Side view of the Moon!

By Phil Plait | September 9, 2010 10:00 am

Sometimes being stuck on Earth is a bummer. We miss a lot of stuff! Like, f’rinstance, this view of the Moon which is literally impossible to get from the surface of the Earth:

lroc_moon_sideview

It looks like the Moon, doesn’t it? But it also looks different. That’s because this mosaic of 3700+ images shows the Moon as if you were seeing it from above its east side — like you were hovering above it and following it as it orbits the Earth!

The images were taken with the Lunar Reconnaissance Orbiter’s Wide Angle Camera, which can snap between roughly 50-100 km (30 – 60 miles) of lunar landscape in one image. As LRO circles the Moon, the camera builds up a map of the entire surface, but only one narrow strip at a time. Astronomers can then use those images to create a mosaic of the Moon as seen from any angle… but it’s not easy.

To get the mosaic to look right, you can’t just take an image from one spot of the Moon and stitch it onto an image from another. The lighting angle will be different, for one thing, making shadows go all wonky. Also, the LRO camera points straight down, so whatever is directly beneath it will be close by, while something off to the side will be farther away. Stuff farther away will look smaller, and you have to correct for that as well.

It’s taken a while, but LRO scientists have figured out how to correct for all that, and are now able to make these cool maps. The big remaining issue are those missing strips, spots the camera missed because another camera was being used at the time. But still, it’s pretty amazing they can make this map at all.

And why is it different from what we see on Earth? The Moon spins almost exactly once for every time it orbits the Earth — that’s a natural consequence of the effect of the Earth’s gravity on the Moon over time. That means we only see one half of the Moon, and the other half is always pointing away from us.

This LRO image shows the east side of the Moon which is the hemisphere of the Moon facing away from its direction of orbital motion (it may help to read a description I wrote of this for a moon of Saturn). As seen from this perspective, the Earth is off the image to the left. So everything on the left half of this picture we can see from Earth, and everything on the right we can’t*.

Over the course of time the black strips will get filled in, and we’ll have something very cool indeed: a complete map of the lunar surface at high resolution, roughly 150 meters/pixel (which is better than we can do here from Earth and is somewhat better than we can get observing the Moon with Hubble). This will be an invaluable tool to future lunar explorers… and it’ll also make for some pretty awesome pictures. And it’ll also open up even more possibilities for people to help astronomers get more accurate ages for the lunar surface… and in the meantime you can amuse yourself zooming in on an interactive LRO map with a resolution up to 400 meters/pixel.

NASA/GSFC/Arizona State University



* Actually, (as usual) the situation is a little more complicated than that; the Moon appears to rock gently left and right over the course of its orbit. This is called libration and it allows us to see a few extra percent of the lunar surface on the farside. It’s a small effect though.

CATEGORIZED UNDER: Cool stuff, Pretty pictures
MORE ABOUT: LRO, Moon, WAC

Comments (56)

  1. Justin

    Is there a particular reason why the right side of the picture (the dark side of the moon) has more craters than the side that faces us? Does it get hit with more space junk than our side? Is there a particular reason why? Sorry if thats a silly question.

  2. This will be an invaluable tool to future lunar explorers… and it’ll also make for some pretty awesome pictures. And it’ll also open up even more possibilities for people to help astronomers get more accurate ages for the lunar surface… and in the meantime you can amuse yourself zooming in on an interactive LRO map with a resolution up to 400 meters/pixel.

    And it’ll allow Google to create even more interactive maps and aps.

  3. I just always used to hate how when you turned around the (what is the word for a moon globe? moon model?) anyways, I used to hate how when you turned it around in science class the names of the features became unpronounceable. Sure, a little xenophobic, but I was 7.

  4. Gus Snarp

    How long can it have taken the LRO scientists to figure out how to correct for size distortion and lighting in mosaicking? We’ve been doing the same thing with images of earth for quite a while now.

  5. Off-topic: It would be nice to have a way for commenters to send a comment or suggestion
    which is not part of a particular thread. Since that apparently doesn’t exist, I’m (ab)using
    a normal comment to do so.

