If the earth did not have atmosphere, would its average surface temperature be higher or lower than what it is now?

Answer the following question: If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now?

A meteorite burns in the atmosphere before it reaches the earth's surface. what happens to its momentum?

If a planet existed whose mass and radius were both half of that of the eawrth. What would be the acceleration due to gravity at the surface of the planet in terms of that on the surface of the earth?