Acadeca: Foundations of Earth Science, Chapter 15, The Nature of the Solar System


The evidence used to unravel the history of the lunar surface comes primarily from studies of crater densities�counting the number of craters per unit area�and radiometric dating of rocks returned from what missions?

Apollo missions

What percent of the mass of the solar system is the sun?


What percent of the mass of the solar system are the planets?


What theory proposes that the Sun and planets formed from a rotating cloud of interstellar gases (mainly hydrogen and helium) and dust called the solar nebula?

Nebular theory

What were the asteroid-sized chunks of material that would eventually become the first 4 planets called?


What planets did the planetesimals become?

Mercury, Venus, Earth, Mars

How many years after the protoplanets formed did it take for the planets to gravitationally accumulate most of the interplanetary debris?

1 billion years

What was the stage of the first four planets after the planetesimal stage called?


The small amount of material that escaped the time period of planets clearing their orbits became what?

Asteroids and comets

Does Venus have a magnetic field?

No (slow rotation and not hot enough core)

What type of minerals make up the mantles of the terrestrial planets?


What variables determine a planet's atmospheric composition?

Solar heating (temperature) and gravity

Why do the outer planets have ice?

Further from the sun so cooler temperatures

What bodies have the best chance of losing their atmosphere?

Small and warm

What craters result from collisions with massive bodies, such as asteroids and comets?

Impact craters

How large can an object be to be stopped by Earth's atmosphere?

10 kg or less

What do central peaks in craters form as a result of?

Crustal rebound

Upon impact, large meteoroids may eject large projectiles that strike the surrounding landscape to generate smaller structures called what?

Secondary craters

What is the daylight temperature of the moon?

107�C (225�F)

What is the nighttime temperature of the moon?

?153�C (?243�F)

What is the density of the moon?

3.3 times that of water

Why doesn't the moon have an atmosphere?

Low mass means low gravity, can't hold gases in

How long ago was the moon formed?

4.5 billion years ago

How long ago was the Earth formed?

4.6 billion years ago

What percent of the lunar surface do the maria cover?

16% (mostly located on the side of the moon facing Earth)

What were the lunar highlands first called?

Terrae (land)

What are the four phases the moon passed through after coalescing?

Formation of the original crust, excavation of the large impact basins, filling of maria basins, and formation of rayed craters

How long ago did the moon's magma ocean begin to cool and undergo magmatic differentiation?

4.4 billion years

What is anorthosite composed of?

Calcium-rich plagioclase feldspar

How long ago did the solar system experience a sudden drop in the rate of meteoritic bombardment?

3.8 billion years

The maria basalts are thought to have originated at what depth?

200-400 km

What are narrow winding valleys on the moon that are thought to be collapsed lava tubes?


What are craters from which light-colored material ejected from the craters radiates outward?

Ray craters

What is the main source of erosion on the moon?


How thick is the regolith?

2-20 meters

What is the longest-known lava channel in the solar system?

Baltis Vallis (on Venus, 6800 km)

What are the dimensions of Maat Mons, the largest volcano on Venus?

8.5 km high, 400 km wide

What type of rock is Venus's highlands?

Silica-rich granitic rock

How large is Mars's diameter?

Half of Earth

What resulted in the fluidized ejecta craters of Mars?

Heat of impacts melted the permafrost

How much of the surface of Mars consists of heavily cratered highlands?


What is the largest visible impact basin on Mars and is about 2300 kilometers in diameter?


Where is Mars's lowest elevation?


What buried crater basin is even larger than Hellas and is where Viking 2 landed?

Utopia basin

What type of volcano on Earth does Olympus Mons resemble?

Shield volcano

What is the dominant force currently shaping Mars's surface?


What streaks on Mars, which appear seasonally on steep, relatively warm Martian slopes, may be caused by the flow of briny (salty) liquid water?

Recurring slope lineae (shown by NASA's Mars Reconnaissance Orbiter)

What colors do Jupiter's three cloud layers appear?

Low: blue-gray, Middle: brown-orange, Top: white

Because of its immense gravity, Jupiter is shrinking by how much each year?

A few cm

What generates most of the heat that drives Jupiter's atmospheric circulation?

Jupiter's contraction

What on Jupiter are regions where warm material is ascending and cooling?

Light clouds (zones)

What regions of Jupiter represent cool material that is sinking and warming?

Dark belts

What direction do the zones and belts of Jupiter flow?

East to west

What causes Io's spectacular sulfurous volcanic eruptions?

Tidal energy (Mostly erupts silicate material lava)

The main ring of Jupiter is composed of particles believed to be fragments blasted from the surfaces of what moons?

Metis and Adrastea

Impacts on what two Jupiter moons are believed to be the source of the debris from which the outer gossamer ring formed?

Amalthea and Thebe

What are Jupiter's rings composed of?

Fine, dark particles similar in size to smoke particles

What are the only satellites in the solar system known to have substantial atmospheres?

Titan and Triton

What term describes the eruption of magmas derived from the partial melting of ice instead of silicate rocks and occurs on Enceladus?


Enceladus has active linear features, called what, which are a source region for cryovolcanic activity?

Tiger stripes

What is a small moon about 30 kilometers in diameter that orbits in the Encke gap, located in the A ring and is responsible for keeping the Encke gap open by sweeping up any stray material that may enter?


What potato-shaped moon's gravity helps confine the particles that make up Saturn's thin F ring?


What is the average size of a particle in Saturn's A and B rings?


How wide are Saturn's A and B Rings?

40,000 km

The Cassini division arises from the gravitational pull of what moon?


What moon of Uranus was recently geologically active?


The outermost ring of Neptune appears to be partially confined by what satellite?


Neptune's rings display red colors, indicating that the dust is composed of what compounds?

Organic compounds

In 2006, the International Astronomical Union organized solar system objects not classified as planets or moons into what two broad categories?

Small solar system bodies, dwarf planets

What type of objects are asteroids, comets, and meteoroids?

Small solar system bodies

Asteroids are small bodies (planetesimals) that remain from the formation of the solar system, which means they are about how old?

4.6 billion years old

How many Earth-crossing asteroids are there?


In February 2001, what American spacecraft became the first visitor to an asteroid?

NEAR Shoemaker (landed on Eros)

The escaping gases from the nucleus of a comet carry dust from the comet's surface, producing a huge dusty atmosphere called a what?


Which tail of a comet is faint and dark blue?

Ion/gas tail

What is a disc of icy objects with roughly circular obits that travel in the same direction as the planets beyond the orbit of Neptune?

Kuiper belt

What is a spherical cloud containing icy planetesimals located roughly 50,000 times farther from the Sun than Earth?

Oort cloud

What is the diameter of the Kuiper belt?

100 AU

What is the diameter of the Oort cloud?

100,000 AU

Meteoroids less than about what diameter generally vaporize before reaching Earth's surface?

1 meter (3 feet)

What are the three categories of meteorites?

Irons, stony, stony-irons

What percentage of an iron meteorite is nickel?


What is the diameter of Pluto?

2370 km (1470 miles)

The bright area in the lower central region of Pluto, sometimes referred to as "the heart of the heart?

Sputnik Planum

Pluto is too cold for its ice flows to be made of water, so they are likely made of what?