The certain mountain or ice tile DOES spawn damaged at the start of the mission, so if you see an already damaged tile when you enter a new match, take a very close look at the tile to see if it is the tile you're looking for. Note that the glow is not always as obvious as the one seen above, however it should always be in the middle of the mountain.
Upon breaking the marked mountain tile, a strange object will drop from it, move your mech on to the object and it will broadcast a signal. Once you end your turn, the FTL jump drive sound (from subset games's FTL: Faster than Light) will play and a strange pod will fall from the sky just like a time pod. Pick up the pod or protect it until the end of the match and you will be able to open it like any other time pod, gaining one of the three secret pilots.
The pod also looks like a broken section of the Federation cruiser from Faster than Light.