Discover article on the Moon

Tuesday, April 13th, 2010

I wrote last week about my New Scientist article on lunar water, which came out in the April 3-9 issue. One of my regrets was that the article took so long in press, so that it was too late to affect any of the debate about NASA’s future strategy in space. (Of course, it was probably hubris on my part to think that one article in New Scientist would do anything more than one pebble thrown into a stream.)

However, I was pleased to see that my article at least “scooped” Discover magazine by a couple days! I got the May issue of Discover in last week’s mail, and right there on the cover was a big picture of the moon with the headline “The New Moon — Surprise: It’s Wet, Weird, and Oddly Inviting.”

The accompanying article was written by Andrew Grant, and it basically touches all the same bases that my article did. It made a big deal out of Larry Taylor, the long-time skeptic of water on the moon who told the New York Times that he would have to “eat his shorts” because of the new discoveries. At the LEAG meeting last November, he got a lot of teasing over the “eat his shorts” comment, and one of the people at the meeting bought him a six-pack of beer so that he could wash them down. Grant’s article also gave his joke a lot of play. I decided not to mention this in my article because: 1) the original comment was made to a New York Times reporter, not to me; and 2) there were plenty of other things to write about besides Larry Taylor’s shorts!

However, that is my only mild criticism of Grant’s article. There are accompanying articles by Jennifer Barone and Andrew Moseman that explore the possibilities for privately funded rockets and moon missions (SpaceX, the Google Lunar X-Prize) in much more detail than my article did.

Anyway, with essentially simultaneous articles in Discover and New Scientist, I’m glad to see the moon continuing to get some publicity.

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New Scientist article

Tuesday, April 6th, 2010

My article for New Scientist about the discovery of more-abundant-than-expected lunar water finally reached the newsstands last week. I’d like to welcome any readers of that article who have come to this blog looking for more information.

This article had quite a long gestation period. I first pitched the idea of an article about the LCROSS mission to my editor about a year and a half ago, but at the time she didn’t really see the news value of the story. Before the LCROSS mission lifted off, there wasn’t a whole lot of excitement about it in the media. But then a lot of things changed. The Chandrayaan-1 discovery of surface water on the moon. David Letterman’s skit that poked fun at the idea of “bombing the moon.” The very successful impact that dug up a lot of water, plus other volatile compounds.

At the same time, a big policy debate was going on about our future in space, with the Augustine Commission issuing its report about the same time as LCROSS was hitting its target. That debate culminated in February, when President Obama recommended the cancellation of the Constellation Program and redirected NASA’s priorities for the next decade.

With all of these things going on, I think it is fair to say that the moon and lunar water was one of the top stories in solar system science over the last few months.

I wrote the first draft of the New Scientist article in December, following the Lunar Exploration Analysis Group meeting in Houston (November) and the American Geophysical Union meeting in San Francisco (December). I really wanted the article to come out then, when it could still (maybe, in some far-fetched scenario) have had some effect on the policy debate.

However, the article got delayed until April, not for any political reasons but just because New Scientist feature articles get put into a queue and it takes some time for them to work their way through that queue. Meanwhile, the Obama decision happened and so I had to revise the article to reflect that reality.

In the end, I failed in my original goal of writing an article that would perhaps have an influence on the future. However, I do think that the article itself came out a little bit stronger as a result of the delay. I was able to replace some of the “ifs” and “possibly”s and “could be”s with more definite statements. In some sense it became a retrospective on the lunar water story of 2009, rather than a story-in-progress as I originally conceived it. However, I would like to emphasize that there is still a story in progress, as the LCROSS data and LRO data continue to come in and become better understood.

Tags: Augustine Commission, Chandrayaan-1, David Letterman, LCROSS, LRO, New Scientist, Obama, retrospective, water
Posted in Media, Meetings, Missions, NASA, Science | No Comments »

The Moon and Easter

Tuesday, March 23rd, 2010

… or, “How to Make a Simple Definition Really Complicated”

Today I was chatting with a friend of mine about when Easter is this year, and he cited the well-known (and incorrect) formula: “Easter is the first Sunday after the first full moon after the spring equinox.”

Although this is a pretty good approximation, and it is correct most years, the actual calculation of Easter is surprisingly complicated. The correct definition is that Easter occurs on the first Sunday after the paschal full moon. This is an artificially calculated date that actually does not correspond to any astronomical event. The best description of the paschal full moon is that it is pretty close to a full moon that is usually the first one after the spring equinox!

How did we get into this mess? Why don’t we just celebrate Easter on the same every day each year, as we do with Christmas? And why does the moon have anything to do with it? That is actually a pretty good story that goes way back in time … back before Christ was even born.

