A 400-million-year-old horsetail plant

 Horsetail plant produces water and looks like it came from space            

Researchers discovered that living horsetails act like natural distillation towers, producing bizarre oxygen isotope signatures more extreme than anything previously recorded on Earth, sometimes resembling meteorite water. By tracing these isotopic shifts from the plant base to its tip, scientists unlocked a new way to decode ancient humidity and climate, using both modern plants and fossilized phytoliths which preserve isotopic clues for millions of years. Water drawn through the hollow stem of a living Equisetum plant, has registered the most extreme oxygen isotope signature ever measured in any terrestrial material. The discovery stretches the known chemical limits of Earth’s water and forces scientists to reconsider how plants, fossils and even desert climates record the passage of evaporation. Along the smooth, jointed stem of a modern horsetail plant, water rises from the base and grows progressively stranger in its oxygen makeup. By sampling water from the bottom to the tip, Zachary Sharp, Ph.D., at the University of New Mexico demonstrated that the stem itself steadily concentrates heavy oxygen as moisture escapes into dry air. Values that began within a typical natural range at the base climbed to levels so enriched at the tip that they exceeded every prior terrestrial measurement. Because that chemical transformation unfolds inside a single plant rather than in an extreme environment, the finding demands a closer look at how evaporation reshapes water long before it reaches a leaf.

Horsetails act as extreme natural distillers, generating isotope patterns once thought impossible on Earth. These signatures, preserved in fossils, offer a novel way to probe ancient climate conditions. A research group at The University of New Mexico has identified how an unusual prehistoric plant may provide new ways to interpret Earth's ancient climate conditions. The study, titled "Extreme triple oxygen isotope fractionation in Equisetum," examines horsetails, which are hollow-stemmed plants which have existed on the planet for more than 400 million years. The researchers discovered that as water moves through these plants, it experiences such intense natural filtration that its oxygen isotope signatures become similar to those seen in meteorites or other extraterrestrial materials. Oxygen in water carries a chemical signature which scientists use to track where moisture came from and what happened next. A water sample holds more than one kind of oxygen, and isotopes, atoms of one element with different weights, mark that mix. When water dries, molecules with lighter oxygen escape first and the leftover liquid keeps heavier oxygen through evaporation. Without careful interpretation, the simple sorting can make a lake, a leaf or a fossil look wetter or drier than it was.

Evaporation kept pulling water out of the stem as it rose, even before reaching any leafy branches. As droplets escaped through the stem wall, lighter water molecules left first, so heavier oxygen stayed behind. Each higher segment started with already-enriched water, then lost more to air, building an extreme gradient toward the tip. Dry wind and heat can push that process harder, which helps explain odd oxygen data from desert plants. "It's a meter-high cylinder with a million holes in it, equally spaced. It's an engineering marvel," Sharp said. "You couldn't create anything like this in a laboratory." The team's results help clarify long-standing puzzles involving oxygen isotope measurements in desert plants and introduce a valuable method for reconstructing climate in dry regions. Oxygen isotopes function as tracers, allowing scientists to learn about water sources, plant transpiration and atmospheric moisture. Heavier isotopes are rare, which makes it challenging to predict how their ratios shift under real environmental conditions. Horsetails have a fossil record reaching to the Devonian, a period about 400 million years ago, which defines their long lineage. In smooth horsetail stem water, the share of heavier oxygen climbed sharply from the base to the tip, reaching levels no one had measured before in a living plant. “If I found this sample, I would say this is from a meteorite,” said Sharp. By stretching the known oxygen range across Earth and the solar system fivefold, the results gave modelers a hard boundary.

For investigation, Sharp's group collected smooth horsetails (Equisetum laevigatum) along the Rio Grande in New Mexico. They tracked how oxygen isotope values changed from the lower sections of the plants to the upper portions. The highest samples produced extreme readings that previously appeared to fall outside any known Earth-based range. But in fact, values do go down to crazy low levels. Three separate oxygen versions in the same water drop let scientists tell whether evaporation or source water drove a change. Sharp’s group tracked three versions of oxygen at once, following how each one changed together in the water moving through the stem. The extra layer matters because heavy oxygen is rare, and small biases can hide when only one ratio is measured. With three signals at once, the team could test plant-water models in a way ordinary measurements cannot. Inside horsetail tissues, silica builds tiny glassy bodies which can survive long after the plant dies. Researchers call these bodies phytoliths, tiny silica casts formed inside plants, and horsetails rank among the highest silica accumulators. In Sharp’s data, the oxygen fingerprint in phytolith silica did not match the water moving through the stem. This mismatch means fossil phytolith readings can point to the wrong humidity story, especially when researchers average the whole stem.

