Exposing PseudoAstronomy

December 31, 2016

Podcast Episode 154: Impact Crater Pseudoscience Mishmash


Impact cratering
Is neat, but crazies like to
Abuse the science.

To end 2016, we have some crater-related pseudoscience. This is an episode where I talked about three different claims related to impact craters and how two of them misuse and abuse impact craters as a way to make their brand of pseudoscience make sense, in their own minds. The third claim falls under the “bad headlines” category and I get to address the Gambler’s Fallacy.

I’m still experimenting with a new microphone setup and you can hear the audio change tone noticeably part-way through. That’s when I moved my computer from off to the side so I was talking into the side of the microphone to more in front of me so I was talking into the top of the microphone. I also have a new laptop and figured out that the clicking/crackling that’s been in some recent episodes is when I stop recording, start again, and for a few seconds, every fraction of a second, the computer just records nothing for a much tinier fraction of a second. In this episode, I spent an extra half-hour editing all those out so there’s much less of it.

Artistic Rendering of Asteroid Impacting Earth

Artistic Rendering of Asteroid Impacting Earth

November 8, 2011

Proof in Science versus the Media, Comets and Water, and Creationism


Introduction

How Earth got its water is an ongoing question in solar system evolution. A new study suggests comets are more likely to be the answer than previously thought. But could the answer simply be too hard for us to figure out; should we just not worry, and can we simply say that a loving God did it?

The Problem

When the solar system formed, there was a basic temperature gradient — it was hot in the center, where the sun was forming, and it got cooler as you went farther away from the nascent star. The location in the solar nebula that was about 100°C (212°F), is called the “Frost Line” where the water molecule would no longer be a volatile gas, but it would be a liquid and could be accreted to a forming object in an appreciable quantity. The frost line is about where the asteroid belt is.

Hence the problem: If liquid water could not form where Earth was, then how did Earth become the relatively water-rich world it is today?

A Solution?

For the last few decades, the favored solution has been delivery by comets. Comets are mostly water-ice, we know they impact objects, and we know that the impact rate was much higher in the very early solar system than it is today (in fact, I’m attending a workshop on the early solar system bombardment history in February where the focus will be on this).

A problem with this has to do with what’s called the deuterium/hydrogen ratio. Basically, water comes in two forms, “normal” water which is the familiar H2O (two hydrogen atoms and an oxygen atom), and HDO (one hydrogen, one deuterium, and one oxygen). The latter is known as “heavy water” and you may have heard about it in relation to nuclear fusion.

Deuterium is a heavy form of hydrogen. A normal hydrogen atom has one proton in the nucleus. Deuterium has one proton plus a neutron, making its mass about twice that of a normal hydrogen atom … hence “heavy water” when it’s incorporated into the water molecule. It’s still considered hydrogen because the number of protons is what determines what atom it is. (And for those who like the extra credit information, tritium would be one proton and two neutrons.)

Getting back to the problem, the deuterium/hydrogen ratio (abbr. as D/H) is the normal ratio of heavy water molecules to normal water molecules found on an object. Earth’s oceans have a D/H of about 1.56 x 10-4, or basically a bit more than 1 out of every 10,000 water molecules is heavy water. Comets, though, have been measured to be about (2.96±0.25)x10-4, or around 70% too high. Asteroids are too low at (1.4±0.1)x10-4.

So where did the water come from?

New Proof that Comets Watered the Earth

So proclaimed the title of an October 11, 2011 Time article. That’s right, “Proof.”

My problem with this statement is that we never have absolute “proof” in science. We have evidence that adds to the “conclusivity” (yes, I just made up a word) of a hypothesis. Proofs are in mathematics. Proofs never apply to real life. If you’re interested in this subject, I’ve written probably two relevant posts on it (post 1, post 2).

The article in question (Hartogh et al. 2011) is about a recent Nature Letter (a very short paper) that measured the D/H value in a comet named 103P/Hartley 2. The D/H measured in that comet came out to be (1.61±0.24)x10-4 … which overlaps with Earth. This particular comet was from a different part of the solar system than previous comets with a D/H measurement, which is part of why this is a new result and why it was hyped up a bit.

The effect of this work is to revitalize the comets delivering water hypothesis, clearing up one of the biggest problems with it: We now do have a potential source for water that matches a significant constraint.

If you’re interested in reading more about it, other than the title, I do suggest the Time article.