[By the way, let me interject that I am not a practicing member of any religious faith. My main reason for being interested in the date of Easter is that I am interested in the ways in which the moon affects our culture. If you are bothered by sentences like "Christ was born," you should mentally add, "according to the Christian religion."]

Let’s start with what the Bible says about Christ’s death. Depending on the book you read, he was either crucified on the date of the Jewish Passover, or the following day. In any case, his resurrection occurred on the Sunday after Passover. Hence, in the early years of Christianity, the practice was to observe Easter on that day.

But determining the date of Passover is itself no easy matter, and that is where the moon comes in. The Jews, like many other ancient civilizations (such as the Babylonians, from whom they borrowed their month names), used a combination lunar-solar calendar. These calendars have the advantage that the new moon always falls on the same day each month; day 1 is the first day after the new moon, and day 14 is (usually) the day of the full moon. Passover was defined as the 14th day of the month of Nisan.

The mischief starts because the lunar cycle is not synchronized to the solar cycle; 365 days is a little bit more than 12 lunar cycles. So if you want the same months to occur at the same time each year (as the Jews did; Nisan was supposed to be the first month of spring, when the barley ripens), you need to insert extra months now and then. In order to prevent your calendar from becoming completely chaotic, it’s nice to have a rule for when to do it.

Fortunately, the lunar and solar cycles do match up very closely every 19 years. Earth takes 19 trips around the sun in almost exactly the time that the moon takes 235 trips around Earth. (The difference is about two hours.) This means that your lunisolar calendar needs to have 12 normal years of 12 months, and 7 long years of 13 months, in each 19-year cycle. (12 x 12 + 7 x 13 = 144 + 91 = 235.) This fact was discovered by the ancient Babylonians and the ancient Greeks; the 19-year cycle is called the Metonic cycle after Meton of Athens. In the Hebrew calendar, it became a standard practice to have long years in years 3, 6, 8, 11, 14, 17, and 19 of the cycle.

This procedure kept the month of Nisan in the spring, where it was supposed to be. However, the Hebrews fiddled with their calendar quite a bit over the centuries; in the early days, the month of Nisan was often determined simply by observing when the barley ripened (a non-astronomical definition if there ever was one!). A controversy arose among early Christians over the facts that (a) the methods used for determining Passover had changed over the years, and (b) in some versions, Passover could occur before the spring equinox. The Nicean council in 325 AD resolved the controversy by adopting the definition that my friend (remember him? See the first paragraph) learned in school.

But that isn’t the end of the story! They didn’t have high-tech computers back then, so Christians continued to use the Metonic cycle of 19 years to compute when full moons would occur. Not only that, they used March 21 as the date of the equinox, which is not always astronomically correct. (For example, this year the equinox fell on March 20.) In other words, they tied the definition of Easter to an approximation of when the full moon occurs and an approximation of when the equinox occurs. This double approximation can result in a date for Easter that is completely different from “astronomical Easter.” The discrepancy arises, in particular, when the full moon occurs very close to the equinox. For example, in 2019 there will be a full moon on March 21, which is not “after the equinox” according to the church but is “after the equinox” according to Earth and the sun. The official paschal full moon that year will be April 20, not March 21, and Easter will be celebrated on April 21 instead of March 24.

But hold on! There are even more complications to the story! Notice that the church defines the spring equinox as occurring on March 21. But which calendar are you using? The Catholic church, and most Western churches, uses the Gregorian calendar, which first went into effect in 1583. However, the Orthodox Christian church uses the Julian calendar, which differs from the Gregorian calendar by 13 days. Why do they do that? Well, because they’re orthodox. Remember that one of the points of the Nicean council was to base Easter on the way that Passover used to be determined in the time of Christ, not the way it is determined now. Similarly, if we’re using a purely solar calendar to determine the equinox, then we should use the solar calendar that was in use during Christ’s lifetime and during the Nicean council — the Julian calendar, not the Gregorian one. That’s what orthodoxy means. You don’t let things like contemporary customs or the contemporary state of science keep you from doing things the right way, i.e., the way that they have always been done.

Thus, Orthodox Easter (or Pascha) frequently differs from the Roman Catholic Easter. This year, and next year, they are the same. But in 2012 Orthodox Easter will be one week later, and in 2013 it will be a whopping five weeks later (on May 5 instead of March 31).

Interestingly, there has been a move afoot in recent years to bring the Western and Eastern customs into alignment. The problem is especially acute in parts of the world (e.g., the Middle East) where Christianity is not the majority religion and where there are also different forms of Christianity in close proximity. The World Council of Churches has proposed what seems like a sensible compromise: to stick to the Nicean definition of Easter, using the true astronomical full moon and the true astronomical equinox. In other words, to adopt the definition that my friend told me. The nice thing about this definition is that nobody has to learn anything new! And it’s not a complete win for either side. The Orthodox churches would have to change more, but the Catholic church would have to change, too (for example, in the year 2019, as explained above).

