Was An Ancient Martian Civilization Destroyed By Nuclear Attacks?

The Fermi paradox asks a simple question: if there are so many planets and stars in the universe, why have we found no trace of an extraterrestrial civilization? Where is everyone? A possible answer to this, given by physicist John Brandenburg, is that these civilizations are being hunted, and we may be next.
According to International Business Times, Brandenburg theorizes that Mars was once the home of two ancient alien civilizations — the Cydonians and the Utopians — who were tragically annihilated by another off-world civilization.
What’s the evidence? Nuclear isotopes on the planet’s surface that “resemble those from hydrogen bombs released on Earth,” along with alleged “eroded archaeological objects.”
In a paper published last year, Brandenburg wrote:
“This Martian civilisation apparently perished due to a planet-wide catastrophe of unknown origin that changed Mars climate from being Earth-like to its present state in a brief period compared to geologic time. However, what ended this civilisation, was it a massive nuclear attack?”
But what would drive one space-faring civilization to destroy another? Competition, says Brandenburg. “It is possible that our interstellar neighborhood contains forces hostile to young, noisy, civilizations such as ourselves. Such hostile forces could range from things as alien as AI (Artificial Intelligence) ‘with a grudge’ against flesh and blood.”
Brandenburg, then, suggests a human mission to Mars is needed to uncover the true fate of these ancient civilizations, and that doing so may help us survive a similar attack.
So, you know, just another day in the Milky Way. Oh, and Reapers.