The collected data allowed the researchers to update their models, helping explain unusual isotope results found in other desert species. Sharp believes these refined models could also help scientists better understand ancient climate behavior. Models that predict plant water chemistry depend on a few constants, and one of them had been slightly off. Using measurements from the entire stem, Sharp’s team adjusted a key number in evaporation models so it better matches how water vapor actually moves through dry air. The updated number helped explain earlier puzzling oxygen readings in desert plants and animals that drink from strongly evaporated water. Better constants will not fix every uncertainty, but they reduce the risk of blaming biology when physics drove the signal. Scientists have tested fossil phytolith oxygen signals as a way to estimate past humidity. Since moisture in the air affects how quickly water escapes from plants, the oxygen pattern left behind can reflect how dry the air was. “We can now begin to reconstruct the humidity and climate conditions of environments going back to when dinosaurs roamed the Earth,” said Sharp." Still, Sharp’s warning about mismatched phytolith signals sets limits on what those fossils can tell without extra context.

Fossil horsetails, which once grew up to 30 meters tall, contain tiny silica particles called phytoliths. These structures may retain isotope signatures for millions of years. According to Sharp, the phytoliths work as a "paleo-hygrometer," or a way to measure ancient humidity. "We can now begin to reconstruct the humidity and climate conditions of environments going back to when dinosaurs roamed the Earth," he said. Back in Albuquerque, New Mexico, the Center for Stable Isotopes ran the samples, and electron microscopes checked the silica growing in stems. The hands-on path matters, because climate tools improve fastest when scientists test them against messy nature. Extreme water fingerprints from a living horsetail give scientists a new way to stress-test climate models and fossil proxies. Future work will need to map similar signals in other plants and environments, especially where drought pushes evaporation to the limit. This research expands UNM's contributions to the geosciences and highlights horsetails, some of the planet's oldest surviving plants, as unexpected yet powerful record keepers of  climate history in our world.

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Retreat of Hektoria Glacier

 Satellite data confirms the Antarctic glacier lost record ice so rapidly  

To say something moves at a glacial pace is to imply sluggish, unhurried change. But what transpired over the course of 15 months at Antarctica’s Hektoria Glacier was uncharacteristically quick. The glacier lost about 25 km's (15 miles) in length. That included a two-month period in which the terminus retreated more than 8 km's (5 miles)—the highest rate of grounded glacial ice loss observed in modern history. A team of scientists published an analysis of Hektoria’s collapse based on a suite of remote-sensing data, finding that its particular geometry enabled the rapid change. Like many glaciers on the Antarctic Peninsula, Hektoria starts on land and extends to the sea, with the last section being a thick, floating plate of ice, or “ice tongue.” The researchers determined Hektoria lost both its ice tongue and an area of grounded ice spread over a flat plain, the latter directly contributing to sea level rise. Although Hektoria is relatively small as Antarctic glaciers go, scientists say that similar events at larger glaciers could be much more consequential.

The scale of the loss of Hektoria’s grounded ice on the eastern Antarctic Peninsula is huge. Hektoria’s terminus remained relatively stable after the sudden loss, the study reported, though the neighboring Green Glacier continued to retreat. The chain of events culminating in Hektoria’s breakup goes back to early 2002. At that time, the Larsen B ice shelf, which served as a backstop for Hektoria and neighboring glaciers, splintered and collapsed in short order. The glaciers then thinned and retreated for several years. In 2011, landfast sea ice in the Larsen B embayment near Hektoria’s terminus filled in enough to allow the glacier to start advancing. But after several years, the new support for the glacier front was suddenly removed. Landfast ice in the embayment broke up in January 2022, likely due to large, destabilizing ocean swells. From that point, rapid change at Hektoria was again underway. Throughout the rest of the austral summer, the floating ice tongue disaggregated in a series of calvings, resulting in a loss of 16 km's. Hektoria Glacier’s sudden eight-kilometer collapse stunned scientists, marking the fastest modern ice retreat ever recorded in Antarctica. Its flat, below-sea-level ice plain allowed huge slabs of ice to detach rapidly once retreat began. Seismic activity confirmed this wasn’t just floating ice but grounded mass contributing to sea level rise. The event raises alarms that other fragile glaciers may be poised for similar, faster-than-expected collapses.

