A thoroughly sporadic column from astronomer Mike Brown on space and science, planets and dwarf planets, the sun, the moon, the stars, and the joys and frustrations of search, discovery, and life. With a family in tow. Or towing. Or perhaps in mutual orbit.

Showing posts with label publications. Show all posts
Showing posts with label publications. Show all posts

The dwarf planet that gets no respect

Quick: name the three largest known objects in the Kuiper belt. If you’ve been paying close attention you will instantly get Eris and Pluto, and, if pressed, you will admit that no one knows which one is bigger. And the third? An unscientific poll of people who should know the answer (my daughter, my wife, my nephew) reveals that not a single one does.

The answer, of course, is Makemake (you remember how to pronounce this, right? Mah-kay-mah-kay, Polynesian style).  Makemake was discovered just months after the discoveries of Eris and of Haumea, and all were announced within days of each other. Eris and Haumea had important stories immediately attached to them (Eris was as big as Pluto! Haumea had suspicious discovery circumstances!), so poor Makemake stayed in the shadow of its more famous contemporaries. It was so overlooked that, in the hastily called press conference in which we announced the discoveries, I couldn’t even remember the official designation of Makemake when asked (it was 2005 FY9, of course; how could I have forgotten that?).

The end of the fall

The fall term always gets a little overwhelming, as classes get into session and lectures need to be written, problem sets graded, exams created. I have an amazingly long backlog of things about which I want to write at this point but which I have not yet had the time to even get started. To top things off, my life appears to be changing forever. Most of these pieces get written on weekend afternoons while Lilah is napping. But the days of napping appear to be coming to a close.I understand intellectually that this is likely, after all, few 10 year olds nap, but I had never really stopped to think about the effect on my life. It’s not all bad; being able to pondering going out to do something with Lilah in the afternoon could be quite fun! But it will definitely gobble up my quiet afternoon writing time. But, today, after a late Halloween night and a no-doubt sugar-induced-early-morning wakeup, Lilah is currently snoozing away and I am going to now type as quickly as possible. Ready? Go! (Halloween? Yes, I started writing this almost a month ago, giving a perfect demonstration of the point I am trying to make.)
Back at the end of August I asked everyone to review my paper on Titan fog, and, to my surprise, many people took the task extremely seriously. The paper was discussed in classes and in on-line forums and was stared at by many eyes. If you recall back in August one of the reasons for attempting this open review was the fear that having only a single official reviewer leads to a huge random factor as to whether or not you will get anything useful out of the process. In this case, I have to say that the official review was pretty difficult to decipher. The reviewer commented on a few typos, complained about the location of the references, and said that the paper was generally incomprehensible.
Incomprehensible? Now, I will admit to having written papers that are incomprehensible before (how about this one; I can barely understand it myself 20 years later), but I actually thought that the paper was pretty clear. What’s more, of the many comments I had gotten from outside the official review process, no one had quite said “incomprehensible.” So what was going on here?
I reread the paper several dozens of times, and reread all of the comments that I had gotten, and realized, I think, the source of the problem. I think I was much too terse in my explanation of what I had actually done. Sure, I discussed fog and its discovery in gory detail. But I perhaps did not do a great job of describing how I really sorted through all of the data to find fog. It’s a pretty crucial step. If you don’t provide enough details in your paper that someone else could come after you and reproduce precisely what you did, you have failed an important point of having a paper in the first place.
One reason for describing all of this poorly was that the real process was actually quite different from the way I attempted to describe it in the paper. The real process consisted of this: I was looking at a bunch of pictures of Titan and said “Whoa; what the heck is that?” That turned out to be fog. I suspect that many discoveries are made that way, but if you read scientific papers you will rarely learn that fact. If you read my paper, you will find something like “Fog is very important so one fine day we decided to go look for fog on Titan. And we found it.”
OK, partially this description is true. After the first few times of accidentally seeing the fog we did, one fine day, systematically search through the entire data set. But that description was all pretty muddled.
The solution was a nearly complete rewrite of the paper. Had I just gotten the official review I would have fixed the typos and reworded a few things here and there and wondered what the heck the reviewer was talking about, but with the strength of the large number of comments, I could really tell what people were seeing and reading and I could make it significantly better. At least I think it is. But don’t take my word for it. Remind yourself of the first version, here. And now go read the new version here as it is about to appears in this week's Astrophysical Journal Letters. You still will not read the new version and realize that the real way we found fog is that we stumbled on it accidentally, but you will at least, I think, have a better idea of precisely what we did and how we did it. Want to go find fog yourself? I think the roadmap is now significantly more clear.
My conclusion from this experiment? I can’t tell you whether this system will always lead to such dramatic improvements in the quality of a paper, but in this particular case there is no doubt that when you read the two versions of the paper and you note any improvements almost all of those improvements came from the open review, rather than the official review. All of the comments that were sent to me were incorporated in one way or another. And for that, I would like to say a hardy THANK YOU to everyone.
But wait, there’s more!
Fresh on the heels of the Titan fog paper, I have submitted a paper to the Astronomical Journal called “The size, density, and formation of the Orcus-Vanth system in the Kuiper belt.”
This paper, I will admit, is less accessible than the paper about fog on Titan, yet, still, would you give it a read? It’s been posted online for a week and one reader already pointed out a rather stupid math error (thanks Alan Martin) of the sort that creeps into papers when you work on them one hour a week for 3 months (the error is still there, until we fix it in the next round of reviews, so feel free to go track it down and marvel at how stupid I sometimes can be).
Normally I would spend a few pages here telling you what the paper is about but, conveniently, I did that last spring, when we were searching for an appropriate name for the moon of Orcus. Go back and reread the post about coming up with names for the moon of Orcus, where I talk about the strange characteristics of what we now call Vanth. And, with a bit of continued Lilah napping over the weeks to come, stay tuned for thoughts about searching for the real Planet X, why I hate the 5 dwarf planets, and strategies for Lilah-weekend-nap-inducement.
And look! Lilah is done with her nap, and ready to start in on last night’s candy. Back to the sugar frenzy. (and with that, Lilah was awake, and we were off, and now it is a month later and Lilah is settled into a post-Thanksgiving nap and I finally have a spare moment to finish and post. Classes end next week for the year, so I look forward to a bit more time for reflection soon. Stay tuned.)