But I Thought Goddidit

This brings us to the Answers in Genesis’ “News to Note” from October 15, 2011, specifically the second item. They don’t necessarily dispute the basic science of the article, rather the “view:”

“Nevertheless, in an effort to avoid a biblical explanation for the origin of all things—in other words, God as Creator—many cling to this explanation despite its aberrant physics. While the isotope ratios in the comets and asteroids are of scientific interest, they tell us nothing about the origin of the solar system. …

“The Bible explains the origin of the water on Earth and the origin of the entire universe. And the time of this Creation, about six thousand years ago, does not exceed maximum comet lifespans or demand a hypothetical birthplace to replenish them. … [God] made the Earth with its generous supply of water, not as a hot molten world that would boil away its water. After providing the Earth with an atmosphere, dry land, and plant life, He created the solar system and the other stars. He specifies that He made the sun, moon, and stars on the fourth day of Creation week. There is no way to blend the Genesis account of Creation with secular ideas of cosmology such as the big bang and the nebular hypothesis without calling God a liar.”

I really don’t think at this point that I need to go into detail about this and my position on it. It really is interesting to see, though, how these people are so willing to stick their heads in the sand and would be perfectly content in the Dark Ages of Europe a thousand years ago.

Final Thoughts

This was an interesting piece of science news, one that I knew some creationist somewhere was going to have an issue with, and one that I hoped the news media would not spin too broadly. I was right on the first, wrong on the second. With the latter point, these things are subtle, but using words like “proof” or “prove,” “hypothesis” versus “theory,” and “believe” versus “think” are words that shape significantly the public perception of science, how it works, and how “definitive” it is.

After over half a decade of fighting, the science-/evidence-based medicine crowd has succeeded in making that the term people use for what had been generally referred to “western” medicine. It’s a long battle, but maybe some day we’ll be able to get people to use some of these basic science terms correctly. At least when referring to science.

September 24, 2011

Follow-Up on the Dino-Killing Asteroid


Introduction

Last night, after making my post “What’s Going on with the Dinosaur-Killing Asteroid?” I contacted the lead author from the original 2007 paper, Bill Bottke (in the interest of full disclosure, I actually collaborate with him and see him about once a week, including yesterday morning).

I asked Bill if he would be willing to glance over the short post and let me know if I got any of the science outrageously wrong. His reply was a bit more than I had expected of a simple “yes” or “no,” where he instead wrote a more elaborate explanation of what was going on. I asked if I could post his response to my blog as an addendum and instead, he sent a more detailed reply for me to post. Since it was somewhat lengthier than the original post, I figured I’d just make a separate one. What follows is Dr. Bottke’s reply, slightly edited for grammar/spelling as he requested.

Note: You should read my original post before reading Dr. Bottke’s response.

Bottke’s Reaction

First of all, this is science, and not every idea is going to work. One has to do the best one can with the available data, and some models do not survive first contact with new observations.

With that said, let me try to realistically assess where we are and where we are not.

From the dynamical end of things, having a smaller parent body and smaller family members means things can get out of the main belt faster than before. If anything, this moves the impact closer to the peak of the impact spike distribution, which is good for our 2007 model. Moreover, many potential impactors can now get out by being injected directly into the “escape hatch” right on top of the family. We did not model direct injection in detail in 2007 because the K/T hit appeared to be made in the tail of the Baptistina shower — those results would not impact our work. Now that things have changed, we can examine this more closely.

Overall, I find it highly suspicious that K/T occurred in the middle of the Baptistina asteroid shower. Asteroid showers are very rare in solar system history, though coincidences do happen in nature. This makes me think the new results could potentially strengthen our story, not weaken it.

A smaller asteroid means there are fewer large projectiles in the Baptsitina population. This hurts our original model. Interestingly, though, new estimates of Ir (iridium) and Os (osmium) associated with K/T that came out after our paper suggest the impactor may have had a diameter 4-6 km, not 10 km, so this may all be a wash. Impact energy is strongly a function of velocity, and impact velocities on Earth can be very high for asteroids, so there is not necessarily a contradiction here. For those that want to know more, see recent papers by Frank Kyte and Paquay et al. (2008) (“Determining Chondritic Impactor Size from the Marine Osmium Isotope Record” in Science).

The main hit to the 2007 story from the recent WISE work is composition. If Baptistina and its family members turn out to be a different asteroid composition than we suggested in our 2007 paper, we cannot link the family to the limited compositional information we have on the K/T impactor. From Cr (chromium) studies of K/T terrains on Earth, it looks like the impactor was a particular kind of carbonaceous chondrite. A high albedo (reflectivity) for Baptistina could suggest it is not actually this composition. Preliminary spectra for Baptistina family members may also work against it being a carbonaceous chondrite, though most of the family has not been examined from a spectral standpoint. Observers have mainly looked at asteroids near Baptistina, not “in it” as defined by our paper, and interlopers in this part of the main belt are a major pain to deal with. What observers need to do is look at the prominent “clouds” of objects observed for the family, where interlopers are less of an issue. This should be dealt with in the near future.