    Skepticism here is correctly directed against anti-vaxxers and others whose wrong ideas
    cause actual harm to people. However, from an intellectual point of view, all forms of
    “baloney”, “voodoo”, “flim-flam” etc should be given the skeptical ridicule.

    Here’s a suggestion: give the skeptical skewering to people who believe genuinely esoteric
    and off-the-wall stuff in regard to tuning their hi-fi systems. Some of this, of course, makes
    sense, like acoustically isolating loudspeakers and vinyl-record–players and cutting down
    the reflectivity of the walls. Other stuff, like special cables, is easily shown to be
    ineffective, not to mention various devices to de-magnetize CDs etc.

  6. J. D. Mack

    In the lower right quadrant of the photo, there is one crater that is partially filled in with dark material and has a lighter colored mountain (hill?) rising out of it. As far as I can tell, it’s the only crater like this on the moon. All the other craters with a dark surface are completely filled in and none have a mountain rising up out of it. What makes this crater special? (Of course, I’m only looking at half the moon as I make this observation, so there may be others like this)

  7. @Phillip Helbig

    Over to the right, under the About Astronomy section you will find this:

    Contact me: The Bad Astronomer “at” gmail “dot” com

    Just for future reference.

  8. Calli Arcale

    Gus Snarp — they’ve known in principle how to do this for a long time, but the devil’s in the details. It’s not so much knowing how to do it as working out the exact math to deform each particular strip in exactly the right way to correct that particular strip for where it will be placed in the final picture. It’s tedious work. I’m sure they used some degree of automation, but there’s still gonna be a lot of manual work to definite exactly how each picture needs to be adjusted until you can build the mosaic.

  9. @Justin #1:

    It’s for pretty much the same reason that the top of your umbrella gets wetter than the bottom.

    Also it’s the far side of the moon, not “the dark side.” All sides of the moon get just as much light as the near side. (Actually, technically the far side gets MORE light in total, because it never gets shadowed by the Earth during an eclipse when it would otherwise be lit.)

  10. Brian

    I was going to ask after reading the entry on Dione the other day if the Moon could have been knocked around 90 degrees at some point in the past, explaining why one side is so heavily cratered. But it seemed unlikely it would have been turned *exactly* 90 degrees. Is there a better explanation as to why the near side has seas and the far side lots of craters?

  11. It’s easy to get remarkable new perspectives on the Moon using the Moon feature of Google Earth.

    http://anothermonkey.blogspot.com/2009/10/google-moon.html

    I’ve always wondered about the north and south polar regions. They seem more densely cratered than other parts of the Moon. Is this just an illusion caused by the longer shadows always present at the poles?

  12. KC

    It’s not quite so simple. I don’t think we have a really clear idea why there’s so much of a difference between the near side vs the far side.

  13. @Kc:

    Aren’t the leading contenders for more cratering on the far side, 1) the earth itself protected the near side from many strikes, and 2) gravitational effects tugged molten material in the core a wee bit closer to the surface on the nearside and it had a tendency to spill out after really big strikes, thus erasing a lot of the existing cratering.

    Been a while since I followed that debate tho, so maybe those theories are not in the lead anymore?

  14. DrFlimmer

    I think, it’s also interesting that not even the Apollo astronauts had such a view. A close-up, yes, but not such a beautiful view of the entire side. They were just too close….

  15. jjmcgaffey

    Part of the reason there are fewer visible craters on the side we can see is that the magma flows (IIRC) of the maria have filled in craters. Of course that begs the question of why all the volcanic activity is (was) on the side towards Earth…oh, probably tidal stresses. And Earth would provide something of a shield, for that matter – far from a perfect one, but a certain number of impactors that would otherwise hit the Moon would hit Earth instead (or burn up in atmosphere).

  16. Childermass

    Fluffy @ #10: It’s for pretty much the same reason that the top of your umbrella gets wetter than the bottom.

    Also it’s the far side of the moon, not “the dark side.”

