For decades, we described the moon the same way in almost every textbook, every documentary, and every classroom on Earth.
A dead rock, a frozen, geologically inactive ball of gray dust and craters that stopped doing anything interesting about 3 billion years ago.
We were taught that the moon had no atmosphere, no weather, no geological activity, and no surprises left to offer.
It was simply there circling our planet, pulling our tides, and doing absolutely nothing dramatic.
That description is now known to be wrong in several specific and important ways.
And the people who found out how wrong it is were not looking at old photographs or running old calculations.
They were using some of the most sophisticated instruments ever sent to space.
And what those instruments found beneath the surface and inside the craters of the moon has changed the entire way NASA is planning its next decade of exploration.
The moon is not dead.
It has a hidden layer of partially molten rock sitting inside it right now that nobody predicted.
It has caves large enough to shelter entire cities.
It is still producing small earthquakes.
Its surface is still shifting and cracking.
And at its poles, in craters so deep and so cold that sunlight has not touched their floors for billions of years, there may be hundreds of millions of tons of water ice waiting.
And then there is Mars, where a perfectly circular hole in the planet’s surface is sitting in NASA images from 2017, pointing straight down into an underground world that no human has ever seen, and that researchers now believe could be one of the best places in the solar system to search for signs of life.
This is the story of what we have recently found on the two most studied worlds beyond Earth and it is nothing like what we expected.
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Let us start on the moon.
The first thing to understand about how the moon changes is temperature.
If you were standing on the moon’s surface during the day, the temperature around you would be approximately 120° C.
Hot enough to boil water.
Then the sun would set and within hours the temperature would fall to around minus 130 degrees C.
That is a swing of 250 degrees between daytime and nighttime.
And this cycle happens over and over again, month after month, for billions of years.
What that does to rock is exactly what you would expect if you heated a piece of material to boiling point and then froze it repeatedly over billions of cycles.
It cracks.
It weakens.
Surface material fractures along its natural fault lines.
And over geological time, entire sections of the lunar surface shift, slide, and sometimes partially collapse.
NASA’s Lunar Reconnaissance Orbiter, a spacecraft that has been mapping the moon in extraordinary detail since 2009, has identified thousands of features on the surface called lobate scarps.
These are essentially small cliffs or fault lines, places where the moon’s crust has buckled under stress and one section is pushed up slightly over another.
What makes them significant is not just that they exist, but that many of them appear to be geologically young.
In planetary science, young means something different than it does in everyday life.
Something that formed 50 million years ago is extremely recent in geological terms when you are talking about a world that is 4 and a half billion years old.
And many of the Lobbit scarps identified by the lunar reconnaissance orbiter appear to have formed within the last 50 million years, which tells scientists that the moon’s crust is still under active stress right now.
not just a memory of the ancient geological forces.
The direct evidence of that stress came from the Apollo missions.
Seismometers placed on the lunar surface by Apollo astronauts in the 1960s and 1970s recorded something that genuinely surprised the scientists monitoring them.
Moonquakes, not gentle vibrations.
Actual seismic events reaching magnitudes of up to five on the scale used to measure earthquakes.
A magnitude 5 moonquake is strong enough to shift surface material, dislodge boulders from slopes, and trigger small landslides in areas where the ground is already unstable.
Computer models of the lunar surface suggest that even a moderate moonquake near the poles, exactly where future missions are planned, could trigger cascading rockfalls down slopes that orbital images show are already prone to movement.
Recent analysis of the Apollo seismic data re-examined with modern computing tools indicates that some of the faults responsible for those quakes may have been active within geologically recent times.
What looked from Earth like a perfectly still silent world is when you look more closely still moving.
The surface changes are visible in the orbital imagery.
In several regions, high resolution images from the Lunar Reconnaissance Orbiter show slopes where material has partially slid downhill, leaving behind fresh-looking surfaces that stand out sharply from the older, more weathered terrain around them.
In some images, the visual effect is dramatic enough that at first glance, it genuinely looks as if a chunk of the moon has broken away.
What is actually happening is a lunar landslide.
loose surface material called regalith moving downhill in response to moonquakes, temperature stress, or the gradual accumulation of micromedorite impacts, loosening the upper layer of dust and rock over millions of years.
The moon has no atmosphere, so even tiny particles from space hit its surface at full speed without slowing down.
Over billions of years, this constant bombardment has shaken the upper surface layer into a loose, fragile condition that makes it particularly prone to movement when other forces act on it.
