astronomy midterm

Of the following planets, which do NOT have satellites (moons)?

Venus

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

hydrogen

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 smaller objects in the solar system made of rock and metal (most of which orbit between Jupiter and Mars) are called:

asteroids

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

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

In general, the further planets are from the Sun, the cooler they are. What other factor can have a significant influence on a planet's surface temperature?

its atmosphere (whether it has one and how thick it is)

During the process of differentiation,

heavier materials sink to the centers of molten planets

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

On which of the planets (other than Earth) could a human being step out of a spacecraft and survive without any protective gear (special suit, oxygen tanks, etc)?

you can't fool me; there is no other planet on which we could survive unprotected

The planet closest to the Sun in the solar system is:

Mercury

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

about 4.5 billion years

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

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

jovians (being larger) rotate significantly more slowly than terrestrials

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 hrs

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

In the far future, a visiting tourist from another planetary system asks to see the most massive object in our solar system. Where would you take him/her/it?

the Sun