7 Nuclear Aliens : This next theory proposes that a humanoid civilization once lived on Mars. The civilization flourished up until it’s population was massacred by another race of aliens by use of nuclear bombs. The man behind the theory, who is an actual physicist, claims that there were two races of Martian. They were called the Cydonians and the Utopians. Both races were wiped out by the bombing. He warns that humans could be next if we aren’t careful. I know this sounds like the plot of a terrible scifi novel.