Questions regarding gravity to hold an atmosphere are common and here are some of them from the video thread:

Commenter Joel K asks an interesting question:

I have serious doubts, if only due to Mars’ diminutive gravitational pull compared to the Earths. If it ever had an earth like atmosphere, the planet must have had a lot more mass. As it stands, Mars only pulls other objects a little more than 2 times the rate the Earth’s moon does, and there’s no atmosphere to speak of at all on it.

Commenter Pepe P responds as such:

That’s an interesting point, however it’s hard to tell that mass determines if a planet, or satellite, will have an atmosphere. See Jupiter’s satellites, some are earth-like size, but they have no atmosphere. Yet, Titan is a Saturn’s satellite with an atmosphere, and even oceans of liquid methane. I think the origin of the planet / astral object plays an important role toward its atmosphere presence.

I happen to agree with Pepe. Of course who really knows. Feel free to comment on this.