P.S. on the problem with science

I should have, of course, provided the two papers in question so you can decide for yourself. I can't quite do that. I can give you the link to my paper, here:

And I can even provide you with a link to their paper:

But it's possible that you can't read theirs. (but wait: read the comments below; people found all of the parts of this article posted online in various locations, so you're in luck!) Why not? Because, even after $1B of taxpayer money going to send Cassini to Titan and get these results, the copyright to the paper is now owned by Nature. And they say you're not allowed to read it unless you subscribe or pay. If you are logged in from an academic institution, you probably will get access from their subscription. But if you're elsewhere you are simply out of luck. Seems a bit crazy, huh?

If you do get the two papers, be sure to check out the supplementary information in the Nature paper: that is where all of the important details (like where there are and are not clouds) lie. At first glance the two papers look more or less like they say there are clouds in the same spots. It helps that the figures are all really really small so details are hard to discern. But when you blow them up and look carefully things just don't match up nearly as well as two papers using exactly the same data should.

Fog! Titan! Titan Fog! (and a peer review experiment)

Look! Titan has fog at the south pole! All of those bright sparkly reddish white patches are fog banks hanging out at the surface in Titan's late southern summer.
I first realized this a year ago, but it took me until now to finally have the time to be able to put all of the pieces together into a scientific paper that is convincing enough that I can now go up to any person in the street and say: Titan has fog at the south pole!
I will admit that the average person in the street is likely to say hmph. Or yawn. Or ask where Titan is. So let me tell you why finding fog at the south pole of Titan has been the scientific highlight of my summer.
Titan is the only place in the solar system other than the earth that appears to have large quantities of liquid sitting on the surface. At both the north and south poles we see large lakes of something dark. Oddly, though, we don’t actually know what that dark stuff is. At least some of it must certainly be ethane (that’s C2H6, for all of you who have forgotten your high school chemistry). Ethane slowly drips out of the sky on Titan, sort of like soot after a fire, only liquid soot in this case. Over geological time, big ponds of ethane could accumulate into the things that look like lakes on Titan. Odd as they sound, big lakes of liquid ethane are, at least to me, the least interesting possibility. They are the least interesting because ethane is a one way street. Once the liquid ethane is on the ground, it can’t evaporate and is there pretty much forever, unless it somehow sinks into the interior.
Why does all of that ethane drip out of the sky? Because sunlight breaks down methane (CH4) to form ethane much the same way it breaks down car exhaust fumes to form smog in big cities. There’s plenty of methane in the atmosphere, so the supply of ethane is near endless. The dripping will not end soon.
But the methane is where all of the potential action is. Methane is to Titan what water is to the earth. It’s a common component in the atmosphere and, at the temperature of Titan, it can exist in solid, liquid, or gas form. Like water on the earth, it forms clouds in the sky. Like water on the earth, it probably even forms rain. But what we don’t know is whether or not that rain makes it to the surface and pools into ponds or streams or lakes which then evaporate back into the atmosphere to start the cycle over again. In short, we don’t know if Titan has an active methane atmosphere-surface hydrological cycle analogous to the water atmosphere-surface hydrological cycle on the earth.
Until now.
Because there is fog.
Fog – or clouds – or dew – or condensation in general – can form whenever air reaches about 100% humidity. There are two ways to get there. The first is obvious: add water (on Earth) or methane (on Titan) to the surrounding air. The second is much more common: make the air colder so it can hold less water and all of that excess needs to condense. This process is what makes your ice cold glass of water get condensation on the outside; the air gets too cold to hold the water that is in it, and it condenses on the side of your glass.
Terrestrial fog commonly forms from this process. That fog that you often see at sunrise hugging the ground is caused by ground-level air cooling overnight and suddenly finding itself unable to hang on to all its water. As the sun rises and the air heats, the fog goes away. You can also get fog around here when warm wet air passes over cold ground; the air cools, the water condenses. And, of course, there is mountain fog that is causes by air being pushed up a mountain side, where it cools and – you get the pictures – can no longer hold on to all of its water so it condenses.
Interestingly, none of this works on Titan.
It’s really really hard to make Titan air colder fast. If you were to turn the sun totally off, Titan’s atmosphere would still take something like 100 years to cool down. And even the coldest parts of the surface are much too warm to ever cause fog to condense.
What about mountain fog? A Titanian mountain would have to be about ~15,000 feet high before the air would be cold enough to condense. But Titan’s crust, made mostly of ice, can’t support mountains more than about 3000 feet high.
We’re left with that first process: add humidty.
On Titan, as on earth, the only way to add humidity is to evaporate liquid. On Titan this means liquid methane.
Liquid methane! There it is!
Evaporating methane means it must have rained. Rain means streams and pools and erosion and geology. Fog means that Titan has a currently active methane hydrological cycle doing who knows what on Titan.
But there’s one more twist. Even evaporating liquid methane on Titan is not sufficient to make fog, because if you ever made ground-level air 100% humid the first thing it would do after turning into fog would be to rise up like a massive cumulous cloud. There’s only one way to make the fog stick around on the ground for any amount of time, and that is to both add humidty and cool the air just a little. And the way to cool the air just a little is to have it in contact with something cold: like a pool of evaporating liquid methane!
Only final fun part of the story. The fog doesn’t appear to prefer hanging around the one big south polar lake or even around the other dark areas that people think might be lakes. It looks like it might be more or less everywhere at the south pole. My guess is that the southern summer polar rainy season that we have witnessed over the past few years has deposited small pools of liquid methane all over the pole. It’s slowly evaporating back into the atmosphere where it will eventually drift to the northern pole where, I think, we can expect another stormy summer season. Stay tuned. Northern summer solstice is in 2016.