However, disputes over matters of faith take a long, long time to resolve, and so I don’t expect to see this one resolved any time soon. I expect that Catholic Easter, Orthodox Easter, and astronomical Easter will remain three different things.

But finally, getting back to the question, “What does the moon have to do with Easter?” I thought the following sentence from the World Council of Churches document answered it very nicely:

“Easter/Pascha has a cosmic dimension. Through Christ’s resurrection, the sun, the moon, and all the elements are restored to their primordial capacity for declaring God’s glory. … Easter/Pascha reveals the close link between creation and redemption, as inseparable aspects of God’s revelation. The Nicene principles for calculating the date of Easter/Pascha, based as they are on the cycles of the sun and moon, reflect this cosmic dimension much more fully than a fixed-date system.”

I hope I have managed not to offend anybody; if you are interested, here are some other sites that discuss the timing of Easter.

Wikipedia is, of course, always a good starting point. This entry on the computus gives you way more information than I have done here. This entry on the paschal full moon is short and to the point.

The World Council of Churches paper, from 1997, is here.

Apparently they’re still talking about it. Here is a pastor’s blog that says (as of 2009) they are getting closer to an agreement.

Here is a page that explains the computation in terms of a formula. Note the prominent appearance of the numbers 19 (the length of the Metonic cycle), 7 (the number of days in a week), 4 (adjusting for leap years?) and 100 (adjusting for the Gregorian calendar). And note a couple of bizarre fudge steps that have no readily apparent explanation.

I find this explanation in tabular format to be much easier to follow. Note that within any given century, the date of the paschal full moon is completely determined by the Metonic cycle.

And what if you just want to know, “When is Easter in 2010?” The answer is that the actual full moon and the paschal full moon are on March 30, and Easter is on April 4.

Tags: 19, Easter, equinox, full moon, Metonic cycle, misconceptions, paschal, Passover, religion
Posted in Just for Fun, Popular culture, Science | No Comments »

Lunar water update

Tuesday, March 2nd, 2010

Now that it doesn’t matter any more, the amount of water on the moon just keeps going up and up and up. Last October, it was a glassful of water per football field of soil. In November, it was twelve 2-gallon buckets of water in a 30-meter wide crater. And yesterday, we found out that we were talking about 600 million tons of water spread over forty craters near the moon’s north pole. According to Paul Spudis, that amount of water, if you converted it all to rocket fuel, would be enough to launch one space shuttle per day for 2000 years.

By the way, my first few words (“Now that it doesn’t matter any more”) were intended to be facetious. Of course, it is common knowledge that the Obama administration last month abandoned the plan (Project Constellation) to send human astronauts back to the moon in the early years of the next decade. So for the short term, yes, it doesn’t really matter how much water there is on the moon.

But for the medium and long term, of course it matters. First of all, there are going to be many opportunities to send robotic precursor missions to the moon over the next decade. In fact, NASA will have more money for this kind of mission now that we have given up on the struggling Constellation effort. There’s a strong case to be made that this is exactly the kind of mission we should be thinking about at this point anyway. The sheer volume of water is such a surprise, and there are so many mysteries about where it comes from and how it moves around. We really should be focusing on unraveling this science story now.

That’s the medium term. And for the long term, humans will go back to the moon eventually. If not NASA, somebody somewhere is going to figure out that the way to establish a permanent presence in space is by using resources that we find in space — and right now, the number one resource in terms of ease of access and usefulness is lunar water.

Now for the details. The latest surge of articles on lunar water stems from a press conference yesterday at the Lunar and Planetary Science Conference in Houston. Just as October was Carle Pieters’ big moment and November was Tony Colaprete’s moment in the sun, this was Paul Spudis’ turn to shine. He has been telling us for several months that he had some really cool data that he couldn’t tell us about officially, because the magazine he was trying to publish in (whose title begins with “S” and ends with “cience”) would not let him. He has apparently given up on publishing there, and so now he is free to talk.

Paul was the principal investigator on Mini-SAR, a radar probe that flew on the Indian Chandrayaan-1 mission. This is the same kind of instrument that made the very first tentative discovery of water, on the Clementine mission, back in 1994. But now it’s a whole lot more sensitive, especially in terms of spatial resolution. Spudis identified at least 40 craters in the north polar region with really significant quantities of water ice. There are also nearby craters that look similar yet don’t have ice in them, so it will be a real challenge for scientists in the future to explain why some do and some don’t. The craters are too small to have official names, but if you have your moon maps handy, some of them are small sub-craters of Peary and Rozhdestvensky. (I’m not sure if “sub-crater” is really a word, but if not I just invented it.)