The glacier’s terminus stabilized during the 2022 austral winter. However, satellite-based laser altimetry data, including ice elevation measurements from NASA’s ICESat-2 (Ice, Cloud, and Land Elevation Satellite-2) mission, revealed that the ice continued to thin during that winter. The thinner remaining ice was still grounded during the 2022 austral spring, the study authors concluded, based on the detection of earthquakes occurring beneath the glacier. They determined the ice was spread out over a relatively flat area of bedrock, forming an ice plain. This geometry allows seawater to infiltrate the glacier’s bed during high tide and intermittently lift ice off the ground. When ice is thin enough, large areas can lift and break away at once. The process, called buoyancy-driven calving, is believed to have caused the second stage of Hektoria’s rapid retreat, resulting in an additional loss of 8 km's in length. Hektoria and Green, once glaciated, are now reduced to drifting ice rubble. A glacier on the Eastern Antarctic Peninsula has undergone the quickest ice loss documented in modern times, according to a major international study. Hektoria Glacier shortened by nearly half its length in only two months during 2023. The glacier shed ice in such a short period, it is comparable to the rapid withdrawals which marked the end of the last ice age. Led by the University of Colorado Boulder (CU Boulder), the global research team, which included Swansea glaciologist Professor Adrian Luckman, determined that the underlying landscape played a major role in accelerating the glacier's retreat.

Hektoria Glacier had been positioned on an ice plain, a level expanse of bedrock located below sea level. Once retreat began, this setting allowed large portions of ice to detach quickly and in sequence. The remarkable speed and scale of the glacier's collapse may now guide researchers as they work to identify other glaciers with similar vulnerabilities and determine which ones require the closest observation. Although Hektoria Glacier is modest in size by Antarctic standards, covering about 115 square miles (slightly smaller than the city of Austin, Texas), its abrupt retreat serves as a serious warning. Comparable events occurring on larger glaciers could significantly influence the rate of global sea level rise. New platforms, such as the NISAR and SWOT satellites developed by NASA and partners, may aid in understanding rapid changes in glaciers. Naomi Ochwat, a glaciologist at the University of Innsbruck and the study’s lead author, is now looking into other glaciers which may be at risk of destabilizing in a similar way. As the Antarctic Peninsula responds to warming, more of its glaciers are losing their ice tongues, and their termini are now resting on the seabed, as Hektoria's does. (Called tidewater glaciers, this type is common in Alaska and Greenland.) New technologies developed by NASA and partners can aid in understanding rapid glacial retreat, said Ochwat and study co-author Ted Scambos, a senior research scientist at the University of Colorado Boulder. 

Glaciers don't usually retreat this fast. The circumstances may be a little particular, but this scale of ice loss shows what may happen elsewhere in Antarctica, where glaciers are lightly grounded and sea ice loses its grip. Although the record indicates some very rapid retreats in the past, the pace of retreat of Hektoria Glacier and its neighbors is unprecedented in the observational record. This is the latest chapter in a sequence of events which started with the collapse of the Larsen B Ice Shelf 23 years ago, marking a landscape-changing event that offers insights into the potential future rates of glacier retreat elsewhere in Antarctica. The NISAR (NASA-ISRO Synthetic Aperture Radar) satellite, for example, can detect the movement of land and ice surfaces down to the centimeter. Its data will be “very useful for structural evaluations of Hektoria and other glaciers in the region,” Scambos said. “In addition to NISAR,” Ochwat added, “I'm particularly interested in learning what SWOT can tell us about rapid glacier changes.” The SWOT (Surface Water and Ocean Topography) satellite’s primary mission is to observe the fine details of Earth’s surface water height. But scientists are also exploring its applications to the cryosphere, such as measuring surfaces of ice shelves and sea ice.

The research team used satellite data and seismic measurements to examine the glacier's breakdown in detail. Their analysis revealed several grounding lines, the points where a glacier transitions from resting on solid rock to floating on seawater. These features confirmed the presence of the ice plain and highlighted how easily the glacier could retreat when exposed to ocean-driven forces. Seismic devices also detected glacier earthquakes, small tremors caused by abrupt ice shifts. These signals showed that the ice was still grounded at the time of retreat, meaning the loss directly contributed to global sea level rise. At Hektoria Glacier, the days of dramatic change are likely past, now to be replaced by slow retreat. Scambos said he would not be surprised to see the ice slowing down. “The glacier has lost so much elevation and mass that it simply can’t continue to maintain the same output,” he said. “It’s on its way to being a fjord, not a glacier.” This kind of lightning-fast retreat really changes what's possible for other, larger glaciers on the continent. If the same conditions are set up in some of the other areas, it could greatly speed up sea level rise from the continent. The authors emphasize the importance of ongoing monitoring efforts and international scientific cooperation to better track and understand changes unfolding across frozen regions of our world.

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