Allow me to ask you a question: “If you
could visit anywhere on the Moon, where would you go?” Look across the crater-pocked, dust strewn
landscape. There are mountains and craters here, scientific
marvels, and mysteries cloaked in pitch-black shadows. But without the proper map, it would be easy
to miss some of the wonderous features of our closest celestial neighbour. Fortunately for us, for a decade and a half,
the LRO - or Lunar Reconnaissance Orbiter – has been compiling just such a map. In ways never seen before it has imaged the
features of the lunar terrain, helping scientists learn more about the Moon’s ever-evolving
surface and the processes that govern it. With over 8 billion different measurements
taken, its complex analysis has made the Moon the most thoroughly measured of any other
non-Earth object in the solar system, and has given us the tools we need to perhaps
one day set up permanent bases there. What did it find? And given that the Moon is an object you’ve
likely seen thousands of times in the night sky throughout the course of your life, it’s
time to find out: how well do you really know it? I’m Alex McColgan, and you’re watching
Astrum. And in this LRO supercut, we will explore
some of the most fascinating discoveries and landmarks imaged by the LRO throughout its
mission to the Moon to date.] The LRO has been scanning the Moon’s surface
since 2009. It’s equipped with a powerful camera, capable
of taking high-definition photos, which it sends to NASA’s Planetary Data System. The LRO can send up to 155 gigabytes of data
per day, or 55 terabytes per year. By comparison, New Horizons took a full two
years to transmit the data from its one Pluto flyby. Although the LRO was launched over a decade
ago, it’s still operational, and we are constantly learning new things about the lunar
surface thanks to its high-powered camera and topographic mapping capabilities. [Let’s see that camera in action. We’ll start with a place rich in incredible
contrast – Jackson crater.] This oblique angle shot [of Jackson Crater
is] sadly not visible to us on Earth as it is on the far side of the Moon. A bit like Tycho crater on the near side of
the Moon, when it formed, it created a ray system stretching over 1000km. Ray systems form when particularly fine material
is ejected far beyond the crater rim, although their formation is still being studied. Jackson crater itself is about 70km in diameter,
and due to its size, it is a complex crater, as can be seen by its terraced walls and uplift
in the central region. This crater is actually tilted, the east of
the crater is 6000m in elevation, and the west side is only 3000m high. The base of the crater has an elevation of
1000m, and the peak comprises of material that was pushed up from another 1000m down! Some of the dark patches you see along the
walls are shadows due to the Sun’s angle in the sky, but there also are sections of
darker materials, compared to the predominantly lighter coloured ground. Although, it’s not as light as this image
would have you think. Your viewing angle and the angle of the Sun
play a big role in how contrasts appear on the lunar surface. Focus here on the central peak in this image. We’ll now switch to a top-down perspective
of this same peak, taken at a different time of the lunar day. Suddenly, the crater basin and the tip of
the mountain peak appear much darker than before. But a side-by-side comparison does show how
the differences in contrast can be seen in both pictures. And that’s not the only optical illusion
the Moon can trick you with. Have a close look at this image. What does it appear like to you? Are these regions of inverted bubbles, or
are these sections actually rising higher than the wiggly textured material surrounding
them? Well, for the longest time, I could only see
it’s inverted. But maybe if you look around the image, suddenly
it will switch perspectives for you. What type of image did you see first? Are you like me and need proof it’s not
actually inverted? Well, have a look at the same region but from
a different angle. Seeing it like this makes me wonder how I
could have seen anything else! This is a small region on the Moon called
Ina. It’s only 2-3km wide, and 64m deep, and
no-one really knows how something like this formed. It’s one of several similar regions on the
Moon, although this one is the most prominent. To a certain degree, a similar optical illusion
can happen with small craters. Do you see domes here, or craters? Sometimes rotating the picture can help get
the right perspective. That’s why the LRO is so useful in my opinion,
not only do we get top-down views, but oblique perspectives too! Moving on to another unusual lunar region,
let’s have a look at Komarov Crater. This crater would be pretty normal by lunar
standards were it not for the fact that it has huge fracture lines running across the
base. Komarov crater itself is even bigger than
Jackson Crater, at 95km in diameter. Meaning these are up to 500m deep and 2.5km
wide! It is believed that 2.6 billion years ago,
magma built up under the crater, causing large amounts of pressure to fracture the crust;
although it appears that the magma never made it to the surface, meaning the fractures were
