We may take the Moon for granted, but what a sight to behold it is in our sky.
It’s big enough and close enough to us that we can easily make out surface details with
the naked eye, like the dark Mare and bright craters.
Just looking at it through a telescope is impressive enough, however what I’m about
to show you in this video will make the telescope view pale in comparison.
You see, we are fortunate enough to have not only have visited the Moon, but also have
an orbiter around it right now with a powerful camera that has been scanning the surface
since 2009.
So, what has it seen?
I’m Alex McColgan, and you’re watching Astrum.
Stick with me in this video, and I will show you some of the LRO’s most recent impressive
and puzzling images of the Moon.
Let’s start off with an innocuous little 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 still 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
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 this 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 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.
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 be 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.
I’ll just leave you with 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.
Want to know more about complex craters?
Then check out this other video in the LRO series I made here.
So, there we have it!
A look at some of the newest and most interesting images from the Lunar Reconnaissance Orbiter.
What do you like about the Moon?
And what would you like to see more of in future episodes?
Let me know in the comments.
Thanks for watching!
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