All of this surface activity is significant for the Aremis program.
NASA’s initiative to return humans to the moon and eventually establish a long-term presence there.
Understanding which areas of the lunar surface are geologically stable and which are prone to sudden changes is not an academic question.
It is an engineering and safety question.
A landing site that appears stable in older imagery but has active fault lines beneath it is a very different kind of challenge than a genuinely stable site.
That is why continuous mapping and monitoring of the lunar surface is one of the highest priorities for the missions currently in development.
But what is happening on the surface of the moon is almost less surprising than what scientists found beneath it.
In 2024, a research team analyzed data from two NASA missions.
The Gravity Recovery and Interior Laboratory known as Grail and the Lunar Reconnaissance Orbiter.
The Grail mission, which operated in 2012, used two small spacecraft flying close to each other in orbit around the moon.
As they flew over different regions, tiny differences in the moon’s gravitational pull caused them to move slightly closer together or slightly further apart.
By measuring these tiny variations in distance with extraordinary precision, scientists could map the gravitational field of the moon in more detail than had ever been possible before.
And from those gravitational measurements, they could infer what was happening deep inside the moon where no camera could see.
New lunar gravity measurements support the idea that a partially molten mantle layer is sandwiched between the rest of the moon’s mantle and its core.
The research team, whose findings were published in the journal AGU Advances in 2024, found that their models of the moon’s interior could not reproduce the observed gravity measurements unless they included a softer, partially molten layer sitting at the base of the mantle between the solid rocky mantle above it and the metallic core below.
Without that layer in the model, the numbers simply did not work.
The gravity data required it.
The research suggests that the layer is composed of the mineral ilmanite, which is rich in titanium and iron oxides.
These minerals might be responsible for maintaining the heat that keeps this layer in a molten state.
Ilmanite is genuinely interesting for reasons that go beyond its geological role.
Titanium is one of the most useful materials in modern engineering and manufacturing.
It is used in aircraft components, spacecraft structures, medical implants, and high performance equipment precisely because it combines extreme strength with low weight and remarkable resistance to heat and corrosion.
If the moon contains a partially molten layer rich in titanium in the form of illmanite and this that is a potential material resource of significant value for any future permanent human presence on the moon.
Building structures or manufacturing equipment using material extracted directly from the moon would be vastly cheaper than transporting the same materials from Earth, where escaping the planet’s gravity well is the most expensive part of any space mission.
The discovery of a partially molten layer has profound implications.
It changes our understanding of the moon’s structure and sheds light on its thermal evolution.
This molten zone likely helps regulate the moon’s temperature and could be playing a role in the moon’s gradual cooling process.
But here’s the question that the discovery immediately raises and that scientists have not yet fully answered.
How is that layer still partially molten? The moon is 4 and a half billion years old.
It should have lost most of its internal heat by now.
The moon’s core is much smaller relative to its size than Earth’s, generating significantly less heat.
And yet something is keeping that layer soft and partially liquid billions of years after the moon was expected to have cooled into a completely solid rock.
The researchers speculate that if the partially molten layer exists, it may consist of a titaniumrich material called ilmanite.
The titanium and iron oxides in ilmanite may be particularly effective at trapping and retaining heat.
But exactly how the layer has maintained its temperature over billions of years remains an open question that follow-up research is actively trying to answer.
Now, let us go deeper into a discovery that completely changes what kind of future human presence on the moon might look like.
For more than 50 years, scientists suspected that the moon might contain underground tunnels, hollow tubes carved out by ancient lava flows billions of years ago when the moon was volcanically active.
The logic behind this suspicion was well established from studying similar features on Earth.
When lava flows across a surface, the outer layer cools and hardens while the hot molten rock continues flowing through the center.
When the eruption eventually ends and the lava drains away, the hardened outer shell is left behind as a hollow tube.
These features exist in places like Hawaii and Iceland where volcanic activity has created extensive underground tunnel systems.
On Earth, lava tubes are typically a few meters to a few tens of meters in diameter.
On the moon, where the gravity is only one sixth of Earth’s and ancient volcanic eruptions were far larger in scale.
The same process produced tubes on an entirely different scale.
In 2024, researchers from the University of Trento in Italy published findings confirming the existence of a massive underground cave beneath the Mar Tranquilatus region of the moon, the same area where Apollo 11 landed in 1969.
