Astrum Space - We Found Something on Mercury That No One Expected

Episode Date: September 5, 2026

Mercury makes no sense. It’s the closest planet to the Sun, yet parts of its surface are freezing cold. It’s so close to Earth, yet almost impossible to reach. And while its surface looks completely dead, its interior tells a very different story. In this video, we’ll explore what the BepiColombo probe has discovered on Mercury’s surface so far, and the unexpected surprises found hiding deep below.▀▀▀▀▀▀Try Brilliant’s new interactive tutor for free and get 20% off an annual Premium subscription at https://brilliant.org/astrum/▀▀▀▀▀▀Astrum's newsletter has launched! Want to know what's happening in space? Sign up here: ⁠https://astrumspace.kit.com⁠A huge thanks to our Patreons who help make these videos possible. Sign-up here: ⁠https://bit.ly/4aiJZNF

Two and five Canadians will hear the words, you have cancer. That's why every step and dollar raised matters. On September 19th, join thousands in Toronto for the Princess Margaret Cancer Foundation Walk. Challenge yourself, friends, and family to walk 21 kilometers in support of life-saving research. Together, we can carry the fire and help create a world free from the fear of cancer. Register today at pmcfwalk.ca.ca. New from Nespresso. Blend wellness into your coffee routine with a coffee plus range infused with functional benefits.

Choose the coffee you love with added B vitamins, like coffee plus B12 to help support immune function, and coffee plus B6 to keep your day moving. Or go with the flow and choose ginseng delight. Our new double espresso with ginseng extract. Whatever lies ahead, don't change your morning. Let your morning change you. Discover coffee plus on Nispresso.com. Mercury is a planet full of contradictions.

How can a rocky world so close to the sun harbor some of the coldest places in the solar system? How can the closest planet to us, on average, have an orbit harder for us to send probes into than Jupiter's? And how can a planet that looks this dead on the surface be geologically active? In many ways, Mercury makes no sense. sense. But that might be about to change. As Bepi Colombo prepares to enter into orbit around Mercury

after not one or two, but six flybys, it's time to take stock of what we've learned about this strange world over the last few years and start to unravel some of those mysteries. And it's a good thing too, because this small, scorch planet may be our key to understanding other rocky planets across the galaxy and beyond. I'm Alex McColgan and you're watching Astrum. Join me today as we uncover the secrets hiding in Mercury's strange craters, explore how its magnetic field could be influenced by diamonds, and reveal why this minuscule planet in our own backyard

could help us understand exoplanets thousands of light years away. We've only been to Mercury twice, making it the least visited terrestrial planet in our solar system. The first craft to visit was NASA's Mariner 10, which performed three flybys between 1974 and 1975. The second was at the start of the century with NASA's messenger mission, which became the first probe to enter into orbit around the planet. And now, Debbie Colombo is on its way.

It has been threading its way across the inner solar system since 2018, traversing more than 8.5 billion kilometers to get there. That's roughly twice the distance. between Earth and Pluto are their closest. But isn't Mercury basically the same as our moon? Why bother traveling so far to visit it? Three times if we have an analog in our backyard. Well, despite being a rocky, heavily created mass,

Mercury doesn't actually share too much at all with our moon, meaning it warrants its own studies. For starters, it is the only rocky planet besides Earth with a global magnetic field. and we still don't really know how it works. Studying it could help us understand not only our own magnetic field, but also possible magnetic fields on exoplanets in other star systems. One of Messenger's key findings was a much higher-than-expected abundance of volatile materials

such as chlorine, sulfur, and potassium on Mercury's surface. The discovery that Mercury might be richer in volatiles than even Mars through a spanner into our theories of solar system formation. Since solar winds are much stronger closer to the sun, we expected these volatiles to be stripped away on Mercury, but to have survived on Mars. So why does the opposite appear to be true? What implications does that have about our theories of solar system formation?

