I am endlessly fascinated by the Moon. There may be an inherent bias there because it is, after all, the closest astronomical object in the sky. Still, it has an amazingly varied surface with lots of really odd features.
One of my favorite types of things to look at are overlapping features. It can produce a very complicated terrain, difficult to understand. Or can also create a lovely tableau that cleanly separates the two features, like this very pretty shot from Lunar Reconnaissance Orbiter (LRO) showing a fresh crater near a graben:
[Click to enlunenate.]
A graben is a crack or fracture. They form on the Moon when the crust is stretched, splitting the surface. They look like long, relatively straight and narrow valleys with steep sides. You can only see a part of it on the right side of the image above; the Sun is shining from the right and illuminating the left-hand side of the graben. The picture below is zoomed out and should help you see the situation.
The crater is clearly younger than the graben feature. The radial streaks around the crater are called rays, and are formed when plumes of material ejected from the impact fall back down to the ground. They’re common around young craters; solar wind, later impacts, and even thermal compression and expansion of rocks over the Moon’s day-night cycle eventually erode them away.
You can see the rays extended over and into the graben, so the crater must be younger. It’s hard to say just how much younger, but even relative ages can help geologists understand the lunar surface better. And detailed images like this – you can see individual blocks of rock inside the crater itself – are crucial for study. Someday, I think, human geologists will be investigating places like this in person, and mapping missions like LRO will make that possible.
Image credit: NASA/GSFC/Arizona State University
One of the more enduring questions about the Apollo Moon missions is seemingly simple: after 40+ years, are the flags the astronauts planted on the lunar surface still there?
It’s an interesting question. Buzz Aldrin claims he saw the flag blow over when the ascent module carrying him and Neil Armstrong lifted off from the Moon – which was never confirmed (until now; hang on for that), but the fates of the flags from the other five missions have never been ascertained. In 2009 there was tantalizing evidence the flags from Apollo 17 was still standing, but the images were just barely too fuzzy to know for sure.
But now, apparently, we do know: the Lunar Reconnaissance Orbiter has now confirmed that the flags at all the landing sites are still there, except for Apollo 11. It looked like Buzz was right!
Here’s an image showing the Apollo 16 flag:
The flag itself is visible in the picture – LRO’s angle on it shows the shadowed side, which is slightly darker than the lunar surface – and the shadow it casts on the surface is obvious.
I have to admit, I’m surprised*. The flags were made of simple nylon, which can disintegrate when exposed to ultraviolet light. I figured that after all this time they’d be nothing more than red, white, and blue powder at the base of their poles. I guess I was wrong. And I’m happy to be! [UPDATE: In the comments below, BABloggee Maxx points out that polymers need oxygen to be degraded by UV light, so this may be why the flags haven't disintegrated.]
That picture from Apollo 16 is impressive, and I have to admit, that’s my favorite flag of the missions. It’s where Charlie Duke took a picture of John Young doing a "big Navy salute" – Young jumped up, and Duke snapped the photo while Young was still off the surface (not while he was in the air, of course, since that’s a commodity the Moon lacks):
Large impacts are fascinating. There’s the thriller-movie aspect of them, of course, spiced with enough reality to make them legitimately scary. But the physics of them is equally enthralling, and complex enough that it will be a rich field for scientists to study for years to come.
The good news for both these aspects is our Moon. Seriously! There are enough craters there for anyone to be happy studying them, and since the Moon is a giant lifeless chunk of rock, impacts there seem less urgently threatening.
I want to show you two craters on the Moon that are very different, and therefore very interesting.
First up, Copernicus. Or more accurately, a small part of this 90+ km (55 mile) wide impact feature: its central peaks.
[Click to enselenate.]
This image was taken by NASA’s wonderful Lunar Reconnassance Orbiter. Copernicus is a big crater, and easy to spot even with binoculars since it sits in a vast lava plain; the surrounding material is darkish grey, while the crater is far brighter. It’s also surrounded by a gorgeous system of rays: linear streaks caused by the collapsed plumes of material after the asteroid or comet smacked into the Moon to form the crater itself.
