Spiny Norman said:
Here’s a photo that gives a bit more perspective as to the size of it. I doubt you could fit your hand into it.


“Curiosity, a rover that’s been exploring the mountain since landing in 2012, took the image of the crevice on May 7. Good said that NASA scientists overseeing the rover estimate the opening is 12 inches (30 centimeters) tall and 16 inches (40 centimeters) wide, or roughly the size of a medium dog door.”
The experts say its a dog door
It doesn’t look wider than it is high to me, but who am I to argue with the experts?