geology

webb-telescope-spots-hints-that-eris,-makemake-are-geologically-active

Webb telescope spots hints that Eris, Makemake are geologically active

astronomy, dwarf planet, Eris, geology, Kuiper belt, Makemake, planetary science, Science / /
Image of two small planets, one more reddish, the second very white.

Enlarge / Artist’s conceptions of what the surfaces of two dwarf planets might look like.

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.

While they would have started off hot due to the process by which they formed, their small size means a large surface-to-volume ratio, allowing internal heat to radiate out to space relatively quickly. Since then, any heat has come from rare collision events or the decay of radioactive isotopes.

Yet New Horizons’ visit to Pluto made it clear that it doesn’t take much heat to drive active geology, although seasonal changes in sunlight are likely to account for some of its features. Sunlight is less likely to be an influence for worlds like Makemake, which orbits at a distance one and a half times Pluto’s closest approach to the Sun. Eris, which is nearly as large as Pluto, orbits at over twice Pluto’s closest approach.

Sending a mission to either of these planets would take decades, and none are in development at the moment, so we can’t know what their surfaces look like. But that doesn’t mean we know nothing about them. And the James Webb Space Telescope has added to what we know considerably.

The Webb was used to image sunlight reflected off these objects, obtaining its infrared spectrum—the amount of light reflected at different wavelengths. The spectrum is influenced by the chemical composition of the dwarf planets’ surfaces. Certain chemicals can absorb specific wavelengths of infrared light, ensuring they don’t get reflected. By noting where the spectrum dips, it’s possible to figure out which chemicals are present.

Some of that work has already been done. But Webb is able to image parts of the spectrum that were inaccessible earlier, and its instruments are even able to identify different isotopes of the atoms composing each chemical. For example, some molecules of methane (CH4) will, at random, have one of their hydrogen atoms swapped out for its heavier isotope, deuterium, forming CH3D. These isotopes can potentially act as tracers, telling us things about where the chemicals originally came from.

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It’s a fake: Mysterious 280 million-year-old fossil is mostly just black paint

Archaeology, forgeries, fossils, geology, paleontology, Science, Tridentinosaurus antiquus / /

A cautionary tale —

The long bones of the hind limbs appear to be genuine. The rest? Not so much.

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image of a reptilian fossil in a rock

Enlarge / Discovered in 1931, Tridentinosaurus antiquus has now been found to be, in part, a forgery.

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.

Yet the fossil had never been carefully analyzed using modern analytical techniques, according to co-author Valentina Rossi of University College Cork in Ireland. “The fossil is unique, so this poses some challenges, in terms of analysis that we can do when effectively we cannot afford to make any mistakes, i.e., damaging the fossil,” Rossi told Ars. “Previous preliminary studies were carried out in the past but were not conclusive and the results not straightforward to interpret. The incredible technological advancement we are experiencing in paleontology made this study possible, since we can now analyze very small quantities of precious fossil material at the molecular level, without the risk of damaging the whole specimen.”

The fossil under normal light (left) and under UV light (right).

Enlarge / The fossil under normal light (left) and under UV light (right).

Valentina Rossi

Rossi et al. focused on the dark body outline believed to be carbonized soft tissue for their analysis. This involved photographing the fossil—plus some fossilized plants found in the same area—in both white light and UV light, and using those images to build a photogrammetric map and 3D model. They also took minute samples and examined them with scanning electron microscopy, micro X-ray diffraction, Raman spectroscopy, and ATF-FTIR spectroscopy.

The entire specimen, both the body outline and the bones, fluoresced yellow under UV light; the plant specimens did not. But coatings like lacquers, varnishes, glues, and some artificial pigments do fluoresce yellow under UV light. There was no evidence of fossilized melanin, which one might expect to find in preserved soft tissue. Also, fossils with preserved soft tissue are typically flattened with little topography; the T. antiquus specimen showed a lot of topographical variation in the dark outline areas.

The authors thought this was consistent with some kind of mechanical preparation, perhaps to (unsuccessfully) expose more of the skeleton. They concluded that one or more layers of some kind of coating had been applied to the body outline and the bones. The granular texture of what had been presumed to be soft tissue was more consistent with manufactured pigments used in historical paintings—specifically, “a manufactured carbon-based pigment mixed with an organic binder,” i.e., bone black paint. Conclusion: T. antiquus is a forgery and scientists therefore should be wary of using the specimen in comparative phylogenetic analysis.