While Spudis’ report was probably the biggest news, Tony Colaprete of the LCROSS mission also revealed some new information. That is the mission that crashed into a crater near the South Pole, called Cabeus A, and found proof of water and other volatile compounds, such as carbon dioxide and simple hydrocarbons. Now Colaprete is reporting that some of the ice was in crystalline form. This is the sort of thing that might make non-savvy readers shrug their shoulders and say, “So what? Isn’t all ice crystalline?”

Well, no. There are lots of different forms of ice, and one possibility was that the ice might be in an amorphous form, scattered through the dirt not in the form of crystals but just as a sort of alloy with the other minerals. If you have ice crystals, that means you at least have little bitty chunks of more or less pure ice. That’s good if you ever want to recover the ice and make rocket fuel out of it. It would be even better if you actually had frozen ponds of the stuff, but I don’t think anyone expects us to get that lucky.

One more comment — the more water you find, and the more other volatile compounds you find, the more likely it becomes that they came from off-world. If the ice came from meteor or asteroid impacts, then there is also a good chance that there are ice deposits underground, possibly covered up by younger, drier material. So there may be even more ice than we know about at the moment.

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Guide to the Cosmos, gold, New Scientist

Monday, January 11th, 2010

As of today, I’m on a podcast! Check out “Guide to the Cosmos,” a podcast hosted by Dr. Robert Piccioni, at www.guidetothecosmos.com. It was actually Christmas Eve Day when we recorded this interview over the phone, and it’s a two-parter. The first part, in today’s episode, is about water on the moon, and I talk all about the recent discoveries by Chandrayaan-1 and LCROSS. The second part is about the origin of the moon, and that part of the interview will air in February.

The audio part of the podcast is actually on a different site, called WebTalkRadio. You can go to their main site, www.webtalkradio.net, and then look for “Guide to the Cosmos” under the “Show podcasts” tab. But I’ll make it easy for you and give you a direct link. Dr. Piccioni also puts some images up on his own website to go with the podcast, which you can look at here as you listen to the interview.

When I recorded the interview I did not know which images he was going to have up on his website, so I wasn’t able to refer to them directly. Let me fill in that gap here. Image #1 shows the impact plume from LCROSS’s crash into the Cabeus crater.

Cabeus impact plume

This cloud of debris was not visible from Earth. The photo was taken from the “shepherding satellite” that passed directly overhead and crashed into the moon 4 minutes later. The spectrometers on the shepherding satellite analyzed both the absorbed and emitted light from this cloud to look for traces of water and other compounds. Image #2 is just a pretty picture of the full moon, nothing else. The LCROSS impact happened way down at the bottom of that picture, in the bumpy area around the south pole. Image #3 is a “wiggly line” from the ultraviolet and visible spectrometer.

Spectrum showing sodium emission line plus something interesting

Interestingly, this is not the data set that Tony Colaprete, the main project scientist, has talked about the most. Unlike the near infrared spectrometer, whose readings they understand pretty well and which show definitive evidence of water, the UV/VIS spectrum requires more interpretation and they are just beginning to work on it. The peak on the right is actually not water but sodium. (This emission band looks yellow to the naked eye, and explains why a sodium lamp is yellow. See this Wikipedia entry to read more about it.)

You can also see two shorter peaks on the left that have not been identified yet. At the AGU meeting in December, Tony said they think that one of them could be gold! Yes, gold on the moon. You read about it here first.

Back in the days before Apollo went to the moon, there was a slightly kooky scientist named Tommy Gold who said that the moon was covered by a layer of dust so deep that any spacecraft that landed on the moon would just sink into it and never be seen again. Fortunately, this didn’t turn out to be the case, but for a while NASA had to take the possibility seriously, and his hypothetical surface layer became known as “Gold dust.” But now lunar gold dust may take on a whole new meaning!

I did not report on this earlier (“LCROSS Strikes Gold!”) because they really don’t know what the peaks are yet, and so Tony’s comment was at least partly meant in jest. If they ever get more serious about it, I’ll be sure to let you know.

Last month I wrote an article for New Scientist online about the moon sessions at the AGU meeting, called “Are We Looking in the Wrong Places for Water on the Moon?” This was a very ticklish article to write, but I was happy with it in the end. Basically, the story is that one of the instruments on the Lunar Reconnaissance Orbiter (LRO) has been seeing lots of indications of water in places where it isn’t supposed to be.

LCROSS went to a permanently shadowed crater because that is where theory says that lunar water, if it exists, should concentrate. It went to Cabeus, in particular, because that is where the Lunar Exploration Neutron Detector (LEND) on LRO saw the highest concentrations of water. But what’s interesting, and controversial, is that LEND has seen no correlation so far between permanent shadowing and hydrogen deposits! There are other regions with just as much water as Cabeus that aren’t in shadow.

