Why the Moon’s Icy South Pole is a Hot Target for NASA
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So if we were standing at the South Pole, maybe on the rim of a crater or some other peak, I think the first thing we would notice is the sun is not just going nicely overhead. It is kind of circling the horizon. Maybe occasionally it dips below or behind a peak, but it's always going to be this pretty extreme lighting.

This is Brett Denevy. She's a planetary geologist, and she's based at the Applied Physics Lab at Johns Hopkins University. And so that means some of the areas like these peaks, you're going to be in sunlight for a lot of the time. And then if you look down into maybe Shackleton Crater right near the South Pole, it's going to be dark.

And it will have been dark for potentially billions of years because the sunlight is never going to make it down in there. As you may have figured out, we're not talking about our earthly South Pole in Antarctica. We're talking about a South Pole almost a quarter of a million miles away, the one on the Moon. As we orbit the Sun, the South Pole here on Earth sees nothing but darkness for half the year. And then the other half is nothing but daylight.

That's because our planet is tilted on its axis. But the Moon orbits Earth almost straight up and down. And that causes this bizarre lighting at the Moon's south pole. You'd see mountain peaks illuminated by an almost perpetual sunset glow, and craters freezing in permanent shadow. And so that's kind of the key defining environmental feature of the South Pole, these areas of bright and areas of dark.

In these cold areas, some of them get down to temperatures that are always colder than Pluto. They're so cold that they may be able to trap water ice for long, long periods of time. It turns out the moon's dry, desolate South Pole is hiding a big secret, a feature it shares with our own South Pole, frozen water.

And now, NASA wants to find it. This is NASA's Curious Universe. I'm your host, Jacob Pinner. Ice on the Moon has NASA's scientists' imaginations running wild. Future lunar explorers could melt it and drink it. They could break up that H2O into hydrogen and oxygen. And then they could use it for breathable air, or even to make rocket fuel. It sounds like sci-fi, but NASA is working to make it a reality.

The Artemis program is preparing to send astronauts back to the Moon. The crew of Artemis III will not only leave the first human footprints on the Moon in more than 50 years, they'll be the first people ever to explore the Moon's south pole.

In the meantime, we're sending robotic explorers as scouts. These robot landers are testing new technologies to help humans stay safe in extreme polar conditions. So today, we're flying you to the moon to learn why NASA is so obsessed with the frigid lunar South Pole and what it takes to land there and survive. For thousands of years, people have looked up at the full moon and seen a face. You know, the man in the moon.

And even if you don't see a face, you can at least notice splotches of dark-colored rock that contrast some lighter gray areas. Those different shades of gray tell the story of how the moon formed. Billions of years ago, something really big crashed into Earth. Like something about the size of Mars. The debris from that impact swirled around in our orbit until it fused into a baby moon.

At that point, Brett Denevy says the moon's surface was a roiling ocean of bubbling magma. It's geologically pretty slow moving today, but it was once a pretty exciting place with literal rivers of lava flowing and carving out channels, huge eruptions of explosive volcanic deposits, and then of course, like giant impact events.

So it used to be a pretty cool place. Over millions of years, that magma cooled into solid rock. But different parts cooled at different speeds. That's how we got some rock that's lighter and some that's darker. The light, dusty highlands near the poles solidified first. Volcanic eruptions continued elsewhere, spewing dark lava across the moon's nearside close to the equator.

When NASA first set out to land astronauts on the moon in the 1960s, we mostly explored those younger, dried-up lava seas near the equator. On the moon, those seas are called "Maria." Compared to the mountainous South Pole, they're pretty flat — a relatively easy spot to land a spacecraft.

Tranquility Base here. The Eagle has landed. Roger, Twink. Apollo astronauts landed at the moon's equator six different times. And when they came home, they brought back more than 800 pounds of moon rocks and dirt. And that material has been crucial for geologists to understand the moon's more exciting past.