Our paper describing these results (written by me, Alex Smith and Clare Chen, two Caltech undergraduate students, and Mate Ádámkovics, a colleague at UC Berkeley) was recently submitted to the Astrophysical Journal Letters. The paper will shortly go out for peer review, which is an integral part of the scientific process where the paper is vetted by experts. Peer review, as implemented in the current world of over-stressed astronomers, has some serious flaws, though. One problem is that the peer review is performed by one person! Sometimes that one person is thoughtful and insightful and provides excellent insight and commentary. Sometimes that one person misses or misunderstands crucial points. It is rare, though, that any one person can be a broad enough expert in all of the topics in a scientific paper to provide adequate review of the whole thing. Plus people are busy.
What is the solution? I don’t know. There has been much talk recently about all of this, and even some interesting experiments done by scientific journals. I thought I would try an experiment of my own here. It goes like this: feel free to provide a review of my paper! I know this is not for everyone. Send it directly to me or comment here. I will take serious comments as seriously as those of the official reviewer and will incorporate changes into the final version of the paper before it is published.
What kinds of things would I look at closely if I were a reviewer of this paper? Probably things like: is the claim of discovery of something fog-like convincingly made? Is the fog-like feature really at the surface rather than simply a cloud? Is our argument of how fog must form convincing? Is it correct? These were, at least, the things I thought hardest about as I was writing the paper. Perhaps you will find more!

