s rings

move in circular Keplerian orbits; the inner particles move fastest.

What is the Cassini division?

wide, dark gap in Saturn’s rings

Why is the F ring much narrower than the main rings?

Two “shepherd” satellites focus the particles into a narrow ring.

The main gravitational effect that organizes the particles in the rings of Saturn into specific narrow orbits is

gravitational perturbations by the large moons orbiting these planets.

Saturn’s moon Titan is different from all other moons of the planets because

it possesses a thick atmosphere.

The composition of the atmosphere of Titan, a satellite of Saturn, is mostly

nitrogen, methane, and other hydrocarbons.

Recent observations suggest that Saturn’s satellite Enceladus possesses all the following features except one. Which feature does Enceladus probably NOT possess?

molten lava flowing from active volcanoes

How would Interplanetary Travel, Inc., advertise a holiday on Titan, one of the satellites of Saturn?

Exquisite ethane lakes, hydrocarbons beyond your wildest dreams, no shortage of fuel!

The surface temperature of Titan, the largest moon of Saturn, is

95 K (–178°C).

Which chemical in the atmosphere of Titan (a moon of Saturn) plays the same role that water plays on Earth by producing “rain,” “snow,” and “ice” at the temperature encountered on Titan?

ethane, C2H6

What are the most abundant gases in the atmosphere of Uranus?

hydrogen and helium, with traces of methane

What gives Uranus its blue-green coloration?

absorption of red light by methane gas

By what angle is the rotation axis of Uranus tilted from the vertical to its orbit?

98°

The expected seasonal changes on Uranus because of its orbital and spin-axis alignments, compared with those on the Earth, are

very much exaggerated.

What is believed to be the basic structure of the interior of Uranus?

rocky core, thick layer of highly compressed liquid water, thick outer layer of liquid hydrogen, thin gaseous atmosphere

The ring system around Uranus was originally discovered by what observation technique?

occultation of light from a star as Uranus (and the rings) passed in front of it

The rings of Uranus are

narrow and very dark.

Most of the satellites of Uranus orbit the planet in

the plane of the planet’s equator and therefore in a plane almost at right angles to the ecliptic.

Miranda, a satellite of Uranus,

appears to have been reassembled from separate parts after being shattered by an impact.

How was Neptune discovered?

by a careful application of Newton’s laws to the somewhat irregular motions of Uranus

What is the visual appearance of Neptune from space?

blue-green with white, high-altitude clouds and dark storms

The Great Dark Spot on Neptune, photographed by Voyager 2 during its flyby of the planet, is considered to be a

relatively short-lived storm system.

Neptune’s predominantly blue appearance is caused by

absorption of the red end of the spectrum of reflected sunlight by the methane in its atmosphere.

One distinct difference between the two otherwise similar planets, Uranus and Neptune, is

the almost featureless visible image of Uranus, compared to distinctly seen storms and clouds on Neptune.

Compared to the Earth, Jupiter, and Saturn, the magnetic fields of Uranus and Neptune

have axes that are tilted a long way from the spin axis of the planets.

The magnetic fields of Uranus and Neptune appear to originate in the

liquid water-mineral mixture in the mantles of the planets.

The electrically charged particles that produce electric currents and therefore magnetic fields when they move inside Uranus and Neptune are

molecules such as ammonia (NH3), which become ionized when in solution in water.

Does Neptune have rings orbiting the planet?

yes, a system of dark rings of particles coated in chemically modified methane ice

Why are the rings of Neptune dark?

The particles are composed of methane ice that has been darkened by radiation damage.

Triton, the giant moon of Neptune, differs from all other major moons of the planets because

it orbits in a retrograde direction, opposite to the planet’s rotation.

What features characterize the visible surface of Triton, Neptune’s largest moon?

wrinkled surface, frozen lakes, and plumes of nitrogen gas

A striking characteristic on Triton, the largest satellite of Neptune, is

plumes of nitrogen gas rising from the icy surface, possibly as a result of radioactive heating.

