Exposing PseudoAstronomy

July 23, 2015

#NewHorizons #PlutoFlyby – The Pseudoscience Flows #7: Very Few Craters ‘Cause of Pluto’s Orbit

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.


  1. The amazingly fresh terrain seen on Pluto instantly struck me as being very young and the result of extreme weathering effects which were created by the constant sublimation and re-freezing of Pluto’s atmosphere. The mass wasting down-slope on the large mountains reminds me of what is seen on the moon, Mars and Vesta. I assume, due to Pluto’s atmosphere, that this is occurring at at much faster rate than micrometeorite bombardment alone? I would think that it would be at least an order of magnitude faster? Just curious as to your thoughts on the subject.

    Comment by GoneToPlaid — July 23, 2015 @ 4:21 pm | Reply

    • While I linked to Sarah’s paper, I admit I have not yet read it. So far, I’m more the crater mapper on the team, while William McKinnon (the third author on the paper) is working more on model crater ages. With that disclaimer, I would say that yes, the atmosphere adds a weathering effect on top of bombardment, but the bombardment rate is significantly less than that in the inner solar system.

      Comment by Stuart Robbins — July 23, 2015 @ 5:03 pm | Reply

      • Hehe. The inner solar system does have that thing called the asteroid belt. Lots of stuff from collisions within the asteroid belt continuously drifts inward to strike the inner planets, in particular the moon and Mercury where such events are preserved due to the lack of any significant atmosphere. So little is known about what might come in from the Oort Cloud. All data pretty much is comets which originate from the Oort Cloud. I haven’t read Sarah’s paper either, but now that you mentioned it, it is on the top of my list of things to read. Did you get my email about Apollo 12? I would also like you have a look at my enhanced images of Vesta and its bright spots. Maybe not so much about the bright spots which I am sure were caused by an impact, but more about the mass wasting on Vesta’s crater rims which look similar to the mass wasting seen on Pluto’s mountains, except of course via different mechanisms. Perhaps, by comparing images of mass wasting on the moon, Vesta and Pluto, and by adjusting the image scales to compensate for the different amounts of gravity, one might gain some insight into the density of the near surface regolith on these worlds. I am just throwing a half baked idea out there as food for thought.

        Comment by GoneToPlaid — July 23, 2015 @ 6:12 pm

RSS feed for comments on this post. TrackBack URI

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Create a free website or blog at WordPress.com.

%d bloggers like this: