In the early morning of 10 August 2025, a mountainside collapsed into the waters of Tracy Arm Fjord in southeastern Alaska.

“It’s like if you have a kid and they said they cleaned their room but really all they did was throw everything in the closet. As soon as you open that door, everything falls out.”

Nobody was harmed by the rockslide or tsunami, but cruise ships were scheduled to visit the fjord later that morning. If the collapse had happened just a few hours later, it could have been disastrous.

“While the [South Sawyer] Glacier is in the fjord, it’s supporting those valley walls, like the buttresses on a cathedral,” said Daniel Shugar, a geomorphologist at the University of Calgary who led the study. “As that glacier retreated over the last few decades, it retreated just past the spot that did fail. It’s like if you have a kid and they said they cleaned their room but really all they did was throw everything in the closet. As soon as you open that door, everything falls out.”

In other words, the glacier that carved the fjord in the first place was also holding its slopes in place, and the ice’s retreat under warming temperatures exposed rock that became vulnerable to crumbling. The proximate cause of the landslide might have been something else—as Shugar noted, rainfall is plentiful in that part of Alaska, which could have weakened the fjord’s walls further—but it might also have been a combination of small, individually insignificant factors. In any case, the removal of that glacial “closet door” was what made the collapse and tsunami possible.

The researchers shared their findings at a press briefing on Wednesday at the European Geosciences Union 2026 General Assembly.

Debuttressing and Slope Instability

Unlike Lituya Bay, which resulted from an earthquake, Tracy Arm provided very little seismic warning before the slope collapsed, requiring forensic work to determine what caused it.

Shugar noted that South Sawyer Glacier had retreated by roughly 500 meters in the spring of 2025 alone, on top of the general trend of shrinking and thinning over the decades. And it’s not alone: Interferometric synthetic aperture radar (InSAR) images taken by satellites indicate that many slopes in Alaska and beyond are in motion, pointing to potential future danger.

“Not every single one, but it seems like a huge majority of [shifting slopes] are above the lower parts of thinning glaciers,” Shugar said. He described this phenomenon as “debuttressing,” as in losing the glacial buttress holding a slope up. He added, “I think in the next 5 years or so, we’ll probably have a much better understanding of just how and how quickly slopes respond to that debuttressing.”

Threats, Hazards, and Climate Change

“We were unbelievably lucky that the [tsunami] occurred with the timing that it did, and not 5 hours later.”

Most tsunamis are set in motion by earthquakes and travel across the open ocean, wreaking their destruction when they reach shallower water near coasts; the word “tsunami” means “harbor wave” in Japanese. The Tracy Arm tsunami joined the ranks of other landslide-driven tsunamis, like the ones in Taan Fiord (Alaska) and Dixon Fjord (Greenland), in being linked to human-driven climate change. Beyond the immediate impact of the waves, this category of hazard requires rethinking potential risks from abrupt catastrophes like debuttressing as well as slower effects such as sea level rise.

“The risk to any particular cruise ship [from a tsunami] on any particular day is very low,” Shugar said. “We were unbelievably lucky that the [tsunami] occurred with the timing that it did, and not 5 hours later. The risk certainly still could be increasing as we build new settlements, new mining camps, or new oil and gas infrastructure.”

Both Shugar and Stearns highlighted the importance of learning lessons from Tracy Arm and related events.

—Matthew R. Francis (@BowlerHatScience.org), Science Writer

Citation: Francis, M. R. (2026), The forensics of a skyscraper-sized tsunami, Eos, 107, https://doi.org/10.1029/2026EO260140. Published on 6 May 2026.

Text © 2026. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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The volcano Ol Doinyo Lengai in Tanzania is unique on Earth: Its lava is rich in carbon compounds that melt at significantly lower temperatures than typical silicon-rich lavas from other terrestrial volcanoes.

It is possible, however, that carbon volcanoes could exist elsewhere, including on exoplanets, or—as suggested in a recently published article in Icarus—perhaps even on planet Mercury.

Despite being known from antiquity, Mercury is very hard to study because of its closeness to the Sun. As a result, the best data so far were gathered within the past 20 years by NASA’s MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) probe. In particular, scientists identified mysterious pits they dubbed “hollows” scattered across Mercury’s surface. The hollows’ relatively bright appearance indicates they were formed in recent geological times, and could even be still forming today. The origins and geochemical makeup of these hollows are unknown.

“Mercury looks like the Moon a little bit, so we don’t expect large volcanoes,” said Maximilian Paul Reitze, a planetologist at Universität Münster’s Institut für Planetologie who is first author of the Icarus study. Without volcanic conditions like those on Earth or even on Jupiter’s moon Io, researchers expect Mercury to be largely geologically dormant. In other words, to explain hollows, “we need some volcanism under the conditions we expect on Mercury,” Reitze said.

