a1.1.7 - extraplanetary origin of water

Question 1

explain the hypothesis that asteroids are responsible for the origin of water on Earth.

Answer 1

numerous planetary bodies, including asteroids and comets, containing large amounts of water. asteroids up to a few hundred kilometers across seem the most likely sources of most of Earth’s water. studies of rocks that date to soon after the formation of Earth suggest that water may have begun to exist on Earth as early as 4.4 billion year ago.

Question 2

state two reasons why water was retained on early Earth.

Answer 2

1. the distance of the Earth from the Sun keeps temperature on Earth below that needed to vaporize water.
2. Earth’s gravity keeps water from escaping the planet.