You don't need pixel perfect for a lunar lander. You can get away with point collision. They did it in the game Clonk Planet (and various other sequels).
You have your object.
You list points relative to the center of that object.
Every frame you check ONLY those points to determine if a collision has occurred with your pixel map world.
This game ran every object that way and it rarely failed. And it long predates Minecraft for having gigantic, computer-intesive maps.
So say you have a guy, like in this game. You have one point at the top of his head, one in the center of his feet, and on his right and left side (and center height.) A mere four points that works in 90% of cases, and each point can be linked to specific events. So someones head being touched triggers the guy to get knocked over, verses his feet touching the ground.
In your case, you can use one for each landing gear leg, one on the top, and two at the sides. That's a mere 5-points.
Here's a diagram of what I'm talking about. The red diamonds are the points you scan every frame.
Of course, you can use more points as necessary, like one in the bottom center to prevent landing on a tall spike from being detected.