Give it to Newt or Kellyann , FFS <| sep |> because of the low gravityIt ' s less about that than it is about the lack of a magnetic field . The sun sends charged particles out throughout the solar system all the time they travel very fast and their collisions strip the atmosphere off planets unless there is a magnetic field that deflects them before they hit the atmosphere . Since Mars lacks a magnetic field , that solar wind has simply stripped most of the atmosphere away over time . Wouldn ' t efforts to terraform Mars using frozen ice just result in failure for this reason ? Well , Mars lacks nitrogen and oxygen , not water . <| sep |> She got a big booty so I call her big booty . Had to defend the genius of that too many times to people .