never filled in and it has remained like that ever since. But although it didn’t happen in this instance,
there are examples on the Moon of magma breaking through and pooling on the surface. One such example can be found west of Plato
crater, a large 100km wide crater seen towards the north of the Moon, visible with a telescope
or binoculars on Earth. This image has a few rather spectacular points
of interest to see, the obvious one being this channel which cuts through the ground. This section here is a lava vent, back when
the Moon was a lot more geologically active. Running out of the vent, in a southwesterly
direction, is something known as a rima, or a rille. These are channels cut out by lava melting
and eroding its way down the slope, kind of like a river on Earth. To the east in this image, we see the crater
rim of Plato. Plato itself was likely filled with lava at
some point, as the base is darker and smoother than the regions northwards. However, in this image we can see that a huge
section of crust has collapsed down from the crater wall, creating a 24km wide slump block! In other words, this section was once connected
to the higher plain, however it has since collapsed under its own weight, breaking away
and falling somewhat into the crater. [For now,] let’s have a look at one more
crater. This breathtaking view is from the Apollo
15 mission, overlooking Aristarchus Crater. Aristarchus is seen towards the north west
of the Moon, and although Aristarchus only 40km across, it’s bright enough to be seen
with the naked eye. From Apollo’s viewpoint, we can see a really
wide angled perspective of the crater. Surrounding it are more rilles and lava vents,
and a small ray system can be seen extending away from the centre. From this angle, with the shadow extruding
out from the rim, you get a sense of how deep this crater is. This complex crater has prominent crater walls;
however the uplift found in the centre seems pretty small. From LRO’s perspective, we have a much higher
resolution view of Aristarchus again, and we can have a close examination of the walls
and crater base. The walls are similar in appearance to Jackson
crater, however, looking at the peak towards the crater’s centre reveals some major differences. Not only is the peak much smaller, it also
has a banded pattern, exposing layers in the crust that would have otherwise been hidden
100s of meters down. The base of the crater was also likely to
have formed from molten lava, rock melted by the impactor. Fracture lines from rapid cooling are evident
all over, and looking at where the walls meet the crater base, you can easily imagine how
this base was once a liquid. [For a place that’s so grey, colour on the
Moon can tell us a lot.] This area is known as Montes Carpatus, and
what’s immediately apparent here are the variations in contrast again. Generally speaking, looking at darker regions
on the Moon indicates older material but it also indicates what the material is comprised
of. The darkest regions in this image are thought
to have formed from explosive volcanic activity over three billion years ago. Lava would have also flown down through valleys
like these ones. Also sprinkling the surface are white dots;
these are small impact craters, and appear white as they are a lot more fresh than the
surrounding regions, and space weathering hasn’t had an opportunity to darken them
yet. The Lunar Reconnaissance Orbiter, unlike the
Mars Reconnaissance Orbiter, has a special ability to be able to take photos from an
angle as well as from a top-down perspective. This means we are able to view the mountains
of the moon as if from the cockpit of a plane, which gives us a better sense of height and
scale. Although, our sense of scale is already seriously
messed up, as on Earth we have visual clues to help us judge how high or far away something
is. For instance, we can tell the background here
must be tens of kilometres away, because the atmosphere makes the mountains quite hazy. Also, we can see the town, some trees, all
of which help us know roughly how big the object is that we are looking at. But on the moon we don’t have any of that,
no trees, no atmosphere, no towns. Just looking at this image, how big would
you say this mountain is? How wide is the foreground in this image? It would be fun to see your guesses in the
comments. But, perhaps surprisingly, the foreground
of this image is about 15 kilometres across, and the foreground mountain is nearly 7km
tall! These two peaks at the back are a massive
200km away, and roughly 4,500m tall. Surprisingly, these peaks aren’t named like
they would be if they were on Earth at that size. The best way to kind of get a sense of scale
for these images is to use this amazing tool NASA has released called Quickmap, where you
can see the moon under various filters, including a topographical map. [I’ll leave a link in the description below
if you want to check it out.] Here’s the mountain in the foreground of
the image, and here are the background peaks. You’ll also notice that these peaks are
found around the rim of a crater. Pretty much all of the mountains we will look
