Hi Simon -

I love it when people talk so definitively about something about which so little is known, so I'm going to engage in some of that here myself. Throw out the conditional, so to speak...

Youre' confusing the major strata with minor layers, about which, as you rightly obaseve, there are millions of them. More on these in a moment...

We can safely rule out any "recent" volcanism on Mars- say within the last seveeral billion years. Mars' molten core had cooled, and there never was any tectonic activity on Mars - Mars simply has no large nearby Moon, or other source for a gravitational effect capable of causing tectonic activity.

Remember also that since Mars lacked a molten core, it also lacked amagnetic field to shield it againts the Sun's wind of charged particles - hence Mars had its volatiles stripped, excpet for those trapped in its lithosphere.

I agree with your assessment of the origin of the asteroid belt, in contradiction to the position fo McSween and just about everyone else - there is simply too much gravitational differentiation seen in meteorites, the samples from the asteroids which we have recovered here on Earth.

That's why Mars' large regular strata must have been produced by comet impact: the fragments of that formative impact, the asteroid belt, were cleaned up in the Late Period Bombarment Event some 3.8 billion years ago [Gya]. On the other hand, what we see on Mars along its canyon walls are large regular strata.

Now the amounts of CO2 and sulfuric acid necessary to form these layers was immense: thus it necessarily follows that large impact processes on Mars work like a chain reaction: the initial CO2 and sulfuric acid release then in turn release yet even more CO2 and sulfuric acid, and so on, and so on, and so on...

Now to the small layers. I see there appears to be some agreement on "aeolian" (CO2) deposition and the binding agent (sulfuric acid) for the minor layers. The CO2 is universal, while local impacts release binding agents. There are many of these, and as more layers form on top, gravity then compresses the earlier layers.

Now for the conditional part: while this may be right, or it may be wrong, any kind of argument about processes on Mars based on Earth analogies is certain to be wrong - physics and chemistry are the only things that hold.

ep

ep

ep