This picturehas always irritated me.  It’s obviously not a footprint, but a torn-off piece of boot sole sitting upside down on some beach.  If you ask me, it’s a pathetic part of the conspiracy to make us think humans actually landed on the moon.  Why it keeps being reproduced, here for example, mystifies me.  Let’s look at this another way: grab your monitor and turn it a quarter turn to the left…never mind, I’ll do it for you:

Note to photo editors everywhere: if it doesn’t look right, maybe having the light come from the top, whence we subconsciously expect it, would help.