at today can be found either on the rims or centres of craters. Including these ones found in the famous Copernicus
crater. When craters form, we all tend to think of
the circle they create, but big craters often have uplift in the centre. Surprisingly enough, this is not predominantly
due to an effect like a water drop impacting a pool of water, or elastic rebound, where
the centre shoots up again after impact. That only happens with material with elastic
strength trying to return to its original shape. Rather, craters have uplift in the centre
due to the surface material attempting to revert to a gravitational equilibrium. Copernicus crater can easily be seen on the
surface of the moon by an amateur telescope, and as a result is one of the moon’s most
viewed features from the ground. These mountains in the centre look impressive,
but they only rise about 1000m above the crater floor. Zooming out a bit, and you can see how dwarfed
they are by the surrounding crater walls, reaching 4000m above the crater floor. Here’s the crater from another angle, and
one thing you will notice is that the basin of this crater is lumpy, but comparatively
flat. This is because after the massive impact that
caused this 100km wide crater, the floor was lava which eventually solidified. Moving on to a new location on the moon, we
come to the Apennine Mountains, an impressive range of 3-5km high mountains found at the
rim of one of the biggest impact craters in the whole solar system; the Imbrium Basin,
or Mare Imbrium. These mountains look interesting next to this
mare, or a solidified lava plain, and this rille, kind of like a gorge found on the moon. But apart from being a very interesting view,
there’s something special about this place. It is in fact where the Apollo 15 mission
landed in 1971, which means there is also a ground perspective to these mountains. Here is the lunar module with these same mountains
in the background. And from here it looks like they are so close,
but remember our perception of things is skewed! These actually rise about 5km high from the
plain the camera is on; higher than the Himalayan front above the Nepalese and Indian plains
on Earth. Astronauts also investigated the rille using
their lunar rover. This rille actually drops down 380m! Rille’s are a bit of a mystery as it isn’t
clear why they are there. One leading theory is that they are the exposed
or collapsed magma tunnels under the surface of the moon back when it was more geologically
active. From the perspective of the Lunar Reconnaissance
Orbiter, the tracks left by the rover can still be seen today, as there is no wind on
the moon to cover up the tracks with dust. So even though the Apollo mission happened
about 40 years before this photo was taken, the remains can still be seen in pristine
detail. It wouldn’t be right to talk about some
of the highest points on the moon without talking about the highest point! Sadly, it doesn’t look too impressive as
it has a really shallow gradient – only 3 degrees. [It’s near one of the biggest impact craters
in the whole solar system, and certainly the biggest on the moon,] the Aitken Basin, which
likely formed 4 billion years ago. [This is where the Chang’e 4 Chinese mission
landed back in 2018, which impressively LRO was able to image!] As you can see, this crater is huge, [2500km
across,] and would have created a lot of ejecta. This ejecta piled up all around the crater,
including what is now known as the highest point on the moon. The basin was likely caused by a low-velocity
impact with an object 200km in diameter, and it would have been at a sharp angle as the
ejecta was flung mainly in one direction. Interestingly, the lowest point on the moon
is not so far away from the highest point! The lowest point, found at the bottom of a
crater within the basin is -9106m, and the highest point is taller than Everest, at 10,786m! Just a side note for all those of you that
are curious, these heights come from comparing the average radius of the moon with the elevation
of that point. As you can see, the surface of the moon is
littered with craters. It doesn’t matter where you are on the moon,
there will be craters of various sizes. This implies that the surface is old and hasn’t
been renewed by lava eruptions from the mantle anytime recently; the most recent eruption
thought to have happened 1.2 billion years ago. There are an estimated 300,000 impact craters
over 1 km across on the surface of the moon facing us, and millions more smaller than
that, like the ones you are currently looking at. The moon can have such small craters because
it has no atmosphere, meaning every meteorite heading for the moon will hit its surface. On Earth, most meteors burn up in the atmosphere. Just imagine how many shooting stars there
are each night. Were it not for Earth’s atmosphere, every
one of them would impact our surface too. What’s interesting about each crater you
see here it that you can roughly estimate how old a crater is by how eroded it is. Craters which appear very smooth are much
older than craters with lighter substances surrounding them, with sharp and defined edges. The bright patches haven’t had so long to
