Our World, Other Worlds

Test your knowledge of how Earth is different from other planets.

1

1. HOW'S THE PORRIDGE?

Earth is called a 'Goldilocks planet' because:

A Goldilocks planet falls within its star's habitable zone and is neither too close nor too far from the star to rule out the existence of liquid water on its surface. Liquid water is a key element in supporting life as we know it.
2

2. ALL DRIED OUT

Mars once had running water that carved canyons and other features into its surface. What happened to the water?

3

3. GO WITH THE FLOW

Earth isn't the only body in the solar system with rivers and lakes. Which other world has similar features?

4

4. HOT STUFF

Earth and Venus are rocky planets of about the same size, but Earth's average surface temperature is about 59° F, while Venus' is 1,350° F, hot enough to melt lead or aluminum. Why the difference?

Venus' atmosphere is almost all heat-trapping carbon dioxide.
5

5. OUT WITH A BANG

Which circumstances could end life on Earth?

Scientists believe the first scenario is a possibility and the second just a matter of time.
6

6. WIND BREAKER

Earth's magnetic field shields us from solar wind and helps hold onto the atmosphere and water. To what do we owe this invisible protector?

The magnetic field is essential for life and a defining characteristic of Earth.
7

7. WATER WORLD

Earth is the only body in the solar system thought to have oceans of liquid water.

Scientists think Jupiter's moon Europa has an ocean of liquid water under its icy surface.
8

8. SWEET SPOT

Earth is smack in the middle of the "habitable zone" around the sun, where temperatures are right for liquid water to exist.

The habitable zone around the sun extends roughly from Venus to Mars. Earth is relatively close to the inner (warm) edge, not the middle.
9

9. MAGMA CUM LAUDE

Exoplanets that have a lot of volcanic activity and exist in systems with many asteroids are bad prospects for looking for extraterrestrial life.

Volcanoes push out water vapor and other chemicals that help make a life-sustaining atmosphere, and icy asteroids and comets might have helped bring water to Earth's surface when it was forming.
10

10. HOME ALONE?

Small, Earth-sized planets are common in the galaxy.

The Kepler satellite mission found that small planets are the most common in the galaxy. Small planets are most likely to have a "rocky" (solid) surface, which is conducive to life at least as we know it.