LCrOSS to impact the Moon, look for water

By Phil Plait | April 10, 2006 12:12 pm

NASA is pretty serious about putting people back on the Moon. But you can’t just build a rocket, stick some folks on it, and ship them off. You need to have a good understanding of the lunar surface, which means high-resolution maps, excellent knowledge of the topography, and even mineralogy of the surface. All these allow you to pick the best landing sites, and not slam into a mountain on the way down.

NASA did mapping of the Moon before Apollo, and they’ll be doing it again before this next round of exploration. The Lunar Reconnaissance Orbiter (LRO) is the first step in this return to the Moon. It will have high-res cameras, an altimeter, and other instruments to help map the Moon. It’s scheduled to launch in 2008.

A few years ago, it was found that there might be water ice on the Moon, locked away in the permanently dark regions of deep craters at the lunar south pole. In reality, hydrogen was detected by earlier spacecraft, and the easiest way we know to have a repository of hydrogen is to lock it up in water (H2O, right?), which is common in the solar system (for example, comet impacts might deposit water in the polar craters). The water doesn’t melt/evaporate there because some craters are very deep, and sunlight in these regions never reaches the crater bottoms. Studies have shown that water could stay in the bottom of these craters for many hundreds of millions of years. This water would make it a lot easier to place laboratories and colonies on the Moon; water is heavy and hard to transport via rockets, so finding some already there would save a huge amount of effort and, of course, cost. The problem is that the water was not directly detected, only hydrogen was. Confirming the existence of this water is a pretty big deal.

It’s so important that NASA decided to take a more pro-active course in finding it. As it happens, the LRO spacecraft is launching on a big rocket, so big that they room left over to add more hardware to the original spacecraft. So NASA got an idea: send a secondary spacecraft along with LRO. While LRO goes into orbit around the Moon, the second spacecraft can do something to try to detect that water.

NASA opened up this idea to the scientific/engineering community, and 19 proposals submitted. The winner was just announced in a press conference today. It’s called LCrOSS: the Lunar Crater Observation and Sensing Satellite. LCrOSS is basically two pieces: one piece is a hunk of metal with steering rockets on it. That part will impact the Moon, sending up a plume of material that will hopefully contain water. The second piece of LCroSS has infrared and visual cameras on it which can detect the impact and the plume, determining if it indeed has water in it.

The impactor will hit the Moon at 2.5 kilometers per second, at an angle of 75 degrees (nearly vertical). The impactor weighs 2000 kilograms (two tons!), so the energy of impact is about equal to exploding more than a ton of TNT on the surface of the Moon. Bang!

The "follower" spacecraft with the detectors will observe the impact, and then 15 minutes later it will pass right through the plume, and then it too will impact the Moon– the course is set to be as close as possible to the impact site to get a good look at it, and the best way to do this is to have it hit the Moon as well.

This is all scheduled to happen well after LRO itself gets to the moon. LRO will get to the Moon first, get into its orbit, and go through the usual shake-down procedures to get it into shape. In the meantime, LCrOSS will be on a long orbit that takes it around both the Earth and the Moon. The orbit is 43 days long, and it will orbit twice (for a total of nearly three months) before the impact. This should be plenty of time to get LRO ready to observe the effects of impact as well.

The crater should be about 100 feet across and 16 feet deep, and the plume may reach heights of 30-40 miles above the lunar surface. It will be heavily observed by telescopes here on Earth, and engineers expect that the plume itself may be visible by amateur astronomers with big enough telescopes (I’ll be watching with mine: count on it!). Incidentally, the target crater is named Shackleton, which is appropriate enough: he was an explorer of the Antarctic, at the Earth’s south pole.

I’ll note that Lunar Prospector tried this same thing in 1999, but it hit at a very low impact angle, so the material was shot out sideways. Plus, the spacecraft wasn’t very massive, so it didn’t create a large plume. Nothing was seen, even by Hubble (much to my chagrin; I was on that project to get the data from Hubble). The difference now is that the LCrOSS impactor hits at a steep angle, and is much more massive, so the plume should be much larger and easier to see.

So what’s my opinion of this? At first I was skeptical; it seems pretty late to add something like this onto LRO. However, the LCrOSS spacecraft is separate from LRO. They launch on the same rocket, but they separate early on. The way it was described in the press conference, there will be minimal impact (har har) on LRO, so the added risk is small. They have a budget cap of $80 million, which is really not very much for a space mission, and it does add a lot of value to LRO, even if no water is detected.