And how can those be corroborated or rejected by exoplanet findings? In order to get those answers, there was no way around it. we had to get back to Mercury. But as with many things, that is easier said than done. Mercury sits so deep in the Sun's gravitational sphere of influence that if you fired a spacecraft straight at it, the pull of the Sun would accelerate it until it was going far too fast to be captured by Mercury's relatively tiny gravitational pull.

So in order for a spacecraft to successfully enter into orbit, you have to slow it down enough so that it matches Mercury's 80s, 8-day orbital period. To do that, Bepicolombo has relied on 9 flybys of Earth, Venus and Mercury to steer its course and slow it down enough to be able to enter orbit around the rocky planet. These flybys have also been incredible photo and measurement opportunities ahead of orbital insertion in November 26. Issa and Jaxa have already taken full advantage of these moments to collect mountains of data and images to help answer some of the of the most burning questions about Mercury. What does its surface actually look like? How young is it?

What is it made of? And what surprises are lurking at its poles? Let's find out. Two and five Canadians will hear the words you have cancer. That's why every step and dollar raised matters. On September 19th, join thousands in Toronto for the Princess Margaret Cancer Foundation Walk. Challenge yourself, friends, and family to walk 21 kilometers in support of life-saving research. Together, we can carry the fire and help create a world free from the fear of cancer. Register today at pmcfwalk.ca.com.com. New from Nespresso. Blend wellness into your coffee routine with a coffee plus range infused with functional benefits. Choose the coffee you love with added B vitamins, like coffee plus B12 to help support immune function.

and coffee plus B6 to keep your day moving. Or go with the flow and choose ginseng delight. Our new double espresso with ginseng extract. Whatever lies ahead, don't change your morning. Let your morning change you. Discover coffee plus on espresso.com. Making exciting discoveries always feels good is the kind of thing that encourages kids to be scientists in the first place.

But sadly, that joy of discovery isn't always conveyed very well in a traditional classroom. setting. School can be hectic and overcrowded, and it can be easy for children to be left by the wayside if they don't understand something. If that feels familiar, then you might want to take a look at the solution offered by Brilliant, the sponsor of today's video. Brilliant's online interactive learning platform helps kids from fifth grade through to college

experience that joy of discovery across a range of maths, science, and programming subjects, but doesn't ever leave them floundering by themselves. built-in tutor, Koji, is always there to guide your child's learning. When I had a question in one of Brilliant's interactive learning exercises, Koji gave me hints and even drew on my screen to highlight key pieces of information I might have missed, clues to help me solve the puzzle myself. As a learner, having that kind of guidance at the right time has been invaluable for me. So why not awaken your child's inner scientist, mathematician or programmer by scanning my QR code or follow my link in the description below to try Brilliant for free. My viewers can even get

20% off a premium annual subscription to unlock all of Brilliant's courses. So, give it a try. But how did Bepi Colombo do in its own search for answers about Mercury? On the 4th of September 24, Beppe Colombo skimmed past Mercury at an altitude of just 165 kilometers above the surface. This was the fourth time it undertook one of these flybys, each getting it closer than before. You can see some of the discoveries from the first few in my last Beppi Colombo video here. As Beppe Colombo pulled away, its monitoring cameras captured something that immediately caught scientists' attention. A massive, perfectly round crater called a peak ring basin. Peak ring basins are some of the strangest landforms in the solar system. They're enormous. The ones on

Mercury measured between 130 and 330 kilometers across and are created by powerful asteroid or comet impacts. They strike the planet to such force that the ground itself rebounds, creating a ring of mountain peaks on the crater floor. You can think of it like a geological shockwave frozen in stone. Now, the existence of these peak ring basins wasn't new information, but these images were the first to showcase them in such high resolution and from so close up. Take a look at this. This is the Vivaldi crater, measuring 230 kilometers across. Because Bepi Colombo approached from

the night side, it managed to capture this dramatic photo emphasizing its terrain thanks to the shadows of the sunrise below. And for the first time, scientists got a glimpse at the visible gap in the ring of the peaks, where ancient lava flows would have entered and flooded the crater. Just a few minutes later, Beppe Colombo snapped a photo of another Peekering Basin, which had not yet been named. Since it came into such clear view, David Rothery, Professor of Planetary Geosciences at the UK's Open University, and part of the Beppi Colombo imaging team, decided to name it in case it would be of interest to Mercury Scientists in the future. And so, the 155-kilometer-wide crater was dubbed Stoddard, after the New Zealand.

