Question

An atmosphere is a layer of gas or layers of gases that envelope a planet, and is held in place by the gravity of the planetary body.​

Answer 1

Explanation:

An atmosphere (from Ancient Greek ἀτμός (atmós) 'vapour, steam', and σφαῖρα (sphaîra) 'sphere') is a layer of gas or layers of gases that envelope a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low.