Look: at some point, we need to find out if this water exists or not. A dedicated mission for this would cost a lot. Adding a special detector to a subsequent mission would be nice, and maybe even necessary, but this is perhaps the quickest and easiest way to look for the water. Sending up a plume makes it possible for telescopes on Earth to look for the water as well, and that provides a lot of backup.

I like the idea of doing this, since it’s not terribly expensive as these things go, has a high probability of working (we’ve done it before under more difficult circumstances), and can be done without affecting the main LRO mission. If — if — all this can be done, then I think this is a good idea.

Also, I think going back to the Moon is a good idea, and I know it won’t fly without public support. Doing something splashy like this (again, har har) will get a lot of attention, and is something people can actually go out and see with their own eyes (well, through a telescope). And it’s not just a stunt; real science may come out of this, science that has a direct impact on future exploration of the Moon. I think this has a pretty good chance of sparking interest in the public.

Based on what I’ve heard, I support this mission, and I’m excited by it! I’ll be very interested to see what happens next.’

CATEGORIZED UNDER: Astronomy, Cool stuff, NASA, Science

Comments (34)

  1. It’s gonna be like a Mythbusters stunt, I love it. :-)

  2. I think it looks like one heck of a cool piggyback.

  3. The Brummell

    “The impactor will hit the Moon at 2.5 kilometers per second, at an angle of 75 degrees (nearly vertical). The impactor weighs 2000 kilograms (two tons!), so the energy of impact is about equal to exploding more than a ton of TNT on the surface of the Moon. Bang!”

    Wait a minute. 2 tons slamming in at 2.5km/s is equal to only 1 ton of TNT at rest going bang? TNT has more stored energy than I realized!

  4. grand_lunar

    Look at what Deep Impact started! First, a comet, now the moon. What else might become a target?

    I hope all goes well for this mission, especially with the finding of frozen water.

  5. Kaptain K

    “The difference now is that the LCrOSS impactor hits at a steep angle…”

    Doesn’t getting into an orbit that impacts the pole at a steep angle require a huge delta V? How is this accomplished? Is it the reason for the two orbits around the Earth-Moon system?

  6. P. Edward Murray

    Now if only the weather will cooperate!:)

    And you are right Phil, we need lot’s more data about Lunar Regolith and bedrock as I recall, Apollo astronauts had a heck of a hard time getting those Lunar core samples!

    We need to design all kinds of new equipment to dig soil or maybe we won’t have to dig much?

  7. Dude

    I guess this is going to be the “resurrection” of the
    Manhattan Project type of American science stunt that people are saying is dying out. I agree. If Bush doesn’t do something bold, I’m going to fall asleep for the rest of Bush’s term.

  8. Dan Gerhards

    I will be out with my telescope, guaranteed! I saw the flash of Deep Impact hitting, and it was incredible to realize what I was watching! This would be just as cool. (Two ton? Wow.)

  9. Miral

    It’s always struck me as wasteful and “messy” to find out about stuff by just smacking into it. Why can’t we just send up a Lunar Rover or something?

  10. MaDeR

    Miral, smack is the easiest way to do something. Humanity is well-trained to hit objects with other objects. From our own fists to newest nuclear toys, we do it often.

  11. jackd

    Would it be feasible to use a piece of orbital junk as the impactor rather than launching that 2000kg? I guess not, since you’d have to match velocities with the junk then have enough reaction mass to get it into the right Moon orbit. But I was originally thinking in terms of the amount of energy needed to get the impactor into orbit, and if there were a large enough hunk of trash just waiting to be hauled off, it would be a cool thing to do.

  12. To send a Lunar Rover, you have to land carefully. This requires propellant: you need rocket fuel to slow yourself down as you descend. You also need a descent-stage rocket you can control and something to control it. Why risk a computer glitch at a critical time? NASA’s early Ranger probes kept missing the Moon entirely, crashing or landing with their cameras dead. Two of the Apollos (11 and 14) had technical difficulties on the way down, I believe. The simplest approach is always best.

