A Response to Mark Hempsell

Posted on April 16th, 2008 by blue collar scientist

Mark Hempsell, the co-author of the book that posits that a copy of an approximately 5,000 year old Sumerian tablet records an observation of an Aten asteroid, prior to its atmospheric entry, which impacted at Köfels, Austria - this being a story which, in the immortal words of The Greenbelt, we “doubt it very much” - has left two comments on this blog, one of them fairly lengthy and, I thought, requiring some reply.

My original takedown is here, and even though I wrote it before I realized that the Bad Astronomer, StumbleUpon, and other internet opinion-makers would make it the most popular post ever on this blog1, there’s very little I’d retract. It is still a crappy press release that evidences precious little understanding of impact processes or asteroid orbital dynamics, and it is still a wildly implausible hypothesis that the authors actively resist subjecting to peer review.

The comment of Mark Hempsell’s that I am addressing is here. Starting in the second paragraph, Hempsell exhibits either a puzzling unclarity or a lack of understanding of, or poor research within, the field.

It [the impactor] is definitely neither stony nor iron (what Aten is?)…

Asteroids are classified according to their spectral types, which are determined by their compositions. As I read it, Hempsell is here saying that Aten-class asteroids are not stony or iron-rich. There are relatively few known Aten asteroids - hundreds, not thousands - and few of them have been observed spectrally.

As far as I can tell, all Atens so far observed are either stony, or iron:

  • (3554) Amun is an M-type - considered to be of mixed iron/stony composition.
  • (33342) 1998 WT24 is E-type - stony or rocky, like an achondrite meteorite, or rather like basalt on Earth.
  • (99907) 1989 VA is an S-type - of silicaceous rocky composition.
  • 1989 UQ is a C-type, which stands for carbonaceous, and is therefore rocky like a carbonaceous chondrite meteorite. In fact, C-type asteroids are (at least in part) where such meteorites are thought to come from.

Oh, and guess what - this list includes (2062) Aten, the first discovered and hence the “type specimen” for the Aten family of asteroids. It is type S, so again, it is made of silicaceous rocks.

A lot of data on this is available in 2008Icar..194..111P (Photometry of Aten asteroids—More than a handful of binaries)2, which lists for a large number of Aten asteroids the B-V and V-R color indexes that are used to constrain asteroidal spectral types. (For my lay readers, B-V and V-R provide the asteroid’s color; it is achieved by measuring the brightness of the asteroid in two defined photometric color bands and then taking the difference - hence the minus sign.)

So to Hempsell’s question, ‘what Aten asteroid is stony or iron,’ the answer is, basically, all of them that we’ve ever checked.

…indeed the impact dynamics…

The impact dynamics? There are no impact dynamics to look at. There’s absolutely no evidence of an impact at Köfels. There is no shocked quartz with PDFs, no impact glass, no crater, no microcraters, no remains of an impactor, no local enhancement of elements and isotopes associated with meteoroids, no ejecta….

I believe the problem here is that Hempsell is looking at Köfels, correctly discerning that the geology suggests there was no impact, and is then making ad hoc adjustments to his hypothesis to compensate. It would be more proper to look at Köfels and acknowledge that no impact occurred there - and then stop. Because one adjustment that needs to be made is extremely implausible:

…suggest a density below 1000 kg/m3.

First, let’s convert to the standard units: 1000 kg/m3 is 1 g/cm3. That happens to be the density of water3. Gasoline (petrol for European readers) has a density of about 0.7 g/cm3. Stuff of this density does not exist in inner solar system small bodies for a very good reason - volatiles that have such low densities evaporate or sublimate, and are lost to the parent body. This is a process we see with comets - sublimation creates the comet’s coma and tail. What you are left with after a few centuries of solar heating and mass loss in the inner solar system are the rocky remains - and it is quite possible that many inner solar system asteroids formed in this way.