Copernicus has a series of mountains in its center, the tallest over a kilometer high. These weren’t created in tectonic events like on Earth, though! Giant impacts that cause big craters have weird physics. The pressure upon impact can be so high that the rock in the surface flows like a liquid. It splashes outward, then flows back in, surging upwards in the middle of the impact point. This video showing water dropping into various surfaces might help:
The Lunar Reconnaissance Orbiter has been circling our nearest neighbor since 2009, taking amazing high-resolution images of the Moon’s surface. When it was first proposed, I remember wondering if it would get good shots of the Apollo sites… and boy howdy, did it. Then, in 2011, NASA decided to lower the mapping orbit from its usual 50 km (30 miles) down to an incredible 25 km (15 miles) — an orbit they can’t sustain, since variations in the density of the Moon would soon crash the spacecraft. But for those short periods, they got amazing images of the Apollo landing sites, including this stunner from Apollo 15:
[Click to onesmallstepenate.]
LRO has looked at the Apollo 15 site before (see the links at the LRO page for more), but never this clearly! The lander descent stage is labeled (the ascent stage took Dave Scott and James Irwin back up to the Command Module, which then brought them home), and is pretty clear (the shadow’s cool too). To the upper left is the ALSEP (Apollo Lunar Surface Experiments Package, containing scientific instruments), and the the right is the rover (LRV). And connecting them all, you can clearly see the astronauts’ bootprints! Arrows point out the fainter ones.
[Cripes, the news is coming so fast I can hardly keep up: in between writing this post and putting it up, the folks at LRO released an image from the Apollo 11 landing site too, and it's also just flippin' amazing.]
That’s not the first time we’ve seen those boot tracks, but still. It gives me chills: human beings walked on the Moon.
And we’ll do it again, I just know it. Soon, I hope. But it will happen.
Image credit: NASA/GSFC/Arizona State University
- LRO spots Apollo 12 footsteps
- Apollo 17, then and now
- LRO spots Apollo landing sites in high res
- Apollo 16 site snapped from orbit
- One Giant Leap seen again
- APOLLO LANDING SITES IMAGED BY LRO!
The Moon is packed with all sorts of interesting features that only come to light — literally, in some cases — when very high-resolution imaging is done. For example, the lunar far side has a bunch of small volcanoes, some only a few hundred meters across, like this one:
[Click to enlunenate.]
The image is about 500 meters across, so this is a hill you could climb pretty easily, even though the low Sun angle implies the slope is greater than 13° (remember, the Moon has 1/6th the Earth’s gravity so that would be a pretty easy hike). Those boulders on the top are weird; they only appear to be on one side, and there doesn’t seem to be anything in that direction that would be a source of them. There are none on the plains around it, or at the bottom of a nearby crater, either. The source must be the volcano itself, I’d wager. Note the crater at the top of the mound, too – you might think that’s the volcanic vent, but in fact it’s not centered on the dome, indicating it’s a coincidental impact crater.
This is pretty neat: an Apollo enthusiast who goes by the handle GoneToPlaid has created a video comparing the Apollo 11 footage of its descent to the Moon with images from Google Moon:
That’s very cool. You can see the same features in the Apollo 11 film footage and in the newer view from Google Moon, which uses images from NASA’s Lunar Reconnaissance Orbiter as well as Japan’s Kaguya mission. The lighting was different so sometimes it makes features hard to spot in both — direct sunlight changes shadows, and also creates a spotlight effect which can hide craters and such — but you can see how well everything lines up. GoneToPlaid provides a link to the KMZ files you can use for Google Moon to check this out for yourself as well.
This won’t convince people who think NASA faked the landings, of course, nor do I really care. What I do care about is how this brings home what the astronauts did all those decades ago. Going to the Moon was hard; it’s another world, with all the dangers and unknowns and difficult terrains that made it necessary to explore it before we went, and to do so once again in preparation for going back. Hopefully sometime soon.
Tip o’ the spacesuit visor to Scott Hall. Image credit: NASA.