What made the article ticklish to write is that there are some people who frankly don’t believe the LEND data yet. I tried to hint at this without pouring oil onto the fire. But there are three groups–one in Russia, two in the U.S.–who are working on the LEND data and they all are saying pretty much the same thing. You can’t just ignore this fact and pretend it isn’t there, while at the same time singing the praises of LCROSS and the LRO camera and the other experiments on LRO. That’s why I felt it was important to write this article, even if the jury is still out on what the results mean.

In a blog I think I can be more adventurous than I can in print, so I’ll hazard a guess as to what it might mean. The LCROSS results are hinting that there is way more water than you can produce by bombarding the moon’s surface with the solar wind–some of the water has to be from meteoroids or comets. LEND can see beneath the surface, and Igor Mitrofanov, the principal investigator for LEND, says that he thinks they are seeing deposits of hydrogen that lie beneath the surface, covered by a layer of dry soil. Putting two and two together, I think that the water is delivered by meteoroids/comets, and is then buried by some process we don’t understand yet (or maybe it’s just in a sufficiently thick layer to begin with?). Once it’s buried, it doesn’t need a permanently shadowed crater to keep it from evaporating. Sure, it might be associated with a permanently shadowed crater, but really any crater will do. Or maybe even something that isn’t a crater! One of the most puzzling things about the LEND data was that one of the hydrogen deposits seemed to be on one side of a mountain range. But maybe that makes sense, if the mountain range was created by the meteoroid/comet impact.

Well, this is just my feeble amateur speculation. The specialists will, of course, hash it out and either come up with an explanation, or agree to disagree. One thing that’s pretty certain is that there is a lot we don’t know yet.

Tags: Chandrayaan-1, hydrogen, LCROSS, LEND, lunar origin, New Scientist, podcast, Robert Piccioni, Thomas Gold, water, WebTalkRadio
Posted in Media, Meetings, Missions, NASA, Science, websites | 2 Comments »

New Year, Halos and Blue Moons

Sunday, January 3rd, 2010

Here in Santa Cruz, New Year’s Eve brought an unusual coincidence of two astronomical events. One of them was a worldwide event: It was the second full moon of the month, or a “blue moon.”

The usage of the term “blue moon” to mean the second full moon in a calendar month actually stems from a mistake in Sky and Telescope magazine in March 1946! This article on Sky and Telescope‘s website explains how the confusion arose. However, as the authors note, the new definition is “like a genie that cannot be forced back in the bottle.”

How often do blue moons occur? That is a very interesting question that you can figure out for yourself if you look at the chart on the bottom of page 2 of the article. The chart reveals an interesting fact that the authors do not mention: blue moons happen on a 19-year cycle.

To see this, notice that 1999 began with blue moons in January and March. Nineteen years later, the year 2018 will begin in exactly the same way. Why is that? Well, 19 is sort of a magic number for moon-lovers. It turns out that 19 solar years are almost exactly equal to 235 lunations. (A “lunation” is the time between one full moon and the next.) So that means if you have a full moon on December 31 this year, you will most likely again have a full moon on December 31 nineteen years from now.

There are only two things that can mess up this pattern. First of all, there is a tiny 2-hour discrepancy between 19 solar years and 235 lunar months, which eventually (over a period of twelve 19-year cycles) will move the full moon forward a day. The other discrepancy results from Leap Day. If you look again at the Sky and Telescope diagram, you’ll see that the blue moon of 2001 (in November) does not match the blue moon of 2020 (in October). According to our 19-year rule, they should be in the same month each year, but the blue moon in 2020 gets pushed forward a month because of the extra day that is inserted in February that year.

This 19-year cycle was very important in ancient times, because many cultures used both a lunar and a solar calendar. To bring the two into rough correspondence, you need 7 intercalated or “extra” months every 19 years. (That is, in 19 years there are 19 x 12 “regular” months, plus 7 “extra” months, for a total of 235.) The rule was discovered by Meton of Athens in 432 BC, and is therefore known as the Metonic cycle.

Unlike the Athenians, we use a purely solar calendar. The “months” in our calendar are no longer lunations; they are merely convenient fictions. For that reason, also, the Metonic cycle no longer has any direct effect on your life — unless you happen to be the kind of person who pays attention to blue moons!

By the way, there is one other intriguing thing about that Sky and Telescope chart. I have said that there are 7 “extra” full moons every 19 years, and so you would think there would also be 7 blue moons. But actually, that isn’t quite correct! If you look at the chart, you will count 8 blue moons from 1999 through 2017! Where did the extra one come from?