Hence the interest in Ol Doinyo Lengai, known as the Mountain of God to the Maasai and Sonjo peoples. This volcano produces lava made up of carbonatites, igneous rocks composed of more than half carbon (and which are known to host critical minerals). These lavas flow at temperatures roughly 100°C lower than Mercury’s blazingly hot daytime temperature of 424°C. If the planet has a carbon-rich subsurface, as Reitze and his collaborators proposed, then the hollows could be Mercury’s version of Ol Doinyo Lengai.

This theory, however, has its skeptics.

“We know that there is carbon in [Mercury’s] crust, but the amount is very low,” said Paul Byrne, a planetary scientist at Washington University in St. Louis, who was not involved in the Icarus study. He also pointed out that the surface regions where carbon is most concentrated don’t correspond to higher concentrations of hollows. “For this to be some kind of carbon-based lava, it would imply a lot more carbon than we might think, given how widespread the hollows are.”

The Making of a Weird Planet

Mercury’s proximity to the Sun means that NASA’s Mariner 10 spacecraft provided humanity’s first-ever views when it flew by in 1974 and 1975. Three decades later, the MESSENGER mission was the first probe to orbit Mercury, mapping the planet’s full surface and turning up unexpected features like the hollows. The BepiColombo mission, a joint project of the European Space Agency and the Japan Aerospace Exploration Agency, is only the third mission ever to visit the planet, so when its two spacecraft settle into orbit in November 2026, it will almost inevitably reveal something unexpected, because it’s a weird planet.

“Basically, Mercury is a molten ball bearing wrapped in a thin blanket of rock.”

Unlike Earth, Mars, or the Moon, Mercury has a freakishly large core and a thin mantle.

“Basically, Mercury is a molten ball bearing wrapped in a thin blanket of rock,” Byrne said. “One explanation is that early in the planet’s life, either one large or several smaller impacts stripped the outer portion away.”

The question then becomes what got vaporized, and what was left behind, particularly when trying to understand hollows. Many planetary researchers proposed that sulfides in the mantle could drive volcanism, but Reitze had doubts.

“The problem with sulfides I see is that they’re stable up to 1,000°C or so, which cannot explain the explosive volcanism that’s needed to form those hollows,” he said.

Instead, he and his coauthors contacted a colleague working on Ol Doinyo Lengai, who obtained a sample of the lava for laboratory study while it was still molten. Because carbonatite lava reacts chemically with Earth’s air very quickly, the researchers needed to isolate it to understand how the unaltered materials might behave under conditions on Mercury, particularly infrared spectra that could be confirmed by the BepiColombo mission.

In the hypothesis proposed by Reitze and colleagues, impacts from meteorites heat the carbon-rich magma below Mercury’s surface, melting it and driving eruptions. The hollows, which are found frequently on the slopes of Mercury’s craters or their central peaks, are the remains of those eruptions. Over time, further meteorite bombardments and intense solar radiation destroyed older hollows, which is why the ones in MESSENGER data were all formed within the past 270 million years—a short time ago, geologically speaking.

“Anytime people have been confident about anything in planetary science, [planets have] shown you wrong.”

“The carbonatite angle is an interesting one, and I certainly wouldn’t rule it out,” Byrne said. “Anytime people have been confident about anything in planetary science, [planets have] shown you wrong. I’m certainly open to it, but is it the only explanation for all of the hollows? I am skeptical of that.”

Byrne and Reitze both dream of a future Mercury lander, a very challenging and expensive proposition nobody expects will happen soon. In the meantime, they agreed that BepiColombo data will help settle the question of whether the most Mercury-like place on Earth is a volcano in Tanzania.

—Matthew R. Francis (@BowlerHatScience.org), Science Writer

Citation: Francis, M. R. (2026), A unique African volcano could solve a mystery on Mercury, Eos, 107, https://doi.org/10.1029/2026EO260176. Published on 2 June 2026.

Text © 2026. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

The solar system is bathed in galactic cosmic rays: protons and atomic nuclei traveling, nearly at the speed of light, from all directions. Earth’s magnetic field and atmosphere shield us from most of this harmful radiation, but outside of that shelter, the bombardment is strong enough to prove a threat to astronauts.

But a new analysis of data from the Chang’e-4 lunar lander published in Science Advances revealed an extended cosmic ray shelter stretching from Earth at an unexpected angle at least as far as the Moon, though exactly how far is unclear. When the Moon passes through this shelter in its orbit of Earth, the lunar surface experiences a roughly 20% reduction in the galactic cosmic ray flux.