The moon's last volcanoes mostly sputtered out a couple of billion years ago. And the moon has sat pretty much unchanged. On Earth, we have water constantly changing the surface. But not on the moon. In fact, scientists can use the moon as a time capsule to understand how our own planet formed. You know, back before annoying things like erosion and life got in the way. The moon samples that we do have are helpful, but they're limited.

All of the Apollo missions landed in the same small patch of the moon's surface. The worst misconception about the moon is that we've been there and so we totally understand it. Great, let's check that off the list. We're done. We've been to a couple of very small locations on the moon.

And so it's kind of like, you know, visiting one teeny tiny spot on Earth and being like, "All right, we're good. We understand it." That's the one that drives me crazy. It's like, "No, there's so much more to learn from the moon."

The rocks Apollo astronauts brought home were mostly those younger, darker volcanic rocks. And they only tell us a part of the Moon's story. It's kind of like if you went to one country, picked up a rock, and assumed rocks everywhere on Earth were just the same. The South Pole has rocks that are lighter colored and older. Scientists think those rocks can tell us a lot more of the Moon's story.

That's why geologists in particular are so excited for NASA to return to the moon. And especially to someplace totally new: the mountainous ancient South Pole. To prepare for an astronaut landing, NASA does a lot of recon. Back in the 60s, we sent early probes to take photos of the moon's surface with tools that sound pretty low-tech today. They would take Polaroid strips

and develop each little Polaroid strip on the spacecraft and scan it and send it back. And so when you look at the images now, they're like these little stripey kind of assembled pictures of the Moon. But they're really high resolution because their job was to find sites for the Apollo astronauts to land. So they had to be able to see things like a boulder that would, you know, be a hazard.

When Brett first started studying the Moon in the early 2000s, that early imagery was all scientists had to work with. She would print out images and paste them into mosaics on her wall at home. But for a 21st century Moon mission, we need 21st century images.

In 2009, NASA launched a spacecraft called LRO, the Lunar Reconnaissance Orbiter. And we chose Brett as one of the senior scientists in charge of the spacecraft's camera. Suffice to say, LRO's cameras are an upgrade from those old Polaroid strips.

They're so good, you can even make out the tracks left behind by the rovers that Apollo astronauts use to drive around the surface. But LRO does more than take photos. It has an instrument that can detect the presence of hydrogen on the moon's surface from space, which is critical since hydrogen is one of the two elements that make up water. The good news is LRO does detect hydrogen. The bad news is the data we have aren't super precise.

Imagine you are looking at the pole from orbit and then you blur your vision even more. You have measurements of hydrogen abundance, but they're very broad regional measurements. LRO has confirmed that the moon does have water ice. Now, if you're picturing a massive ice sheet like Antarctica with penguins swimming around, I want to temper your expectations a bit. It's safe to say there's probably not massive ice.

like ice skating rink kinds of ice deposits on the moon. But it may be in much smaller, finer deposits in relatively small abundances scattered throughout these polar areas. There might be some permanently shadowed areas that have more ice and some have less, but we don't know how long the ice has been there, what its origin is, really what its form is,

The ice hiding in those shadowy craters could be right on the surface, kind of like the frost you see first thing in the morning. Or it could be in big chunks buried dozens of feet deep. Brett has been looking for a slam dunk answer, but she hasn't found one yet.

And the attempt at the slam dunk was actually like a real slam, was the LCROSS experiment. Where NASA just like chucked the upper stage of a Centaur rocket into a permanently shadowed region to see what would happen.

and watched the ejecta plume that came out of there and found some evidence for ice. At least in that one spot, there was about 5% water seen in the ejecta that came out of that crater. ♪♪

Ultimately, we may want to use that ice for drinking, breathing, or refueling rockets. But first, we'll have to get it out of the regolith, which is the technical word for the moon's soil. And we can't do that until we know exactly how much ice there is and how deeply it's buried. If you're trying to study it and it's all buried under 20 meters of regolith, that makes things more complicated.

