Mars once had intelligent alien life but it was wiped out in a nuclear attack by another civilisation, a physicist has said.

John Brandenberg, author of Death on Mars: The Discovery of a Planetary Nuclear Massacre, due for release next year, says two Martian civilisations known as the Cydonians and Utopians were killed by another, unidentified alien race.

He said there is evidence to support his claims – many of the nuclear isotopes in the Red Planet's atmosphere resemble those from hydrogen bombs released on Earth.

Publishing his findings in the forthcoming edition of the Journal of Cosmology and Astroparticle Physics, Brandenberg says the composition and colour of Martian soil is consistent with mixed fusion-fission explosions.

He writes: "The high concentration of Xenon-129 atmosphere, the evidence from Krypton-80 and the detected pattern of excess abundance of Uranium and Thorium on Mars surface, relative to Mars meteorites, first seen by the Russians and now confirmed by the Mars Odyssey Spacecraft Gamma Ray Spectrometer, mean that the surface of Mars was apparently the site of massive radiological events, which created large amounts of signature isotopes and covered the surface with a thin layer of radioactive debris enriched in certain elements relative to its subsurface rocks.

"This pattern of phenomenon can be explained as due to two large anomalous nuclear explosions on Mars in the past."

Physicist claims mankind must prepare against similar nuclear attacks that wiped out life on Mars. NASA, ESA, and J.-Y. Li (Planetary Science Institute)

Brandenberg has held his beliefs about life on Mars – and its violent end – for several years. In an interview in 2011 with Supreme Master TV he told how the two ancient civilisations were similarly advanced as the ancient Egyptians. He says the area in which they lived – which has archaeology on it – was targeted by another, external force.

In his latest paper, he said: "The existence of a dead humanoid civilisation on Mars is completely consistent with its apparent long-lived Earthlike past climate and the Principle of Mediocrity, the idea that humanoid intelligence is not exotic or miraculous, but is a natural consequence of any long lived Earthlike biosphere.

"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?"

The physicist says the biggest danger to intelligent life is other, more advanced intelligent life. He notes that previously, astronomer Edward Harrison said older civilisations would wipe out younger ones as soon as they become detectable through radio broadcasts.

"The motivation for such genocidal actions would be to avoid later competition," he writes. "The discovery of dead civilisation on Mars, whose end was apparently catastrophic and due to unknown causes, reinforces our understanding that the cosmos can be a dangerous place and requires a vigorous response from the human race, to reduce the probability that we will perish the same way."