Exposing PseudoAstronomy

April 23, 2015

How Do We Know How Old Stuff Is on the Moon?


Introduction

While this movie is branded under “Exposing PseudoAstronomy” for legal reasons, it has less to do with popular misconceptions/conspiracies/hoaxes and more to do with real science. This is my third more modern, lots of CGI movie, and my second to explain a research paper that I wrote.

In the movie, I go through how the lunar crater chronology is the fundamental basis for how we estimate the ages of surface events across the solar system. I also explain how my work affects the lunar crater chronology and what can be done to better constrain it.

I’m still waiting for a young-Earth creationist to claim that because of a factor of 2 uncertainty, 4.5 billion becomes 6.019 thousand.

I also wrote a blog post about this for The Planetary Society. Because it was posted there over two weeks ago, I think it’s fair game to repost here. You can click on any of the images for larger versions, and all of them are screenshots from the YouTube movie.

Planetary Society Blog Post

Three years ago, I started a project to replicate work done by various groups in the 1970s and 1980s. When the project was completed, the result implied that much of what we think we know about when events happened in the solar system were wrong, needing to be shifted by up to 1 billion years. I presented this in a talk at the recent Lunar and Planetary Science Conference at 8:30 AM, when most people were learning about the latest results from Ceres.

The project started simply enough: I downloaded some of the amazing images taken by NASA’s Lunar Reconnaissance Orbiter’s Wide-Angle Camera (WAC) that showed the Apollo and Luna landing sites. Then, I identified and measured the craters (my dissertation work included creating a massive global crater database of Mars, numbering about 640,000 craters).

The reason to do this is that craters are the only proxy we have for ages on solid surfaces in the solar system. We can determine the relative age of one surface to another (is it older or younger?) by looking at which has more craters: The surface with more craters will be older because, when you assume that craters will form randomly across the body, then the surface with more craters has had more time to accumulate them.

How to Use Craters to Understand Ages

Basic principle behind this work. (Background image © NASA/ASU; composite © S.J. Robbins.)

If we want to use craters for an absolute timeline – as in, actually put numbers on it – then we need some way to tie it to real ages. This was made possible only by the United States’ Apollo and the USSR’s Luna missions that returned rocks from the moon that could be radiometrically dated in labs on Earth.

With these radiometric ages, we then identify the craters on the surface those rocks were gathered and say that a surface with that many craters per unit area is that old.

That’s the lunar crater chronology: The spatial density of craters larger than a standard size versus radiometric age (we use 1 km as that standard size). This crater chronology is then scaled and used as a basis for the chronology across the rest of the solar system. When you hear someone say that something on the surface of Mars is X number of years old, chances are that’s based on the lunar samples from the 1960s and 70s and the crater counting done 40 years ago.

Apollo 15 Landing Site

Example landing site area, Apollo 15 (yellow star). Blue outlined areas indicate regions on which craters were identified, blue shaded areas were removed because they are a different type of impact crater, and blue circles are the craters mapped and measured. (Background image © NASA/ASU; data and composite © S.J. Robbins.)

And, that’s where my project came in. While the rock samples have continued to be analyzed over the decades, the craters were not. It’s easy to assume that the researchers back then did a great job, but by the same token, science is about replication and re-testing and we have developed new ways of doing things in the crater community since the Apollo era. A simple example is that the crater chronology requires a spatial density, and therefore you need to know the area of the surface on which you have identified craters. Over the past 40 years, we have better understood the shape of the moon and now have computers to allow for much more precise area calculations. This can result in changes by 10s of percent in some cases.

When I had finished my reanalysis, my results differed for many of the landing sites, in some cases by a factor of 2 from what the standard is in the field. I was surprised. I checked my work and couldn’t find any mistakes. So, I combed through the literature and looked to see what other people had published. I ended up finding a range of values, and only in one case was my result at the extreme low or high of all the published results. I showed my work to colleagues and none of them could find any issue with it. So, eventually I published it, early last year.

The Lunar Crater Chronologies

The new (blue) and old (red) chronologies and the data used to fit the model. The vertical axis shows the spatial density of impact craters larger than or equal to 1 km in diameter, and the horizontal axis shows the age of the surface from radiometric dating of collected rock samples. (© S.J. Robbins)

When I fit my crater data to the radiometric ages, my fit function showed a difference with the standard that has been used for three decades: Surfaces assigned a model age of about 3.5 to 3.7 billion years under the old chronology were older, by up to 200 million years. And, surfaces younger than about 3.4 billion years under the old chronology are younger, by up to about 1 billion years.