There's a lot we don't know yet, and we won't know until we actually get on the surface and start making higher resolution measurements and bringing materials back from the moon to analyze them in the laboratory. But Brett isn't as interested in using the ice. She's a scientist. Like the South Pole's rocks, she wants to study it, to learn more about our own place in the universe.

The reasons that I care about the ice on the Moon, I'm just more interested in how did it get there? Was it delivered by comets? Was it delivered by asteroid impacts? You know, asteroids have some water molecules in them too. So imagine that long, long ago, an icy comet crashed into the Moon's equator, the same general area where the Apollo astronauts landed. But today, the water we see is tucked away in these shadowy craters at the poles.

So how did it get there? Yeah, I mean, so the reason that water gets stuck in these permanently shadowed regions at the poles is because they're cold traps. They're so cold that if a water molecule finds its way in there, it's just stuck. It's not going to ever evaporate or make it out. But on the rest of the moon, you have this daily temperature cycles.

Because of the way the moon orbits the Earth, at the moon's equator, you get 14 straight days of sunlight and then 14 days of night. And the temperature can swing wildly between day and night, from more than 250 degrees Fahrenheit to almost minus 300 degrees Fahrenheit. So you're heating up a lot, but then you have a lot of time to cool down and, you know, no atmosphere to help insulate.

So you can get areas that are cold and maybe water is stable on the surface temporarily at night, but then as the sun rises, it rapidly heats up the surface and that water molecule is going to start bouncing around trying to find a new place that it is stable. So eventually maybe it'll make it to somewhere it's permanently stable like the poles or maybe it'll keep bouncing around

in this kind of water cycle on the moon. The more we learn about the moon, the more we learn about ourselves. Scientists don't know how Earth first got water, and solving the mystery of how the moon got its water could help us unravel the origin of water here on Earth too. Earth has a lot of water for being so close to the sun, and so was some of Earth's water delivered after it formed by

comets and icy bodies coming from the outer solar system. Things are so mixed up and churned on the Earth that it's hard to answer here, but if we have ancient ice deposits on the Moon, we can use the composition of those deposits to understand where they came from. The Earth and the Moon are two bodies in space, closely bound. And the Moon is a precious way to look into our own past.

Even though we've learned a lot about the moon's south pole, there's no substitute for sending human explorers to look for themselves. We don't know what the ice on the moon is like because we have not been anywhere on the ground, scuffed our boots on the regolith to see what's in there and dig down a bit and look to see what form that ice is in.

We have so far really only tackled this problem from kind of far away, mostly from orbit. Now, Brett won't be scuffing her own boots on the moon's surface, but she gets to do the next best thing. She was chosen to be the top geologist for Artemis III, humanity's return to the moon.

Actually, how my daughter explains what I do, I've heard her tell her friends. My mom looks at moon rocks and she's going to tell astronauts what moon rocks to pick up. That's her more succinct version. From Mission Control, Brett will direct Artemis astronauts on the moon to gather samples. Scientists hope those samples will shed light on four big questions:

How did the moon form? How have impacts shaped its surface? How has its regolith evolved? And what does its ice look like? Brett is already practicing with astronauts. They're going on virtual reality lunar excursions. And she's guided them on rehearsal missions in moon-like terrain in Arizona. I am really curious about

what it will be like for the Artemis III astronauts when they step onto the surface in that weird South Pole environment. I'm really like more than curious. I'm dying to know what kinds of rocks they're going to bring back. How right we were, how wrong we were with some of our predictions and

I'm really curious to see how our lunar exploration in science will evolve as we continue to work through the Artemis mission. We're just kind of taking the first baby steps again of exploration of the moon. At NASA, every baby step and every giant leap is made possible by planning, practice, and more planning.

