Enlarge / Artist's conceptions of what the surfaces of two dwarf planets might look like. (credit: SWRI )

Active geology—and the large-scale chemistry it can drive—requires significant amounts of heat. Dwarf planets near the far edges of the Solar System, like Pluto and other Kuiper belt objects, formed from frigid, icy materials and have generally never transited close enough to the sun to warm up considerably. Any heat left over from their formation was likely long since lost to space.

Yet Pluto turned out to be a world rich in geological features, some of which implied ongoing resurfacing of the dwarf planet's surface. Last week, researchers reported that the same might be true for other dwarf planets in the Kuiper Belt. Indications come thanks to the capabilities of the Webb telescope, which was able to resolve differences in the hydrogen isotopes found on the chemicals that populate the surface of Eris and Makemake.

Cold and distant

Kuiper Belt objects are natives of the distant Solar System, forming far enough from the warmth of the Sun that many materials that are gasses in the inner planets—things like nitrogen, methane, and carbon dioxide—are solid ices. Many of these bodies formed far enough from the gravitational influence of the eight major planets that they have never made a trip into the warmer inner Solar System. In addition, because there was much less material that far from the Sun, most of the bodies are quite small.

Enlarge / Discovered in 1931, Tridentinosaurus antiquus has now been found to be, in part, a forgery. (credit: Valentina Rossi)

For more than 90 years, scientists have puzzled over an unusual 280 million-year-old reptilian fossil discovered in the Italian Alps. It's unusual because the skeleton is surrounded by a dark outline, long believed to be rarely preserved soft tissue. Alas, a fresh analysis employing a suite of cutting-edge techniques concluded that the dark outline is actually just bone-black paint. The fossil is a fake, according to a new paper published in the journal Paleontology.

An Italian engineer and museum employee named Gualtiero Adami found the fossil near the village of Piné. The fossil was a small lizard-like creature with a long neck and five-digit limbs. He turned it over to the local museum, and later that year, geologist Giorgio del Piaz announced the discovery of a new genus, dubbed Tridentinosaurus antiquus . The dark-colored body outline was presumed to be the remains of carbonized skin or flesh; fossilized plant material with carbonized leaf and shoot fragments were found in the same geographical area.

The specimen wasn't officially described scientifically until 1959 when Piero Leonardi declared it to be part of the Protorosauria group. He thought it was especially significant for understanding early reptile evolution because of the preservation of presumed soft tissue surrounding the skeletal remains. Some suggested that T. antiquus had been killed by a pyroclastic surge during a volcanic eruption, which would explain the carbonized skin since the intense heat would have burnt the outer layers almost instantly. It is also the oldest body fossil found in the Alps, at some 280 million years old.

Enlarge / Each panel shows the modeled effects of early Earth’s bombardment. Circles show the regions affected by each impact, with diameters corresponding to the final size of craters for impactors smaller than 100 kilometers in diameter. For larger impactors, the circle size corresponds to size of the region buried by impact-generated melt. Color coding indicates the timing of the impacts. The smallest impactors considered in this model have a diameter of 15 kilometers. (credit: Simone Marchi, Southwest Research Institute)

When it comes to space rocks slamming into Earth, two stand out. There’s the one that killed the dinosaurs 65 million years ago (goodbye T-rex, hello mammals!) and the one that formed Earth’s Moon . The asteroid that hurtled into the Yucatan peninsula and decimated the dinosaurs was a mere 10 kilometers in diameter. The impactor that formed the Moon, on the other hand, may have been about the size of Mars. But between the gigantic lunar-forming impact and the comparatively diminutive harbinger of dinosaurian death, Earth was certainly battered by other bodies.

At the 2023 Fall Meeting of the American Geophysical Union, scientists discussed what they’ve found when it comes to just how our planet has been shaped by asteroids that impacted the early Earth, causing everything from voluminous melts that covered swaths of the surface to ancient tsunamis that tore across the globe .

Modeling melt

When the Moon-forming impactor smashed into Earth, much of the world became a sea of melted rock called a magma ocean ( if it wasn’t already melted ). After this point, Earth had no more major additions of mass, said Simone Marchi , a planetary scientist at the Southwest Research Institute who creates computer models of the early Solar System and its planetary bodies, including Earth. “But you still have this debris flying about,” he said. This later phase of accretion may have lacked another lunar-scale impact, but likely featured large incoming asteroids. Predictions of the size and frequency distributions of this space flotsam indicate “that there has to be a substantial number of objects larger than, say, 1,000 kilometers in diameter,” Marchi said.

