This is kind of fascinating. How shapes and such get formed without human interaction is always intriguing.
https://mars.nasa.gov/raw_images/1064629/?site=msl
image.png You have insufficient rights to see the content.
If that wasn't in a government website, I'd be saying it was a hoax created by someone lol
But according to some
Scientist it appears that the one meter (3 foot) "door" is caused by natural forces.
As they believe the picture is taken in what is now a dried out riverbed... and that winds damage over many many years is damaging the now dried out ground.
And the door, is probably, not certain, but probably caused by rocks above falling on it, such as the rock you see just to the right of the door.
While that's certainly not a perfect answer, it's better than any others, unless there is more than dirt at that door...