    Actually there is nothing wrong with the “Dark Side.” It is a name that has been used for a very long time. But even literally it is not false because the term “dark” did not refer to lack of light, but rather to another meaning of the word. Dark in this context means unknown. When Dark Africa was used in the 19th Century they were not referring to the day/night cycle or to the skin color of the natives, they were simply saying it was unexplored and/or unknown.

    Maybe I should start accusing those who use the words “sunrise” and “sunset” of falsely claiming the Sun orbits the Earth.

  17. Bouch

    I find it interesting that you only see the “seas” on the side which faces Earth…

  18. There is a crater? on the middle left in the dark areas. It looks like a water erosion. Is that magma flow?

  19. Ray

    Ha! You can’t fool me! The Moon is really an artificial base! Its not even finished yet and in your hubris you’ve posted pictures.

  20. Leon

    “Over the course of time the black strips will get filled in”

    But Phil! You can’t fill in the gaps–that’s where God’s hiding!

    (Sorry, couldn’t resist)

  21. Trebuchet

    @#6, J.D. Mack:
    That mountain in the crater is called a “central peak”. They’re actually pretty common, created, IIRC, by material rebounding in toward the center after the impact. I can see several others in the picture as well.

    @#5, Philip: James Randi has done a great job in the past of skewering the Hi-Fi nonsense. He actually got a manufacturer of extremely expensive speaker cables to apply for the Million Dollar Challenge. They backed out, of course.

  22. If that pic were a clock, at about 2:30 there’s a large dark crater and off to the right are a bunch of what look like gashes (maybe ridges? I can’t tell. You have to follow the link and zoom in there to see them). What caused these? And why aren’t there more of them? I can only see a few similar gashes down by the southern pole.

  23. Wayne on the plains

    While one side of the moon faces us and that side has more maria, one did not cause the other to happen. I think it would be more accurate to say that both characteristics have a common cause – that the interior of the moon is asymmetric. This asymmetry both caused the “heavy” side to face the Earth and caused more volcanic activity which erased many smaller craters. Also, the far side isn’t more cratered due to more impacts, but because the surface is older (so it “remembers” more impacts).

  24. Chris A.

    One of my pet peeves is when an image of the nearly-full Moon taken from Apollo 11 (http://nssdc.gsfc.nasa.gov/imgcat/hires/a11_h_44_6667.gif) is used as a stand-in for the Moon as seen from Earth. Most commonly, I see it on news broadcasts during the weather segment, where they are using a Moon image to indicate a nighttime forecast. It drives me nuts to see the Moon, with Mare Crisium almost dead-center, half covered by clouds. It’s a view NEVER seen from Earth.

    Why should I care? To me, it’s roughly the equivalent of showing an image of Saturn as seen from above one of its poles, with the rings making a “bullseye,” to represent the view of Saturn through a telescope from Earth. It’s simply wrong, and builds an incorrect mental picture of the universe in anyone who doesn’t know better (which is most people).

  25. Tribeca Mike

    That is mighty neat, thanks. And Harold, thanks for that Google link. Cartography is Fun!

  26. Aputsiaq

    Here’s one question:

    Will the side that’s facing us now always be facing us? If the moon spins a bit slower or faster than its orbit will our great great great grandchildren see a whole other moon?

    Just curious. :)

  27. k

    Bah! I’ve been taking pictures of the moon and it never looks like anyone else’s anyway, what’s one more whacky picture, LOL

    I’m thinking it’s because I’m down here in Florida so my moon ain’t YOUR moon (or the images in texts and google images), but that’s just a slight tilt difference. Don’t even ask about my moon at noon. It’s completely different.

  28. t-storm

    That photo is fake.

  29. alfaniner

    “Does my Mare Imbrium look fat from this angle?”

  30. Gavin Flower

    ‘Click to enJOVianate’

    should be

    ‘Click to enSATianate’

    ???

  31. @Gavin Flower, #31: “A moon by any name is just as awesome.” :D

    Fabulous photo of a not-generally-seen side of the Moon.

