The Cydonian Hypothesis

The archive holds one argument here and no sighting. In the single telling, John Brandenburg says that excess xenon-129 and argon-40 measured at Mars match the isotope signatures left by thermonuclear tests on Earth, and that the match points to a nuclear catastrophe in the planet's deep past. He places it at Cydonia. The telling has him reaching the idea at Sandia, the weapons laboratory. His reading of the Face and its neighbours as the wreckage is folded into the Face on Mars page.

What is on the record

Brandenburg is the archive's only claimant, on one channel. The telling adds a detail that rests on his own account: that Carl Sagan telephoned him to ask why he was causing so much trouble. The archive holds no document and the fact sheet carries no date, because the event proposed sits in vast antiquity. Outside the archive's holdings Brandenburg published the hypothesis in the Journal of Cosmology in 2014 and presented it at the Lunar and Planetary Science Conference in 2015. The explanation of record for Mars's xenon-129 is ordinary: it is the decay product of iodine-129 in the young planet, outgassed from the interior and then concentrated as the rest of the early atmosphere was stripped away, with no crater or debris field to mark a blast. The journal that carried the paper is itself criticised for what it publishes.

Why it sits where it does

L0 is one person saying it, and that is what the archive has: a credentialled physicist making this claim in print and on camera. Whether the isotopes mean what he says is not resolved here.