Kind of neat. I'd want to see a bunch more models show the same thing, but to the extent more studies seems to be showing how an early giant Northern impact can explain apparent puzzles, the more likely that looks as an answer.
I agree. Don't get me wrong, I'd be tickled pink if we could see clear-cut evidence of a novel dynamo like this, from which much about the Martian interior could be inferred. However, the pattern of magnetization is already easily explained by the patterns of cratering and tectonism that is already apparent from orbital imagery.
Take into account the Borealis "impact" crater with Hellas, Argyre, and Isidis. Given the combination of heating and shock in the region of these craters, it's not apparent what more needs to be explained about the vestigial crustal magnetism.
That said, I haven't read the paper, just Emily's digest.
Space/Science » in reply to Mars "Borealis" impact and magnetic dichotomy
re: Mars "Borealis" impact and magnetic dichotomy