painter, Margaret studded. Mercury's surface was littered with these formations, making them one of the highest priority targets for Bepi Colombo to investigate once it slots into orbit around the planet. By analysing the material in the peak ring, we can get a better idea of what Mercury's subsurface is made of, which could inform our theories on how rocky planets and exoplanets form. But this wasn't the only strange surface marking, Bepi Colombo observed. Three months later, on the 1st of December, 2024, it swung by the planet again, and for the

first time in history captured its surface in mid-infrared light, and what it revealed, completely flipped a decade's old assumption about Mercury on its head. Researchers used the Mercury Radiometer and Thermal Infrared Spectrometer, or Mertis, to scan the surface of the planet in an attempt to better understand what it's made of. See, when a material is bombarded with mid-infrared wavelengths, the chemical bonds within the molecules absorbs specific frequencies of this light, causing them to vibrate in distinct ways. Because every molecule has a unique set of bonds, the resulting absorption pattern acts

as a definitive chemical fingerprint which can be cross-referenced with known substances. So for example, the chemical fingerprint of graphite looks like this, while the chemical fingerprint of sulfur looks like this. Mertis operates at wavelengths between 7 to 14 micrometers, the ideal range for fingerprinting rock-forming minerals. Harold Hesinger, the Mertes' principal investigator from the University of Munster, is optimistic. With Mertis, we are breaking new ground, and we'll be able to understand the composition, mineralogy and temperatures on mercury much better, he says.

And the image the team got back after analysis did not disappoint. The first thing the team noticed was the striking variation in the surface brightness. Some patches of Mercury's surface shine more intensely than others, shaped by differences in temperature or roughness. These variations could give us clues to how different parts of the planet evolved or how their geological activity might have differed in the past. Some variations are, of course, caused by differences in mineral composition, many of which differ greatly from anything we've seen on our home planet.

Since Mercury exists in an oxygen-poor environment, it has what researchers call a reduced geochemistry. In such environments, elements behave in ways that have almost no parallel on Earth. Mercury's rocks are rich in sulphur and other elements that flourish without oxygen, forming unusual minerals like iron and calcium sulfides. What Mercury's surface is made of, and why it's so dark, are two of the remaining mysteries Epi Colombo hopes to solve over the next few years. In fact, this unexpected chemistry has far-reaching consequences that might have been easy to overlook initially. On Mercury, we see

polished-looking lava planes spattered across the surface, and now we think this unusual characteristic could be actually the result of the unique chemistry of the planet itself. For example, on Earth, lava is built from silicon oxygen bonds that form long, sticky, polymer-like chains, which is why generally our larva is so viscous and flow so slowly. Longer molecules mean more opportunities for intermolecular forces that can tangle polymers together reducing flow. On mercury, however, since there is a lack of oxygen, sulfur bonds with silicon instead,

creating much shorter, less connected structures that flow more like maple syrup than earthly lava. This chemically modified, faster flowing lava may explain why Mercury's volcanic planes are so remarkably smooth. But there's an even bigger story hidden here. If Mercury's ancient volcanism looks fundamentally different at the atomic level, then when we search for signs of volcanic activity on other worlds, including worlds in other planetary systems,

we might be scanning for Earth-like signatures and walking right past alien geology just because it doesn't match our templates or assumptions. Once Epiclonvo reaches orbit, Mertis will produce a global mineral map of Mercury's surface at 500m meter resolution. That map will be unlike anything we've created for any other planet, and may force us to rethink our entire concept of planetary geology entirely. But these smooth planes aren't the only mystery left on Mercury's surface. Just over a month after the breakthrough mid-infrared images of Mercury's surface,