The team used radar data combined with advanced computer analysis techniques to look beneath the surface, sending radar waves down and analyzing how they reflected back from different underground structures.
What they found was a cave at least 100 meters deep and potentially hundreds of meters wide.
one of what they believe is a network of similar structures distributed across the lunar surface.
The cave beneath Mar Tranquilatus appears to be part of a lava tube system, a remnant of the volcanic activity that shaped the moon’s surface billions of years ago.
The implications for human exploration are significant.
A natural underground cave on the moon would provide something that no surface structure can match.
Radiation shielding.
The lunar surface is constantly exposed to solar radiation, cosmic rays, and micromedorite impacts.
Any human habitat built on the surface would require heavy shielding to protect its occupants.
A cave cut into solid rock provides that shielding automatically with no construction required.
NASA’s own measurements have found that some areas just below the lunar surface maintain a remarkably stable temperature of around 17° C regardless of what is happening at the surface above.
In the context of a world where surface temperatures swing by 250° between day and night, a natural shelter that stays at a steady 17° is an extraordinary resource.
Engineers are already discussing the possibility of establishing the first permanent lunar base inside a lava tube rather than on the exposed surface.
But even a cave requires water.
And water on the moon leads us to the poles.
The moon barely tilts on its rotational axis, only about one degree compared to Earth’s 23°.
On Earth, that tilt is what creates our seasons.
On the moon, the near absence of tilt means that the sun never rises very high above the horizon anywhere near the poles.
In the deepest craters at the lunar south pole, the sun never rises above the crater rim at all.
Some of these craters are among the largest impact structures on the moon.
The Shackleton crater at the South Pole is over 20 km wide and more than 4 km deep.
The floor of Shackleton has not seen direct sunlight in billions of years.
The temperatures there stay aroundus 200° C.
In that permanent ancient cold, any water that arrived in the crater has nowhere to go.
It stays frozen.
In 2009, NASA deliberately crashed a rocket stage into a permanently shadowed crater near the lunar south pole and sent a following spacecraft through the debris cloud to analyze what the impact threw up.
The result was confirmation of water ice in the lunar soil, the first direct detection of water on the moon.
Subsequent analysis has suggested that the amount of water ice concentrated in the permanently shadowed regions of the lunar poles could be in the hundreds of millions of tons.
Some estimates run as high as 600 billion kg.
This is not water you could scoop from a lake.
It is microscopic ice crystals mixed into the lunar regalith frozen in place for billions of years.
Extracting it would require drilling into the soil and heating it to release water vapor, then capturing that vapor before it escapes back into the vacuum of space.
The engineering challenges involved are significant.
But the resource value is enormous.
Water on the moon is not just for drinking, though that matters.
Water can be split into hydrogen and oxygen through electrolysis using solar power.
And hydrogen and oxygen are rocket propellant.
A lunar base with access to water ice could manufacture its own rocket fuel on the moon, turning the lunar south pole into a refueling stop for missions heading deeper into the solar system.
Launching from the moon requires far less energy than launching from Earth because the moon’s gravity is only one sixth as strong.
A rocket leaving the moon to head to Mars or the asteroid belt needs far less fuel than the same rocket leaving Earth.
If that rocket can refuel at the moon using locally produced propellant, the economics of deep space exploration change completely.
The moon stops being a destination and becomes a departure point.
Now let us cross to Mars because some of what is happening there connects directly to the same questions we have been asking about the moon.
In 2017, NASA’s Mars Reconnaissance Orbiter photographed a region of Mars where the surface appeared to be riddled with holes.
Most of the holes in the image were relatively small, showing dark soil beneath a thin coating of frozen carbon dioxide.
But one hole stood apart from the rest in a way that drew immediate attention from researchers.
It was perfectly circular, approximately 100 m across, with a clearly defined crater ring around its edge.
And unlike the other holes in the image, it appeared to go straight down into an underground space of unknown size.
Scientists who studied the image believed the hole was created when a meteorite impact punched through a thin section of surface rock and opened an entrance into a much larger cave system below.
The cave itself, whatever size it turns out to be, would have been there long before the impact that opened it, carved out by ancient volcanic activity when Mars was geologically active billions of years ago.
Why does a hole in Mars matter? Because of what caves mean for life.
The surface of Mars today is one of the harshest environments in the solar system for biology.
There is no significant magnetic field to deflect incoming radiation from the sun and from space.
The atmosphere is extremely thin, providing almost no protection.
The surface is dry and bitterly cold.
