Where did Earth's water come from?

What percentage of Earth's surface is covered in water?

• 70%
• 10%
• 30%
• 50%

Why is water important for life on Earth?

• It makes Earth look pretty
• It is necessary for survival
• It is fun to swim in
• It helps plants grow

What is the amount of fresh water on Earth?

• Less than 1%
• 70%
• 50%
• 30%

How did the solar system form?

• A comet hit Earth
• A black hole sucked in matter
• A cloud of gas and dust collapsed into a swirling disk
• A giant explosion

What was the role of dust particles in the formation of water on Earth?

• They acted as condensation nuclei to let droplets form
• They carried water to Earth
• They created more water molecules
• They prevented water vapor from condensing

What is the difference between water molecules in Earth's mantle and on the surface?

• Water molecules in Earth's mantle are not independent H-two-O molecules, while on the surface they are
• Water molecules in Earth's mantle are made of different elements than on the surface
• Water molecules in Earth's mantle are independent H-two-O molecules, while on the surface they are not
• Water molecules in Earth's mantle are not made of hydrogen and oxygen

What is the role of asteroids and comets in bringing water to Earth?

• They contain only oxygen and hydrogen
• They contain only water molecules
• They contain only raw ingredients
• They contain water molecules and their raw ingredients, oxygen and hydrogen

How can we tell if most of our water came from asteroids or comets?

• By analyzing the age of water molecules
• By analyzing the composition of water molecules
• By analyzing the composition of asteroids and comets
• By analyzing the location of asteroids and comets

Where did much of the water on the surface of Earth come from?

• From the Sun
• From the Moon
• Inside Earth's mantle
• Farther out in the solar system

What is one possible location of primordial H2O?

• Inside the Sun
• Inside the Moon
• Embedded within minerals
• On the surface of Earth