Pepe Colombo approached for one final flyby. On the 8th of January 2025, the spacecraft came within 295 kilometres of the planet's surface, flying directly over its north pole, giving us a completely new perspective of the rocky world. It looked almost straight down into craters that, despite being closer to the sun than any other planet, have never seen sunlight. The rims of craters like Prokofiev, Kandinsky, Tolkien, and Gordema are nearly 5km as tall, high enough to permanently block the sun's rays from ever reaching their floors. And because Mercury has almost no axle tilt and no atmosphere to redistribute the heat,

those floors turn into cold traps that are among the coldest places in the entire solar system. Even though surrounding polar regions can reach up to 226 degrees Celsius, marked here in red, the coal traps, marked in blue, stay at a glacial minus 100. 128 degrees Celsius. And even more shockingly, there's tentative but tantalizing evidence that some of these very craters might contain frozen water. How it got there is one of Mercury's most compelling mysteries, and one will come back to a little later. But first, here's something else hiding in plain sight on Mercury's surface, something that suggests this dead planet

might not be so dead after all. For decades, everyone assumed Mercury was an ancient scarred rock baking in the sun. Whatever violence had marked its surface was surely billions of years old. But a new 2026 study led by Valentin Bickel from the University of Bern found something in the planet's crust that flipped this assumption completely on its head. Even though Messenger was decommissioned in 2015, researchers are still sifting through its data more than a decade later. And thanks to new data analysis techniques and better technology,

new findings are still emerging. For example, we now think that Mercury's surface might actually be geologically active and as young as a few hundred thousand years old in some places. You see, scattered across Mercury's surface are hundreds of bright streaks called Linear, running down into the steep inner slopes of craters. They're hundreds to thousands of metres long, less than 20 metres tall, and they appear geologically young. Their edges are crisp and no small craters have formed on top of them.

Whatever made them, it didn't happen in the distant past. These are recent scars. Scientists had noticed them in messenger data before, but had so far not been able to explain them. So Bickle and his team decided to apply machine learning to analyze 112,000 high-resolution messenger images, systematically analyzing 402 linear and for any patterns that might emerge. We have these modern data science approaches now, machine learning, deep learning that help us look into all those old data sets and find completely new science discoveries in them, Bickle said. And what they found was striking. 90% of Linnaei

are located within craters and they show a strong preference for the equator-facing side of crater slopes, the side that receives the most direct sunlight. That asymmetry was key to developing a new theory to explain their formation. Bickle proposed that volatile substances, sulfur and other light elements, are trapped beneath Mercury's thin volcanic crust. When a meteorite punches through that crust and creates a crater, it exposes the volatile rich layer underneath.

Solar radiation then warms the exposed material, driving those volatiles to the surface, where they drip down the crater walls and leave behind. behind the characteristic bright streaks. It will explain why the streaks are mainly seen on the sun-facing side of the craters and why they appear as newer features. If this is true, a planet we'd assume to be geologically dead is actually alive and kicking, and continuously losing material from its interior in an active, ongoing process. So what exactly is going on inside Mercury?

To really understand what's driving this planet, we need to look deeper, all the way down to its core. And what better way to do that than by measuring the planet's magnetic field? Luckily, PEPI Colombo has already done so. But alongside the conventional magnetosphere map, arose a few surprises too. Mercury's core is a bit of an enigma. It takes up about 85% of the planet's radius, and yet only generates a magnetic field one. percent the strength of Earth's. It's also slightly off-center, tilted away from the planet's

geographic equator in a way that no existing model fully explains. Plus, the magnetosphere is so tiny, it only took the spacecraft 30 minutes to fly through it. So, why does the magnetic field even matter? Well, for starters, it's a way to probe what might be concealed within the depths of Mercury's core directly. A planet only generates a magnetic field if it has a power. partially molten, electrically conducting core that's actively churning, which Mercury does. In fact, in 2024, a team of researchers led by Yongshian Tzu found that Mercury might have a layer of diamonds between its core and its mantle. They recreated the crushing pressures and temperatures of Mercury's deep mantle in the lab

