Space Stuff: A Door on Mars...

 

At the back of a cave is rock, but that doesnt mean it has secrets. A black  substance is in the corner. And acording to the colour picker that substance is orage-pink. And that in turn identifies as manganese or cobalt flouride. So its  entirely possible that this mineralization was the biological byproduct of life.

 So lets go back to the door and reach inside.