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 »

LCROSS Results Tomorrow

Thursday, November 12th, 2009

Last month the LCROSS satellite crashed into a crater near the Moon’s south pole, in an experiment designed to look for water ice. At that time the principal investigator, Tony Colaprete, said that they would probably announce the results from the mission within two months. Well, they’ve beaten that timeline by a month. Tomorrow there will be a press conference at NASA Ames at 9:00 am Pacific time (12 noon Eastern time) to announce the first findings.

As I wrote in my previous post, the LCROSS impact was sort of a dud from the point of view of public relations.  It was not possible to see the debris plume from an amateur telescope, as the mission planners had hoped. Nevertheless, the instruments on the spacecraft definitely did see the debris. Thus, from an engineering point of view, the mission was a success. They landed the spacecraft where they wanted to land it and they got data.

So that leaves one more question: Was the mission a success scientifically? And in particular, did they find water? That’s the question that I am almost certain will be answered, one way or another, tomorrow. And of course it is the most important question from the viewpoint of future exploration of the moon.

I don’t have any inside information, but Tony Colaprete did say this in an e-mail to me a couple weeks ago: “We have a wonderful data set … It amazes me a little more each and every day.” Read into those tea leaves whatever you will!

In related news, Colaprete and other members of the LCROSS and LRO missions are going to present their early results next week in Houston, at the annual meeting of the Lunar Exploration Analysis Group. Of course the press conference tomorrow will cover anything really big and important, but I’m sure there will be many more details and more discussion at the Houston meeting.

Fortunately, New Scientist has commissioned me to write an article about the status of the lunar water question, taking into account all the results that have been announced this year, from Kaguya to Chandrayaan-1 to LRO and LCROSS. I will attend the Houston meeting, and this will give me a chance to do lots of interviews.

I think we are now at a crossroads in lunar exploration. We’ve gotten a big influx of new data this year, with tantalizing signs that there is more water than we expected on the moon. Now is the time for planning the next steps. Do we shrug our shoulders? Do we invest $3 billion more into the NASA manned flight program, as the Augustine Commission suggested? Do we plan new robotic missions? If so, what should they do?

Lots of questions. Hopefully I’ll find out a few answers, starting tomorrow.

Tags: Houston, LCROSS, LEAG, New Scientist, Tony Colaprete, water
Posted in Media, Missions, NASA, Science | No Comments »

“That’s Daddy’s rocket!”

Tuesday, August 25th, 2009

In an earlier post I wrote about the LCROSS mission, which is due to make its crash landing on the moon on October 9. (Mark your calendars!) In July I talked with Tony Colaprete, the Principal Investigator for the mission. I apologize if there is a bit of unevenness in this interview, because I have cobbled it together from three sources — our conversation at the Moon Fest, an e-mail, and his presentation at the Lunar Science Forum. Answers have been edited for length but I have tried to preserve Tony’s wording.

Tony Colaprete (NASA photo)

DM: You told me that you were born the week before the Apollo 11 landing. So, happy birthday! How big an inspiration have the Apollo missions been to you?

TC: I was born July 16, 1969, the day Apollo 11 launched. My father was heavily involved in the Apollo program, and one of my early childhood gifts was the classic Snoopy dressed in an EVA suit. So, yes, the Apollo mission was a huge influence, not only because they were so amazing but also because of my father’s involvement. … I am amazed to think that the folks who did Apollo were on average around 25 to 27 years old! The commitment, devotion, and guts those people had is inspiring.  I just hope I can do things half as right as they did for the Apollo program.

DM: When and how did you decide that you wanted a career in space exploration? How did you prepare for it?

TC: When I graduated from high school I knew I wanted to either go into the sciences or art. Luckily for us all, I decided to go into the sciences. … Very early on, though, I loved being in the woods near Boulder, Colorado, where I grew up. I would go for hours by myself and just watch what went on around me. So very early on I knew I loved systems, how things work together and influence each other … I still do.

I worked on instrumentation at the University of Colorado through the Space Grant College and the Laboratory for Atmospheric and Space Physics for a few years after getting my bachelors degree in physics. I was taking a few graduate classes (including my first planetary atmospheres class, taught by a very inspiring David Grinspoon), when I realized I wanted to pursue a graduate degree in planetary sciences. Luckily, CU is a great place to do that!

