Bill Hartmann is a wonderful artist, and an experienced and reputable scientist, and so are you (I like your illustrations, but if you tell me you have your "people" do them for you, I will be so disappointed.) . I have nothing but respect for the work you and others do to attempt to comprehend planetary history and geology.

But when anyone -- planetary scientist or not -- shuts their mind or their eyes or relies on the pronouncements of authority to support their argument without critically examining those pronouncements, or without admitting the wide error margins intrinsic to those pronouncements, then planetary science is done no favors.

I ask simply that minds be kept open, that authority be questioned, and that observations be conducted from many points of view -- and that we all resist making conclusions based on a paucity of evidence or on misperception.

Crater-counting for age dating on Mars fails when circular formations on the surface are routinely misidentified, as I maintain is too often the case and has been too often the case since 1965, when the presence of craters first shocked the field.

Hartmann's arguments go back to those days. He's done tremendous work, and he's got a very good system for paralleling age-dating by crater counting between the Moon and Mars.

Hartmann also uses the "dust obliteration" argument to rationalize absence of small craters in some areas of Mars, which then leads to the "buried craters being exposed" arguments, and many other tortured arguments, all of which can be used to support hypotheses that may have nothing to do with what is really going on on the surface of Mars and other planets. This is the problem.

When the origin of the circular formations you are studying is assumed to be impact, but the formations themselves may have originated from a wide variety of internal rather than external processes, on time scales presently unknown, the whole exercise is cast into doubt. Remember "geosynclines?" How fiercely the "old farts" of geology fought against the insights of Wegener and how work toward an understanding of plate tectonics was basically suppressed -- for decades? And how tortured and ridiculous the arguments became? This is called "saving the phenomena."

At the rate things are going, it'll be forty/fifty more years before the field catches up with these simple insights about the varied origins of circular formations on Mars. But it will catch up, oh yes, and some young pup who hasn't even been born yet will do a victory dance because he has finally broken through the barricades and walls thrown up by the old farts to preserve their precious impact -- or other -- hypotheses (a sufficient number of the old farts will have finally died off, too).

You should know better than most folks here that's how it works. And you -- of all people -- should be a fierce advocate for more open mindedness about Mars.

Instead, it looks like you close your own mind, you uncritically accept the word of authority, and you shamefully attack people like Bob Clark who are doing their damnedest to ask pertinent questions and provide potentially useful references for everyone's eventual enlightenment. You should be celebrating that.

As for the swath of cratering that would result from the breakup and impact of Phobos on Mars, you're of course correct. There are several such swaths already tentatively identified, strongly suggesting that in fact such events have occurred in the past, and their orientations suggest that the location of the Martian equator has significantly shifted repeatedly. Oh. Dear. How to account for that on a cold-dead-ice-ball? Well, of course, just push everything back billions and billions of years, and you don't have to deal with it.

The point I tried to make -- which you sidestepped -- is that hundreds of large impact craters and thousands of smaller ones would result from the breakup and impact of a satellite like Phobos, all within a very short timeframe, thus significantly distorting any conclusions derived from age-dating by crater counting. So far as I know, Dr. Hartmann does not address this issue. I could, of course, be wrong.

But I start from a position of ignorance. I try to ask questions, to observe what I can, to wonder, to maintain an open mind, to study and to learn as best I can.

It's OK to be wrong. Everyone is, more often than not. ;-)

Cheers, BFelix