We Found Something on Mercury That No One Expected

0:00This episode is brought to you by Facebook. So you were scrolling on Marketplace. And there it was. The bike you've been searching for. You sent a message, and it turned out the seller was super chatty, kind of funny, and an avid cyclist. The next thing you know, you're in a cycling crew. Well, a community cycling group. The thing about Facebook, you might find more than what you're looking for. From a browse to a bike ride, this summer find more on Facebook. This episode is brought to you by Google Chrome. You think you know a browser, but Gemini and Chrome? That's new. It can help you with practically anything on the web. Like restoring a vintage motorcycle from a 50-page restoration block. Or finally break down that long article you've had open for weeks. Gemini and Chrome is here for it. Ready to make anything online make sense? There's no place like Chrome. Check responses set up require compatibility and availability very 16+. Mercury is a planet full of contradictions.

1:00How can a rocky world so close to the sun? How are 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. But that might be about to change. As Beppy 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, scorched planet may be our key to understanding other rocky planets across the galaxy and beyond. I'm Alex McColligan and you're watching Astrum.

2:00Join 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 miniscule 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 of 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, Beppy Colombo is on its way. It has been threading its way across the inner solar system since 2018, traversing more than 8.5 billion kilometres to get there. That's roughly twice the distance between Earth and Pluto at their closest.

3:00But isn't Mercury basically the same as our moon? Why bother travelling so far to visit it? Three times if we have an analogue 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 SolarWinds are much stronger closer to the Sun, we expected these volatiles to be stripped away on Mercury, but to have survived on Mars.

4:05So 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 cooperated 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 find a spacecraft straight at it, the pole of the Sun would accelerate it until it was going far too fast to be captured by Mercury's relatively tiny gravitational pole. So in order for a spacecraft to successfully enter into orbit, you have to slow it down enough so that it matches Mercury's 88-day orbital period. To do that, Beppi Klombo 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.

5:06These flybys have also been incredible photo and measurement opportunities ahead of orbital insertion in November, 2026. Hecer and Jaxzer have already taken full advantage of these moments to collect mountains of data and images to help answer some 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! This episode is brought to you by Facebook. So you were scrolling on Marketplace, and there it was. The bike you've been searching for, you sent a message, and it turned out the seller was super chatty, kind of funny, and an avid cyclist. The next thing you know, you're in a cycling crew, well a community cycling group. The thing about Facebook, you might find more than what you're looking for. From a browse to a bike ride, this summer, find more on Facebook.

6:06This episode is brought to you by Google Chrome. You think you know a browser, but Gemini and Chrome? That's new. It can help you with practically anything on the web, like restoring a vintage motorcycle from a 50-page restoration block, or finally break down that long article you've had open for weeks. Gemini and Chrome is here for it. Ready to make anything online makes sense? There's no place like Chrome. Check responses set up require compatibility and availability varies 18 plus. 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 5th 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.

7:13Brilliant's 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 in the 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 Beppy Colombo do in its own search for answers about Mercury? On the 4th of September 2024, Beppy Colombo skimmed past Mercury at an altitude of just 165 kilometres above the surface. This was the 4th time it undertook one of these flybys, each getting it closer than before.

8:14You can see some of the discoveries from the first few in my last Beppy Colombo video here. As Beppy Colombo pulled away, its monitoring cameras captured something that immediately caught scientists' attention. A massive, perfectly round crater called a Peacering Basin. Peacering basins are some of the strangest landforms in the solar system. They're enormous. The ones on Mercury measured between 130 and 330 kilometres across, and then created by powerful asteroid or comet impacts. They strike the planet with 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 Peacering 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 213 kilometres across.

9:18Because Beppy 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 egg limbs 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, Beppy Colombo snapped a photo of another Peacering Basin, which had not yet been named. Since it came into such clear view, David Rotary, professor of planetary geosciences at the UK's Open University, and part of the Beppy Colombo Imaging team decided to name it in case it would be of interest to make recircitis in the future. And so, the 155 kilometres wide crater was dubbed studded, after the New Zealand painter, Margaret studded. Mercury surface was littered with these formations, making them one of the highest priority targets for Beppy Colombo to investigate once it slots into orbit around the planet.

10:19By analysing the material in the Peacering, 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 Beppy 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 use the Mercury radiometer and thermal infrared spectrometer, or Mertus, 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 absorb 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-reference with known substances.

11:26So, for example, the chemical fingerprint of graphite looks like this, while the chemical fingerprint of sulfur looks like this. Mertus operates wavelengths between 7 to 14 micrometers, the ideal range for fingerprinting rock forming minerals. Harold Heissinger, the Mertus' principal investigator from the University of Munster, is optimistic. With Mertus, we are breaking new ground, and will 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.

12:32Since 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 sulfur 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 Beppe-Klomo 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 lava is so viscous and flow so slowly.

13:34Longer 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, who might be scanning for Earth-like signatures and walking right past alien geology just because it doesn't match our templates or assumptions. Once Vepiclombo reaches orbit, Mertis will produce a global mineral map of Mercury's surface at 500 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.