So before we send astronauts to leave footprints at the Moon's south pole, we have a scout team of robots making their own mark.

really learning from these robotic missions is what excites me too. How can we make that human mission more successful from the data that we can get back now? That's Michelle Monk. She's NASA's chief architect for the Space Technology Mission Directorate. Michelle is hard at work on an upcoming robotic lander mission called IM2, a collaboration between NASA and the private company Intuitive Machines. In early 2025, IM2

IM2 will launch to the Moon's south pole. We really call this a space technology mission because it is filled with space technology demonstrations and we're really excited about that and it's really groundbreaking for the future of our technology deployment on the Moon.

IM2's key technology demonstration is a tool called Prime 1. It's a drill specially designed to penetrate three feet deep and collect a sample of lunar regolith. In the future, Artemis astronauts could use a similar drill.

So Prime 1 is a really key demonstration of drilling into the lunar surface and looking for elements that we could use in the future, water, ice, oxygen, or hydrogen, to make rocket fuel or water or breathable atmosphere.

The technology of being able to get through this unknown surface, deal with the materials, and then be able to make valid scientific measurements is really interesting and has been a great challenge for the team.

So, to get ready for primetime, Michelle's team has tested the drill in all kinds of ways. They've flown it on high-altitude flights to simulate lunar gravity. They've run it through special chambers that mimic the moon's thin, almost non-existent atmosphere and create extreme temperatures. They've even tried it on simulated lunar regolith with all the properties of the real thing. Besides the drill, IM2 also carries another, smaller robot.

It's got this tiny rocket engine that it'll use to jump out of the lander and hop into craters to explore them. In fact, it's called the Micro Nova Hopper. The little hopper will communicate with its lander by testing the first 4G LTE cellular network on the moon, designed by Nokia. When Artemis astronauts land, they'll need the bandwidth to send photos and video back to mission control and to navigate the surface.

We're all so spoiled here on Earth with our pocket supercomputers and Google Maps to tell us where we are and where we're going. You know, it's a little bit daunting to think about not having that support system in a new location like the Moon. Another tiny wheeled rover will also drive out of the lander and take the first 3D images of the Moon's surface.

and it'll beam those back to the lander through that same cellular network. But for all those technology tests to work, IM2 has to land on the surface safely. And that's up to our partner, Intuitive Machines.

We kind of think of it as the FedEx service to the moon, and so we put our experiments on the truck and we don't ask what kind of engine the truck has or how it actually navigates to where it's going so much as we just like to get our data back from the moon.

This is part of an initiative that NASA calls Commercial Lunar Payload Services. We're partnering with several American companies to take on routine launches of science instruments and tech demonstrations to the moon. The truck here is a cylinder with eight sides and six legs. It's a little bit taller than a basketball hoop, and it's named Athena.

So this commercially-led approach comes with some risk, but it also comes with a lot of economic advantages, both in cost savings to the government, but also in supporting the broader space economy. That means more money and time for NASA to focus on the harder stuff, like landing humans on the Moon and Mars and sending robot explorers deeper into the solar system.

If you've been keeping an eye on space news, you've probably seen that in recent years, lunar landers from Russia, China, and India have crashed into the moon while attempting landings. Other landers have made it. But the point is, just because NASA has been to the moon before, doesn't mean it's an easy place to go back. And the extreme South Pole is an especially hard place to land. Intuitive Machines has tried this once before too.

IM-1 landed on the moon in 2024, but it immediately tipped over. Tense moments inside of mission control with the most qualified folks. We're picking up a signal from our high-gain antenna and transmitter. It's faint, but it's there. So, stand by, folks. We'll see what's happening here. But NASA's still got some good science results. And every attempt teaches us new lessons we can use for next time.

We're excited about the opportunity to refly that system and use the lessons learned of intuitive machines from the first one. And I know they're all in on making that landing successful. So second time, you have a lot more benefits from doing it once before. Michelle Monk's background is in entry, descent, and landing technologies. That is all the engineering that goes into landing a spacecraft safely on another planet.

