Hmm...Anyone with enough chemistry kmowledge to guess why some scientists think Mars water broke down into....

[ProfessorGAC]

3. The Only Thing I Can Think Of...

...is uV & the presence of abundant metal oxides on Mars.
I'd still like to see the data though, because there is a lot of light energy required, even catalyzed, to split the water.
The fact that the atmosphere is nearly nonexistent means a lot of uV, even at 50 million miles farther from the sun.
I don't see a thermal route (requires over 1,500 degrees & metal oxides).
I suppose I can buy the uV route after the vast bulk of any water would have vaporized due to the very low pressure on Mars. I've used vacuum ovens with a 2 stage pump still have more pressure than the atmosphere on Mars.
I'm not, however, understanding how the metal come into contact with such a tiny mass of water diluted over such a huge volume. The mass transfer barriers seem insurmountable.
It's also highly endothermic, even with catalysis.
I'm dubious, but willing to be shown how they think it works.