The long road to a Titan storm

Look in your newspaper this Saturday, and you may see a paragraph about Saturn’s moon Titan and a giant storm that moved across the surface last May and what that means. With luck they’ll even print it with a tiny little picture of Titan to catch your eye. Your response, if you have one, will likely be “huh.” It’s OK. I’m not offended. It’s hard to distill the richness of a full scientific paper into a paragraph. And it’s even harder, still, to distill the richness of a decade of scientific inquiry into a short scientific paper. But if you’re curious about what that little paragraph means, and how it came to be in your newspaper, and what we’ve been doing for the past decade, read on. It’s a long story, but that’s somewhat of the point.
I became interested in Titan ten years ago, almost as a matter of convenience. It was an excellent solar system target for the then-new technique of Adaptive Optics, which attempts to undo some of the effects of the smearing of starlight caused by Earth’s atmosphere. Titan was a great target because it is just small enough to be completely smeared by the atmosphere, but big enough that, if you could unsmear it, you would still have a nice view. Just as importantly, no one had ever had a nice view of the surface of Titan before because the satellite it covered in a thick layer of smog which mostly doesn’t let light penetrate to the surface. When the Voyager spacecrafts flew by, they took pictures of Titan which look like a big orange billiard ball. I should have said, though, that visible light doesn’t penetrate to the surface. On the earth, red light penetrates smog better than blue light (hence the nice red sunsets on a smoggy day in Los Angeles). The same happens on Titan. Red penetrates better than blue, but infrared penetrates better still. In fact, if you go far enough into the infrared, you can take a picture of Titan and almost not notice any smog there at all. Conveniently, the new technique of Adaptive Optics works best in the infrared. Hence Titan became a natural target to try out the new techniques on. Antonin Bouchez, then a relatively new graduate student at Caltech, signed on to do this project as part of his Ph.D. thesis.
Our first goals were to obtain maps of the then-almost-totally-unknown surface of Titan. And what a strange looking surface it turned out to be! We speculated endlessly about what all of those dark and bright spots on the surface might be (for the most part it is fair to say that we – and everyone else – had no idea whatsoever until we got better images from Cassini a few years later). And then, in late 2001, we found a cloud sitting at the south pole of Titan.
A cloud!
It doesn’t sound like such a big deal, except that it had long been predicted that Titan was incapable of having clouds. Occasionally there was speculation that clouds of methane might be present, but that, if so, they would be tightly confined to the equator. And yet there it indisputably was: a cloud at the south pole.
Antonin and I were so astounded by this that we put Sarah Horst, then an undergraduate at Caltech, at work looking through a tiny 14-inch telescope on the roof of the astronomy building at Caltech. We had developed some special telescope filters which would – we hoped – be capable of penetrating the haze deck and seeing if Titan got a little brighter due to a cloud or two. We wouldn’t be able to tell anything else, but that would be enough to go back to the giant Keck telescope and say “Look now! There will be a cloud!”
It worked. Just a month after our first cloud detection Sarah saw something that looked just like what we expected a cloud to look like. We called people at the Keck telescope and begged them to snap a picture, and there it was. A much bigger splotch, still near the south pole.
I’m an astronomer, not a meteorologist. I had to spend six months learning about how clouds worked, trying to understand precisely why people thought they wouldn’t occur on Titan, and figuring out what was wrong. On a long summertime flight across the country where we continuously skirted afternoon thunderstorms, it all came together: no one had ever previously bothered to consider the effect of Titan’s surface heating. Like Arizona on a summer afternoon, Titan’s surface can heat up and eventually drive convective clouds over it. On Titan, though, it doesn’t happen in the afternoon. It happens in the summertime, when the south pole spends something like 10 years in continuous sunlight.
It was a compelling story, and, I think true. But, even better, it made some fairly clear predictions. The clouds were at the south pole when we discovered them only because it was very close to southern summer solstice. Titan (and Saturn) takes 30 years to go around the sun, so its seasons are quite long. But if you had the patience to watch, you should see the clouds move from the south pole to the north pole over the next 15 years before coming back 15 years later.
Antonin eventually got his Ph.D. and moved on to take a job working with the technical team continuing the development of Adaptive Optics at the Keck Observatory. It was the perfect place to be. Whenever there was a spare moment or two at the telescope, he would swing it over towards Titan and snap a picture. The clouds were nonstop. Sometimes there were just a few tiny specks, but occasionally there would be a huge outburst. It was a thrilling show to watch.
Emily Schaller entered graduate school at Caltech at just about that time, and she decided to do her thesis on watching and understanding these developing clouds on Titan. The first year was exciting, indeed. She saw a monster cloud system cover the south pole of Titan and remain for more than a month (disappearing just as one of the first close Cassini flybys went in to take pictures; Cassini saw a few wispy little clouds but missed almost all of the action). Henry Roe, a recently graduated Ph.D. from the University of California at Berkeley who had been using the Adaptive Optics on the Gemini telescope to study Titan, moved down to Caltech to work with us, and the odd discoveries about the clouds poured in. They appeared to finally move north from the pole; they appeared tied to one spot at 40 degrees south latitude for a while; they untied themselves; bright clouds in one spot seemed to foretell bright clouds in another. It was clear that we were amateurs here. We enlisted the help of Tapio Schneider, a professor of environmental engineering at Caltech and one of the world’s experts on atmospheric circulations, to help us make sense of what was going on. Things were finally falling into place.
In one final piece of exceedingly clever astronomy, Emily Schaller replaced our clunky nightly observations with a 14-inch Celestron, originally begun by Sarah Horst, with a sleek set of nightly observations from NASA’s Infrared Telescope Facility on top of Mauna Kea. The IRTF would take a quick spectrum of Titan every night possible, and Emily could quickly look at the rainbow of infrared light to tell precisely how many clouds were there. And when they looked good, she could tell Henry Roe, who would get the Gemini telescope to examine them.
And then the clouds stopped.
For years and years Emily would look at her data in the morning and walk across the hall to my office to mournfully say “no clouds again last night.” Seeing no clouds is scientifically interesting, and she dutifully wrote papers and indeed an entire chapter of her Ph.D. thesis demonstrating and trying to explain this years-long lack of clouds. But, really, I understood. Explaining a lack of something is not nearly as satisfying as actually getting to see something happen. As her advisor, I would have been happy to fly to Titan to perform a little cloud-seeding, but no one had yet figured out exactly what chemicals or incantations might do the trick.
On April 14th last year, Emily walked across the Caltech campus to finally turn in her thesis. Then she did what she did most mornings: she walked to her office, downloaded the data from the night before, and checked to see if Titan had clouds. That morning, I suspect, she came close to falling out of her chair. She was likely exhausted from those final stretches of thesis writing, and I am sure that the first time she plotted her data she did what I always do when I see something astounding: she assumed she had made a mistake. She probably re-downloaded the data, double-checked the coordinates, and shook herself a little more awake. But it was no mistake. Titan suddenly had the largest cloud system seen in years. She likes to say it was Titan throwing a graduation party for her. But I know better: I think Titan likes to hide its secrets as long as possible, and knew it was finally safe to let go.