Tridentinosaurus antiquus.” height=”428″ src=”https://cdn.arstechnica.net/wp-content/uploads/2024/02/fakefossil2-640×428.jpg” width=”640″>

Enlarge / Valentina Rossi with an image of Tridentinosaurus antiquus.

Zixiao Yang

How could scientists have presumed the dark outline of carbonized soft tissue for so many decades? “This fossil was discovered in 1931 and back then fossils were treated very differently than today,” said Rossi. “Application of paints, consolidates and lacquers on fossil bones was the norm, because that was the only way to protect the specimens for further deterioration. It was also sometimes to embellish specimens by making them sleek and shiny. Unfortunately, in the case of Tridentinosaurus, the mechanical preparation did most of the damage and then the application of a black paint created the illusion of a lizard-like animal impression on the surface of the rock.”

This analysis also casts doubt on the validity of the fossil’s assigned taxon, which was based on observations of the body proportion and measurements of limbs, neck, and abdomen. Part of the fossil, at least, appears to be genuine—the long bones of the hind limbs—but that doesn’t mean it will be easier now to determine species or where the specimen fits in the fossil record. “The bones that are recognizable appear to be very poorly preserved, so it might be very difficult to extrapolate any information,” said Rossi. “But perhaps the discovery of new fossil material from the same area where this specimen was found might help identify this ancient animal.”

So how can paleontologists prevent this kind of error from happening in the future? Rossi recommends reporting such finds via scientific journals with a detailed explanation of the methods that were used to characterize the surface materials on both the fossil and the rock. “It’s important to be aware that certain practices are not acceptable anymore, and not just because it creates—whether intentionally or by genuine mistake—misinformation and distorts our perception of a specimen,” said Rossi. “But also because the fossil will be irreparably damaged, and we might have lost key information about the original aspect and preservation state of the fossil.”

Paleontology, 2024. DOI: 10.1111/pala.12690  (About DOIs).

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What would the late heavy bombardment have done to the Earth’s surface?

asteroids, craters, Earth science, geology, Impacts, planetary science, Science, tsunamis / /

Under fire —

Early in Earth’s history, bombardment by enormous asteroids was common.

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Image of a projection of the globe, with multi-colored splotches covering its surface.

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.

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.

Unfortunately, there’s little obvious evidence in the rock record of these impacts before about 3.5 billion years ago. So scientists like Marchi can look to the Moon to estimate the number of objects that must have collided with Earth.

Armed with the size and number of impactors, Marchi and colleagues built a model that describes, as a function of time, the volume of melt this battering must have produced at the Earth’s surface. Magma oceans were in the past, but impactors greater than 100 kilometers in diameter still melted a lot of rock and must have drastically altered the early Earth.

Unlike smaller impacts, the volume of melt generated by objects of this size isn’t localized within a crater, according to models. Any crater exists only momentarily, as the rock is too fluid to maintain any sort of structure. Marchi compares this to tossing a stone into water. “There is a moment in time in which you have a cavity in the water, but then everything collapses and fills up because it’s a fluid.”

The melt volume is much larger than the amount of excavated rock, so Marchi can calculate just how much melt might have spilled out and coated parts of the Earth’s surface with each impact. The result is an astonishing map of melt volume. During the first billion years or so of Earth’s history, nearly the entire surface would have featured a veneer of impact melt at some point. Much of that history is gone because our active planet’s atmospheric, surface, and tectonic processes constantly modify much of the rock record.

Balls of glass

Even between 3.5 and 2.5 billion years ago, the rock record is sparse. But two places, Australia and South Africa, preserve evidence of impacts in the form of spherules. These tiny glass balls form immediately after an impact that sends vaporized rock skyward. As the plume returns to Earth, small droplets begin to condense and rain down.

Spherule bed from impact S3 in drill core. Here, S3’s spherule beds were deposited in deep enough water to not be diluted by other detritus.” data-height=”2560″ data-width=”1735″ href=”https://cdn.arstechnica.net/wp-content/uploads/2024/01/Image2-IMG_1552-scaled.jpg”><span class=Spherule bed from impact S3 in drill core. Here, S3’s spherule beds were deposited in deep enough water to not be diluted by other detritus.” height=”1446″ src=”https://cdn.arstechnica.net/wp-content/uploads/2024/01/Image2-IMG_1552-980×1446.jpg” width=”980″>

Enlarge / Spherule bed from impact S3 in drill core. Here, S3’s spherule beds were deposited in deep enough water to not be diluted by other detritus.

Nadja Drabon, Harvard

“It’s remarkable that we can find these impact-generated spherule layers all the way back to 3.5 billion years ago,” said Marchi.

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