In the last few days, I’ve seen a few blog posts about Saturn being a young system on the usual creationist sites or those responding to the creationist sites, and being a bit behind in my blog, I thought I’d check out the usual suspects. Predictably, I found the article posted yesterday, May 7, 2009, on the Institute for Creation Research by my own favorite, Brian Thomas (who I picked apart in this blog post.
The article in question now is entitled, “Planetary Quandaries Solved: Saturn Is Young.” Okay, I admit I needed to take a deep breath with this one before reading it. After all, you’d think that if scientists had really discovered that Saturn had been created/formed recently, it would be all over the news, right? So right off the bat, the title is misleading, but understandable for a creationist website.
Then I picked through some of the references. Why? Because I actually do research on Saturn’s rings. I will be submitting revisions to a 50-page manuscript to the journal Icarus in the next 3 days that should be published in a special edition of the journal at some point this summer, and the conclusions from my simulations are that the ring system is at least 2 times as massive as before, likely more, and the implications are that the system can then easily be a corresponding amount older (e.g., at least 2 times older).
And, lo!, one of the references in the article directly cites my work — a ScienceNews article from September 2008. (Check out paragraph 4 of the article.) So now, it’s personal — Brian Thomas is using MY research (in part) to advance his creationist agenda, and I will not be silent about it. Hence this blog post. 🙂
What Is the Evidence the Saturnian System Is Old?
Let’s ignore all of the outside evidence that it’s old. Let’s ignore solar system formation models. Let’s ignore standard conventional wisdom. Let’s ignore the scientific problems about biblical creation. What is the evidence that the system is old, or at least not young.
Well, being a crater counter when I’m not running simulations of Saturn’s rings, I point to craters. Craters are used throughout the solar system as the only cross-planetary method of relative dating methods. In other words, how many craters a solid object has is the only thing that we can measure, at present, that gives us the relative ages of two solid surfaces.
Crater ages have been calibrated via Apollo lunar sample returns, and so – at least for our moon – we know that a certain number of craters per unit area corresponds with one age, and a different number corresponds with a different age — and we know what those ages are to reasonable accuracy for the moon.
Much work has been done and is being done to try to extrapolate what we know from our moon to other solid bodies, including Mercury, Venus, Mars, and the giant planets’ satellites. While the work isn’t perfect and uncertainties remain, the state of the research is that we can tell the difference between an object that is 6000 years old or 4 billion years old.
The surface of Titan? The last number I saw is that there are around 150 impact structures that have been observed, so the present-day surface age of Titan is reasonably young. Yes, I admit that — I’m not hiding it.
What about the surface of the other moons, such as, say, Iapetus? Well, take a look at the image to the right. There are A LOT of craters there, and the surface age of Iapetus is likely on the order of a few billion years (I say “likely” because I haven’t actually done the crater counts there). Now, unless you’re going to engage in some very special pleading, this is pretty good independent evidence that at least some parts of the Saturnian system is old.
Enter the Argument for Youth: Saturn’s Rings
I grew up reading that Saturn’s rings were young – probably formed only 100 million years ago after the breakup of a medium-sized moon, about the size of Saturn’s moon Mimas (shown on the right). That was based on a few things, including estimates of its mass from Voyager data as well as spectroscopic observations showing that the rings are fairly “fresh,” showing relatively little contamination by, basically, space dust.
This was still the predominant idea in 2002, when Jeff Cuzzi made his quite that Brian Thomas uses in the second paragraph of this article:
A history of mystery surrounds the youthful features of Saturn’s rings. Jeff Cuzzi, a planetary scientist at the NASA Ames Research Center, said in 2002, “After all this time we’re still not sure about the origin of Saturn’s rings….There’s a growing awareness that Saturn’s rings can’t be so old.” Cuzzi said, “There are two reasons to believe the rings are young: First, they are bright and shiny like something new. It’s no joke.” Indeed, after millions of years, the icy rings should have collected so much space dust that they should be charcoal-colored by now. Second, after only a few million years, the little moons embedded among the rings should have “flung away. This is a young dynamical system.”
And, this was still an issue in 2006, when I was just starting my simulations. The third paragraph of this article cites Josh Colwell in a presentation he gave. He was listing some of the current problems in a few-billion-year-old rings system, but the problems were still based on old data estimates for both the mass of the ring system and the viscosity of the particles (viscosity can be thought of as how well particles can transfer energy from one to another or how well they flow — water is not very viscous but molasses is).
Enter the simulations. I use Mark Lewis’ code for these simulations, and I make a point of that because Mark is quoted in the fourth paragraph of the ICR article:
Mark Lewis of Trinity University in San Antonio cautioned that it is still not known how they really clump. “It isn’t as straightforward as saying that high-density particles would lead to more clumping.”
This is true. There are many different parameters that go into these simulations to model the physics involved. Even though I explored a huge range of parameter space in my simulations, performing over 150 different N-body simulations that took over 27,000 CPU hours to run, I still did not explore the whole range of space, and a few of those parameters do affect how ring particles clump together.
Clumping is important because it directly affects how we estimate the mass of the rings. If the rings do not clump at all, then for every particle it will block an equal amount of light. Kinda like if you spread a lot of sand on a sheet of paper and you spread that sand evenly around, you will only see a little of the paper through the sand. But, if you use the same amount of sand and start to make little sand piles, you will see more and more of the paper.
That’s how we estimate the mass of the rings – by how much paper (how much light) can be seen through the rings. And, if the ring particles are clumped together, then you need many more ring particles to get the same amount of light blocked. What my simulations show is that clumping plays a much larger role than previously thought, and so we need more material in the rings to match the observed light-blockage.
Why do more massive rings mean that the ring system is older – or can be older? Because more massive rings means the viscosity is higher and so they spread out more slowly (one of the arguments they were young is that they would spread out too quickly). Also, it means they can be older because the same amount of pollution will get spread out over a larger area, and hence they won’t be as “dirty.” So, arguments that they are young because they don’t show a large amount of pollution can be answered that the pollution is just better hidden than we thought because there is more material within the rings to get polluted.
What was the connection to me here? Well, they’re my simulations. And that fourth paragraph has a quote from an article that talked about my results. Hence why I take this a little personally.
Moving On to Enceladus
In paragraph 5 of his article, Brian Thomas says that Saturn’s moon Enceladus “shows no hint of being 4.5 billion years old, but instead appears remarkably young.” I’m not going to harp on Brian’s grammar mistake here because I’m sure I have made my fair share of mistakes in this article grammar-wise, but I will say that it’s a poor journalist who doesn’t know what a sentence fragment is.
Anyway … this statement is simply wrong. It is true that the geysers that were discovered coming from Enceladus’ south polar region were a surprise, and they have made many people in the planetary community excited to find out why they are there. (Note – yes, new discoveries that challenge old models make scientists happy, not upset, as creationists would have you believe.) And a lot of Enceladus’ surface does appear to be young. However, a fair portion of the surface also appears to be very old, as shown in the picture on the right. Yes — I’m talking about all those craters.
That’s really the point of this article. So, no, the planetary quandary has not been “solved” to say that Saturn is young. Rather, the ring system can still easily be old based on the latest (and if I do say so myself, the greatest) simulations, and even though some features of Enceladus appear young and active, there are other parts of the moon that tell the tale of being ancient.