The scientific paper that Emily wrote along with Henry, Tapio, and I that appears in Nature describes the big cloud outburst and its scientific implications. And the implications are pretty fascinating. This big cloud outburst – the biggest ever seen – began in the tropics of Titan, where it has been speculated that clouds, if they ever form, should be weak wispy things. The tropics are where, of course, the Huygens spacecraft that landed on Titan took dramatic images of things that look like stream beds and shorelines and carved channels. How could those be at the equator if there are never clouds and never rain? People asked.
This discovery doesn’t actually answer that question, because we don’t know why there was a huge outburst of clouds in the tropics of Titan. But it does perhaps answer that lingering question: How could those be at the equator if there is never rain? Because there is rain.
Now, however, I am going to allow myself to speculate a bit more than we were comfortable speculating in the scientific paper. I am going to ask: Why? Why were there clouds in the tropics? Why did they appear suddenly at one spot? What is going on?
What I think is going on (again, I warn you, rampant speculation follows…) is that Titan occasionally burps methane, and I think Emily found one of the burps. For many years scientists have wondered where all of the methane in Titan’s atmosphere comes from, and, I think, here is the answer. The surface occasionally releases methane. Call it what you want. Methane geysers? Cryovolcanoe? Titanian cows? Whatever happens, the methane gets injected into the atmosphere and, at that location, instantly forms a huge methane cloud. Massive rainout ensues downwind. The stream channels, the shorelines, and everything else in the otherwise desert-seeming regions are carved in massive storms.
Evidence? Evidence? Where’s the evidence? You scream. Fair enough. I am giving you a snapshot of how science is done, and, at this point, this is the hypothesis stage. Or hunch. Or speculation. This hunch is the type that then guides what we go off to try to observe next. What will we see? Will the spot Emily found burp again? That would be pretty striking confirmation. Will other spots blow? (I should mention that we do indeed think we saw a different spot burp a few years ago).
At this point we have observed Titan well for about 7 years, from the winter southern solstice until the northern spring equinox, which actually just occurred last week, the terrestrial equivalent of late December to late March. What will the rest of the year reveal? We’re still watching, waiting. Maybe in 23 years, when we’ve finally seen an entire season, we’ll call it a day.

The Joys of Rejection and Lake-effect clouds on Titan

Remember my new paper that describes my interesting discoveries about Titan (see Your Saturday Newspaper)? submitted it to Science magazine a few weeks ago in the hopes that it will be published and some day make it to your Saturday newspaper. But it won't. It has been rejected.
It was a kind rejection. They didn't say "we think you're paper is wrong." Just, "we don't find it of general enough interest to publish in our journal."
Rejection is always hard. My first response was generic sputtering “wha.. wha… what?” and then disbelief “this can’t be!” and anger and dismissal “those idiots don’t even know what they are missing.” This sequence lasted about 7 seconds, and then I got over it. After about 1 minute I became excited.
Why be excited about rejection from Science? Along with the publicity benefits of publishing a paper in somewhere like Science comes the hard part. You agree not to publicize or discuss the paper before the publish it. This process can take 6 months or longer.
But having been rejected from Science, I quickly turned around and submitted the paper to a more specialized journal -- Geophysical Research Letters (aka GRL) -- which has no such restrictions, and then I went a step further and submitted it to an on-line electronic archive ( which means you can go read it right now! http://lanl.arxiv.org/abs/0809.1841 ).
Scientists these days are increasingly speeding up the slow process of formal publication with an informal process of web publication. Such web publication has good and bad aspects to it. Good: instant. Bad: unreviewed.
Anything that is published in a major journal has had one or two experts read it closely and suggest changes. My paper on Titan is currently undergoing this process at GRL, and, when the reviewers are done, I will modify and respond. But my paper is on the electronic archive for everyone to see before that even happens.
