Will this become the new Mars Face?
I am willing to bet that the "door" is a trick of light and shadow, but then
again so was the Mars Face and that didn't stop tons of speculation and
even whole books on the subject.
It is a neat looking feature even without the "door" (and why the heck
is it so big?), but like I said, had the orbiter captured the image at a
different time of day, nothing unusual would have been noticed.
Mars Anomalies will never die, even when astronauts are standing right
there to examine them.