While I was doing my graduate work I continued to work on instrumentation for sounding rockets, space shuttle flights, and small spacecraft. This combination of science and engineering (again, systems!) was key, I think, to helping me get where I am now.

DM: How did the idea for the LCROSS mission come about?

TC: When LRO moved up to a bigger rocket, they had room for an extra 1000 kilograms on board, and a call for proposals went out for a co-manifested mission. And by the way, they said, you have only 2½ years to get it done, and you can’t spend more than $80 million.

When the call was announced, we [at NASA Ames] formed a “Tiger Team” to come up with ideas. Early on in the process we considered an impact mission, but I concluded that with only 1000 kilograms to work with, the impactor mass would be too small.

Another person in the group, Geoff Briggs, suggested using the spent upper stage of the launch vehicle. He has since said that he got the idea from someplace else. I ran some numbers and convinced myself that an impact by an object of about 2000 kilograms would produce a cloud observable from earth.

At about the same time, Northrop Grumman submitted a [proposal] that was also using the upper stage and also had a small shepherding satellite that could make observations. An engineer on the Tiger Team saw the idea and told me about it. We had a couple Northrop Grumman scientists come up and we discussed our ideas and the rest was history. So I don’t think it was any one person’s idea, but just enough people with the same idea!

In the end, LCROSS was selected out of 17 proposals. We cheated the 1000 kilogram limit — it’s 3200 kilograms, because we held on to the spent Centaur [rocket stage], which is about 2300 kilograms.

DM: Have you ever watched a launch in person before? If so, how was it different, knowing that it’s your own experiment that is going up?

TC: I’ve flown payloads on sounding rockets and shuttle flights, and have seen those go before. This Atlas moved so slow at first! I thought to myself, “You’d better pick up some speed or you’re not going to make it!” The sounding rockets and the shuttle use solid fuel, whereas the Atlas V is all liquid — it’s a big difference!

My biggest concern at launch was whether we could get off on the 17th or the 18th [of June], because those two days result in very good impact observing conditions for the continental U.S. The 19th was not so good, and on the 20th [there were no good times] at all. So I was very glad the weather broke in time for us  to go on  June 18.

DM: Have there been any exciting moments since the launch?

TC: I held my breath when we turned on the instruments for the first time. That was a moment of sheer terror and anxiety for me. Also, I’ll hold my breath again on August 1, when we turn them back on. Radiation and vacuum can have effects on detectors, so they always degrade over time. Once we know that they are working, I will be very confident that the payload will survive until the impact with the moon. [According to the mission page, the checkout of the infrared cameras and spectrometers on August 1 went very well. They took spectra of Earth and -- stop presses! -- detected oxygen, water, and vegetation! -- DM]

DM: What are you expecting to see when LCROSS hits the moon?

TC: There are a couple different models of how the water gets to the south pole and two different predictions for how it is distributed. We describe them as the smooth versus chunky models. In the smooth model, the ice is uniformly distributed on the scale of this room, with about a 1 percent concentration of ice. If that model is correct, LCROSS will have very good chances of detecting it. LCROSS should be sensitive down to concentrations of half a percent.

However, if the ice is chunky, with smaller pockets of up to 10 percent ice, then we might have a 10 percent chance of hitting something. If we hit one of the “peanuts” in the chunky peanut butter, we’ll know. This would immediately distinguish between the two competing models.

My biggest fear is that we won’t see anything — that it will be a dud. But even in that case, then we’ve learned that the distribution isn’t smooth. That is important to know, because it means that your next mission [i.e., a lander to search for ice on the ground -- DM] had better be mobile.

DM: How does the LCROSS mission compare with other spacecraft that have crash-landed on the moon (Lunar Prospector, the European SMART-1, and the Japanese Kaguya)?