The problem is, once again, February. In 1999 there were no full moons at all in February, and therefore we had two in March as well as two in January. Thus, from 1999 through 2017 (the current Metonic cycle) we will have 8 months with an “extra” full moon and one month (February 1999) with none. In other words, we will have a NET of 7 “extra” full moons, just as we are supposed to.

**************

As I mentioned, there was other wonderful astronomical phenomenon on New Year’s Eve. This one was local, rather than global. When I went outside at ten minutes before midnight, I was stunned to see a beautiful, huge halo around the moon — just like the one in the photo at the beginning of this post. (By the way, that is not my photo. It was taken by an Aussie photographer named Anthony James, who kindly gave me permission to post it in my blog. Click here to see his Flickr page, which specializes in beautiful nighttime imagery.)

A lunar halo is much easier to understand than a blue moon. It is formed in the same way as a rainbow, by the refraction of light off of ice crystals or drops of water in the atmosphere. That night was very misty and cloudy here in Santa Cruz. In fact, according to the newspaper, we weren’t supposed to be able to see the moon at all that night. However, by 11:50 PM enough of the haze had evaporated that the moon was very clearly visible. However, there were no stars — it was as if everything in the sky had been turned off except this enormous eye looking back down at me.

That’s really what it looked like — an eye, or the photographic negative of one. The lunar halo looks like the iris and the moon looks like the pupil (white, instead of black!). I think that Anthony’s picture gives you some idea of the effect.

What an incredible night–a blue moon, an eye in the sky, and the beginning of the year, all at once! I’m certain that combination will never happen again in my lifetime.

Tags: eye in the sky, Flickr, lunar calendar, Metonic cycle, Sky and Telescope, solar calendar
Posted in Just for Fun, Popular culture, Science | 2 Comments »

More from the AGU: Pink Moon, White Mountains

Friday, December 18th, 2009

My last two posts were about the American Geophysical Union meeting, held this week in San Francisco. The meeting is now over, but I’m not done writing about it yet — not by a long shot!

In 1971, Nick Drake recorded a song called “Pink Moon” that became a posthumous hit in 1999 when it appeared in a Volkswagen commercial. Now it turns out that he was really on to something. On Wednesday afternoon, Carle Pieters, the lead scientist for the Moon Mineralogy Mapper on Chandrayaan-1, the Indian spacecraft that circled the moon for ten months, talked about her discovery of a new, magnesium-rich pink spinel.

Well, okay, it isn’t really a pink moon. But if you go to the moon’s far side and land your spacecraft on the edge of the Moscoviense basin — a very attractive place, with one of the few maria on the moon’s far side — she says that you can dig up all the pink spinel that you want.

Because we have never landed anything on the moon’s far side — human, robot, or other — we’ll have to wait a while to find out if she is right. The evidence from the Moon Mineralogy Mapper (M-cubed for short) is a very distinctive spectrum, with no absorption at 1 micron and a “whopping” (Pieters’ technical term) absorption band at 2 microns, that is totally unlike any other known moon rocks but a very good match for pink spinel measured in the laboratory.

Jessica Sunshine also talked about spinel, but hers is very dark, not pink, and is probably mostly chromite. M-cubed found this deposit — also previously unknown — at only one place on the near side of the moon, a region called Sinus Aestuum. Why only there? Dunno. How much is there? Dunno. But this would be a great spot to explore once we start sending robots or astronauts back to the moon. (2015? 2020? 2100? Never?)

The good thing, and the bad thing, about both of these talks is that they were just good ol’ talks about rocks, the sort of things that geologists like to talk about when the press isn’t watching. Lest we forget, M-cubed was not really intended to look for water ice. The whole business about water was really an unexpected bonus. If they had really expected to see water, they would have made the spectrometer sensitive out to 3.6 microns. (3 microns is enough to see the peak absorption bands of hydroxyl and water at 2.7 and 2.8, but not the full spectra.)

Neither Pieters’ nor Sunshine’s findings are going to make headlines, but they are good examples of a scientific instrument doing what it was meant to do, and finding new stuff. The take-home message for non-geologists is just that the moon is not a homogeneous place; it has stuff we haven’t seen before and it most likely has stuff we haven’t even thought of yet. The other message is that all of these discoveries allow us to piece together a few more puzzle pieces to understand lunar geology.

In the case of the spinel, Larry Taylor explained in his talk how these deposits were probably formed by secondary intrusions of magma into the anorthosite layer at the top of the lunar magma ocean. In her final talk, Pieters also mentioned the magma ocean, which is believed to have encircled the moon immediately after its formation by a giant impact. She said that M-cubed found a “massive amount” of anorthosite in the Inner Rook Mountains in Mare Orientale, which she described as “very strong evidence for the magma ocean hypothesis.”

This comment made me sit up in surprise. I tend to think of the magma ocean as a done deal; I wrote about it in my book as one of the major discoveries, perhaps the major discovery, of the Apollo missions. Why would you care about proving something you already know?

