Timeframe: The timeframe for Namor and Mar-Vell flying to space is extremely small as they were flying to space with a bomb
so I'll use 10 seconds for the timeframe
The pixel scaling for the earth and the panel
Diameter of the earth is 12,742 km
Next using the angsizing formula
2atan(tan(70/2)*(object size in pixels/screen height in pixels))
2atan(tan(70/2)*(527/887)) = 0.54881881537 Radians
0.54881881537×180°/π = 31.445001838° Degrees
Using this calculator to plug in the values
http://www.1728.org/angsize.htm
Angsizing yields 22631 km
Which is 22631000 meters a second
22631000/10
2263100 meters a second or Mach 6650.5