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 »

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 »

LEAG Conference, part 1

Thursday, November 19th, 2009

I’m back from the Lunar Exploration Analysis Group (LEAG) meeting in Houston, which ran from Monday through Wednesday this week. There was plenty of talk about LCROSS, which one member of the LCROSS science team calls “the little mission that did,” and also lots of discussion about the future of lunar exploration. The big theme of the meeting was sustainability: How do we go back to the moon in such a way that we can keep on going there indefinitely? Many, though not all, of the participants interpreted that question to mean: How can we make the moon economically viable? Of course, the LCROSS mission has a great deal to say about that.

Of course, the talk I looked forward to the most was by Tony Colaprete, the principal investigator for LCROSS. He gave only a few more scraps of information beyond what was reported in the news conference last Friday, but nevertheless I felt that the scraps fit together into an interesting story, which I wrote for the New Scientist website. You can find it here. I concentrated on the discovery of other volatiles besides water, because that was clearly what most interested the people I talked with.

I had to do a little soul-searching, because I go a little farther in the article than Colaprete would go in saying where the water and volatiles probably came from. But isn’t that my job as a journalist? If the experts are pretty sure about piece A, and they are pretty sure about piece B, and if there is only one way that piece A and piece B fit together and everybody knows it, shouldn’t I tell the public about that? Or do I have to wait until, ta-dah!, they hold a press conference and say they are ready to draw conclusion C?

Anyway, there were lots of other interesting and fun things at the meeting. For my blog I will concentrate on personal impressions rather than scientific news.

First, one thing I really loved about this meeting was how much joking and camaraderie there was. I don’t know whether it’s because it is a small enough community that everybody knows each other, or because certain people who are leaders in the community set the tone with their irreverence, or whether it’s just because everyone was in high spirits over the LRO and LCROSS results (and let’s not forget the Chandrayaan-1 results before that). Or maybe it’s just because geologists and planetary scientists are by nature goofy people.

Anyway, the big running joke at the meeting was Larry Taylor’s shorts. After the LCROSS press conference, he was quoted by the New York Times saying that he would have to “eat his shorts.” He was one of the scientists during the Apollo days who came to the conclusion — with good cause, I might add — that the moon rocks were “bone dry” and did not have a scrap of water. He told me that his grandfather used to say that he would “eat his shorts” if he were proved wrong, and so Larry told the newspaper reporter that he would have to eat his shorts now that water had been found in abundance. He had no expectation that this quote would be featured prominently in the Publication of Record. But then he got about 50 e-mails the next day asking if he would have a side of fries with the shorts, and what else he wanted to eat along with them. At the meeting several speakers ribbed him about this, and he finally said that he would eat them if they were served with a bottle of Guinness. Well, with unbelievable alacrity, a four-pack of Guinness beer materialized at the front of the lecture hall! I’m afraid I am not sure whether he eventually made good on his promise (I rather doubt it), but it shows how much fun people had at this meeting.

One of my favorite moments from the meeting was listening to a conversation between Wendell Mendell, another scientist who has been around since the glory days of NASA in the early 1970s, and Igor Mitrofanov, who is sort of his Russian equivalent. They swapped stories about the beginning of the Space Age. Mitrofanov described how when Sergei Korolev wanted to launch the first Russian satellite, he went to the Academy of Sciences, who of course loaded it down with more and more things that they wanted the satellite to do. It looked as if it would take forever, and Korolev was worried that the Americans would launch a satellite first. So he went to Khrushchev, the leader of the Soviet Union, and asked if he could launch a satellite that would just go beep beep beep. Khrushchev said sure, and Sputnik was born. Khruschchev didn’t think much of it, but when Sputnik flew in October 1957 and he saw how panicked the Americans were, he called Korolev back into his office and said, “I want another satellite by November!” (The over-complicated Academy of Sciences satellite did finally get launched, Mitrofanov said, but it was their third satellite.)

Mendell said that President Eisenhower was actually glad to have the Russians launch the first satellite … until he saw the furor that it caused. He wanted to be able to fly satellites over Russia to take spy pictures, because the U-2 airplanes that were doing this job were at risk of being shot down. If the Russians launched the first satellite, they couldn’t very well complain when the Americans launched one of their own. Nice plan, until everyone in the U.S. got hysterical about Sputnik, and the U.S.’s first attempt at a satellite launch blew up.

I guess these stories are probably pretty well known, at least the U.S. side, but I loved the idea of these two scientists, once separated by an Iron Curtain, being able to talk and laugh about these things.