Last week, NASA released new, higher-res images of three Apollo landing sites taken by the Lunar Reconnaissance Orbiter. BABloggee Rick Sheppe had a cool idea: why not compare these to ones taken by the Apollo astronauts themselves? In fact, by grabbing a frame taken by a 16mm movie camera on board the Apollo 17 ascent module as they left the Moon, you can compare the views seen by astronauts and LRO directly!
So I did it. I took a frame from the 16mm camera on Apollo 17, and the LRO pic of the same area. After rotating and adjusting the contrast of the original Apollo 17 picture a wee bit, here is what I got:
Coooool. The original Apollo 17 picture is on top, and the LRO pic on bottom.
If you’re curious, NASA has labeled some of the features in the Apollo pic. In that original picture you can clearly see the bottom half of the lunar module on the surface (the bug-like landing module had two parts; a lower half (the descent stage) that stayed on the Moon to save weight, and an upper half (the ascent module) that is what carried the astronauts back to orbit, and is where the camera was that took this shot), as well as several craters, boulders, and the scuffed surface tracks from the astronauts’ boots and the rover as they ambled and rode across the Moon.
I was interviewed by WGN radio host Mike McConnell this morning about the new Lunar Reconnaissance Orbiter pictures of the Apollo landing sites that were released yesterday. The interview is online, or you can grab the file directly.
We talked about why Hubble can’t see the landing site hardware, how the astronauts walked on the Moon, why the flags may no longer be there, why Moon Hoax stuff is silly, and so on. I had a funny moment of confusion when I was trying to count how many people had walked on the Moon, but that was quickly resolved. All in all it was a fun conversation, and I’m impressed with McConnell’s knowledge of Apollo. It’s always nice to talk to another Apollo fan!
Last night, at 02:56 UTC, it was the 42nd anniversary of humans putting a bootprint on another world. Before Apollo 11 touched down on the Moon, though, NASA and the USSR sent a fleet of unmanned probes there. Since that time we’ve sent many more, including the Lunar Reconnaissance Orbiter, one of my favorite spacecraft of all time. It takes amazing high-res images of the Moon… and to celebrate today’s anniversary, they released this mysterious picture:
Cooool. Click to enlunenate.
This image is about 400 meters across, and shows an impact site with two lobes of material laid down to the sides. This butterfly-shape is a clear indication of a low-angle impact; it’s seen on many bodies in the solar system including the Moon, Mars, and even Earth (though the physics of exactly how the bi-lobed patterns form is still not well understood). Features like this are very rare… but it’s known that when a satellite orbit decays, it will impact at a low angle.
As the LRO site notes, in October 1967, the Lunar Orbiter 2 spacecraft impacted the lunar surface, possibly very near this spot. Could this be the final resting ground of an early NASA robotic explorer? It’s hard to say. When something hits hard enough to excavate material, it’s common to see ejected junk of different brightnesses, and here we see the dark patterns overlaid on a brighter surface. If that’s the impact area, though, the size of the impact looks too big for the mass and speed of the probe. Maybe it coincidentally hit a brighter area, but that stretches credulity, given the darker area all around.
So what happened here? The folks at LRO are planning follow-up observations to see if they can get pictures at a different Sun illumination angle, which will make any crater easier to spot. That might clear things up.
Or it might not. The Moon is the nearest astronomical object in the heavens by far, but it also has 38 million square kilometers of surface to explore! That’s four times the size of the Unites States… and LRO sees it at a resolution of roughly a half a meter. That’s a whole lot of pixels, and a whole lot of landscape in which to hide fun little mysteries. I hope there are many, many more.
If I ask you to close your eyes and picture a crater on the Moon, I bet what would come to your mind is a bowl-shaped depression, a raised rim, and maybe a central peak. You might also picture the surrounding area, which looks pretty featureless except for other craters.
I would also bet you wouldn’t picture anything like this:
Isn’t that lovely? [Click to enlunanate.] Looking like a kilometer-wide flower on the lunar surface, it’s an unnamed crater just south of Mare Crisium, on the Moon’s eastern limb near the equator. This image, from the Lunar Reconnaissance Orbiter, spans a distance of about 2.2 km (1.3 miles) across and the full-res image has a resolution of roughly 1.5 meters per pixel.
It’s not your run-of-the-mill crater. Read More