have a weathering effect happen on them. But weathering on the moon? How can that be? Well, this weathering is not caused by water
or air, but rather but tiny micrometeor impacts and intense radiation from the Sun which dull
the thin outer layer of the Moon. If we speed along to the end of this image,
we can see a relatively fresh crater only a few hundred meters across. Using LRO’s narrow angle camera, we can
see a close-up view of the effects of such an impact on the lunar surface. These linear patterns are the effects of the
ejecta from the impact. Finer dust would have been blown across the
surface with some force, larger boulders not quite making it as far, although leaving a
trail from where they rolled away from the impact. The crater itself isn’t super clear in this
image due to the time in the lunar day this was taken, the Sun close to the horizon casting
long shadows across the surface, although you can still see fresh exposed material along
the crater wall. Comparing this to an old crater, here you
can see a much smoother and darker looking crater, although still brighter than the heavily
weathered surface in the surrounding area. What I like about this image though is that
zooming in, you can see some ejecta that landed from another impact off the image. Here’s a boulder that landed on the crater
wall and then rolled halfway down. The only thing with these top-down perspectives
is that you don’t get a great concept of depth in the image. How shallow or deep can craters get? Luckily the LRO doesn’t just scan the surface,
but can take more oblique shots of the moon too, which can definitely help us appreciate
depth. Look at this fantastic image. This crater is around 21km across, and it
has some fascinating details all around it. Again, we can see the trails left by huge
boulders rolling down the slopes, and very bright walls implying it is a young crater,
yet darker material at the base. The contrasts are really quite vivid, and
it almost looks like some parts could have been liquid at some point. The impact would have initially melted the
rock into lava, which flowed to the bottom, collecting in pools which have since solidified. The impactor was likely 2km in diameter, and
hit the moon ten times faster than the speed of a bullet. That would have been some collision indeed! Another great image I have to show you is
this, a crater 10km across. What’s special about this one is its interestingly
raised rim. This is another example of rock melting from
the impact, but rather this time slopping beyond the rim and flowing down, before solidifying
again. If we look closely around the crater, you
can also see ejecta scattered across the surface, disturbing the ground and leaving brighter
patches exposed. See? Once you know what you are looking at, even
the Moon becomes very interesting. But these have been very pristine craters. What if a meteor lands somewhere a little
less conventional? Here is a crater within a crater. The impactor hit the wall of the larger crater,
meaning it has quite an unusual shape, although from a top-down perspective, it still looks
quite circular. Just as a side note, this image is a true
colour image of the moon. Most other images of the moon are taken in
black and white to save bandwidth, astronomers prefer resolution over colour, although the
lowest resolution camera on the LRO is capable of colour, and this is an example of it. But certain craters can be unconventional
in other ways too. There’s a little understood phenomenon on
the moon that scientists have so far struggled to explain, and that is cold patches found
on the moon after the Sun goes down. So far, we have really only focused on the
cameras equipped on the LRO, but it has a host of other instruments onboard, including
the Diviner Lunar Radiometer Experiment which has mapped the Moon’s surface temperatures. There are two thousand points on the moon
that cool down more than the surrounding areas when the Sun goes down. When the Sun rises on the spots again, they
normalise their temperature and quickly blend in with the background. The only thing these spots seem to have in
common? They are always found around young craters
no smaller than 50m and no bigger than 2.3km. But the spots themselves are much larger than
the craters. Here’s a heat map of the crater I was just
showing you. White is the hottest parts of the image, blue
the coolest. As you can see, a large cool region surrounds
the young crater. There is an ongoing investigation to find
out the cause. What do you think it could be? [Speaking of cool areas, let’s jump now
to one of the coldest locations in the solar system. It’s an image I personally find] breathtaking. This crater, found near the South Pole of
the Moon, is almost always in shadow. The Sun never rises high above the horizon
here, meaning only the peaks of the crater stick out enough to be enveloped in light. What you are left with is a stunning contrast,
almost like the yin and yang symbol. This is certainly my new desktop background
image. But this region isn’t just an eerily beautiful
place, but is actually one of the candidates for the future Artemis mission to the moon. The lunar South Pole is of particular importance