The Roche limit around a planet is defined as the

distance at which a planet creates tides on its moon’s surface high enough to pull its moon apart.

Mercury is always much closer to the Sun than Venus is, and yet it never appears brighter than Venus, even at maximum brightness. Explain.

Mercury is small, has a dark surface, and has no reflecting clouds.

Mercury, unlike the Moon, has extensive plains between craters. The reason is thought to be that

the plains on Mercury are older than the maria on the Moon. Thus, more time has elapsed during which cratering has erased evidence of earlier maria on Mercury.

Craters on Mercury appear to have been produced by

impacts from objects from space early in the planet’s history.

What is the Caloris Basin?

multiringed impact basin on Mercury

The Caloris Basin appears to have been produced by

the impact of a massive object in the early phases of the planet’s formation, soon after the initial cratering period.

How was Mercury’s jumbled, hilly terrain formed?

by seismic waves generated by the Caloris impact

The history of Mercury can be summarized as

thin crust forming at first, followed by extensive bombardment, the craters from which were then covered by lava flows that produced extensive lava plains between the remaining craters.

Mercury can be characterized as having

a Moonlike surface and an Earthlike interior.

Mercury’s central core is probably composed of

solid and/or molten iron.

The internal structure of Mercury is

a dense iron core taking up almost half of the volume of the planet and a rocky mantle surrounding the core.

Why is there no plate tectonics on Mercury?

the planet cooled too rapidly and the mantle became too rigid.

Which feature deflects solar wind on Mercury?

magnetic field that, like the Earth’s, produces a magnetosphere surrounding the planet

Mercury’s magnetic field is

weak but clearly present.

How does Mercury rotate relative to the Sun?

Mercury alternately turns one side (Caloris Basin) toward the Sun at one perihelion and the opposite side toward the Sun at the next perihelion.

Why is Mercury in a 3-to-2 spin orbit coupling?

Mercury’s orbit is very eccentric, so its orbital speed varies while its rotation rate remains constant, preventing a 1-to-1 lock.

Unexpected compound on Mercury

water ice at the north and south poles

Source of Mercury’s water ice

unknown at the present time.

Mercury’s atmosphere consists of

traces of hydrogen, helium, potassium, sodium, and oxygen.

Which properties of Venus are similar to Earth?

mass and radius and hence average density and surface gravity

When Venus is brightest it is

the brightest celestial object in the sky other than the Sun and the Moon.

Why Venus appears bright

it is covered by very reflective clouds.

Surface conditions on Venus

a high-pressure, high-temperature, carbon dioxide atmosphere.

Cloud altitude on Venus

almost 70 km

Cloud structure of Venus

a clear layer at the surface, a haze layer above it, and then a high, thick layer of permanent cloud.

Sulfuric acid clouds on Venus

are confined to a narrow layer about 60 km above the planet’s surface and cover the whole planet.

Why spacecraft failed on Venus

high temperatures, high pressures, and corrosive acid clouds and mist.

Condition NOT a concern on Venus

very cold nighttime temperatures

Main reason for Venus high temperature

absorption of visible radiation by the Venusian surface and the subsequent trapping of infrared radiation emitted by the surface by the atmosphere and clouds.

Why greenhouse effect stronger on Venus

Carbon dioxide, which traps heat from the planet’s surface, is the major component in the very dense Venusian atmosphere, while it is a only a minor constituent of the Earth’s.

How Venus surface was mapped

radar methods from Venus-orbiting spacecraft, measuring radio echoes from the surface.

Venus surface description

mostly volcanic plains, with two continent-sized uplands and a number of large volcanoes.

Venus surface compared to Earth

almost completely flat and relatively smooth, except for two high volcanic mountain ranges

Why few craters on Venus

lava flows and surface melting have covered all but the most recent craters.

Maximum age of Venus surface features

about 700 million years, due to constant resurfacing of the planet by lava flows.

Venus magnetic field

no magnetic field.

Venus rotation

in the opposite direction from the Earth but very slowly.

Cause of Venus retrograde rotation

impact of a massive object on it early in its history.

Length of Venus solar day

117 days.