It has a much larger fraction of co2 than either of

it has a much larger fraction of CO2 than either of the other two atmospheres.
it has a significant fraction of oxygen in it.
it has a higher pressure than these other planetary atmospheres.
2. The age of Earth is considered to be 3. 4. Earth was formed about 4.6 billion years ago, but most of Earth's surface is
5. What is the direct source of the energy that warms the lowest layers of our atmosphere?
infrared radiation from the ground
visible radiation from the Sun
heat still emerging from Earth as it continues to cool from its initially molten state
ultraviolet radiation from the atmosphere
6. Which one of the following techniques can be used to determine the mass of a planet most easily?

Measure the period and size of the orbit of a satellite moving around it.
Observe the “wobble” its gravitational pull causes in the motion of the Sun.
Observe the spectrum of radiation reflected from its surface.
7.
8. Which one of the following processes was important for melting the entire Earth about 4.6 billion years ago? 10. The core of Earth occupies what fraction of its radius?
about 25%
less than 10%
roughly half
almost 80%
11. The waves that geologists and geophysicists use to probe the inside of Earth are