More meeting thoughts and recollections in my next post …

Tags: Chandrayaan-1, Dwight Eisenhower, economics, humor, Igor Mitrofanov, LCROSS, LRO, New Scientist, Nikita Khrushchev, Sergei Korolyev, Sputnik, sustainability, Tony Colaprete, Wendell Mendell
Posted in Just for Fun, Meetings, NASA, Science | 4 Comments »

Water on the Moon — Bring your Buckets!

Friday, November 13th, 2009

As usual, the LCROSS press conference had a lot of Power Point slides, but probably the most memorable thing about it was an empty 2-gallon industrial bucket. Tony Colaprete, the lead scientist for the mission, said: “I’m here today to tell you that yes, indeed, we found water on the moon, and we didn’t just find a little, but we found a significant amount.” Then he held up the bucket. ”In the 20-30 meter wide impact crater that LCROSS made, we found about a dozen of these 2-gallon buckets. And that is probably a lower bound.”

Let me back up and give a little bit of context. Earlier missions, Clementine and Lunar Prospector, had found evidence for water ice but no direct proof. This year, three different missions simultaneously reported proof of water ice, because they detected not just the spectral signature of hydrogen (H) but also the hydroxyl molecule (OH). [It doesn't take too much knowledge of chemistry to see that hydrogen, H, plus hydroxyl, OH, equals water, HOH.] Not only that, the hydroxyl comes and goes over the course of a lunar day, which suggests that there is some chemistry going on at the moon’s surface. Carle Pieters, the principal investigator for the Chandrayaan-1 mission’s Moon Mineralogy Mapper, estimated that you could get a liter of water from a football field-sized area of the moon’s surface. This was exciting news, but as a reality check, it still makes the moon drier than Earth’s driest desert.

LCROSS has found an oasis in the desert. It was targeted for a specific crater near the south pole, Cabeus, where remote sensors had detected a high concentration of hydrogen. It excavated a 30-meter crater, only a third the size of a football field. Within that region, it dug up not just a liter of water, but 100 liters. Again, for context, one reporter asked Colaprete how this compares with Earth’s driest deserts. He said, “If you stand on that beach [the sandy spot where LCROSS impacted], I can say that it is wetter than some deserts on Earth.”

Does this contradict the Chandrayaan-1 findings? Of course not. It just re-emphasizes how little we know. Chandrayaan-1′s measurements were taken over a broad swath of the moon. By comparison, LCROSS is just looking at a tiny pinprick on the surface. Also, Chandrayaan-1 was measuring only the water that is right at the surface, up to a few microns deep. On the other hand, LCROSS excavated to several meters below the surface. To me that was one of the most exciting things about LCROSS; unlike measurements from orbit, it really sees what is underground. (However, it turns out that I was not entirely correct when I thought that LCROSS would be the first mission to do this. Radar measurements can penetrate one or two meters. Chandrayaan-1 carried a radar instrument on board, but those results have not been published yet. When they do get published, Paul Spudis promises me that they will be good.)

So basically, we now have one data point where we had zero before. We know that at one particular location, we have found an oasis. It remains to be seen exactly how concentrated the water ice is there, how heterogeneous it is, how hard it is to find other areas with lots of water, how deeply it is buried, etc. Not only that, there is a whole new suite of questions: How does water get to the moon? Once it’s there, how does it get transported to the poles? There are lots of theories, and at this point absolutely no way to choose among them.

What we have here is the appearance, in less than two months (since Pieters’ paper), of a whole new field of science that didn’t exist before: lunar hydrology. The next step, of course, will be for the LCROSS team to continue analyzing their data and nail down the concentration of water at their impact site. Also, LRO (the Lunar Reconnaissance Observer) will continue making large-scale observations  to figure out where else on the moon we might find water. But then, if we’re really serious about following up on this discovery, the next step needs to be a lunar rover (or even several of them) to poke around these permanently shadowed craters and start answering the questions in the previous paragraph.

There was one other very interesting thing mentioned at the press conference, which Colaprete was clearly eager to say more about but he just doesn’t have the data yet. LCROSS found lots of other volatile elements in the debris plume and/or the vapor cloud released by the impact. These may include:

• carbon dioxide
• methane
• methanol
• ethanol
• ammonia
• other organic molecules

The case for these is not as clear yet as the case for water. Colaprete said that it is absolutely certain that some of them are present, but they can’t yet pin down which ones and in what amounts. The science team is going to continue working hard to answer those questions, but they felt that the detection of water was so clear and of such overriding importance that they voted to go public with it now (instead of waiting another month, as per the original plan). But still, stay tuned for news about these other volatile compounds, because this story ain’t over yet.

Tags: buckets, carbon dioxide, Carle Pieters, Chandrayaan-1, hydrology, LCROSS, LRO, methane, oasis, Paul Spudis, Tony Colaprete, volatile compounds, water
Posted in Media, Missions, NASA, Science | No Comments »