Posting a paper on-line before it has been reviewed can lead to great embarrassment. What if the paper has fundamental flaws and needs to be withdrawn or rejected? What if the referees point out places where major changes need to take part? All of this is certainly possible, and should make any on-line submitted wary. But, for me, the benefits outweigh the risks. I am sufficiently confident in the accuracy of what I did that I am not worried about any of these major problems. While there is no doubt that the reviewers will suggest some improvements, I don’t believe the overall conclusions of the paper will change significantly. And I think the conclusions are sufficiently interesting that I relish the idea that people will begin to read the paper and think about the results now, rather than 6 months from now. So I submitted.
And now, even better, I can talk about the discovery of lake-effect clouds on Titan.
Earlier this summer, while looking through NASA’s on-line archives of images of Saturn’s satellite Titan taken from the Cassini mission, I began to notice a recurring pattern up near the north pole of the satellite. The north pole of Titan has been in the darkness throughout a long long winter (a full year on Titan takes 30 years; winter is almost a decade) and is just now emerging into some spring time daylight. As it began to emerge, I noticed what appeared to be tiny little clouds popping up and disappearing right over the pole.
Titan is in some ways bizarre and exotic yet in some ways very earth-like. Both earth and Titan have mostly-nitrogen atmospheres; on both the surface pressure is about the same (the big difference on Titan: it lacks that minor contaminant – oxygen – that makes the earth a more interesting place….).
Titan and earth are the only bodies in the solar system known to have large expanses of liquid at the surface. On Titan, though, the temperature is so low that water is frozen solid. The lakes of Titan are made, instead, of methane and ethane. If you could figure out a way to get a pipeline there, Titan’s lakes could supply all of our needed natural gas for years to come.
On earth the liquid water is globally distributed. On Titan it appears that the liquid methane and ethane is confined to the poles.
Finally, Titan and earth both have clouds in its atmosphere, and these clouds are made from the dominant liquid on the surface. On earth: water. On Titan: methane.
Now, back to the little clouds I had seen popping up at the north pole during Titan’s early spring.
These clouds surprised me; they appear to be cumulous clouds – like large thunder heads. On the earth we only get such clouds in hot, humid places. Arizona in August. Year-round in the tropics. Temperate latitudes during summer storms. How could such clouds possibly be up at the north pole just as winter is waning?
It occurred to me that we do get winter cumulus-type clouds on the earth in at least one case: lake-effect clouds and storms. Lake-effect storms on the earth are those winter storms that blow across the Great Lakes, pick up moisture, and then proceed to dump many many feet of snow on places like Buffalo, New York.
The effect occurs in many other places around the world. Or, I should say, they same effect occurs in many other places around the solar system. I believe this process is precisely what is causing the sporadic clouds at the north pole of Titan.
Like everything else, Titan and earth have similarities and differences in their lake-effect clouds, too. On the earth, the formation of these clouds is greatly aided by the fact that deep lakes stay relative warm over the winter. So as cold air passes over these lakes the air both picks up humidity and a little heat. This heat causes the air to rise (like a hot air balloon) which, in turn, causes those cumuli and the subsequent snow.
On Titan, a decade of polar winter means that none of the lakes retain any heat, so passing air only picks up humidity (methane humidity, in this case). Something else needs to help push the air higher to cause those cumuli. In the paper, we speculate that there might be mountains at the north pole that help, but really that is just a wild guess.
Cold lakes won’t evaporate, so these clouds have only started to become active in the last few years as sunlight has started to every-so-slightly heat the lakes. Every time the lakes warm up just a bit, a huge dollop of evaporation occurs, which re-cools the lake, and we see a cumulus cloud pop up. The lake then has to wait for some more sunlight before it happens again.
If our general story is correct – and I think it is – then as spring and then summer approaches at the north pole, the sunlight will increase dramatically, and the lake-effect clouds will start to go crazy. And we’ll be watching. The Cassini spacecraft is slated to continue flying past and taking pictures of Titan for several more years. And we might find more exciting things.
And what will we do when we find exciting things? Well, in the end I will probably never learn my lesson. We’ll submit them to Science. Or we’ll submit them to Nature. And then we will have to wait for months to talk about them. And maybe they will get a paragraph in your Saturday paper. But, if we – and you – are lucky, we will instead be rejected, we’ll post to a freely available on-line archive, and everyone can hear early about the latest happenings on this bizarre satellite.

