In this way, the terrestrial planets, strongly heated by
the Sun and having only a weak gravitational grasp, lost
their primary atmospheres early in their evolutionary development.
The giant planets, on the other hand, are far
more massive than their terrestrial cousins and are situated
in the cooler environment of the outer Solar System.
Stronger gravity and lower temperatures enabled them
to retain nearly all of their massive primary atmospheres,
which we explore further in Chapter 10.