In fact, she worked on the heat shield that let the Curiosity and Perseverance rovers land safely on Mars. So, she offered to walk us through IM2's upcoming journey, from launch to landing. So, let's go. Buckle up, keep your hands and feet inside the rocket at all times. Step 1: Take off.

In the grand scheme, launching from Earth is pretty routine at this point. NASA, private companies, and other space agencies do it all the time. Step two: you need a big, propulsive maneuver to get the spacecraft out of Earth's orbit and on course to the moon.

What an incredible sight to see, the IM-1 Nova Sea lunar lander drifting away from Falcon 9's second stage right before it begins its eight-day journey to the moon. Step three is especially tricky. Landing.

you only get one shot at getting it right. That's one of the things that makes descent and landing at any destination particularly intriguing for me is that there's really no viable abort scenarios. Once you're on your way, you are not stopping. You're going to land there either safely or not. So it's a very difficult problem, no matter who you are and how many times you've done it.

In the Moon's orbit, you wait for the right lighting conditions. Over the last 24 hours, Odysseus has maintained its trajectory in low lunar orbit, waiting for suitable lighting conditions to begin its autonomous descent near the south pole of the Moon.

The spacecraft also needs Earth to be in view so that it can communicate. And then you burn your engine to send your spacecraft toward the surface. The lander is continuing to decrease its altitude until the power descent initiation, an 11-minute braking burn that sets Nova-C up for the final moments prior to touchdown. The spacecraft uses its cameras to look at the landing site, and it has to compare what it's seeing to the images it has from LRO in real time.

So it's kind of like, you know, you have a picture that you've been looking at, you've picked your landing site and you know that there's a crater here and a boulder there. And then when you're approaching the surface, if you take similar pictures of that area, you can pinpoint those landmarks and kind of know better where your vehicle is compared to those. And that really helps. Since the moon doesn't have much of an atmosphere, parachutes are no good.

You have to use rockets. And so that's the tricky part. Everything has to go well, has to be well planned in terms of when you turn your engines on. You want to get rid of all your horizontal motion so that you're just coming down vertically towards the surface. Sense how high we are from the surface and then touch down safely.

On IM-1, that last part was where things went a bit wrong. The lander hit the moon's surface at a higher velocity than the team expected. That broke two of the spacecraft's landing struts and caused it to tip over. As you'll recall, the South Pole has weird lighting, which makes landing there even trickier. The long shadows of almost perpetual sunset can confuse the spacecraft's cameras.

And compared to the flat, dried-up lava seas of the equator where the Apollo astronauts landed, the South Pole is a lot rougher. We're not quite sure yet all the challenges that we'll meet at the South Pole. But, you know, if you just look at the terrain, the maps that we have from Lunar Reconnaissance Orbiter and other previous missions, it looks a lot more rugged at the South Pole.

There are mountains, there are huge boulders, and there are even craters deeper than Earth's Grand Canyon. The challenges don't stop after a safe landing. The next step is keeping your robot alive, and that means regulating its temperature. That's hard anywhere on the moon long term. Remember, at the equator, you have long days and long nights. That's a lot of time to get very hot and then very cold.

It's like being in the desert almost with very low humidity. You know how the daytime to the nighttime temperature swings are very dramatic, even more so on the moon because you don't have that atmosphere at all. The Apollo astronauts all landed during the hot, sunny lunar day. So their technology had to have ways to cool off in the bright sunlight. But at the South Pole, it's more like being in Antarctica or Alaska during the summer.

The sun will bob along the horizon a lot of the time. Cooling off won't be the problem. At the South Pole, we will still have periods of complete darkness where the sun is not in view.

but the sunlit times will be a little less dramatic. So it will be cold a lot of the time, so we need low temperature batteries to keep our systems running. We need components and mechanisms and electronics that are tolerant to freezing, or we need some way to heat them up, keep them warm.