The problem here is very serious: Hempsell is hypothesizing that the asteroid was an Aten, which by definition spends all its time in the inner solar system. But it couldn’t have had such a low density if it had spent even a few thousand years in the inner solar system, because the fluffy stuff would have long since been lost. If you run integrations on well-observed Aten asteroids, we find they’ve had more-or-less stable orbits for millions of years. (Sources: see here, and here.)

Hempsell seems to hypothesize an asteroid made of something like gasoline, in terms of density, which can’t exist - or can it? Perhaps the asteroid was a rubble-pile. Maybe rubble-pile asteroids have lower densities than water. Shall we check that out?

It is easy to do. The NEAR-Shoemaker spacecraft orbited asteroid (433) Eros, and then landed on it, in 2000-2001. This resulted in very good measurements of its density, which was, indeed far lower than many expected. But the density was still 2.4 g/cm3. If Hempsell is calling for an 0.8 g/cm3 asteroid, this is three times too dense - a massive discrepancy between observation and hypothesis.

The impact effect will be over estimated by Marcus, Melosh, and Collins because of the Alpine terrain.

No, it won’t. Marcus, Melosh, and Collins evaluated different terrain types (PDF). From their abstract:

The program requires six inputs: impactor diameter, impactor density, impact velocity before atmospheric entry, impact angle, the distance from the impact at which the environmental effects are to be calculated, and the target type (sedimentary rock, crystalline rock, or a water layer above rock).

So, unless we believe that Austria is made of feather pillows, it looks like they’ve got the situation covered. In fact, the geology of the area is mixed sedimentary and crystalline rock, and using either target type results in a huge crater, even from an asteroid made the density of gasoline. Go check it out for yourself.

Back to Hempsell:

The way it [ejecta] reaches the south east Mediterranean is the back plume which is deflected by the low pressure region behind the object, an effect well documented during the Shoemaker/Levy 9 impact.

Unfortunately, the SL-9 impact on Jupiter was into a dense gaseous atmosphere with no solid-surface impact, and the dynamics of that impact are thought to be very different from solid-body impacts. Hence, the mechanism that created the Jovian plumes isn’t looked for on Earth. This is for the simple reason that a low-pressure region on Earth cannot achieve as large a pressure difference as on Jupiter4. Earth’s atmosphere is significantly less dense to begin with. (Sources: Here, here, here….)

However, suborbital ballistic trajectories of ejecta are expected with large Earth impacts, as happened with the Chicxulub impact (at the K-T boundary - you know, the one that contributed to killing off the dinosaurs). Unfortunately, you don’t get ejecta without a crater. It is the process that forms the crater which causes the ejecta. I’m sure we’ve all noticed that craters are holes in the ground. Ever wonder what happened to all the dirt and rock that used to be where that hole is? Some of it vaporizes, but much of it turns into ejecta.

So, the lack of a Jovian-density atmosphere on Earth means you can’t have SL-9 style plumes, and lack of a crater means you can’t have ejecta. So much for the material supposedly thrown all over Egypt and the Levant, accounting for the destruction of Sodom and Gomorra, and all that.

Hempsell then goes on to suggest that we - the multitudes of asteroid experts, anthropologists, textual critics, and so on, who find all this material laughably amateur, and say so in the comments to my original post - are somehow lacking in integrity and qualification because we haven’t read the book.

…if you want to publically slag it [the book? the hypothesis?] off as delusional pseudo-science please do us the courtesy of finding out what we are actually saying first.

The fact of the matter is that a press release was widely circulated by the home institution of one of the book’s co-authors. It is entirely legitimate to be called to account for false and implausible claims made on one’s behalf in a press release that has the imprimatur of the claimant’s academic institution, and I shall not back down.

In response, apparently, to my offer to read the book and post again, Hempsell says:

A final point on free copies; we have sent around 100 copies to journals and researchers in the field, (and in a strange reversal of the current argument several expressed surprise saying they had expected to buy it). I am sorry if you did not end up on that list, but I hope you can see the problem of sending copies to every anonymous web blogger.