The reason is that in science, nothing is ever really a done deal. A hypothesis may eventually become a theory, and it may become conventional wisdom, but you always want to collect new data and look for new evidence. The magma ocean hypothesis is based on a few anorthositic dust samples and anorthositic rocks collected by the Apollo astronauts. Until now, we hadn’t really seen any large-scale structures made of anorthosite. Now we have seen a whole mountain range of the stuff, or at least Pieters thinks we have, from orbit. The next thing to do is send a geologist there and see if she is right. Do we have any volunteers to go and look for Carle Pieters’s white mountain range?

Tags: anorthosite, Carle Pieters, Chandrayaan-1, Jessica Sunshine, Larry Taylor, lunar magma ocean, Mare Orientale, Moon Mineralogy Mapper, Moscoviense, Sinus Aestuum, spinel
Posted in Future exploration, Media, Meetings, Missions, Science | 1 Comment »

I’m a Geoblogger!

Thursday, December 17th, 2009

At the American Geophysical Union meeting this week I dicovered that I belong to a small community that I didn’t even know about: I’m a geoblogger! There was a luncheon on Wednesday for people who blog about earth or space sciences, and so I got to meet about fifteen other people who do the same thing.

One of the things that struck me was the diversity of the blogs: the different types of sites, the different reasons for blogging, the different people doing it. Every blog has its own flavor. The majority of the geobloggers were graduate students or faculty, but there were a few journalists too.

So who was there, you ask? Let me introduce you!

Reia Chmielowski came from the longest distance — all the way from Milano. She is a postdoc in metamorphic petrology. Her blog, The Musings of a Life-Long Scholar, takes a personal tone, and it might be of interest to academics outside of geology.

Larry O’Hanlon is a professional journalist who will be blogging for “two more weeks” at Discovery News before passing the blog on to someone else; however, he will still remain very much involved with the site.  He notes that it’s kind of hard to tell the blog apart from the regular news now, because a recent redesign of the site has merged the two.

Claus Haslauer, Dave Petley, Pawam Gupta, and Steve Easterbrook had different approaches to the faculty blog. They are your go-to guys if you are interested in geostatistics, landslides, aerosols, and climate change informatics respectively. To a large extent their blogs are oriented toward colleagues rather than to the public. (Gupta said this explicitly — the purpose of his blog is to “review peer-reviewed papers.”) However, Petley’s blog in particular gets a lot of hits from outside academia, especially when a natural disaster hits. He also says that he attracts a lot of students with his blog, and has begun to be better known for his blog than for his own research! Faculty everywhere, take note!

Carrying the grad student torch were Cassaundra Myers and Julian Lozos, both of UC Riverside. Cassaundra’s blog, UCR GEOP Chalkboard, is more of a departmental blog that other students contribute to (but she does the most work on it). Julian was a wannabe musician, and is now a wannabe seismologist. He has been doing social media of one sort or another since he was a kid, and said that his choice of topics has graduated from “What is your favorite Pokemon?” to “Earthquakes are not the bogeyman.”

Actually, this last comment raises an interesting point. Julian says that people always ask him how he can study something as depressing as earthquakes, but in fact earthquakes give us lots of fascinating information about our planet. Like carnivores with big claws and big sharp teeth, they get a bad rap. To read more about them, check out his blog, Harmonic Tremors.

If there was one blog whose title made me immediately want to go read it, it was probably Brian Shiro’s. He is currently in training to become an astronaut. By some quirk of fate, he learned about an opportunity to apply for astronaut training the very same week he started his blog, Astronaut for Hire. That’s right, he started his blog first and then became an “astronaut for hire”! This is a true example of the power of positive thinking. By the way, his “geo” credentials are that he works at the Pacific Tsunami Warning Center, and his blog contains some posts about that topic as well.

There were two interesting blogs from people who, like me, are academic castaways. Andrew Alden is a former geologist with the US Geological Survey who now is the Geology Guide for about.com. He uses his blog as a front end to his main informational pages on about.com, which get the most traffic. He noted that when he started with about.com, he would write long informative posts, but he has since found that about 80 percent of the people who visit the site just want to look at pictures of rocks!

I hope that Michael Tobis doesn’t mind me describing him as an “academic castaway” because he is in fact employed at the University of Texas, but it sounds as if his job is not really his raison d’etre. “My blog has been the core of my intellectual and social life for the last two years,” he said. His passion is climate change and his blog is called Only In It for the Gold, and you need to check it out.

The name, by the way, is a reference to something someone once said to Tobis at a party. When he told the hostess that he worked on climate change, a hush fell over the room. (Living in Texas, in the heart of oil country, that’s probably as good a conversation-stopper as saying you are an atheist.) His hostess, fumbling for something cheerful to say, said, “Well, I’m sure there is good money in that!”