Michelle's work shows it's easier to keep your robot warm with heaters than to make it freeze tolerant. Of course, you need power to do that. And you guessed it, power is another challenge. At the equator, that bright sunlight that beats down for 14 days straight is pretty great for generating solar power. But here at the South Pole, you have that constant, cold, dim sunset glow and those long shadows.

That means we need innovative solutions to generate enough power. One of the things that we've been investing in is solar arrays that are on tall poles or masts that can be kind of raised up so that your solar panel can see sunlight even though your lander on the surface may not be getting any sunlight directly on it. So that way you can have power without actually being in the sun.

That might be a good solution for explorers who have to venture into shadowed regions to look for ice and leave sunlight behind. Then there's one more challenge to contend with: dust.

The dust on the moon is extremely abrasive because if you think about the Earth or Mars where there's been running water and atmosphere and wind, the dust that we deal with on the Earth is kind of rounded. All the little particles, if you look at the grains of sand on the beach, right, they're round. Not so on the moon. And so you have all these little jagged pieces of dirt.

The Apollo astronauts complained endlessly about the sharp, statically charged dust. And they only had to put up with it for a few days. They had a lot of cleaning to do and one of the astronauts said, "You know, if I never have to dust again, I would be happy." Because they spent so much time cleaning and making sure that the dust didn't get into their systems.

Let me tell you, is Justin gonna be fun tomorrow? I didn't know I had the Lunar Dante fever.

For long-term settlements on the Moon's south pole, that dust will be more than annoying. So once we start sending humans and bringing them back, we'll have landings and launches of very big vehicles. And if you think about those engines pointing towards the surface of the Moon, they're going to kick up a lot of dust and debris and send it for kilometers.

Future moon bases might need things like dedicated landing pads to keep dust down. And that's just the start. I think, you know, advancing for now and then really understanding what it takes to live long term is really going to require a leap in technology, which is what really we're working on today so that we'll be ready when the astronauts are ready.

When she closes her eyes, Michelle imagines a moon that we can call home. One made possible by the technologies her team is testing right now. She sees cranes to unload cargo, communications and GPS networks, habitats chock full of scientific equipment, and nuclear surface power systems to provide electricity, even in the dark. Also, rovers. Lots of rovers.

ways to drive around the surface to take little camping trips and excursions many kilometers away to get to that really exciting science location. And of course, being able to live off the land, so either using regolith or ice deposits to make water or make rocket fuel on the surface so that

You know, it's more regular and inexpensive to get between the moon and orbit and between the Earth and the moon. So there's a whole ecosystem and infrastructure that we see really making that future a reality. This is NASA's Curious Universe. This episode was written and produced by Christian Elliott. Our executive producer is Katie Konins.

The Curious Universe team also includes Mattie Olson, Michaela Sosby, and of course, Patti Boyd. Christopher Kim is our show artist. Special thanks to the team at NASA's Space Technology Mission Directorate.

Our theme song was composed by Matt Russo and Andrew Santaguida of System Sounds. If you're interested in other upcoming NASA robotic missions headed to the Moon, we have a page on the nasa.gov website listing all the upcoming commercial landers and their landing sites. Just look up NASA's Commercial Lunar Payload Services Program. As always, if you enjoyed this episode of NASA's Curious Universe, let us know.

We want to take you on wild and wonderful adventures about our universe. So how are we doing? Let us know in a review and also tell us what you're curious about and what you'd like to hear on NASA's Curious Universe. You can also follow us in your favorite podcast app to get a notification each time we post a new episode. When I started studying the moon, Apollo was just such ancient history to me. And I didn't even really think about it.

people going back. I was content to study, you know, this kind of historical data. And now to have the chance to actually go back and get new rocks to answer new questions, that feels almost too good to be true. I want all of the rocks. Three, two, one. This is an official NASA podcast. NASA Jet Propulsion Laboratory, California Institute of Technology