TC: None of those other missions were designed as impactors. The biggest difference is that they typically hit the moon at a low, grazing angle, because they were in orbit around the moon. LCROSS is not, it’s in orbit around the Earth. [This is a rather non-obvious fact that is illustrated on the flight director's blog at this link. LCROSS doesn't "go to the moon." It goes into an orbit around Earth that is the size of the moon's orbit, and then the moon just runs into it! - DM] So it will hit at a very steep angle, around 85 degrees. Also, we’re bringing quite a bit of mass. So those missions can’t be compared to LCROSS for visibility, size, and impact angle.

DM: How big a crater will the LCROSS impact make?

TC: We’ve done simulations using Apollo-era technology, and we expect the crater to be about 20 meters wide — the size of a tennis court. We expect the plume to contain about 300 to 400 metric tons of material.

DM: On the LCROSS website you have a list of several possible target craters. Do you have a favorite on this list?

TC: Faustini would be my preference. It’s a very old, large crater, so the material in there has been in shadow for a very long time — around two and a half billion years. We want to hit somewhere that is flat and fluffy, not blocky and steep. One thing against it is that it’s right on the limb of the moon. So the ejecta have to go up 2 kilometers in order to be illuminated by the sun. In some of the other target craters, the ejecta only have to go up about 500 meters. But for earth observers, a position on the limb means that you get high contrast [against the darkness of space -- DM], and that’s good.

DM: I think it’s interesting how you have been able to use the results of other recent missions to narrow down the list of targets for this mission. Can you talk a little bit about  the synergy between missions, and especially the Japanese Kaguya spacecraft?

TC: The topography from their laser altimeter has been invaluable. First, it lets us calculate the slope of the ground. You don’t want to hit a slope [because you would then lose the benefit of a high impact angle -- DM]. Kaguya also gave us amazing information on the depth of the craters. Some of the errors in the previous estimates were significant, on the order of 500 meters to a kilometer. From the Kaguya terrain camera we got information on the surface roughness and albedo [reflectivity] of the craters. So, overall, they matured our current data set.

Also, with new LRO data coming online, we’ll be refining our numbers continuously to make the wisest choice of target. We will finally make an impact site selection by 30 days before impact, roughly the first week of September.

DM: How can ordinary people contribute to the LCROSS mission?

TC: Amateurs have already contributed, and with an impact with the moon high and the skies dark as far east as Texas, I hope many more will continue to contribute.

One thing to realize is that professional astronomers typically don’t point their telescopes at the moon. To most of them, the moon is a source of light pollution. So when we asked the best in the world to look at the moon for a change, there was a steep learning curve. One thing they needed to learn was how to find the crater you want to point to amongst a hundred or so other craters that look very similar. The shadows and bright areas change dramatically with small changes in the sun angle, so finding one’s way around the moon can be difficult if one has never looked before. To help, we asked the amateur community to image the moon at all phases and tilts so that we had a library of sorts for the various light conditions.

During the impact, amateurs with a minimum of about a 10-12 inch telescope can observe the impact. We will be soliciting these observations and will share them with others. [There is a Google Group for amateur observers at this link -- DM.]

DM: Finally, do your kids know that “Dad is a rocket scientist”? If so, are they proud of it, and are they paying any attention to the LCROSS mission?

TC: I have a son who is two and a half and a daughter who is five years old. They came to the launch, and when they look at the moon now they say, “Daddy’s rocket is flying to the moon!” After the launch my wife and children took a different flight home than I did. During the layover, on one of the cable news channels playing at the gate, they showed a replay of the launch. My children both yelled, “Daddy’s rocket!” My wife says that the people around them looked with a bit of a skeptical stare until she said, “Actually, it is their daddy’s rocket.”

Tags: Ames Research Center, Apollo, chunky, craters, interviews, Kaguya, LCROSS, LRO, Northrop Grumman, smooth, telescopes, Tony Colaprete
Posted in Missions, Science | 3 Comments »

LRO’s “BFF”

Monday, August 3rd, 2009

The second of the two moon missions that NASA launched in June is called LCROSS, an acronym for Lunar Crater Observation and Sensing Satellite. According to Tony Colaprete, the chief scientist for the LCROSS mission, “The younger folks at Goddard Space Flight Center have started calling it LRO’s BFF… at least until October 9.”

