This famous Yellowstone geyser is birthing “eggs” – and it could rewrite our origin story

Old Faithful’s Geyser Eggs

Old Faithful erupts every 90 minutes or so, blasting up to 8,400 gallons of boiling water as high as 185 feet into the Wyoming sky.

Millions of tourists watch it happen every year.

But the geyser also creates something most visitors never notice: small, smooth rocks scattered in the thermal pools nearby. Scientists call them geyser eggs.

In 2018, a team of researchers got permission to remove one for the first time, and what they found inside could change how we understand the origin of life itself.

Silica Hardens Like Candy

Geyser eggs form layer by layer as silica from the steamy waters of geothermal pools precipitates out of solution, making each layer a snapshot of pool conditions at the time it was formed.

The process works like making hard candy. Silica left behind clings to whatever is available, and over time it builds up into smooth, oval pebbles.

Candy makers heat sugary water to high temperatures, dissolving much more of the sweet stuff than colder water could handle.

Then, as the solution cools, the sugar begins to crystallize. The same thing happens when hot, mineral-rich geyser water cools down.

Scientists Get One Precious Sample

Strong protections within the national park have long prevented scientists from getting their hands on the eggs.

Yellowstone’s thermal features are closely guarded, and removing anything requires extensive permits.

But recently, for the first time, a team of geologists were allowed to remove a single Old Faithful egg. The sample was roughly 35 mm long by 18 mm wide by 26 mm high, about the size of a silver dollar.

Lead researcher Bridget Lynne of the University of Auckland called it the largest collection of these rare rocks she had seen in her scientific career.

They Cut It Open and Scanned It

To study the egg, the researchers sliced it in half and subjected it to a battery of tests to determine its composition and structure.

They used CT scans, electron microscopes, and X-ray diffraction.

The geyser egg architecture consists of alternating smooth and porous concentric bands of opal-A silica around a nucleus.

The CT scans mapped changes in density throughout the sample and revealed concentric banding of varying density around a core.

Each ring told part of the story of what was happening in the pool when it formed.

The Rings Record Chemical Changes

The egg contains concentric rings of varying density and composition.

According to geologist Duncan Foley, the team was seeing what are probably changes in the chemistry of the geyser waters through time.

These alternating bands are signatures of changes in the degree of silica oversaturation of the discharging fluid.

The changes in density may reflect seasonal cycles like frost and thaw. As geyser eggs grow, they are actively recording any shifts in elemental composition.

Ancient Microbes Left Their Mark

The eggs are not just mineral deposits. SEM observations showed the geyser egg has an abiotic origin with subsequent microbial filamentous void infill creating an abiotic-biotic sinter structure.

In plain terms, the egg started as pure rock, but bacteria moved in and left their traces between the layers.

The distinct pattern of alternating filamentous and non-filamentous horizons suggests a cyclic pattern of changing hot pool conditions from those that suit microbial filaments to those that do not.

350-Degree Water From Below

The water that feeds Old Faithful comes from deep underground, where temperatures exceed 350 degrees Fahrenheit.

The famous geyser’s waters collect in a large underground teapot-shaped chamber before periodically erupting, but they first travel through a web of underground crevices.

Along the way, the roiling water dissolves minerals from the surrounding volcanic rock, changing the water’s chemistry.

How those twists and turns change through time remains a mystery. The eggs may hold answers.

Bacteria Thrive in the Chaos

Old Faithful seems like a hostile place for life, but new research shows that it’s a thriving ecosystem for extremophiles, microscopic organisms that flourish in extreme environments.

Thermocrinis ruber, the dominant bacteria in Old Faithful, accounts for over 60% of its microbial population. These bacteria cannot use sunlight for energy because the geyser is too hot and too dark.

Instead, Thermocrinis ruber takes CO2 outgassing from the geyser and turns it into carbon forms that feed other microbes in the community.

Where Life May Have Started

Some scientists believe hot springs like those at Yellowstone may have been where life on Earth began nearly four billion years ago.

Hydrothermal fields provide sources of heat and chemical energy to drive polymerization reactions in films of concentrated organic solutes that form on mineral surfaces.

The wet-dry cycles that happen when geysers splash water on surrounding rocks could have helped simple molecules combine into the first living cells.

Scientists discovered a 3.48 billion year old geyserite that seemingly preserved fossilized microbial life.

A Guide to Finding Alien Life

The research has implications beyond Earth.

Other planetary bodies, such as Saturn’s icy moon Enceladus and Jupiter’s moon Europa, appear to house geysers beneath their surface.

If life can thrive inside Old Faithful, similar organisms might exist in those extraterrestrial geysers. Now that we know for sure that terrestrial geysers can host life, the race to find it on planetary geysers is on too.

Researcher Lisa Keller pointed out that before her study, scientists had never even sampled microbes from a geyser on our own planet.

Only One Egg So Far

With just a single sample, scientists can only learn so much. When you’ve only got one of something, you never know if it’s typical, noted geologist Brian Jones.

The growth rate of geyser eggs remains uncertain.

Studies of similar eggs in New Zealand suggest they may grow at roughly 0.35 mm per year, but whether that holds true for Old Faithful is unknown.

Researchers hope to get permission to study more eggs in the future, because each one could contain thousands of years of geyser history locked inside its layers.

Visiting Old Faithful, Wyoming

Old Faithful sits in the Upper Geyser Basin of Yellowstone National Park.

The Old Faithful Visitor Education Center posts predicted eruption times, usually accurate within about 10 minutes.

Eruptions happen roughly every 90 minutes and last between 1.5 and 5 minutes. The park is open year-round, though some roads close in winter.

Entrance fees are $35 per vehicle for a seven-day pass.

Arrive early during summer months to get a good viewing spot on the boardwalk, and stick around to explore the dozens of other thermal features within walking distance.

This article was created with AI assistance and human editing.

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