I swear this time, a very quick post. As with the last one, I’ve seen this claim not only on science forums but also pseudoscience forums and radio. The form goes like this: Pluto has surprisingly few craters because its orbit is inclined 17° relative to the plane of the solar system, where most impactors would be.
I’ve said it before (especially with respect to global warming deniers), and I’ll say it again here: Scientists, in general, are not stupid.
We take that into account. We also take the very low impact speeds into account. And the expected porosity of impactors. And potentially different impactor populations. In fact, Sarah Greenstreet’s thesis work was just published a few months ago, “Impact and cratering rates on Pluto,” that explicitly models a s— -load of different possible impactor populations and therefore possible crater populations, explicitly integrating the orbit of Pluto through time that – ¡gasp! – takes into account its orbital inclination. As an aside, I don’t know what “blogs” Richard Hoagland happens to be reading, but I can guarantee that scientists involved on the mission science team are not assuming that the impact rate and type at Pluto are the same for the inner solar system.
And besides that, it’s not entirely “surprising” that it has so few craters. This was predicted at least over a year ago to be a consequence of sublimating and refreezing of the atmosphere. What is surprising is the relatively few craters on Charon, though the one decent pixel scale image with favorable sun for mapping craters that we have so far does show many dozen.
Scientists unfortunately often forget that they know lots of stuff that other people don’t know, and things are taken for granted. I think, unfortunately, that when people have remarked about the “surprisingly few” craters observed on Pluto, that is taking into account Pluto’s orbital characteristics. It’s implicit, because it’s a “duh” point for those who tend to talk about it, and they forget to mention that this is implicit.