This suspicious scribbling, made with an unknown device on what appears to be a strip of metal (also undetermined), was recently discovered in a desert canyon. The "metallic" strip is bonded to a rock wall by unknown means. Similar writing has been found elsewhere, but not of this color. Whether that represents a message in itself is unknown. There are a lot of unknowns here.
Two theories have been put forth to explain this mystery. The more likely one is that the writing is a message left by Aliens who were on a reconnaissance mission in advance of an invasion. The writing is instructions left for the invaders. (But what happened to that invasion? Will it still take place?)
The other theory is that this was left by Aliens as a prank. Is there, somewhere, a group of extra-terrestrials, watching this unfold on Earth, and laughing their heads off (assuming they have heads)? This is yet another unknown.