14:43But these smooth planes aren't the only mystery left on Mercury's surface. Just over a month after the breakthrough made infrared images of Mercury's surface, Vepiclombo approached for one final flyby. On the 8th of January 2025, the spacecraft came within 295 kilometers 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 Gordemer are nearly 5 kilometers tall, high enough to permanently block the sun's rays from ever reaching their floors. And because Mercury has almost no axel 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.

15:45Even though surrounding polar regions can reach up to 226 degrees Celsius marked here in red, the cold traps marked in blue stayed at a glacial minus 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 the new 2026 study led by Valentin Bickel from the University of Ben found something in the planet's crust that flipped this assumption completely on its head.

16:49Even 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. There are hundreds, two thousands of meters long, less than 20 meters 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 Bickel and his team decided to apply machine learning to analyze 112,000 high-resolution messenger images, systematically analyzing 402 linear for any patterns that might emerge.

18:01We have these modern data science approaches now, machine learning, deep learning, that help us look into all those all data sets and find completely new science discoveries in them, Bickel said. And what they found was striking. 90% of linear 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. But asymmetry was key to developing a new theory to explain their formation. Bickel 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 trip down the crater walls and leave behind the characteristic bright streets. It would explain why the streets are mainly seen on the sun facing side of the craters, and why they appear as newer features.

19:09If 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, Bickelomo 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 1% the strength of Earth. It's also slightly off-center, tilted away from the planet's geographic equator, in a way that no existing model fully explains.

20:10Plus, 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 partially molten, electrically conducting core that's actively churning, which Mercury does. In fact, in 2024, a team of researchers led by Yongshian Tu 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 come. It's a way to make the Earth a planet for carbon to crystallize into a solid layer of diamond, anywhere from a few hundred meters to 15 kilometers thick. That's right, diamonds. It might sound outlandish, but the model fits the data.

21:11Mercury'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. The 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 do the next best thing. Send Beppi-Kolombo to sweep the magnetosphere for clues. During its flybyes, it activated its Mercury plasma particle experiment, an instrument designed to examine the particles moving through Mercury's magnetosphere.

22:14We sample 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 Lena Hadid, formerly of Issa, and now at the Labatoire de Physique, this plasma's at Paris University. This episode is brought to you by Facebook. So, you were scrolling on Marketplace, and there it was. The bike you've been searching for, you sent a message, and it turned out the seller was super chatty, kind of funny, and an avid cyclist. The next thing you know, you're in a cycling crew, well a community cycling group. The thing about Facebook, you might find more than what you're looking for. From a browse to a bike ride, this summer find more on Facebook. This episode is brought to you by Google Chrome. You think you know a browser, but Gemini and Chrome? That's new. It can help you with practically anything on the web, like restoring a vintage motorcycle from a 50-page restoration block, or finally break down that long article you've had open for weeks.

23:17Gemini and Chrome is here for it. Ready to make anything online makes sense? There's no place like Chrome. Check responses set up required compatibility and availability varies 18 plus. The Mercury Plasma Particle Experiment confirmed some expected magnetosphere structures, like the Bowshock, 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, the 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 kilometers above the surface.

24:35But in this position, 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. The Beppi-Klombas findings could rewrite our understanding of how magnetosphere can look on rocky worlds close to their stars. It also turned out that this finding could be key to understanding planets beyond our own solar system too. As our exoplanet catalogues 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 ion-rich core, making up a disproportionate fraction of the planet's total mass. They're called super-mirkries. And we think they're quite rare. But we've identified if you're already, like the two orbiting the same star, HD23472 127 light years away.

25:35Because 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 counter-intuitive for a planet scorching in the planet. 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 from Mercury's polar regions, the kind associated with water ice.

26:42Mercury's messenger mission later confirmed vast deposits of frozen water are indeed preserved inside the cold traps of polar craters. But now, in 2026, a team of researchers led by planetary scientists Parvathy Prim think it might have been delivered on a water-rich comet or asteroid. The researchers 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 70 kilometers wide, travelling under 30 kilometers per second, would have been capable of such a feat. So, landing 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 thick enough to partially shield itself from the Sun's ultraviolet radiation,

27:45salowing the breakdown of water molecules and buying precious time. Over the following Mercury and Day, which lasts nearly six Earth months, the water vapor gradually migrated towards the poles, where it condensed and froze inside the permanently shadow 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, Beppi Klambo 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, it spewed volatiles from the inside out.

28:49Its 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 2026, the real science begins, and Beppi Klambo'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 Pommier, experimental geophysicist at Carnegie Air Science and planets laboratory put it, in a universe full of rocky planets, the one that breaks all the rules might be the key to 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.

29:56Mercury 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 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 to ask you to take less than a minute to check out the Astrum Patreon. It's not just add free videos, but it's a way to make Astrum's videos less reliant on sponsors and algorithms. The link is below. Your membership directly helps ensure that future videos can stay independent, high quality and consistent, created for curiosity, not clicks. Thanks so much for considering it. I'll see you next time.

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