Chapter 7

Radioactive dating techniques have revealed that our Earth and Moon are approximately how old?

4.5 billion years

Which of the following places is most likely NOT to be differentiated?

A small asteroid

The smaller objects in the solar system composed mainly of ices (frozen gases) that usually orbit far from the Sun are called:

Comets

What is one way that astronomers have actually gotten an idea of the age of the surfaces of terrestrial planets other than the Earth?

Counting craters

In radioactive dating, the measure scientists use to note how long (on average) a particular radioactive nucleus will take to decay is called its

Half-life

If you were to take a large sample of the four giant planets, the most common element you would find in them is:

Hydrogen

What other factor can have a significant influence on a planet's surface temperature?

Its atmosphere

In a bad late-night science fiction film, a villain is using a large collection of rare radioactive atoms as energy for a weapon to threaten the good guys. The atoms have a half-life of 1 hour. The villain has 4 kilograms of the radioactive material now, and he needs a minimum of 1 kg. for his weapon to work. After how much time will the weapon no longer be a threat?

Just a little after 2 hours

Today, the chemistry of the terrestrial planets does not include a lot of free hydrogen. Chemists call the chemistry in places like the Earth:

Oxidized

The material that would eventually make all the major bodies in our solar system first gathered together as smaller pieces which astronomers call:

Planetesimals

The first trans-Neptunian object astronomers found (in 1930) is called

Pluto

On Earth, we can get the age of various parts of our planet by finding rocks that contain radioactive atoms. Which other world do have a good number of rocks from to do this kind of age analysis?

The moon

A future interplanetary tourist whose parents kept him too warm as a baby asks for your help to find a "really cold place" in the solar system. Which of the following would be the coldest place to take him?

The moons of Neptune

Our best evidence and theoretical calculations indicate that the solar system began with a giant spinning system of gas and dust that scientists call:

The solar nebula

Of the following planets, which do NOT have moons?

Venus

On which planet (besides the Earth) do we still see a high level of geological activity on the surface today?

Venus

Why is Pluto a TNO?

Where it orbits

When chemists say that a planet's upper regions are reduced, they mean that these regions

are dominated by the element hydrogen and its compounds

One piece of evidence that can help astronomers sort out how the planets in our solar system formed is

finding circumstellar disks of material around nearby stars

During the process of differentiation,

heavier materials sink

In studying the surfaces of solid bodies in the solar system, astronomers have learned that the number of craters (per unit area):

is roughly proportional to the age of the surface we are examining

The inner planets are made mostly of rock and metal because:

it was so hot where the inner planets formed that the lighter materials evaporated

Why is Pluto considered a dwarf planet?

it's large enough to be round

Which of the following ways that jovian (giant) planets differ from the terrestrial planets is NOT correct?

jovians (being larger) rotate significantly more slowly than terrestrials

The rate at which a collection of the same radioactive atoms will decay depends on:

only on internal processes within the atoms; nothing external matters

All the planets (without exception)

revolve around the Sun in the same direction

In the four terrestrial planets, the densest, heaviest materials are at the center and not evenly distributed throughout the planet. Scientists interpret this observation to mean that:

the four terrestrial planets must once have been hot enough to be molten (like a liquid)

Which of the following characteristics do all four terrestrial planets have in common?

they all have solid surfaces with signs of geological activity on them

What is the most important reason that astronomers have learned more about our planetary system in the last 30-40 years than all of history before then.

we have been able to send spacecraft to gather information about planets and moons up close

Which planet in the solar system has not been examined by spacecraft instruments that have either flown by or orbited them?

you can't fool me, spacecraft have visited all the planets in our solar system