Whatever life might have existed on Mars when the planet was warmer and wetter billions of years ago would have had enormous difficulty surviving on the surface today.
But underground is different.
Underground, rock provides shielding from radiation.
Underground, temperatures are more stable.
Underground, any water that exists in the form of ice or brines would be protected from the extreme cold and dryness of the surface.
The same logic that makes lunar lava tubes attractive for human habitation makes Martian caves attractive as potential refugees for microbial life, either surviving today or having left traces of its past existence in the rock.
In 2019, NASA produced a map showing more than 1,000 potential cave entrances scattered across the Martian surface identified from orbital imagery.
The scientific case for exploring those caves as priority targets in the search for life has grown steadily since then.
The European Space Ay’s Mars Express mission has also found evidence of ancient lava tubes beneath extinct volcanoes on Mars, extending the potential network of underground hollow spaces far beyond what any single photograph can show.
And then there is something else happening across the surface of Mars that scientists have been trying to understand for more than 50 years.
Approximately 2 million dark streaks run across the slopes, crater walls, and ridges of Mars.
These are called slope streaks, and they appear as long dark lines running downhill, as if something liquid had flowed down the slope and stained the rock beneath it.
When they were first photographed in the 1970s, nobody could explain what caused them.
For decades, the leading theory was that they were caused by some form of liquid water temporarily melting from ice and flowing briefly down slopes before refreezing or evaporating.
That theory was attractive because liquid water would have been the most exciting possible explanation.
Where there is liquid water, there is the possibility of life.
A study published using data from NASA’s Mars Reconnaissance Orbiter collected between 2006 and 2024 and covering approximately 2.
1 million individual slope streaks found that the water explanation does not fit.
The pattern of when and where new streaks form, combined with the seasons in which they appear, points to a completely different mechanism.
The streaks form primarily during periods of strong Martian winds in regions where loose surface dust has accumulated on slopes.
When the wind reaches a certain threshold speed, it begins to lift and move dust.
As the loose material on a slope becomes unstable, it slides downhill, revealing darker, less weathered rock beneath the surface layer, which appears as a dark streak from orbit.
It is essentially a dry dust avalanche triggered by wind, not a water flow at all.
The streaks fade over decades as new dust settles over them.
What makes this finding significant is not just correcting the water theory.
It is the scale.
The same study calculated that approximately 80,000 new slope streaks form on Mars every year.
Combined with the millions already existing across the surface, slope streaks collectively disturb enough dust that they may be one of the largest ongoing contributors to dust in the Martian atmosphere.
Martian dust affects everything.
Weather patterns, surface temperatures, how much sunlight reaches the ground, and the conditions that any future human colony would have to manage to survive.
Understanding where the dust comes from and how it moves across the planet is not just scientifically interesting.
It is directly relevant to planning human missions to Mars because dust storms have already threatened existing rovers and dust accumulation on solar panels is one of the primary limiting factors for longduration surface operations.
Put all of this together and what emerges is a picture of our nearest neighbors in space that looks almost nothing like the one most people carry in their heads.
The moon has a partially molten layer inside it that nobody predicted, composed of a mineral rich in titanium, somehow still warm after 4 and a half billion years.
Its surface is still cracking and shifting under temperature stress and small but real moonquakes.
Beneath its surface sit lava tubes large enough to shelter future human colonies.
And at its poles and craters that have not seen sunlight since before complex life existed on Earth.
There may be enough water ice to supply a permanent human presence and manufacture rocket fuel for missions beyond.
Mars has holes in its surface that open into underground cave systems that may be the best places in the solar system to search for evidence that life once existed somewhere other than Earth.
And across its slopes and crater walls, tens of thousands of dry dust avalanches unfold every year, slowly redistributing the planet’s surface in ways that will shape the environment for any humans who eventually go there.
None of this was in the textbooks a generation ago.
Some of it was not known 5 years ago.
The tools we have built and sent to these worlds are showing us that both of them have far more going on, far more complexity, far more activity, and far more potential than the word dead ever captured.
The moon is not dead.
Mars is not dead.
And the more precisely we look at both of them, the more this keeps turning out to be true.
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There’s one more thing worth adding to the moon story, and it connects the underground world to something completely unexpected that Apollo astronauts discovered when they came home.
When the astronauts returned from the moon in the late 1960s and early 1970s, they brought back something in addition to their rock samples and scientific data.
They brought back dust.
