Chapter 1: What fascinating details can we observe on the Moon's surface?
We may take the Moon for granted, but what a sight it is to behold 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 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 around 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.
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Chapter 2: What discoveries have been made by the Lunar Reconnaissance Orbiter?
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 a look at another asymmetrical crater and try to 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 the 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 and 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 Apinus Crater, a crater found near the north pole of the moon.
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Chapter 3: How do concentric craters form on the Moon?
I'll just leave you with a couple more islands in the darkness, this time from the far side of the moon, found in Ba Ba crater. These are the central peaks found in the middle of this 80km wide complex crater. Do you believe the moon to be barren, grey and uninteresting? Well to me, that couldn't be any further from the truth.
The moon is packed full of secrets about its past, and has clues dotted all over its surface which gives us information about how it formed and evolved over time. From global events that created some of the largest craters in the solar system, to tiny hills exposing layering in the moon's crust.
each helps us get a better picture of our closest celestial neighbour, and as a result, expands our understanding about the formation of the solar system as a whole. It's no wonder then that NASA has a spacecraft called the Lunar Reconnaissance Orbiter, which is in orbit around the Moon right now, mapping out its entire surface.
I'm Alex McColgan, and you're watching Astrum, and in this episode of the LRO series, we will investigate some of the most unusual terrain found on the Moon's surface, and hopefully I'll be able to make the grey, barren and uninteresting world into something fascinating and wonderful for you. Let's start with a place rich in incredible contrast.
This oblique angle shot is of Jackson crater, 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 side 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 are also 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 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?
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Chapter 4: What evidence suggests that the Moon's surface is not static?
The danger is that this phenomenon is combined with an already strained system, even more strained than it was in 2015. Climate change has resulted in steadily rising sea levels. When the next node aligns with the Sun in the mid-2030s, this will likely lead to a dramatic increase of floods on planet Earth.
Worryingly, a new study led by NASA's sea-level change science team predicts that almost all US mainline coastlines, Hawaii and Guam, will have a huge leap in flood numbers when this happens. Some predictions claim this node alignment could cause four times the amount of flooding from one decade to the next, which will damage infrastructure and change our coastlines around the world.
This means human life will inevitably be affected by these floods, impacting shelter, clean water supplies, electricity, as well as the increased risk of waterborne disease outbreaks like hepatitis A and cholera. Plus, the receding flood water can create stagnant pools of water where mosquitoes gather, which can spread other diseases like malaria.
This has a knock-on effect on economic issues, as these natural events can make coastal life unaffordable, with increased cost of insurance on these homes, or an inability to find insurance at all, which could cause a reduction in asset value in the community.
Consequently, this lunar nodal cycle will damage the quality of life in coastal communities, where infrastructure may not be rebuilt or adapted to this force of nature. It's not just bad for humans. Ilya Roshlin, a visiting professor at Rutgers University, analysed that the peak of the lunar wobble, where high tides are higher, can drown salt marshes.
Salt marshes are a habitat for a range of species, such as invertebrates, and these floods can cause these creatures to drown, which means that other species like fish, seabirds, and others who rely on invertebrates to survive also suffer. and they aren't the only ones that rely on salt marshes, as salt marshes hold a multitude of marine life, which includes 75% of all fishery species.
This means that the lunar wobble impacts the food chains of humans and animals, causing disturbances to their natural habitat and impacting their populations. While this all does seem fairly doom and gloom, it's interesting to note that not all ecosystems on the planet are negatively affected by flooding and high tides. Ecologist Neil St.
Alain of Macquarie University analysed that the lunar nodal cycle impacts heavily on the expansion and contraction of mangrove canopy cover over most of the Australian continent, The analysis showed that the peaks of the lunar nodal cycle coincided with the cover of the mangrove canopy.
It showed that when the lunar wobble is at its minimum phase, it causes the mangrove ecosystems to become very dry, which leads to thinner canopy cover. Yet, when lunar wobble is at its maximum phase, mangrove cover increases. Mangrove canopies are beneficial to Earth's environment as they are complex ecosystems that fight against climate change, protect wildlife, and shield coastlines.
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Chapter 5: What is the significance of the Messier crater's unusual shape?
Well, lots of moons are extremely close to their parent planets, meaning their hill spheres are very small. Let's take our Moon as an example. Against the Earth, the Hill Sphere of the Moon is only 60,000 km radius, or only one sixth of the distance from the Moon to the Earth. Moons like Io have an even smaller Hill Sphere, as it is competing against the gravity of Jupiter.
This makes it quite hard for moons to capture an object, but not technically impossible. So surely there must be a moon that has a natural satellite somewhere, right? Well, most moons also have one other major problem. They tend to be tidally locked to their parent planet.
Because of this, any satellite that orbits a tidally locked object will have its orbit decay from tidal forces until it eventually crashes into the moon. Now this still takes a lot of time over astronomical standards, but it means if any of the moons in our solar system did have a satellite at one point, chances are that it has since crashed into it. This leaves one question I think.
Why don't moons of planets also eventually crash? The difference is that none of our planets are tidally locked to the Sun, as they are far enough away from the parent star, which means their moons have a stable orbit
This is one of the reasons we believe that none of the TRAPPIST system planets have moons, as they are so close to their parent star that we assume the planets are all tidally locked. I hope this didn't disappoint you too much, so I'm going to leave you with this.
There are some other curious objects in the solar system, far away from any other object so that they aren't tidally locked to anything. This particular asteroid, called Ida, looks like a standard 30km wide asteroid as seen by the Galileo spacecraft, but you might notice this little blob here. This is actually Ida's moon, Dactyl. It's only 1.5km across, and orbits only 60km away from Ida.
We don't know especially how stable this orbit is, but a very cool thing to observe nonetheless. We are used to tectonic activity on Earth, it being a daily occurrence somewhere on the planet. But what about our closest neighbour, the moon? During the Apollo missions, seismometers were left on the moon to detect the presence of moonquakes.
From these instruments, we now know that the moon does have quakes, and relatively frequently too. But unlike Earth, most can be attributed to meteors striking the moon's surface. Although, there is also evidence to suggest that a small percentage of these quakes could be due to the moon shrinking and contracting.
Early in the solar system's life, most of the celestial objects were hot, a result of the process of how they were formed, and followed up by a period of heavy bombardment. Since then, impacts have become much less frequent, and these objects, including the Moon, have cooled down. As something cools, it contracts.
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