  13. icemith

    Wow, it’s on again. and about time! Is there any hope in seeing anything with an old Celestron C90? Being in the southern hemisphere on Earth (Aust.), and assuming direct observance, I guess we would have a very slight edge viewing the S/H of the Moon. On second thought it would be a negligable difference at that distance!

    Would the target be an actual ( say small crater that _may_ contain frozen water ), or be anywhere nearby that would throw up soil samples in the form of dust from the impact, and exprapolate from that if there is any significant hydrogen or even water vapor? Could the impact raise the temperature of the ejected matter enough to realise that proposition?

    Anyway, I’ll be watching.


    PS…… Like the newer layout and color scheme. Though on opening this blog re the moon-blast thingie, I found myself back with the older layout, then couldn’t find a place to comment. Finally did of course but I was expecting same as we were shown in the last blog re the change, with the blue borders etc. I clicked on the almost insignificant ‘Comments’ link and this did bring up the new ( newer? ) page. I am getting to like it, even with its blue borders. If one does not like it, one only has to re-size the page width to lose it. I am using Safari, whether this works in other platforms, I neither know, nor care. Ivan.

  14. Stargirl

    JackD asked
    “Would it be feasible to use a piece of orbital junk as the impactor rather than launching that 2000kg?”

    As I recall during the Apollo era several of the third stage rockets were impacted on the Moon as part of the seismology experiments set up by the astronauts. Just to be on the safe side the impacts occurred after the astronauts had left.

  15. Actually, it was the other way around. The SIV-B third stage hit the moon before the astronauts arrived. Obviously the impact was monitored by seismographs left by previous missions.

    If you think of it, the stage couldn’t have done otherwise. When they left Earth orbit, both the SIV-B and the CSM/LM were on the exact same trajectory aimed straight at the moon. The spacecraft did a course correction to put it on a “free return” path (and later braking into orbit) while the third stage just plowed ahead (uh, that’s “ploughed” ahead for our UK friends) straight into the moon. It had no way of braking or changing course.

    – Jack

  16. Martin

    Couldn’t they use two tons of TNT instead of two tons of steel? It seems to me that the yield of the explosion could be doubled that way.

  17. Markk

    Couldn’t they use two tons of TNT instead of two tons of steel?

    The problem with that is when doing the spectral analysis of the plume you have all these wacky organic compounds in different stages of decomposing to sort out. You want something very simple and mono-elemental, if you can, to make it easy to subtract out the effects of the projectile.

  18. PK

    Also, with a projectile you might get material from deeper in the moon’s surface to fly up.

  19. Tom

    The 2000kg in question as the primary impactor is the used Centaur upper stage that send LRO and LCROSS on their way. The instrumented portion of the mission stays attached to the booster, then steers it into the lunar collision. So they are using space junk as the impactor.

  20. Ed

    How much frozen water are they hypothesising? What if it’s something like a permafrost, where there is water but it’s integrated with the Lunar soil? It seems like it would be a thorny problem to be able to extract enough water, and hence hydrogen, to supply a lunar base and also create fuel for martian exploration. Lunar enviromentalists will go up in arms if we have to strip mine entire craters to get some water.

  21. What kind of resolution do LRO’s cameras have? Are they powerful enough to resolve the lunar lander? That would be a big step in shuting up the HBs.

  22. ‘Grand-lunar’ asked : What will they bang into to crash test next?

    Hope its not the Earth …too likely to get some unfortunate people with nasty bruises on their heads crawling out the resulting crater and launching lawsuits against you.

    The Sun would be kinda impractical .. as would Venus and any of the gas giants.

    ‘Dude’ : No danger of going to sleep while Bush the Lesser is your Pres. I’m afraid – not for halfway sane mortals wondering which contry he’s going to invade – or worse nuke – tomorrow. I’m hoping his next and last bold move will be to prove to the world and himself that he really *is* the God he seems to think he is by jumping off the nearest convenient really, really high point with the predictable consequences – and lands on Cheney scoring a double fatality! Better yet, he gets his whole Republican party of lunatic far-right neo-con televangelists to jump with him! 😉

    (Yes thats NOT space-related I know but has to be said,methinks)

    As for the LRO-LCOSS impacting idea it strikes me as dramatic test but a bit too wasteful for my liking.

    What happen to the material in the plume? Is it broken down and lost for ever when it could be better left for human use in colonising the Moon?