to future human missions as there is thought to be millions of tonnes of water ice to be
found in this region, at the bottom of craters like this, forever protected from the Sun’s
rays. If there is to be a future colony on the Moon,
this is roughly where it would be located. [While massive craters, pristine mountains
and shadow-dappled landscapes are all eerily beautiful to look at, a large part of why
the images taken by LRO are so important is how well it advances our scientific understanding
of the Moon’s formation.] Let’s take a look at one of these images. At first glance, it may seem unremarkable,
but a deeper look tells a different story. See those two large, round depressions? Those are impact craters, much like countless
others that blanket the lunar surface. But if we zoom out, we see that these craters
are located on an unusual dome-like structure. This is Mons Gruithuisen Gamma. Look how the western side of the dome appears
lighter where the Sun’s light is reflecting off its steep slope. By contrast, the western sides of the craters
are plunged into shadow due to their low elevation. Shadows on the moon are so dark compared to
Earth due to the absence of Rayleigh scattering in the atmosphere. The Moon has no atmosphere, so the only light
that reaches shadowy regions are reflections from the lunar surface itself, which isn’t
actually that reflective. It is generally very dark, with an average
albedo of 0.12, about as dark as wet soil. Directly to the dome’s east is a dark shadow
cast by the dome itself, and it gives you a sense of how tall it is. The dome is towering, with a slope of up to
20 degrees and rising 1500 meters above the lunar surface. With a diameter of 20 kilometres, it’s equivalent
to the metro area of a midsize city. That’s pretty massive! Zooming out further, we see that the dome
is surrounded by darker and much flatter terrain. This plain, or mare, is the result of basaltic
lava flows that flooded the topographic lows around 4 billion years ago, resulting in the
even surface you see now. Think of it like ice cream dripping into the
crevices of a wafer cone. Zooming out further still, we see a second
dome located to the southeast of Mons Gruithuisen Gamma. This is Mons Gruithuisen Delta, and it’s
even bigger than its cousin, towering 1800 meters above the surrounding surface and spanning
27 kilometres in diameter. The dark basalt plain that surrounds both
domes is part of a vast mare [we saw earlier] – Oceanus Procellarum, or “Ocean of Storms,”
which covers a full 10.5% of the lunar surface. I don’t know about you, but I think “ocean”
is a fitting word. The domes look a bit like islands! It is believed that the Gruithuisen Domes,
like the Oceanus Procellarum, were formed by ancient lava flows. But why did they leave these unusual structures? Believe it or not, there may be clues here
on Earth. This is Mount Saint Helens, an active stratovolcano
located in America’s Pacific Northwest. Maybe you can see where I’m going with this. As you can see, it’s shaped a bit like a
dome. Stratovolcanoes like this one are the result
of pyroclastic flows of silica-rich materials like rhyolite, dacite and andesite. Once expelled from the Earth’s crust, these
high viscosity lavas move slowly as they cool, hardening into domelike or conical formations
over time. We suspect that the Gruithuisen Domes, like
terrestrial stratovolcanoes, are made of highly silicic material, and recent thermal measurements
by the LRO’s Diviner instrument support this theory, suggesting the domes are compositionally
different from their surrounding plain. So, unlike the Moon’s basalt lavas, which
settled into smooth, low-lying surfaces, these more viscous, silica-rich lavas extruded slowly,
like thick molasses, eventually cooling and leaving the massive domes you see now. But here's where it gets strange. On Earth, stratovolcanoes like Mount Saint
Helens are a unique product of water and plate tectonics. At the convergence of two tectonic plates,
a subduction zone can occur where colder and denser material from an oceanic plate is thrust
under the less dense plate and back into the Earth’s blazing hot mantle. The remelted material results in silica-rich
magmas like rhyolite or dacite, which then rise. But unlike here on Earth, neither liquid water
nor plate tectonics are present on the Moon. So how did these silica-rich magmas form? We’re not sure! One explanation suggests that when lunar magma
had nearly cooled and crystalized, it left a residual liquid that could have been extremely
rich in silica. The problem, however, is that this process,
known as fractional crystallization, would produce only small quantities of silicic material,
which wouldn’t be nearly enough to explain a massive 27-kilometre goliath like Mons Gruithuisen
Delta. A second model suggests that silicic materials
formed when basalt magma rose upward, causing rocks on the lunar surface to partially melt
and form rhyolites and dacites. If this were indeed the case, then the Gruithuisen
Domes should be nearly the same age as the surrounding basalt plain. We don’t know if this is true yet, but future
research could shed light on both the chronology and composition of these mysterious structures. To me, the most exciting part is that we may
