Today, September 16, 2010, one of NASA's most successful missions - the Lunar Reconnaissance Orbiter - completes the primary phase of its exploration mission. Far from this meaning the end of the mission, it actually means LRO can begin the next phase: science!
In honor of this milestone, I have collected a few of my favorite LRO pictures from the past year and put them together in this gallery; use the "filmstrip" at the top of this post to see them all.
We've been observing the Moon for thousands of years, but it wasn't until LRO that we started to get a comprehensive and extreme close-up view of this neighboring world. Remember, when you look at these pictures you're seeing the Moon from a camera just 50 km (30 miles) above the surface, with a resolution of half a meter (18 inches!). The exploration phase of LRO has been nothing short of amazing; what will the science phase bring?
All image credits: NASA, NASA/GSFC/Arizona State University
I gotta tell you, if I had to make a list of things we'd find on the Moon, a natural bridge would've been pretty much at the bottom! On Earth, these bridges form due to erosion from air and water, but you may note there's a lack of those on the Moon. So why is there one of these bridges in this LRO picture?
To be honest, no one knows. It's sitting in the "impact melt" from King crater, a region where the entire area was liquified from the impact. It's possible that lava tubes or cavities formed at that time as the molten rock solidified into a crust. Pockets could've formed, and then part of the roof caved in to leave this 20-meter-long bridge.
Amazingly, the same strip imaged from LRO shows a second such bridge, too! Whatever happened at the crater happened more than once... meaning it may have happened at other craters as well. One thing I know for sure, the more we examine LRO images, the more surprises we'll find.
More info: NASA's LRO Natural Bridge page
I first heard about NASA's plans to build LRO long before they cut any metal for it, and my first thought was, "I hope they take pictures of the Apollo landing sites."
I had to wait a few years, but man oh man, was it worth it! This picture shows the Apollo 11 lander, some of the equipment left behind by the astronauts, and you can even see their bootprints in the lunar dust!
And that red arrow? That points to the Lunar Modules's landing leg equipped with a ladder... and it's the one Neil Armstrong descended to become the first human in all of history to set foot on another world.
I still get chills thinking about. Amazing. I can't wait until we go back.
Original Post: One Giant Leap seen again
Apollo 12 is in some ways a forgotten mission: sandwiched between the triumph of 11 and the near-disaster of 13, it still accomplished some amazing goals. Chief among them was pinpoint precision in its landing: NASA wanted them near enough to the Surveyor III robotic lander so they could walk to it... and this picture shows how well they did.
The Apollo 12 astronauts did in fact walk over to Surveyor. They were also able to remove some of its parts to return to Earth for study as well.
I have a wine label made in honor of Apollo 12, showing astronaut Al Bean holding a glass of wine. Years ago I got him to sign it, and it's one of my most cherished mementos.
Original post: LRO spots Apollo 12 footsteps
This LRO image shows the Apollo 17 landing site, the last of the missions to land on the Moon. You can see the descent stage of the Lunar Module, and also labeled is something amazing: the flagpole placed into the lunar surface by the astronauts!
You can even see the pole's shadow. I don't think any of the original flags are still there; the merciless blast of ultraviolet light from the Sun should have long-ago disintegrated the nylon in the flags. Perhaps when we go back we'll see tri-colored dust at the poles' bases.
But even if the flags are gone, the accomplishment remains. We went to the Moon six times, and brought those men home safely again.
Original post: ... and the flag was still there
As LRO orbits the Moon, it takes pictures of whatever is directly underneath it no matter what time of day it is locally. So it might be snapping images of the landscape at sunrise, or at sun set... or at high noon, as it did for this shot of the Apollo 16 landing site.
While the lack of shadows makes craters harder to see, it actually accentuates where the dust was disturbed by the astronauts' activities. The lander is obvious, and even the last parking spot of the lunar rover!