Hmmm… I can see some puzzled looks out there. Okay, I’ll explain. LRO is the Lunar Reconnaissance Orbiter (LRO), which launched on the same rocket as LCROSS on June 18. BFF is Internet-speak for “best friends forever.” (But you knew that already, right?) And October 9 is D-day for the LCROSS mission.  Unlike LRO, which will accumulate its results slowly and steadily over a period of one to three years, LCROSS will go out in a blaze of glory, and will do all of its most interesting science over the course of 5 minutes.

LCROSS consists of two main pieces — a spent rocket booster and a “shepherding satellite.” On October 9, around 4:30 AM Pacific time, the bigger rocket booster will slam into a crater near the moon’s south pole. Imagine an SUV crashing head-on into the ground at more than 5000 miles per hour! That’s what the impact is going to be like. It will be equivalent to the explosion of about a ton of dynamite. 

The explosion will be big enough, in fact, to be seen from Earth. That is the whole idea — to time the impact so that it can be tracked by all of the big telescopes on Hawaii, as well as the Hubble Space Telescope. Colaprete says that even a 10-inch telescope (well within the range of many amateur astronomers) should be able to see the flash, if it is pointed in the right place at the right time. If you don’t have access to a 10-inch telescope, you can also watch the impact over the Internet.

A minute or so after the big kablooie, the shepherding satellite will come swooping in, flying right through the debris plume. While it’s getting buffeted about, it will hopefully be able to sniff out any volatile compounds that have been excavated by the blast, including water vapor — the number one target of the mission.

We’ve seen tantalizing hints of water ice from orbit, but nothing that absolutely confirms it. We know that there is hydrogen in the permanently shadowed craters near the south pole, but there is no guarantee that the hydrogen is bound up with oxygen to make a water molecule. There’s only one way to find out for sure, and that is to “reach out and touch it,”  as Colaprete says. Or perhaps “reach out and blow it up” would be a slightly more accurate wording.

After it flies through the plume, the shepherding satellite will itself crash into the moon a few minutes later, creating a second and smaller blast. Colaprete is deliberately not building up any great expectations for this one, because it will be harder to control where the shepherding satellite lands. However, it will give scientists a second chance to look for signs of water, or at least to understand the mechanical properties of the ground that LCROSS is crashing into.

Last month I had a chance to interview Colaprete by e-mail and then in person at the Moon Fest. I also went to his talk at the Lunar Science Forum. In my next post I will try to reproduce these three “conversations” as if they were all one interview.

By the way, the LCROSS mission reminds me of something interesting I learned when researching my moon book. After Russia launched Sputnik in 1957 and when our scientists and politicians were debating what we could do to respond, one of the crazy ideas that was floated was to nuke the moon. That’s right, launch a nuclear missile at the moon and blow it up, thereby proving somehow that we were bigger and badder than the Russkies.

What a stupendously bad idea this would have been, because we would have learned nothing from it. The response we chose instead — sending men to the moon — was vastly more difficult, but we got so much more out of it, including a real understanding of the moon’s origin and makeup, plus the fleeting goodwill of all of the rest of the world.

It’s just a tiny bit ironic, then, that on our second round of missions to the moon, one of the first things that we are doing is slamming a rocket as hard as we can into the moon to create a big explosion. I mention this parallel with some hesitation, because I don’t want to make LCROSS seem like just a stunt. That is exactly what it is NOT. There are two huge differences between this mission and the stunt that was proposed back in the late ’50s:

1. A spent rocket booster is not a nuke.
2. The LCROSS mission was designed with a specific scientific purpose in mind: to excavate water ice, to see first of all if there is any ice there and secondly how much there is and how easy it is to get it out. These are vital things to know if we are ever going to set up a permanent moon base.

Maybe these points are obvious and didn’t even need saying, but I just wanted to explain why the LCROSS mission is not just about some engineers blowing things up for fun.

(Still, blowing things up is fun … See any episode of Mythbusters for proof!)

Tags: blaze of glory, hydrogen, ice, kablooie, LCROSS, Mythbusters, nuke, Tony Colaprete, water
Posted in Science | 2 Comments »