be just a year away from getting an answer. NASA plans to send a Commercial Lunar Payload
Services rover to this region in 2025. This mission will explore the Moon’s surface
and collect rock samples that should shed light, not just on the mysterious Gruithuisen
Domes, but on lunar volcanism in general. And high-definition images taken by the LRO,
like the ones we’ve been studying today, will provide NASA with crucial information
for selecting a safe and navigable landing spot. It’s exciting to imagine how this mission
will add to our current understanding of the Moon with on-the-ground imaging and rock samples,
and honestly, I can’t wait. Which of the two theories to explain the formation
of the Gruithuisen Domes do you think sounds more plausible? I’d love to hear your ideas in the comments! [As you can see by now, not everything on
the Moon is fully understood. For example, let’s turn to this] innocuous
unnamed crater. As you can see, there are plenty of tiny craters
within it. And this crater is within another crater again. Maybe you can see where I’m going with this. Zooming out, not only are these craters in
another crater, but apparently, they are contained within two very nicely aligned craters. Or is that really what this is? Well, we aren’t sure. Both of these craters are named as one, the
Bell E crater. This peculiar type of crater is known as a
donut, or concentric crater. It is possible that they are the result of
two impactors aligning up nicely, but further investigation suggests otherwise. If they were the result of chance collisions,
then there should be a random distribution of concentric craters across the surface of
the Moon. However, that is not the case. Have a look at this. The population of concentric craters actually
clump up around certain areas, especially around the edge of this region of the Moon
here, called Oceanus Procellarum. Another factor to consider is that most of
these craters are of similar ages. Looking for clues in the crater itself also
reveals something interesting. This outer crater should be around twice as
deep as it currently is when comparing it to other similar sized craters around the
Moon. Now, while a few concentric craters on the
Moon will certainly be the result of double impacts, the location, age and depth of most
craters means that something else must be at play. One theory is that some of these impacts occurred
during a time when the surface of the Moon in this region was in a state in between solid
and liquid, with a consistency similar to cool lava or honey. As the impact happened, it caused ripples,
which propagated outwards, but then stopped and never smoothed off until it was fully
cooled and frozen in place. Although this is seen as an outside possibility. The most likely theory is that when the Moon
was more geologically active, craters in the region were pushed up from beneath by magma
trying to escape onto the surface. This would explain the shallowness of the
crater, and why we see concentric craters mainly around specific points on the Moon. However, while this is the best theory we
have at the moment, we don’t know for sure. What do you think it could be? Now, apart from the occasional meteor, you
probably think the surface of the Moon barely changes at all. And while you are mostly right with that,
we have found evidence that material does move on the Moon occasionally. See if you can spot what I’m talking about
in this image here as I pan across. This is the edge of a large 32 km wide crater
known as Kepler Crater, and what you may notice along the crater wall is evidence that landslides
have occurred here, with the dark material apparently having fallen down the slope. Let’s have a closer look at what’s going
on by zooming in on the most prominent of the landslides in this crater. The material seems to originate from box canyons
towards the top of the crater rim. The material coming down here is clearly very
fine, certainly less than a metre across, as no individual rocks can be resolved within
the slide. However the largest rocks that got dislodged
seem to have all made it to the bottom of the crater floor. What’s interesting is that the main mass
of the slide seems to actually be made up of many smaller slide masses. Look at these individual trails here. So, it probably didn’t all happen at once,
but is happening over time. The slides were likely triggered by tiny meteors
striking the crater wall. These tiny impacts and the subsequent landslides
round off the edges of the crater, which is why the oldest types of craters on the Moon
look so smooth compared to the freshest craters. Here’s another puzzle to try and solve. Here, we have the remarkable Messier Crater. Typically, craters are round, but not Messier
Crater. It is elongated with a slit for a crater floor. What is going on here? The mystery continues if you zoom out a bit. Directly next to Messier Crater are two more
craters. The one on the left seems much older than
the other, as it seems to have been weathered away compared to the fresh impact crater on
the right. Did the newer crater just so happen to cover