Note that if Baptistina family members turn out to have a radically different composition than carbonaceous chondrite, it would imply we were strongly misled by the Sloan Digital Sky Survey colors for Baptistina. Nearly 300 objects have been examined, and they have been classified as C/X-types of asteroids, which link to most objects as carbonaceous chondrite-like objects (see Parker et al., 2008).

There is also the surprising and unusual possibility that some asteroids that look like carbonaceous chondrites may have higher albedos that we expect. For example, interesting work on (21) Lutetia, which was recently visited by the Rosetta spacecraft, has a high albedo and a composition that many say looks like a carbonaceous chondrite. For those that know and love asteroid taxonomy, K-types asteroids look like they may be able to produce many kinds of carbonaceous chondrites, yet they are spectrally similar in many ways to those asteroids that may produce ordinary chondrites.

Note that even if composition is knocked away, one could question whether Cr is diagnostic, or whether different parts of the asteroid could have different Cr signatures. However, this strikes me as a desperation ploy, and I will do no more than mention it until new information on Cr comes to the fore.

Final Thoughts

With that response from Bill – more technical than I normally have in my blog but I think important for those who are interested – I’ll close out by reminding readers of what he stated at the beginning and what I have stated many times on this blog: This is how science works. We make observations, gather data, create models, make predictions, and in light of the evidence revise our models or make new ones. Contrast that with the way many creationists, conspiracy theorists, UFOlogists, astrologers, etc. work.

September 23, 2011

What’s Going on with the Dinosaur-Killing Asteroid?


Introduction

A NASA press release spawned many, many headlines this week in pretty much all newspapers and online news sites, both major and minor, with variations on the theme of, “The origin of dino-killing rock is back to being a mystery.” If somehow you managed to miss the news, I invite you to read the BBC version, though you could also read the original NASA press release.

So, what’s going on here? Is this another case of the media blowing headlines out their collective … well, mouths? Or is there something to this where we’re no longer sure what may have ended the dinosaurs?

2007 Paper

As may have been obvious from the way I worded the question, the answer is very much the former: Headlines are meant to grab you and to be sensationalist so you’ll read the story. Stretching the story or even missing the point are generally irrelevant.

The actual story goes this way: In 2007, Bill Bottke and two co-authors had a paper in the journal Nature entitled, “An asteroid breakup 160 Myr ago as the probable source of the K/T impactor.” The article was actually much more than that, and an extension from their conclusions was that based upon their modeling, the timing for an asteroid breakup would work dynamically for spawning the asteroid that killed the dinosaurs.

Yes, the asteroid theory for the destruction of the dinosaurs is still valid, it is still by far the best one out there and the one that fits the most data the best. So let’s get that sensationalist headline grabber out of the way.

Again, the crux of the Bottke et al. article was that they dynamically modeled an asteroid family (a group of asteroids that travel together and likely formed from an original, larger asteroid, that broke up). This particular family is called the Baptistina family. Based on an assumed brightness for the asteroids, they can estimate their mass and subsequent sizes. Based on how spread out the family is, they can model when it broke up, and the mass also factors into this calculations. Based on all these, their results show that the Baptistina family formation event could have spawned the asteroid that we pretty much “know” resulted in the destruction of the dinosaurs.

Edited to Add: I have a follow-up post from the author of the 2007 paper, Bill Bottke.

2011 Paper

This brings us to the press release and subsequent hubbub this week. The new paper talks about a lot of things, but what’s most applicable is that they have a better measurement of the brightness of these asteroids, and it’s around a factor of 5 times brighter than what Bottke et al. assumed (based on some of this paper’s teams own assumptions, though it’s likely a more accurate result).

The result is that there is much less mass and smaller sizes of the asteroids in the Baptistina family. Meaning that it disperses more quickly (so would have broken up more recently). And finally meaning that the likelihood that it was the source of the asteroid that led to the death of the dinosaurs is much smaller.

To Repeat

No, this does not mean that an asteroid didn’t wipe them out. It does not mean it was a comet. It does not mean it was aliens. It does not mean it was volcanoes. It does not mean it was the Earth growing in size so the dinosaurs got crushed under their own weight. It does not mean it was [insert: whatever the person you read before coming here invented].

It means that the likelihood that the impactor is from the formation event of this family of asteroids is now significantly smaller.

Final Thoughts

Really, that’s about it. But “Higher reflectivity of asteroid family means scientists less certain of the source of the asteroid that likely killed the dinosaurs” does not a good headline make. Oh well.

Edited to Add: I have a follow-up post from the author of the 2007 paper, Bill Bottke.

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