and found that conditions at the boundary with Mercury's core are just right for carbon to crystallize into a solid layer of diamond. anywhere from a few hundred metres to 15 kilometres thick. That's right, diamonds. It might sound outlandish, but the model fits the data. Mercury's surface is unusually rich in carbon, mostly as graphite, and we think much more is locked away inside. Under the right mix of pressure, temperature,

and mercury's unusually high sulfur content, that carbon could take the form of diamond rather than graphite. Remember, Mercury's magnetic field is generated by the churning of its molten core, the convection current driven by hot liquid rising, cooling at the top and falling back down again. Diamond happens to conduct heat better than almost any other material we know of, so a diamond shell wrapped around the core could influence how the planet cools, and ultimately the magnetic field itself. While we can't slice the planet open to reveal the diamonds inside, we can't slice the planet open to reveal the diamonds inside,

we can do the next best thing. Send Beppe Colombo to sweep the magnetosphere for clues. During its flybys, it activated its Mercury plasma particle experiment, an instrument designed to examine the particles moving through Mercury's magnetosphere. We sampled the type of particles, how hot they are and how they move, enabling us to clearly plot the magnetic landscape during this brief period, said Lina Hadid, formerly of Issa and now at the level. Boitre de Physique as Plasmas at Paris University. Two in five Canadians will hear the words you have cancer.

That's why every step and dollar raised matters. On September 19th, join thousands in Toronto for the Princess Margaret Cancer Foundation walk. Challenge yourself, friends and family to walk 21 kilometers in support of life-saving research. Together, we can carry the fire and help create a world free from the fear of cancer. Register today at pmcfwalk.ca. New from Nespresso. Blend wellness into your coffee routine with a coffee plus range, infused with functional benefits. Choose the coffee you love with added B vitamins, like coffee plus B12 to help support immune function,

and coffee plus B6 to keep your day moving. Or go with the flow and choose ginseng delight. Our new double espresso with ginseng extract. Whatever lies ahead, don't change your morning. Let your morning change you. Discover Coffee Plus on Nespresso.com The Mercury plasma particle experiment confirmed some expected magnetosphere structures, like the bouchok where the solar wind slams into the planet's magnetic bubble,

and the plasma sheet, that hot ribbon of charged gas streaming out behind mercury like a tail. But it also found something unexpected. The spacecraft detected a turbulent boundary layer at the edge of the magnetosphere, packed with particles spanning a wider energy range than anything ever previously recorded at Mercury. And more intriguingly, it found energetic, hot ions trapped near Mercury's equator, forming a ring current. But there's a problem. Given how small and compressed the magnetosphere is, a ring current like this shouldn't be possible here. On Earth, ring currents exist tens of thousands of kilometers above the surface, where there's enough space for particles to drift in stable loops.

At Mercury, since the magnetosphere is so small and compressed against the planet on the sun-facing side, the ring current would have to sit just a few hundred kilometres above the surface. But in this position, the particles don't have enough room to complete a stable orbit around the planet before crashing into it or getting swept away by the solar wind. So whether this ring is complete or partial is still being debated. But BepiColomba's findings could rewrite our understanding of how magnateospheres can look on rocky worlds close to their stars. It's also turned out that this finding could be key to understanding planets beyond our own solar system too. As our exoplanet catalogs have grown over the last decades, astronomers have started noticing something striking.