Differences Between the Lunar Crater Chronologies

The new and old chronologies in blue and red (top), and the difference between them in terms of model surface age. (© S.J. Robbins)

There are a lot of implications for this. One is that volcanism on the terrestrial planets may have extended to more recent times. This would imply that the planets’ cores stayed warmer longer. Another implication is that the large reservoirs of water thought to exist around 3 billion years ago may have existed for another 500 million years, with implications then for favorable environments for life.

But, something that I added near the end of my LPSC talk was the question, “Am I right?” The answer is an unsatisfying, “I don’t know.” I of course would not have published it if I thought I was wrong. But by the same token, this type of science is not about one person being right and another being wrong. It’s about developing a model to fit the data and for that model to be successively improved as it gets incrementally closer to explaining reality.

And, there are ways to improve the lunar chronology. One that I’m a big advocate of is more lunar exploration: We need more data, more samples gathered from known locations on the moon’s surface. We can then date those samples – either in situ or in labs on Earth – and along with crater measurements add more tie points to the lunar crater chronology function. Right now, there is a glaring gap in the sample collection, one that spans 2 to 3 billion years of lunar history. A single point in there could help differentiate between my model and the classic model. And more data would be even better.

Until we land robotic missions to send back samples from other planets or that can date samples there, the moon is still our key to ages across the solar system.

April 16, 2015

Podcast Episode 130: Dealing with Pseudoscience at Scientific Conferences (and #LPSC2015)


The Iv’ry Tower
Of science: Who can get in,
And who remains out?

Second in the three-part series: Have you ever wondered how decisions are made about who can and who cannot present at a scientific conference? Then listen to this episode! I interviewed Dr. Dave Draper, who chairs the program selection committee for the largest annual planetary science conference in the world. We talked about a lot of things, from the basics on the (incredibly minimal) requirements of submitting a presentation request to how decisions are made. We also discussed a few hypotheticals using real-world examples of pseudoscience that I’ve talked about on the blog and podcast.

The episode, like most of my interviews have been, is nearly an hour long, but I found it an interesting discussion and learned some things, so hopefully you will, too. There were not other segments in this episode, though I did do a follow-up because of what happened to air on Coast to Coast that evening, a mere 12 hours after Dave and I had finished recording, and it led me to disagree with him at least a bit on one point.

The next episode is going to be a bit of a catch-up on things that have been piling up since I started the Hale-Bopp saga back in March. I’ll do a bit of pseudoscience with whether or not the lunar eclipse we had in April was really a full one – and implications for the “Blood Moon” crapola – a lot of feedback including discussion about some points raised by Pamela Gay in episode 130, and the Leonard Nimoy tribute.

April 4, 2015

April 1, 2015

Podcast Episode 129: The Saga of Comet Hale-Bopp and its Fugacious Companion, Part 3


Great Comet Hale-Bopp,
Part 3: The cult members’ death
And continued bull.

Second in the three-part series: The saga of the great and powerful Comet Hale-Bopp and the conspiracy, mystery, intrigue, lies, schemes, hoaxes, and suicides that accompanied it. The idea came when I started listening to a new Art Bell set of interviews that I had obtained, and I realized early in the episode (November 14, 1996) that I was listening to THE interview that started the whole thing. I found another dozen or so interviews and decided to make an episode out of it that has blossomed into three episodes.

The three episodes are meant to be stand-alone in that they don’t need the others to be understandable. But, put them together and they tell the story in a lot more depth. This third part is all about the “meat” of the issue: The tragic suicide of the cult members of Heaven’s Gate. I devote the first half to them and the second half to a discussion of the continued pseudoscience related to Comet Hale-Bopp that persisted after their deaths.

The logical fallacy of the episode is the Straw Man.

Looking ahead, the next episode is an interview with Dave Draper on potentially pseudoscientific conference submissions and what the program committee of a conference does when they get work that appears to be pseudoscience.

Looking back, I was a guest panelist on episode 342 of The Reality Check podcast. It was fun, and I recommend checking them out.

And, finally, I plan to do a small tribute to Leonard Nimoy on the episode 131, due out on May 1. The tribute will be from you: If he or any of his characters affected you (especially as perhaps related to an interest in science or astronomy or critical thinking), please send in a few sentences. Or, record no more than 30—60 seconds and send the file to me.

Blog at WordPress.com.