A particle subject to a planet's gravitational pull has a total mechanical energy given by , whereis the particle's mass.M the planet's mass, and Gthe gravitational constant. It may escape if its energy is zero that is, if its positive KE is equal in magnitude to the negative PE holding if to the surface. Suppose the particle is a gas molecule in an atmosphere.
(a) Temperatures in Earth's atmosphere may reach . Referring to the values obtained in Exercise 45 and given that and . should Earth be able to "hold on" to hydrogen ? 10 nitrogens ? (Note: An upper limit on the number of molecules in Earth's atmosphere is about ).
(b) The moon's mass is times Earth's. its radius 0.26 times Earth's, and its surface temperatures rise to . Should it be able to hold on to these gases?