Been in a haze of political activism... sometimes in order for our pet theories to get accepted we have to have people in office who give a damn. On the other hand, some things speak for themselves.

There's no doubt that most *not all* circular formations on the southern highlands superficially resemble impact craters such as those found on the Moon. The problems with the identification have been known since Mariner 4, however. Most are rimless or nearly so, most are very shallow for their breadth, and few show any subsidiary signs of impact, such as remnant ejecta blankets, secondary craters and so on. There are some very good arguments regarding why these anomalies should be so, and I'm aware of most of them (well... "aware" ... you get to a certain age of distraction, and it's hard to know what you're aware of any more... but I digress)

Rather than accepting these arguments uncritically, I say, "Wait. What if these anomalies were actually indications of a non-impact origin, exactly what some of these craters look like? How would that work, and are there examples elsewhere in the solar system of non-impact generated circular formations?"

There are obviously many thousands of impact craters on the surface of Mars. Their formation by impact is all but certain due to the characteristics of the formations: terraced and upthrust rims, central peaks, ejecta blankets, secondary craters and so on... some of these obvious impact craters appear to be very old, indicating that erosive forces have been insufficient to erase or bury them. That being so, one should immediately question the notion of "buried craters being exhumed" conceptually. How so? One should demand an explanation of the burial and exhumation processes in detail before accepting the concept uncritically. Unfortunately, the concept quickly became institutionalized, and once it was, it was almost impossible to question it. Consequently, there may be many circular formations on Mars that are categorized as impact craters (or the ubiquitous "buried craters being exhumed") that have other origins. Because it is useful for crater counting to uncritically accept all (or almost all) circular formations as impact craters, and Hartmann himself says he didn't count them, lay volunteers did, there has been little or no critical investigation of the origin of most craters on Mars.

I think we are in for some significant surprises, therefore (and it would hardly be the first time).

We do find on Venus and we do find on Io and we do find on the icy moons of the outer solar system circular formations that are not impact generated. We find them in abundance. As thinking about Mars has evolved, the Lunar Paradigm has largely been discredited -- except for the crater origin issue.

My suggestion is that thinking about Mars can further evolve by critically examining (to the extent we can) the origins of Martian craters.

Inspect this paper if you haven't already for a widely accepted view and ask questions: http://www-geol.unine.ch/cours/geol/marsediments.pdf

Here's another type example: Incipiant Chaos Terrain

This sort of thing is found all over Arabia Terra, especially, as well as associated with the major canyons. The larger crater in the context image seems to have some attributes of impact origin, such as an extensive, relatively uneroded ejecta blanket, yet the crater's floor is turning into typical broken chaos terrain. Is it possible that the creation of the chaos itself -- perhaps by undermining and subsurface flooding -- is also responsible for the apparent "impact" features? ie: through explosive release from the interior?

Cheers, BFelix

(Back to campaigning.)