Lunar dust had worked its way into every fold of their equipment, into the creases of their suits, into the interior of the lunar module.
When that dust mixed with the oxygen inside the cabin, something unexpected happened.
The astronauts noticed a smell.
They described it as burning metal or gunpowder or fireworks.
It was strong enough to be immediately noticeable and unusual enough that multiple astronauts from different missions reported the same thing.
Lunar dust has nothing chemically in common with gunpowder or fireworks.
What it does have is a surface structure that makes it extraordinarily reactive.
The lunar surface has no atmosphere and no weather to smooth around the edges of dust particles.
Every grain is sharp, jagged, and irregular at the microscopic level, like tiny shards of broken glass rather than the rounded grains you would find in beach sand on Earth.
And because there is no air, no moisture, and no chemistry happening at the surface, those particles sit for billions of years in a kind of suspended reactive state, waiting.
The moment they come into contact with oxygen, which they had never encountered before the astronauts brought them inside, they react immediately and intensely.
That reaction produces the burning smell the astronauts noticed.
It also poses a genuine engineering challenge for future lunar explorers because the same reactivity that makes fresh lunar dust smell like fireworks also means it is abrasive enough to damage equipment seals and filters.
Engineers designing the suits, habitats, and machinery for Aremis missions are actively working on ways to manage lunar dust because the Apollo experience showed it gets everywhere and it is not a minor inconvenience.
Future explorers will almost certainly notice that same burning smell.
And now they will know exactly what they are smelling.
A world that has been waiting in chemical terms for billions of years for something to react with.
The moon, the Mars slope streaks, the lava tubes, the molten layer, the polar ice, all of it points toward the same conclusion.
The further we look, the more carefully we look, the more we find that words like dead, inactive, and unchanging were never accurate descriptions of any of the worlds in our solar system.
They were descriptions of the limits of what we could see at the time.
Every time we build better instruments and point them more carefully, the universe turns out to be more interesting than the previous description allowed for.
That is what makes this particular moment in space exploration worth paying attention to.
The tools exist right now to answer questions that have been sitting open for decades, and the answers consistently are turning out to be more surprising than the assumptions they replaced.
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Let us spend a moment on what extracting that lunar water ice would actually look like in practice.
Because the gap between confirming that water exists and actually using it is enormous and it is worth understanding clearly.
The water ice at the lunar south pole is not sitting in a lake or frozen river.
It is mixed into the regalith at concentrations that vary from location to location, sometimes as low as a fraction of a percent by weight in the soil.
Extracting it means digging or drilling into extremely cold material in a crater where temperatures stay around -200° C using equipment that has to function reliably in a temperature range that would cause most metals to become brittle and most lubricants to stop working.
The permanently shadowed craters where the ice is most concentrated are also by definition places where solar panels produce zero power.
Any operation inside the crater would need to be powered either by nuclear generators or by cables running from solar panels positioned on the sunlit crater rim high above.
NASA has identified certain ridge lines near the lunar south pole that receive nearly continuous sunlight because of the moon’s minimal axial tilt.
These areas, which researchers have called peaks of eternal light, sit close enough to the permanently shadowed craters that running power from one to the other is at least theoretically feasible.
The same combination that makes the South Pole challenging, permanent darkness next to near permanent sunlight, also makes it uniquely valuable.
A solar farm on a sunlit ridge, a mining and processing operation in the shadowed crater below, and a habitat in a nearby lava tube with natural radiation shielding represent a configuration that planners at multiple space agencies are treating as the baseline for what a long-term human presence on the moon could look like.
China’s Changi program is developing missions specifically aimed at investigating the South Pole region.
Japan and India have both sent missions to the South Pole in recent years.
Private companies including Firefly Aerospace and Blue Origin have contracts to deliver equipment and experiments to the lunar surface.
The Aremis program is planning crude missions to the south polear region with the goal of characterizing the ice deposits well enough to plan extraction operations.
The convergence of national space agencies and private companies all targeting the same part of the moon within the same decade reflects the same underlying calculation.
The lunar south pole contains resources that make a permanent human presence on the moon not just possible, but potentially self-sustaining.
The moon we thought we knew was a destination we had already visited and largely understood.
The moon we are discovering is a world that still has major secrets, is still geologically active in ways we underestimated, and may hold the resources that make everything beyond it more accessible.
That is a very different place from the dead gray rock of the old textbooks.
The better our instruments get, the more clearly that difference comes into focus.