Original post: Apollo 16 site snapped from orbit
This odd picture is actually three mountains poking out of the center of a crater. Don't believe me? Then let's take a step back, shall we:
Aha! See it now? Those three mountains are actually the central peaks of the crater Bhabha, a 64 kilometer (40 mile) wide impact scar on the far side of the Moon. With really big impacts, the shock waves bounce around inside the crater bowl, making the rock flow like a fluid. The rock flows outward, then sloshes back inward, splashing up to form peaks. Usually there’s only one, but Bhaba has three.
LRO caught these peaks just before the slow lunar rotation brought sunset to them. One of the many things I love about LRO pictures: they're not just interesting scientifically, they're also lovely and artistic.
Original post: Lunar triple sunset
LRO doesn't just take pictures of the Moon! In June 2010, LRO turned its cameras back to the home it can never again reach, and returned this stunning greyscale image of our planet.
Having trouble figuring out which part of Earth is visible? Then check out this reference image NASA made to help out.
Original post: A living world, from 370,000 km away
This is one of my absolute all-time favorite pictures of the Moon. It shows the far-northern crater Erlanger, which sits at 87° north latiutude. That close to the pole, the Sun hardly gets above the horizon. Shadows are always long, and only things poking up above the local landscape get illuminated well.
In this case, that's the rim of the crater! The floor and surrounding region are in the dark, but the rim sticks up just high enough to catch a few rays. On the flip side, the floor of many craters near the poles of the Moon never see sunlight and are locked in eternal frigidness. There may be ancient ice locked up under those crater bottoms, which would be very useful for future colonists.
Original post: Lunar boreal halo
Not all craters on the Moon are from asteroid and comet impacts: this one is from a rocket. On April 14th, 1970, the upper stage booster of the Apollo 13 rocket slammed into the Moon, creating this roughly 30-meter-wide crater.
Some of the rays - the streaks of material blasted out of the crater from the impact - can be traced for over a kilometer! These are pretty violent events, and in fact were used by later missions to create moonquakes so that scientists could learn about the lunar structure. Seismographs placed on the surface by astronauts showed us that there are still some small moonquakes going on even today.
Original post: One of the newest craters on the Moon
I like to think of the Moon as being entirely different from the Earth, but LRO keeps reminding me we do share some features! This picture shows a landslide down the wall of a crater called Marius. The grey slopes of the crater are clearly disturbed by debris as they ran down, leaving brighter streaks behind.
What could have caused this? A more recent impact jarring the Moon? A moonquake? At the moment that's not clear. But it does give scientists a view of both the surface and what lies just below, so features like this are a bonus.
Also? It's just so cool!
Original post: LRO sees a landslide
Sometimes, something really big hits the Moon. This impact scar, called the Orientale Basin, is nearly 1000 km across! Whatever hit our satellite all those billions of years ago did it some serious hurt. But then, it must have been 100 km across - 1000 times the mass of the asteroid that wiped out the dinosaurs. Ouch.
On the LRO website you can zoom in on this amazing feature and spend a lot of time seeing how much damage was done.
Original post: Zoom in a HUGE lunar bullseye!
Not all the craters on the Moon are from impacts. This is almost certainly a cinder cone from a volcano located in Lacus Mortis - the Lake of Death, mwuhahaha. The pit is about 400 meters across (the whole image is 900 meters across) and is certainly billions of years old.
If this truly is a volcano, the last time it saw any action was when the Moon was much younger and more active. There are other features on the lunar surface that we're pretty sure are volcanoes, but it's still hard to tell from images like this. The only way to know for sure is to go there and see!
Original post: Ash hole on the Moon
This 100-meter hole in the Moon is actually a skylight, the collapsed roof of an underground tunnel carved by lava. These are commonly seen on Earth near volcanoes, but had never been seen on the Moon before LRO was able to map so much of the surface at such high resolution.
The hole itself is also about 100 meters deep. If you were to fall in, it would take about 11 seconds to plummet to the floor, and despite the low gravity you'd impact at about 60 kph (40 mph). Any future astronauts wanting to explore such features - and they will, since these holes give access to parts of the Moon untouched for billions of years - they'd better bring very good spelunking gear!
Original blog post: There's a hole in the Moon!