What are icy objects that mostly travel in long, elliptical orbits around the sun?

The icy objects that mostly travel in long,elliptical orbits around the sun are known as COMETS. 

A comet is a miniscule solar system body that is made up mostly of ices mixed with smaller amounts of dust and rocks. The main body of the comet is called and the nucleus which primarily contains water, methane, nitrogen and other ices. 

If the earth’s gravity were much less powerful our atmosphere would be similar to The moon's