an older one? But let’s zoom out again. What other clues can we see? Actually, a big clue are these lines coming
away from the crater. These are called rays, and they reveal the
direction the debris fell after the impact. On rounded craters, debris can go in all directions,
like the ones that originate from Tycho Crater. However here, debris goes in three distinct
directions, north and southward from this crater and only westward from this one. So, what would cause that? Well, the answer is, an impactor striking
the surface at a very low angle, less than 15 degrees. And in this particular case, it seems like
the impactor had already broken apart into three parts before it even hit the Moon’s
surface. Yes, all three of these craters likely hit
the Moon at just about the same time, even the “older” crater. What actually happened here is that ejecta
from this second crater likely fell directly on top of the other crater due to the low
angle of the impact, which means that it has been artificially aged. There are some other really interesting aspects
of this image though, like the solidified pond of impact melt found at the bottom of
the crater, or this region here which appears to have caved in a bit. The impact melt in the first image also appears
to have flowed down towards the left of the image. It really is a fascinating set of craters. Let’s have look at another asymmetrical
crater and try and figure out why it has the shape it does. While it could be that this crater is also
the result of two impacts, or one impactor breaking up into two just before it collided
with the Moon, scientists think that this is likely not the case here. Notice the shadows in this image, above and
below the crater. It is apparent that this crater is right on
the cusp of a peak. Zooming out and looking at a topographical
map of the region reveals that this is the case. In fact, this may well have been the tallest
peak in the local area, until by chance, this impactor came along a totally wiped it out. Imagine Everest suddenly being taken out by
a meteor! The shape of this crater was probably not
only caused by the angle the impactor approached from, but also because it hit this steep slope. It might not look that steep from the oblique
angled shot, however over only about 20km, there’s an 8km difference in elevation from
the peak here to the bottom of this nearby crater. In this next image, there’s not too much
to see. The only thing visible in this wide expanse
is this peak, basking in the light of the Sun. Why is this significant? Well, this peak is on the rim of Aepinus crater,
a crater found near the north pole of the Moon. As I mentioned, future colonies on the Moon
will be located somewhat near the north and south poles, because tucked away at the bottom
of the craters here where the Sun never shines are large pockets of water ice, essential
for any colony to subsist off of. Water can be used for drinking, washing, cooking,
and farming, plus breaking the h2o down into oxygen and hydrogen provides breathable air
and rocket fuel. These poles also have the added benefit that
there are peaks here that are almost always in the Sun, unlike other parts of the Moon
where the day and night cycle is 28 days long. 14-Earth-days in constant darkness is not
good for a solar powered power system. A peak like this one however, poking out in
the Sun while the surrounding area experiences night-time, would be an ideal location for
solar panels and powering a colony there. It’s not a perfect solution, as peaks like
this one will eventually also become covered in darkness depending on the time of year,
but 89% of the time is definitely better than other regions on the Moon where you’d get
sunlight for roughly 50% of the time. [While I’m at it, let’s enjoy] a couple
more islands in the darkness, this time from the far side of the Moon, found in Bhabha
crater. These are the central peaks found in the middle
of this 80 km wide complex crater. [Islands in the dark are an appropriate way
to end our exploration of the Moon through the eyes of LRO. When it comes to space, that’s all the Moon
is – that’s all any astronomical body is. An island, floating through a sea of blackness,
sprinkled with stars. And yet in these islands, such incredible
beauty and wonders can be found. The LRO remains operational, and will continue
to run through 2024 and into 2025. As it carefully circles the Moon across time
and seasons, perhaps it will find new wonders – new craters and impacts from asteroids,
or new rockslides caused by lunar quakes. The Moon’s surface is slowly evolving even
now. And finally, once it has run its course and
has taken its last image, LRO will gracefully fall from orbit, and will contribute to the
history of the Moon by creating one last crater. This small crater will not be as large as
the Aitken Basin, but given the lack of wind or weather on the Moon it will likely remain
there for millennia – a testament frozen in the regolith of the orbiter that did so
much to map the Moon’s landscape for us. After all, by giving us this knowledge, it
may just have paved the way for the first humans who will set foot on the Moon and call
its eerie, beautiful, crater-marked landscape home.]