Finally, three representatives of mainstream publications were also there. Carolyn Gramling blogs for www.earthmagazine.org, Mouse Reusch is one of several writers for the Big Wide World graduate student blog at www.newscientist.com, and Harvey Leifert is a rather infrequent blogger at the Climate Feedback blog at www.nature.com. We forgive Harvey because he is the former public information officer for the American Geophysical Union and thus has done more to promote public understanding of geophysics than all the rest of us put together.

I apologize to any other bloggers who were there whom I haven’t written about, because I had to duck out of the lunch early (actually, at its scheduled ending time) to hear the great debate over the Younger Dryas Boundary. The question: Did an impact from an extraterrestrial object cause the climate cooling 12,900 years ago that maybe caused sabertooth tigers to die out and the Clovis culture to end? To me, the most convincing talk by far was given by Alan Harris of the Space Science Institute. The intrinsic probability of such an event, a 4-kilometer asteroid hitting Earth in the last 13,000 years, is so low that you need extremely compelling proof to overcome it. As a mathematician, I would use Bayes’ Theorem to explain this, but there is an old saying of Carl Sagan that works just as well for non-mathematical folks: “Extraordinary claims require extraordinary evidence.” And the evidence for the alleged impact, so far, falls way way short of being extraordinary.

Well, none of this has much to do with the moon, but it’s just an example of the incredible variety of interesting stuff you can hear about at the AGU meeting.

Tags: aerosols, AGU, astronaut, climate change, Discovery Channel, Earth Magazine, earthquakes, extraordinary, geobloggers, geostatistics, landslides, Nature, New Scientist, off-topic, Younger Dryas Boundary
Posted in Meetings, Science, websites | 5 Comments »

Naked Astronauts, etc.

Tuesday, December 15th, 2009

Sometimes the best questions are facetious.

This morning I was attending the moon sessions at the American Geophysical Union conference in San Francisco. One of the talks was by Justin Kasper, who works on the cosmic ray detection experiment (CRaTER) on the Lunar Reconnaissance Orbiter. After his talk, one of the audience members (Mark Robinson of the LRO Camera team) asked what have to be the most unexpected questions of the meeting:

“So, is an astronaut’s suit dangerous? In a theoretical sense, would it be better for an astronaut to go naked?”

Before I tell you the answer, let me tell you why the question is not as crazy as it seems.

Kasper had just reported on the most unexpected finding so far by the cosmic ray experiment. It was supposed to measure how much radiation on the moon is coming from outer space (cosmic rays) and the sun (mostly protons from the solar wind). But they have found that the moon itself is a significant source of radiation.

In open space, CRaTER counted about 33 cosmic rays per second. (By the way, that’s an unusually high number. The sun is currently in one of the most quiet phases ever recorded in its magnetic cycle, which means that it is not doing as good a job as usual of blocking cosmic rays from outside the solar system.) When LRO got into lunar orbit, about 50 kilometers above the surface, the count dropped to 22 cosmic rays per second. Sounds great — you’re safer on the moon than in outer space.

But here’s the catch. If you’re on the moon, the moon ought to block half the cosmic rays coming from outer space! Even if you’re orbiting 50 kilometers above the moon, the moon should still block about 14 out of 33 cosmic rays, letting only 19 through. Because CRaTER is recording 22 per second, the remainder of the radiation (3 events per second) must be coming from the moon!

At this point, they can’t be sure why, but Kasper conjectured that this radiation is produced by cosmic rays that hit the surface, smash up an atomic nucleus, and re-radiate back into space.

What does this have to do with space suits? Well, your space suit contains lots of heavy atomic nuclei for the cosmic rays to smash into. So if you’re an astronaut, you’re going to be exposed to some radiation emanating from your space suit, for the same reason. That’s why Robinson asked his question.

Now really we don’t recommend future astronauts to do the full moon-ty. There are good reasons for wearing a space suit, such as the inconvenient fact that humans need air to breathe. However, Kasper did say that we should think carefully about what we make space suits out of. Are some materials better at absorbing cosmic rays than others? It’s also relevant for building shelters on the moon. “The results suggest that building a wall is a little more helpful than building an umbrella,” he said.

Actually, this comment was facetious too, because a flimsy umbrella isn’t going to help you much against cosmic rays. In an interview last week, Jack Burns of the University of Colorado, a science advisor for NASA, told me that one of the best defenses against cosmic rays is actually a tank of water. (That is one more reason why discovering water on the moon is important.)

Tags: AGU, cosmic rays, full monty, LRO, radiation, sun
Posted in Future exploration, Just for Fun, Meetings, NASA, Science | 1 Comment »