  32. robbak

    @Aputsiaq: No. The same side of the moon will always face earth, baring a large impact that makes it spin.
    The moon’s spin is ‘tidally locked’ – meaning that the moon, for many eons, was spinning with respect to the earth, but that spin was slowed down by ‘tides’ in the moons rocks: Earth’s gravity was enough to squash, squeeze and even liquefy the moons rocks. When the moon stopped spinning, it would have ‘rocked’ back and forth until it’s heavier side pointed to earth.
    There should be a remnant of that rocking motion remaining. I don’t know how much it is, or if it is measurable.

  33. EricH

    @robbak: The Earth does appear to move east to west and back in the Moon’s sky, over the course of the lunar cycle. This happens because of the eccentricity of the Moon’s orbit, which means that it moves around the Earth slightly faster than it rotates, for part of the month, and slightly slower the rest of the month. (There is also north-south motion, because of the Moon’s axial tilt.) IIRC, neither component amounts to more than 12 degrees of angle, so the Earth will always be found in the Moon’s sky within a box 12 degrees on a side. (And it’s probably less than that, but I’m having trouble quickly locating any references with hard numbers, so I’m relying on my memory.)

  34. Messier Tidy Upper

    Sometimes being stuck on Earth is a bummer. We miss a lot of stuff! Like, f’rinstance, this view of the Moon which is literally impossible to get from the surface of the Earth.

    Yes – and you know who’s responsible for that don’t you?

    Thankyou for killing off human space exploration Barack Hussein Obama – NOT.

    Obama’s NASA policy means we’re going to be grounded and confined to Earth, stuck going nowhere for decades. The bi-racial pro-Muslim current US president has set us back a very long way indeed and has utterly betrayed space flight supporters, scientists generally, future generations and the legacy of past Apollo glories.

    I cannot and will not forget or forgive Obama for this. But, hey, the Muslims are happy .. Oh wait no, they still hate us and always will – until we become Muslim ourselves and end our free way of life. :-(

  35. DrFlimmer

    @ Messier Tidy Upper

    Just by posting THAT over and over again and again doesn’t make the statement more convincing. We all know how you feel about it! But repeating it ALL the time makes it look like trolling! Would you mind stopping it? Thanks!

  36. Markle

    Stop with the trolling MTU. Why don’t you ask Gillard to give your country a manned spaceflight program, period?

  37. MarkW

    WTF does Islam and Obama’s skin colour have to do with NASA?

    Or am I just feeding the troll?

  38. BigBob

    @Messier Tidy Upper

    “for killing off human space exploration”

    When did that happen? The Russians and Chinese are still going to be flying right? So human exploration continues. If you mourn because the guys heading for the Moon won’t be your own citizens, join the club – my countrymen never went there in the first place. My only concern about the forthcoming return to the Moon is that the Chinese are (I’m assuming) likely to be less open, less inclusive about sharing the results with armchair astronauts like me who can’t get enough of it. Plus when would I get the chance to visit their launch sites and hardware museums like we do in Florida? Unlikely.

    My understanding of the cancellation was, (and BA wrote extensively on this) that it would allow NASA to focus on deeper (allbeit non manned) exploration, while private concerns, (and the Russians and ESA) took care of LEO missions.

    NASA not returning to the Moon is a wrench. We were looking forward to that. But if the Chinese are willing to breech the political/cultural divide then just maybe we can engage with their manned Moon missions too.

    BigBob

  39. Nigel Depledge

    Dr Flimmer (36) said:

    @ Messier Tidy Upper

    Just by posting THAT over and over again and again doesn’t make the statement more convincing. We all know how you feel about it! But repeating it ALL the time makes it look like trolling! Would you mind stopping it? Thanks!

    Seconded.

  40. Nigel Depledge

    @ Eric H (34) -

    That was a really clear and concise explanation. I always knew that the moon (as observed from Earth) rocked about a bit so we see about 52% of the surface over time, but I didn’t really understand why. Thanks!

  41. Zippy the Pinhead

    The question is, what is NASA? Is it space science or human transport? For the price of human exploration to the Moon, we could fund 10-100 robotic probes. To Mars, it’s easily over 100 science missions. Human space travel means loss of science missions. You can’t have both at a reasonable price.

  42. Stacy L Mason

    Behold the arrow slits of the Moonenites which PROVE the moon landings were hoaxes :P Our puny space capsules could never repel firepower of that magnitude!!!

