How then can it have 1/6 of Earth gravity?
Hey, believe whatever you want. Here’s something for you to puzzle over, Mars is about ten percent the mass of the Earth, and yet...
http://www.nineplanets.org/mars.html
“The average pressure on the surface of Mars is only about 7 millibars (less than 1% of Earth’s), but it varies greatly with altitude from almost 9 millibars in the deepest basins to about 1 millibar at the top of Olympus Mons.”