Your Saturday Newspaper

I don’t know about other newspapers, but every week my local -- the Los Angeles Times -- devotes about a half a page to a few science stories. I love these, not just for learning a little bit about the universe around us, but also for getting a quick glimpse into the life of some scientist somewhere finally getting his or her paragraph of fame. This week: estrogen may ease psychosis; mummified fetuses from King Tut’s tomb are going to have their DNA tested, a hidden tribe of gorillas was found, virus can get sick from other viruses, and Antarctica used to have moss. Having a paragraph or two of your science appearing in your daily newspaper is both exciting – “my research is interesting to the world” – and depressing – “I spent two years on this project and all that makes the newspaper is that schizophrenic women should take estrogen.”
The route from doing research to that Saturday paragraph is indeed a long one, and one of the important steps after the research is all completed is publication of the results in the right scientific journal. Scientific journals are not all the same. Some are trade journals that specialize in a specific field (I publish much of my research in, not surprisingly, “The Astronomical Journal”) and accept most of the papers submitted to them (after a sometimes lengthy review and revision process). Others are more general with the implicit promise that the papers published there are more interesting, more important, and will get more notice. And, of course, it is much harder to get a paper published in one of these. Reporters know which journals are those top exclusive general ones, and so, when looking for stories for that Saturday column, they peruse those journals (and read press releases, presumably) and never bother with the trade journals.
The two top general journals in which everyone seems to want to get papers published are Nature and Science. If you start looking at those Saturday columns you will be amazed by how many of the stories come from papers published there.
Interestingly, though, along with publishing important ground-breaking papers appears to come the requirement that a larger than usual fraction of the conclusions published in these journals turn out to be incorrect. This leads to the semi-joking line that you often hear amongst astronomers: “Just because it is published in Nature doesn’t necessarily mean that it is wrong.” But it also leads to the real ambivalence that some feel for results published in those journals. People sometimes consider them to be flash and hype with no real substance and turn their noses up at the papers published inside.
I’ve been known to fall into this camp myself.
So it might be amusing to know that, tomorrow, my hope is to have a new paper ready for submission to Science. Why would I do this when I then turn around and scoff at others? Hypocrisy, I think is the answer. Or, as my friend Caltech oceanographer Jess Adkins likes to say: Nature and Science are the People Magazine of science. And like People, no one wants to admit to reading it, but everyone wants to be in it.
And so I submit.
The process is an interesting one. By tomorrow, I should have the full manuscript describing all of the results and with a few figures demonstrating important points and a slew of references to previous work all written in the precise format demanded by Science. I’ll log on to their web site and do all of the submission there. And then I’ll wait.
I think the rest of the process goes something like this (I may have some of the precise details mixed up here, but you’ll get the general idea). The paper will first go to an editor in the field of astronomy/planetary science who will decide whether or not there is even a chance that the results are interesting enough to warrant publication in Science. If the editor doesn’t think so, I will get a rejection notice within days. If the editor likes it, the paper will go to an editorial staff meeting with all of the other editors where it can again be voted up or voted down. I can again get that rejection notice (this one would be in, perhaps, two weeks).
If the editorial board likes it, the editor will send it out for peer review. The manuscript will get mailed to (typically) two experts in the field who will offer their detailed advice on the technical merits of the paper and whether or not it warrants publication in Science.
As is often said: peer review is a highly flawed system, but it beats all of the alternatives. It is easy to imagine some of the problems that could arise at this stage. A few that I have run across: reviewers who are competitor, reviewers who just don’t like you, reviewers who aren’t knowledgeable enough about your field. With only two reviewers for most manuscript, the process can be thoroughly random. The same paper sent to twenty different reviewers would get twenty different reviews. But, sadly, it beats all of the alternatives.
With luck, the two reviewers will like the paper and, with even more luck, suggest ways to improve the paper. They may point in flaws in the paper and how those flaws can be fixed. Or they may point in flaws in the paper and say they are not fixable.
If the reviewers don’t like the paper sufficiently that is the end of the line and you are rejected. If they potentially like it but with reservations you are given a chance to respond to their suggestions or complaints and modify the paper accordingly and then they get to review it again.
Finally, again, with luck, the editor send you that email saying the paper is accepted, and you sigh from relief. Or you get the rejection email, and you decide what to do next: another general journal? Reformat to go to a trade journal? Sulk in irritation for a while? I have done all of these and more.
The whole process can take a long time. If I submit the paper tomorrow, there is a chance that it might appear in your newspaper in, perhaps, January. Keep your eyes peeled to that Saturday section. But don’t look for an article on dwarf planets or on the Kuiper belt or on the early solar system. I’m taking a break from those this summer to pursue research on what I think of as my hobby field, Titan. Titan is a fascinating world with methane lakes at the north pole, dark dunes at the equator, a thick atmosphere that is almost like the Earth’s (it’s just missing a minor component [oxygen] that we like so much), and a Los Angeles-like haze that makes the surface hard to see. It’s my favorite body inside the Kuiper belt, and, when I get a little tired of studying the little points of light that make up the Kuiper belt, I move in to the relative warmth of the Saturn system and see what’s new on Titan. During my break this summer I think I discovered something pretty interesting. Interesting enough to be published in Science, even. But we’ll all have to wait to see if I can navigate that laborious publication paper and make it to that one paragraph in your Saturday newspaper.

Planet X uncovered (again?)