There seems to be a whole class of rocky worlds that share Mercury's enormous iron-rich core, making up a disproportionate fraction of the planet's total mass. They're called supermercuries, and we think they're quite rare, but we've identified a few already, like the two orbiting the same star, HD 23472, 127 light years away. Because Mercury's Magnetosphere is so compressed, it sits at the extreme end of what a planetary magnetic field can look like. That makes it ideal for stress testing our models

and understanding how much protection a magnetosphere can afford, or how it gets stripped away over time. Changing our understanding of this would redefine how close to a star the habitable zone of exoplanet systems could be, and might open up far more candidate planets than we currently consider, some of which might even have water on their surface. Speaking of which, remember those freezing cold craters on Mercury's North Pole? Well, we've suspected for a while now they might contain frozen water ice, which seems incredibly counterintuitive for a planet scorching in the sun. But perhaps the most surprising theory to come out of the last two years is how that water came to be there.

In the 1990s, Earth-based observations picked up anomalous bright radar reflections for Mercury's polar regions, the kind associated with water ice. Mercury's messenger mission, later confirmed vast deposits of frozen water are indeed preserved inside the cold traps of polar craters. But now, in 2006, a team of researchers led by planetary scientists Parvathy Prim think it might have been delivered on a water-rich comet or asteroid. The research has ran computer simulations to understand what kind of event might have deposited such stores onto the planet, and of all the possibilities, only a very slim configuration of variables yielded the result we actually see on the planet today.

The simulation predicted a single impact of more than 17 kilometers wide, traveling under 30 kilometers per second, would have been capable of such a feat. Slaving into the planet, it would have released an incomprehensible amount of energy, instantly vaporizing the water it was carrying, temporarily coating the planet in a vapor-based atmosphere in just over an hour. That dense cloud of water vapor was thickened, enough to partially shield itself from the sun's ultraviolet radiation, slowing the breakdown of water molecules and buying precious time. Over the following Mercurian day, which lasts nearly

six Earth months, the water vapor gradually migrated towards the poles, where it condensed and froze inside the permanently shadowed craters, layer by layer, creating the deposits we see today. This theory also helps explain something that has puzzled scientists for years, why Mercury's ice is so pure. If the deposits had been built up gradually over billions of years and from cometary dust and solar wind interactions, you'd expect them to be dirty, contaminated and mixed with other material. Instead, they're remarkably clean,

which is consistent with a single rapid delivery event rather than a slow accumulation. In just two years, Beppe Colombo has already rewritten what we thought we knew about one of the solar systems most overlooked. planets, and it has really only just arrived there. A world we assumed was dead is spewing volatiles from the inside out. Its alien chemistry is forcing us to rethink how we read volcanic activity anywhere in the universe. Its magnetosphere is defying our models, and even though

it's the closest to the sun, it stores frozen water in its poles, which are colder than almost every other part of the solar system. Come November 26, the real science begins. and Bepi Colombo's probes will build up something we have never had, a continuous evolving picture of Mercury, what is made of both on the surface and deeper inside, whether it is truly geologically alive or not, and where the polar ice might have come from. As Anne Pomeyer, experimental geophysicist at Carnegie Earth Science and Planets Laboratory put it in a universe full of rocky planets, the one that breaks all the rules might be the key understanding them all. As astronomers discover more rocky worlds around distant stars,

Mercury serves as a crucial benchmark, close enough to study, yet alien enough to challenge our ideas about how planets form and evolve. Mercury is so off. It has this huge core, weird chemistry and a magnetic field that doesn't quite add up. In a way, it's like an exoplanet in our own backyard. I have a feeling the next The next decade is the decade of Mercury. So sit tight, we are just getting started. Thanks for watching! If you've been enjoying Astrum's videos and want to help keep this channel thriving, I want

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I'll see you next time. Two and five Canadians will hear the words, you have cancer. That's why every step and dollar raised matters. On September 19th, join thousands in Toronto for the Princess Margaret Cancer Foundation walk. Challenge yourself, friends, and family to walk 21 kilometers in support of life-saving reasons.

Research. Together, we can carry the fire and help create a world free from the fear of cancer. Register today at pmcf walk.ca.ca.com.com. Advertising on Spotify with audio and display ads helps brands turn attention into results. Download the 2026 performance playbook and discover why Spotify belongs in your media plan.