I can indeed see the problem of sending the book to every anonymous “web blogger”5. However, I’m not one of them: my real name is disclosed on this blog.

Furthermore, my field of research is asteroids. Let’s not push that too far - I’m not as expert as many, many academics working in the field, and I’d not rate my knowledge equivalent to that of a PhD employed full-time in the field. However, I am not in an entirely unrelated discipline such as astronautics engineering; I’m actually employed in a capacity in which I study these bodies in a scientific way, as a part of a team at an astronomical observatory that has, at this point, thousands of peer-reviewed publications on asteroids, some with my name on them6.

I’m also, as commentator “Don Amache” points out, pretty well known as a magazine writer and critic, having been employed to review software and books for several years at Sky and Telescope.

And finally, I’ve also managed to give this particular hypothesis a lot of bad publicity. I’m up to about 20,000 hits on the original posting alone, and there’s still a lot of traffic coming in.

One way to respond to bad publicity, if you have the confidence in the hypothesis that Hempsell claims to have, is to send the work over for reading and further review. And it doesn’t have to be a book - I do all of my reading of scientific papers via PDF these days. The cost to e-mail a PDF is insignificant.

Nevertheless, the authors’ claims, as made in the press release, and as made here, on the blog, are in some cases false, and in all other cases wildly implausible. I predict it won’t bear professional scrutiny, or even a semi-professional fact-checking and inspection. I doubt I shall see the book, and I’m not losing sleep over it. We already have enough to know this crazy idea is all wrong.

  1. That’s not necessarily hard to do with a young blog, mind. []
  2. Sorry - as far as I know, Icarus prohibits its investigators from participating in arXiv or other free-access solutions. []
  3. At 4° C. []
  4. Think of it this way - the lowest possible pressure on Earth is zero. Sea level pressure is almost 15psi, making the largest delta 15 psi. On Jupiter, pressures are available that are hundreds of times larger, leading to deltas of many hundreds, or thousands, of psi. Apologies for the SI units. []
  5. Are there bloggers who are not on the web? []
  6. This is absolutely no reason to believe what I say here, by the way. I raise these matters only to show that I do have some qualifications to review such a book. []

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4 Responses to “A Response to Mark Hempsell”

  1. Zach Miller Says:

    Wow, sir. Way to layeth down the smack! I greatly enjoyed both posts, and the prior’s subsequent comments.

  2. Blue Collar Scientist » Blog Archive » A Sumerian Observation of the Köfels Impact? Almost Certainly Not…. Says:

    [...] Update #2: Some very specific claims were raised by Mark Hempsell in the comments below; I’ve responded to them here. [...]

  3. Don Ameche Says:

    You could have utterly crushed this just with your discussion of the the “Aten asteroid” with a density less than water. Such a thing has never been seen in the entire history of astronomy, and there’s good reasons from physics why such things don’t exist. But no, you had to crush it, then smash it some more, then give it a few solid kicks, then beat it about the head with a club. Nice job.

    This whole hypothesis is like that famous Norwegian Blue parrot - what I mean is that it’s stone dead, it’s bleeding demised, it has expired and gone to meet it’s maker, it is bereft of life and rests in peace, it has shuffled off its mortal coil, the hypothesis has kicked the bucket, and run down the curtain to join the choir invisible. Two guesses about who the pet store clerk might be.

  4. Mark Hempsell Says:

    Well Jeff you have me on the composition of Aten Asteroids they are indeed almost all spectrally stony and none are C Class. However the tentative conclusion in the book that our asteroid may have had a density between 1200 kg/m3 and 600 kg/m3 (and thus is most likely to have been a C class object) is feasible in light of measured bolide, comet and asteroid densities. But this is not a key part of conclusions and if the object were denser, and hence heavier, the only real change is the bang gets bigger and I can live with that.

    If anyone is still following this I have added two posts on the FAQ section of the Köfels research website one on the lack of crater and the other on the density/composition question. This is at

    http://www.bris.ac.uk/aerospace/research/dynamicsandsystems/kofels

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