In 1846, more than 50 years after the discovery of Uranus, both John Couch Adams in England and Urbain LeVerrier in France independently realized that Uranus was not precisely following its expected path around the sun, but rather was being perturbed by some unseen force. Using the recently developed methods of physics and calculus, they both calculated that everything could be explained if there was another planet beyond Uranus slightly tugging Uranus from its expected path. Moreover they knew right where to look. LeVerrier contacted astronomer Johann Gottfried Galle in Berlin and gave him precise coordinates at which to point his telescope. On the very first night of his search Galle found Neptune gleaming in his eyepiece. Adams and LeVerrier were correct! And, moreover, their chains of reasoning were correct. Neptune was indeed responsible for giving Uranus a tug, and that tug pointed right at the new planet. The discovery was a spectacular triumph of the new physics; the universe itself was now within the grasp of the mind.
If one new planet could be found this way, why not more? Very soon other astronomers were looking very closely at the orbit of Neptune to see if it, too, was perturbed. It was, or so it appeared at the time. Several astronomers immediately tried to use the same method as Adams and LeVerrier and predict precisely where to find this Planet X (X for unknown and X for 10, though at least one astronomer called his hypothesized body Planet O, a less catchy name which rarely gets mentioned these days).
Percival Lowell, an astronomer from a wealthy family in Boston, even decided to construct an entire telescope (at what is now the Lowell Observatory in Flagstaff Arizona) with the main purpose being to find the planet. Lowell died before the search began in earnest, but in 1930 Clyde Tombaugh, carrying out Lowell's program, discovered just what he thought he was looking for: Pluto, in orbit beyond Neptune. Planet X discovered! Except that it wasn't. Pluto is far too small to even be noticed by Neptune, much less tug it away from its orbit. Its discovery, though inspired by Lowell, had nothing to do with his prediction. In fact, these days we know that the early measurements of the position of Neptune were simply in error and, as far as anyone can tell, Neptune goes precisely where it is supposed to go. Pluto was not the predicted Planet X, nor does Neptune do anything unusual that would require such a planet.
The idea of finding something large outside of Neptune still remains appealing, though. Over the years different astronomers have revisited the idea to explain a variety of things including the periodic extinction of the dinosaurs, the orbits of comets, and many more.
The latest attempt at Planet X predicting comes in a paper in the April issue of the Astronomical Journal by Patryk Lykawka and Tadashi Mukai at Kobe University in Japan. The essential idea is unchanged from 1845: look for the gravitational affect of an unseen planet. But Lykawka and Mukai have a great advantage over the early 20th century Planet X seekers: they have much much more than simply Uranus or Neptune to go on. We now know of more than 1000 tiny objects in the region beyond Neptune known as the Kuiper belt, and each one of these is affecting by whatever planets are out there.
In the outer solar system, these tiny bodies in the Kuiper belt function like the debris left over after a flood: while the water from the flood may be long gone, you can still use the location of the debris to trace the rivers and currents of the flood and the highs and lows of the water. The Kuiper belt objects similarly trace catastrophic events that we can no longer see but can now infer. In the outer solar system these catastrophic events were mainly the migrations of the orbital positions of the giant planets and the subsequent gravitational rivers and currents that swept through the tiny bodies of the Kuiper belt as the giant planets swirled around them. Today we see only where the small bodies ended up, but these locations are an intimate product of what the giant planets were doing.
For a while now we have known, however that some aspects of the orbits of the objects in the Kuiper belt simply cannot be explained by the giant planets. The most dramatic of these unexplainable orbits is that of the extremely distant extremely eccentric object known as Sedna. Sedna has an orbit so distant from the sun that it take 12,000 years to complete a single orbit. During the course of this orbit it moves from about 80 times the distance from the earth to the sun to about 1000 times the distance from the earth to the sun. Such a peculiar orbit is an almost certain sign that sometime in its past Sedna got a large gravitational kick by something big, knocking it far away. But Sedna is currently so far away from any giant planet that there is nothing that it ever comes close to that could have kicked it around. Sedna on the outskirts of the solar system was like finding an overturned truck 20 feet above the high water line of the flood. Something put the truck there, but it certainly wasn't the flood. While Sedna is the most extreme case of strange orbits in the outer solar system, there are many others.
So what helped rearrange the Kuiper belt besides the giant planets? Several ideas have been proposed, each of which can explain some, but not all of the anomalies seen. The ideas fall into three main categories: something from outside the solar system, something from inside the solar system that has escaped and is now gone, and something from inside the solar system that is still here but has yet to be found.
The Lykawka and Mukai proposal falls into the latter category. They demonstrate that if an approximately Mars-sized body once existed in the region of the Kuiper belt, and if all of the conditions were just right, it could not only provide just enough gravitational kicking-around to sculpt the Kuiper belt into something that closely resembles what we see today, but the Mars-sized body could also conveniently find itself on an orbit sufficiently distant from the sun to have escaped detection. It’s a tidy proposal which explains much about the outer solar system all in one shot.
Planet X discovered? Well, not yet. Unlike the calculations of Adams or LeVerrier, those of Lykawka and Mukai are unable to provide any prediction at all of where in the sky their object would be (the technical reason for this difference is that the main effects of the Lykawka and Mukai planet were in the distant past, so its current precise position has little effect, and thus can't be determined).
But the good news is that, in the past few years, searches of the outer solar system (including my own) have already begun to specifically target the more distant regions where the predicted object would reside. If any such large object is out there it could be discovered anytime, perhaps even tonight (by my survey, if the object is on the bigger or closer side) or, more likely, by one of the next generation all sky surveys that will be operational over the next decade.
So is the Lykawka and Mukai prediction right? Maybe. Their paper is a thorough and exhaustive demonstration of just how this Mars-sized planet could explain many of the oddities of the outer solar system. But just because such a planet could explain the oddities doesn’t mean that it does explain the oddities. To make everything work out, Lykawka and Mukai need their planet to do some very specific things. It has to be neither too large nor too small, neither too distant nor too close. It needs to follow a rather precise history from its formation on the inner edge of the Kuiper belt to its eventually ejection by Neptune to a distant orbit. The number of coincidences that must have happened is enormous. The probability that such a chain would have occurred seems slim.
And yet the probability of almost anything specific is slim. The moon, going around the earth, was only created because of an impact that happened to hit the earth at the right angle and the right speed. If the impact had occurred slightly differently: no moon. The whole solar system itself might be a coincidence caused by a precisely timed supernova that went off nearby just as a cloud of dust and gas was beginning to coalesce. I am married to my wife only because of an improbable chance encounter in a basement seven years ago. So coincidences happen. Coincidences are what take general cases and make them specific. Still, scientists shy away from specific explanations, because while they may work once, they won’t ever work again. They are less satisfying. But that doesn’t mean they are not true.
Nonetheless, I suspect that most astronomers will file this new Planet X prediction away with the rest of the possible explanations for the oddities in the outer solar system. They will consider it plausible, but not very likely. Other explanations will continue to be sought. Other observations will continue to be made. But those of us who have been scanning the skies for a long time looking for whatever might be out on the edge of the solar system cannot help but to secretly grin and hope that maybe – just maybe -- Lykawka and Mukai are on to something. Some night, perhaps, someone somewhere will point a telescope at the sky and see a bright distant object slowly wandering across the path of the stars and get to say, in the words of Galle, sending a telegraph to LeVerrier after he found Neptune just where it was supposed to be: “the planet whose place you have [predicted] really exists.