For the benefit of others, Nick, ectoterrestrial, and myself discussed this paper last November (shortly after its publication) in another forum. Below is an excerpt from one of my posts responding to someone else's comments, which are preceded by ">". To both Nick and ectoterrestrial, I know I am violating my own self-imposed "rule"; however, as a moderator, I'll make this one exeception ;-)

Note: For those who do not have access to JGR-Planets, an ~123 Kb PostScript file of this paper in preprint form is available here.

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> If I could add my $0.02 worth, the
> paper starts off in "normal"
> territory and then takes a strange
> twist and I'm amazed that it got
> through review.

[...]

> The author speculates about the
> electromagnetic consequences of this
> without doing a reality check to see if
> other evidence is compatible.

As an AGU member I have access to the final version of the paper published online, so I did not read the preprint and therefore do not know if any changes happened during the review process. That said, I'll note that in the Acknowledgments section Janhunen specifically thanked a "referee for the encourgement to explore the magnetic anomaly topic further." It's possible that the reviewer(s) may have felt the same as you; however, whether Janhunen's acknowledgment reflects the possibility that he intended to develop fully the electromagnetic portion of his presentation or not is anyone's guess, though I suspect the latter is more likely owing to the passage "We do not attempt to discuss in detail the mechanisms that could primarily generate the 40 kA current in the ocean." Frankly, even Janhunen notes that the "~ +/- 40 nT magnetic anomalies" over the northern plains, which were observed in the MGS MAG/ER data by Acuna et al., can be explained by the (perhaps simpler) model of Acuna et al. that invokes remanent magnetism.

For what it's worth, though, the paper (very brief for a typical JGR-Planets submittal), is only offered as speculative piece of work. Even the author notes that, other than the putative the "anomalous" magnetic readings, there is a dearth of direct observational data to support his model. It appears that Janhunen is taking an admittedly speculative model (i.e., extrapolation of the Galileans analog to Mars) and attempting to tie in "anomalous" magnetic readings, thermodynamic modelling, etc. In fairness, though, it's not as if speculation has not passed peer-review, is it? Can anyone say "White Mars"? :-)

> However, even were his model true,
> the work of Frey et al., Tanaka
> & co. and Head etc. on buried craters
> shows that the thickness of
> the total cover over basement in the
> Northern plains averages 1.4
> km and only reaches a maximum of 4
> km in rare local deeps.

Yes, I agree that Janhunen is, to put it charitably, "reaching" in this regard. As you note, the MGS MOC NA imagery (Malin and Edgett) and the MGS MOLA data (e.g., Frey et al, Head et al., etc.) indicate that while the "northern plains" are fairly flat and homogeneous at macroscales, at decameter scales the surface appears rougher and less smooth (i.e., a "thin" cover where the rims of buried craters poke through). One might also note that the References section of Janhunen's paper, with the exception of the citation of last year's Clifford and Parker paper in Icarus, includes mostly works from 1999 and before. Whether this was due to a lengthy passage of time between submittal of the initial manuscript and acceptance of the final version is unclear, but close observers will note that no less than Jim Head, among others, is backpedaling somewhat from his original "shoreline" interpretation of Parker's Contact 2, which he published in Science (and which was cited by Janhunen).

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Alex R. Blackwell
University of Hawaii