    Hidden Lunar ice is likely to be a rare and precious resource that has taken bilions of years to accumulate and has then laid there preserved for aeons and now we’re going to simply destroy or degrade it just so people get or regain some interest in space exploration. This sounds like buying a new Mercedes to use in a demolition derby to me!

    I’m with those suggesting a rover – human driven or teleoperated – mission would be the better option here. As ‘Sojourner’ and the current Mars rovers have proved, it wouldn’t even need to land with retro-rockets – we could just stick it in air bags and bounce it down to a stop …

    That I’d love to see! :

    With apologies to ‘The Police’

    To the tune of “Walkin’ on the Moon” circa a fair no. of years ago ..


    Giant leaps are what we take
    Bouncing on the moon
    I hope our airbags can take
    Bouncing on the Moon

    We can bounce fore-ever
    Bouncing on, bouncing on the the Moon ..

    Some may say
    This is a better way
    Finding ice along the way
    Lunar way
    Tomorrow will be today ..

    Guess the ice in place
    and safe

    etc …


  23. concerned earthling

    Is it really smart to go banging that forcefully on something that controls our oceans’ tides?? Furthermore, why are we looking for water on the moon?? Bored scientists??? Just seems like a waste of time and money.

  24. Tinman

    Has anyone considered that this might be a bad idea? What if it messes the moon’s orbit? What if something unexpectedly wrong happens? Or a huge chunk of the moon 20 years later breaks off for Earth? Ever see the moon in Time Machine? not to hollywood-ize things, but everone’s saying cost good blah, plume this blah blah.
    Just cause something can be done doesn’t necessarily mean it should be done. You want a giant coca-cola add projected on the moon too?

  25. Jerry Abbott

    An education should be required for posting to an astronomy blog.

    concerned earthling: The impact of 2 tons at 2.5 km/sec makes a big boom on the human – personal – laboratory scale, but it isn’t significant to something as large as the moon. The moon’s orbit won’t be changed. The moon has been hit millions of times by objects larger, and moving faster, than this probe.

    The scientists are looking for water on the moon because many people, not including yourself perhaps, want to establish a lunar colony, and knowing where water could be found already on the moon would make doing that a lot easier. It’s not a “waste of money,” whether or not you approve of this particular kind of expenditure.

    What does “waste money”? Money spent in futility wastes money. Money spent corresponds to resources terminated, used up, permanently ended. We ought to demand that something be permanently gained in return for money spent. Knowledge is one of the things that, once obtained, can potentially be kept forever. Another is a human occupation of moons and other planets. Once science figures out how to keep them going without any subsequent reliance on Earth, something vastly important and permanent will have been accomplished.

    Now, instead of space colonization, what would YOU do with the money? Feed the hungry, perhaps? Do you know what will happen if you do that? They will breed. They will increase their numbers to the limit of supply of food available to them. They will be hungry once again. Not only will they be hungry again, but an on-going burden would have been assumed by the country that provided their food relief. Should the donor country’s own agriculture ever falter, should it ever need its food for its own citizens, then the people in the “hungry” country will not only be hungry, they will die, starve to death, en mass, as in MILLIONS OF PEOPLE DYING OF STARVATION IN A SHORT PERIOD OF TIME. When you want to identify something futile to spend lots of money on, it’s hard to beat “feeding the hungry.”

    Humans are far into energy resource overshoot primarily because short-sighted sentimental folks were determined to spend money trying to palliate human miseries in ways that did not constitute a permanent cure. The “feeding the hungry” idea was one of these. This sort of thing never should have begun; it is long past time to put an end to such wasteful projects. Human quantity is not nearly so important as human quality.

    Space colonization is the way to go.

  26. Raul

    Just Like concerned earthling I too and concerned about lack of though. Has anyone considered that mining water would change the Gravity of the Moon and studied what effects it could have on Ocean and Large Lake Tides and the affect it could have on earths Eco System? It probably took comets billion of years to deposit water please let it be.

  27. Shelly

    This is STUPID!!!!!! I am only 12 years old and I know that NASA will be very upset if they do not find ice or co2 in the moon!! (And yes people I do research on NASA.) Does NASA have to do this??? How about a robot drilling into the moons surface?? Couldnt you find water that way? And by the way, I am in highschool no lie. This is why I love science so much! Highschool teaches better science! Anyway, I do not agree to this move by NASA. They are wasting thier money if they fail…


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