'Living fossil' reveals cosmic secrets of Earth’s ancient climate

Some answers to Earth’s ancient mysteries hide in plain sight. Growing along riverbanks and ponds are horsetails – plants older than the dinosaurs.

Scientists at The University of New Mexico now say these survivors might help reveal what the planet’s climate once felt like. Their new research shows how water inside horsetails changes so drastically that it mimics the chemistry of meteorites.

This finding surprised even seasoned geochemists. Horsetails, often dismissed as simple or primitive, display a natural process more complex than expected. Their stems act like miniature laboratories, distilling water with astonishing precision.

Climate clues in horsetails

Each droplet that passes through the horsetail plant carries a unique chemical signature shaped by evaporation, sunlight, and air.

Studying these changes gives researchers clues about humidity and temperature millions of years ago.

What once seemed like ordinary plants now appear as powerful tools for decoding Earth’s long climate record, showing that the past can still speak through the quiet persistence of living things.

A marvel of nature’s engineering

The study was led by Professor Zachary Sharp from UNM’s Department of Earth and Planetary Sciences.

The research team explored how water moves through horsetails – the strange, jointed plants that have endured for over 400 million years.

“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.”

Sharp’s team found that as water travels through horsetail stems, it undergoes extreme natural distillation. The result? Oxygen isotope ratios that look more like those from space rocks than from anything on Earth.

Strange water changes in horsetails

Oxygen isotopes work like natural tracers, helping scientists follow water’s journey through air, soil, and plants. But modeling how these isotopes behave has always been tricky because the heavier forms occur in very small amounts.

To tackle this, Sharp’s team collected smooth horsetails (Equisetum laevigatum) along the Rio Grande in New Mexico.

The researchers measured water from the base to the tip of the plant. The readings at the top were shocking – far outside normal Earth values.

“If I found this sample, I would say this is from a meteorite,” Sharp said at the Goldschmidt Geochemistry Conference in Prague. “But in fact, these values do go down to these crazy low levels.”

Those unusual results helped solve a puzzle that had stumped geochemists for years.

Decoding Earth’s ancient weather

The team used the new data to improve isotope models that explain how water interacts with plants and air. Earlier readings from desert plants had always seemed off, and now the scientists could explain why.

Sharp believes this refined understanding could help reconstruct ancient climates, especially in dry regions where records are scarce.

By comparing isotope ratios in old plant remains, researchers can piece together how humid or dry the air once was. Each horsetail becomes more than a plant – it becomes a record of ancient weather.

Horsetails may reveal Earth’s climate

Prehistoric horsetails once stretched nearly 30 meters tall, shading wetlands that teemed with life. Their tissues contained tiny silica structures called phytoliths.

These grains can trap isotope data and hold it for millions of years. Sharp calls them “paleo-hygrometers,” or ancient humidity gauges.

“We can now begin to reconstruct the humidity and climate conditions of environments going back to when dinosaurs roamed the Earth,” he said.

Tiny fossils of horsetails could help scientists build a detailed picture of ancient climates – what air felt like, how much it rained, and how plants adapted.

Plants with a memory of the past

The discovery gives new life to one of Earth’s oldest survivors. Horsetails now stand not only as relics from the past but as living instruments that measure the planet’s long memory.

Sharp’s team has shown that even the simplest plants can reveal cosmic-level secrets. Through their hollow stems flows a record of time itself, linking the living world to the earliest chapters of Earth’s story.

Their work changes how scientists look at vegetation that has existed for ages without much attention. It reminds us that even familiar species can hold data as valuable as rock cores or ice layers.

Horsetails offer a fresh, biological way to track climate shifts that shaped ancient ecosystems.

As researchers continue exploring isotope patterns in these plants, they might uncover new connections between life and atmosphere.

This research may ultimately reshape how we read Earth’s environmental history and prepare for the climate challenges still to come.

The study is published in the journal Proceedings of the National Academy of Sciences.

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