Enlarge / The John C. Boyle Dam, one of the dams slated for removal. (credit: NOAA )

Wending its way from the Olympic Mountains to the Strait of Juan de Fuca, Washington’s Elwha River is now free. For about century, the Elwha and Gilnes Canyon Dams corralled these waters. Both have since been removed, and the restoration of the watershed has started.

The dam-removal project was the largest to date in the US—though it won’t hold that position for long. The Klamath River dam removal project has begun, with four of its six dams—J.C. Boyle, Copco No. 1, Copco No. 2, and Iron Gate—set to be scuppered by the end of the year, and the drawdown started this week. (In fact, Copco No. 2 is already gone .)

Once the project is complete, the Klamath will run from Oregon to northwestern California largely unimpeded, allowing sediment, organic matter, and its restive waters to flow freely downriver while fish like salmon, trout, and other migratory species leap and wriggle their way upstream to spawn.

Enlarge / Modeling has shown how material ejected from the Earth by a massive collision could have formed the Moon. Now the models are being used to look at what happened inside the Earth. (credit: NASA )

Seismic waves created by earthquakes as they travel through the planet's interior change speed and direction as they move through different materials. Things like rock type, density, and temperature all alter the travel of these waves, allowing scientists to gradually build up a picture of the Earth's crust and mantle, spotting things like the rise of plumes of hot mantle material, as well as the colder remains of tectonic plates that dropped off the surface of the Earth long ago.

There are some things that show up in these images, however, that aren't easy to explain. Deep in the Earth's mantle there are two regions where seismic waves slow down, termed large low-velocity provinces. This slowdown is consistent with the materials being higher density, so it's not really a surprise that they're sitting near the core. But that doesn't explain why there are two distinct regions of them or why they appear to contain material that has been there since the formation of the Solar System.

Now, a team of scientists has tied the two regions' existence back to a catastrophic event that happened early in our Solar System's history: a giant collision with a Mars-sized planet that ultimately created our Moon.

Enlarge (credit: MARK GARLICK/SCIENCE PHOTO LIBRARY )

Classic whodunit mysteries work because just about every character ends up being a murder suspect. The demise of non-avian dinosaurs is a lot like that. The Chicxulub impact and its aftereffects created a huge range of potentially lethal suspects. Whodunit? A giant fireball and massive tsunamis? Wild swings in the climate? Global wildfires? A blackened sky that shut down photosynthesis? All of the above?

Modeling these impacts, combined with data on the pattern of extinctions, has led to various opinions on what proved decisive regarding the extermination of so many species. In the latest look at the end-Cretaceous extinction, a team of scientists largely based in Brussels has revisited deposits laid down in the aftermath of the impact and found that much of the debris came from fine dust. When that dust is plugged into climate models, global temperatures plunge by as much as 25° C, and photosynthesis shuts down for almost two years.

Dust to dust

There was a lot going on in the atmosphere in the years after the impact. Debris thrown up by the impact would have re-entered Earth's atmosphere, burning up into fine rocky and sulfur-rich particles in the process. The heat generated by this process would have set off massive wildfires, adding a lot of soot to the mix. And all of that was churned up with the debris from the impact that stayed within the atmosphere.

Enlarge / Image showing a dust storm over the northern hemisphere of Mars. (credit: ISRO)

If the explorers from Journey to the Center of the Earth were to journey to the center of Mars instead, they definitely wouldn’t come across the subterranean oceans or live dinosaurs they encountered in the movie, but they would probably see something different from our planet’s core.

Earth has a mantle of rock that moves like a sluggish liquid. Beneath the mantle is a liquid iron outer core and solid iron inner core. Because Earth and Mars are both rocky planets, and might have even had similar surface conditions billions of years ago, does that mean we should expect the same interior on Mars? Not exactly.

When two teams of researchers used data from NASA’s InSight lander and other spacecraft to get as close to the core of Mars as they could in a lab, they found that the red planet is not much like Earth on the inside. Data from NASA’s InSight lander’s SEIS (Seismic Experiment for Interior Structure) project had previously suggested that Mars has a large core that is not very dense. But the new analysis, which included additional seismic signals, indicates that what was once thought to be the surface of the Martian core is actually a thick molten rock layer. The actual core of Mars is most likely much smaller.