“We found Earth casts kind of a shadow in the galactic cosmic ray space,” said Robert F. Wimmer-Schweingruber, a space physicist at Kiel University in Germany. “This was unexpected, and to me that was the cool part of this paper.”

The surprise came in part because the shape of Earth’s magnetic field is well understood: It forms a strong protective region around the planet known as the magnetosphere, with a long “tail” shaped by the solar wind of charged particles streaming from the Sun.

If the magnetotail is like a person’s shadow cast behind them by sunshine, this newly discovered bubble would be like if that shadow extended to the front of the person as well.

“You would expect an effect inside the tail or as [the Moon goes] through the tail, but we find an effect of the tail ahead of the tail,” said Wimmer-Schweingruber. He noted that if the magnetotail is like a person’s shadow cast behind them by sunshine, this newly discovered bubble would be like if that shadow extended to the front of the person as well and tilted rather than lying along a line connecting Earth, the Sun, and the Moon.

“The observed region of reduced [galactic cosmic ray] flux on the sunward side of the Moon’s orbit outside the geomagnetic field where it is compressed by the solar wind is unexpected,” Brian Flint Rauch wrote in an email. Rauch, a cosmic ray physicist at Washington University in St. Louis who was not involved in the Chang’e-4 study, added that any reduction in cosmic ray exposure is noteworthy for potential astronauts on the Moon.

A 20% decrease in flux during part of the lunar orbit is unlikely to make a large difference in determining when it’s safest for astronauts go out onto the lunar surface. But it might help guide individual decisions in the moment because while spacesuits won’t protect astronauts from cosmic rays, the metal of a habitat or lander would.

Shelter from the Storm

The China National Space Administration’s Chang’e-4 spacecraft was the first successful mission to the lunar farside, landing in the Von Kármán crater on 3 January 2019. As part of its suite of scientific instruments, the probe carried the Lunar Lander Neutron and Dosimetry experiment (LND) developed by Wimmer-Schweingruber and collaborators at Kiel University in an astonishingly rapid 18 months. This detector was designed in part to gauge conditions for human exploration by measuring the radiation on the Moon’s surface, including cosmic rays.

LND collected data between January 2019 and January 2022. Though Apollo astronauts carried radiation dosimeters, those instruments did not provide detailed information about fluctuations in exposure, making LND the primary source for such information from the lunar surface. For that reason, it provided the best data on galactic cosmic rays, which consist mostly of protons accelerated to nearly the speed of light in the remnants of supernovas.

Measurements show the ambient radiation dose on the lunar surface is more than twice as high as on the ISS and nearly 200 times as high as on Earth.

These protons arrive in the solar system from every direction, often undeflected by the magnetic fields of stars or planets. However, Earth’s magnetosphere is strong enough to repel many galactic cosmic rays in low orbit, where the International Space Station (ISS) resides. Meanwhile, measurements show the ambient radiation dose on the lunar surface is more than twice as high as on the ISS and nearly 200 times as high as on Earth, which is a matter of concern for long-term human presence on the Moon.

All of these reasons are why everyone was surprised when LND data revealed Earth’s magnetic protection extends far beyond the magnetosphere and at an angle to the line connecting Earth and the Sun. Lead author Wensai Shang of Shandong University in Weihai, China, worked out that the angle corresponds to the twisting of the Sun’s magnetic field.

“As the Sun rotates, it pulls the solar wind along the solar magnetic field,” Wimmer-Schweingruber said. “That produces a spiral.” Apparently, an unanticipated interaction between this twist in the solar magnetic field and Earth’s magnetic field produces the cosmic ray shelter revealed by LND.

Wimmer-Schweingruber noted that he was extremely skeptical that such results were possible at first. He warned Shang, a graduate student he worked with, that he might be wasting his time looking for cosmic ray anomalies in the Chang’e-4 data. It was only after Shang provided ironclad analyses ruling out other possibilities that he was swayed.

With the LND instrument shut off, researchers need other sources of data to continue the work. Wimmer-Schweingruber expressed particular interest in understanding how cosmic rays produce secondary radiation—especially neutrons, which are very dangerous to humans—when they impact the lunar soil. In the meantime, the general understanding of the radiation environment provided by Chang’e-4 shows we still have some surprises in store as humans explore the solar system.

—Matthew R. Francis (@BowlerHatScience.org), Science Writer

Citation: Francis, M. R. (2026), Moon mission data reveal unexpected cosmic ray “shadow,” Eos, 107, https://doi.org/10.1029/2026EO260137. Published on 4 May 2026.

Text © 2026. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.