  43. EricH:

    The Earth does appear to move east to west and back in the Moon’s sky, over the course of the lunar cycle. This happens because of the eccentricity of the Moon’s orbit, which means that it moves around the Earth slightly faster than it rotates, for part of the month, and slightly slower the rest of the month.

    Perhaps this video of a series of images over the course of a month would help?

    http://antwrp.gsfc.nasa.gov/apod/ap051113.html

    http://en.wikipedia.org/wiki/Libration

    Of course, that’s the Moon from the Earth. I wonder if any of the cameras left on the Moon have taken such a series of images of the Earth?

  44. Nice work LRO team! Though I’ve seen many amateur images that achieve higher resolution than this map; perhaps even the downloadable TIF file is also downsampled. Have a look at Wes Higgin’s amazing lunar images:
    http://higginsandsons.com/astro/

  45. Gary Ansorge

    Hey, I think I can see my property from here. All 4900 acres of it.

    Too bad I’d actually have to BE there for the claim to stick(as in, possession is nine points of the law).

    I REALLY need to get my nuc rocket built. Anybody here have access to plutonium rods?

    Cool pics. I never knew we could actually see 52 % of the lunar surface from earth. It just never occurred to me that the moon REALLY rocks..

    Gary 7

  46. Tribeca Mike

    Please don’t ask why, but the photo reminds me of the time the Irish writer Samuel Beckett was interviewed while shooting pool on his home table in Paris (he was known to be a wicked billiards hound). The interviewer asked what went through his mind when he played — perhaps the spinning spheres of the cosmos or the inexorable collisions of inevitable fate, free will and primal existence?

    “No,” he replied, “I play to win.”

  47. WJM

    @6 & @22, that crater has a very close, if smaller, analog on Earth, in the Mistastin crater-lake in northern Labrador. Check it out on the internets.

  48. Curt

    @robbak (or anyone else) … A clarification please.

    Phil wrote: “The Moon spins almost exactly once for every time it orbits the Earth.”

    Why “almost”?

    I understand the orbital speed variations due to the eccentricity of the orbit. But ultimately (because of “tidal lock”), as the Moon completes exactly one orbit, hasn’t it also rotated exactly one time?

    What is it that I’m not understanding?

    Thank you.

  49. Jon Hanford

    @6@22@48, That unusual crater you’re commenting on is Tsiolkovskiy: http://en.wikipedia.org/wiki/Tsiolkovskiy_%28crater%29

    Interesting Tsiolkovskiy trivia: ” Apollo 17 Astronaut Harrison “Jack” Schmitt and other scientists (Schmitt was the only trained scientist, a geologist, to walk on the moon) strongly advocated Tsiolkovskiy as the Apollo 17′s, or a later flight’s (which were all canceled), landing site, using small communications satellites deployed from the Command/Service Module for communication from the far side of the moon. NASA vetoed the idea as too risky, and Apollo 17 instead landed in the Taurus-Littrow valley on December 11, 1972.” – wiki

  50. NelC

    Curt @49: from the point of view of Earth, that’s apparently so, but the situation is complicated by the fact that the Earth orbits around the Sun while the Moon orbits around the Earth. From the point of view of an observer on the Sun or from the (almost) unmoving stars, if the Moon spun at exactly the same rate as its orbit around Earth, after six months it would have turned completely around and would be showing the opposite face to Earth. So (if I’ve got it the right way around) it must spin a little faster than it orbits to maintain the same face to the Earth.

  51. MaDeR

    Hey Messier Tidy Upper, anyone told ya you are troll and spammer? Go to some political blogs, you will feel in home with other rightwing xenophobic nutjobs.

  52. @fluffy #10:

    Are you sure that the far side gets more light in total because of the eclipses?
    What about the sunlight reflected from earth to the near side?

  53. Murray

    I can’t wait till they do this on Mars!

  54. I’m no scientist,just a lifetime wanna’be astronaught…but I just had to say WOW!!!! Thank you for showing us this marvelous picture(and info)!!!!!!

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