Level 1 — Absolute Beginner

A long time ago a rock from space hit Oklahoma. It made a big hole in the ground.

Today the hole is under the earth. You cannot see it from outside. There is oil and gas inside it.

Scientists thought the rock hit 467 million years ago. Now they say it hit about 370 million years ago.

They looked at tiny crystals in the rock to find the new date. At that time many animals in the sea died.

rock

A hard piece of stone.

space

The area outside the Earth where the stars are.

hole

An empty space in a surface.

ground

The surface of the Earth.

oil

A thick liquid from under the ground, used for fuel.

scientist

A person who studies the world to learn how it works.

crystal

A small hard piece of a mineral with flat sides.

million

The number 1,000,000.

Level 2 — Elementary

Under the small town of Ames in Oklahoma there is a crater several miles across. A meteorite made it, and layers of rock have covered it since. Oil and gas companies drill into it, which is how geologists know so much about what is down there.

For years scientists believed the impact happened about 467 million years ago. A team at the University of Texas at Austin, led by Elizabeth Catlos, now says the real date is closer to 370 million years ago.

The team used zircon crystals. Zircon contains uranium, which turns into lead very slowly at a known speed, so measuring the two elements gives an age. Working with NASA, the researchers also photographed the crystals to find the damage that only a meteorite strike can cause.

The old date came from the teeth of conodonts, small eel like animals. Those teeth were already millions of years old when the meteorite arrived, and the crash mixed everything together, so they gave the wrong answer. The new date puts the impact close in time to a mass extinction that killed much of the life in the sea.

crater

A large round hole in the ground made by an explosion or an impact.

meteorite

A piece of rock from space that reaches the surface of a planet.

layer

A flat sheet of material lying on top of another.

geologist

A scientist who studies rocks and the history of the Earth.

impact

The moment when one object strikes another with force.

uranium

A heavy metal that slowly changes into lead.

element

One of the basic substances that everything is made of.

mass extinction

A period when a very large share of all species dies out.

Level 3 — Intermediate

The Ames impact structure is one of the strangest pieces of geology in North America: a crater several miles wide, buried beneath the town of Ames in Oklahoma, invisible at the surface and productive enough that oil and gas wells have been drilled straight into it. A team from the Jackson School of Geosciences at the University of Texas at Austin, led by associate professor Elizabeth Catlos, has now shown that almost everyone has been dating it wrong by about a hundred million years.

The accepted age was roughly 467 million years, which placed Ames in the Ordovician period and inside a proposed cluster of North American impacts sometimes attributed to a ring of asteroid debris that briefly encircled the Earth in the way Saturn's rings encircle Saturn. The new work, published in Meteoritics and Planetary Science in July 2026, puts the strike at about 370 million years ago, in the Late Devonian, which takes Ames out of that cluster altogether.

The method is what makes the result hard to argue with. The team measured uranium and lead inside zircon crystals, a clock that runs at a known rate, and collaborated with NASA to image the crystals using cathodoluminescence and electron backscatter diffraction. Those techniques expose patterns of recrystallisation that only the shock of a meteorite strike produces, which separates grains affected by the impact from older material swept into the debris. As Catlos put it, no matter what technique they used, the answer kept coming back to this younger signal.

The earlier figure rested on conodont teeth, the hard remains of small eel like animals found at the site. Those teeth were already millions of years old when the meteorite arrived and were then jumbled through the shattered rock, so they recorded the age of the layers rather than the age of the explosion. The correction matters beyond bookkeeping, because 370 million years sits uncomfortably close to the Frasnian and Famennian extinction around 372 million years ago, one of the worst collapses of marine life in the planet's history, and a strike of that size nearby is now part of the conversation about what caused it.

impact structure

The geological scar left in rock by a meteorite strike, including buried examples.

cluster

A group of similar events or objects close together in time or space.

asteroid debris

Broken rocky fragments left over from a collision in space.

recrystallisation

The rearrangement of a mineral's internal structure under heat or pressure.

shock

The sudden extreme pressure wave produced by a violent impact.

grain

A single tiny particle of a mineral within a rock.

jumble

To mix things together in a disordered way.

collapse

A sudden and complete failure, here of living populations.

Level 4 — Advanced

Dating an impact crater sounds like a solved problem until you consider what an impact actually does to the evidence. The Ames structure in northern Oklahoma, several miles across and entirely buried, has been read for decades as an Ordovician event roughly 467 million years old. Work from the Jackson School of Geosciences at the University of Texas at Austin, led by associate professor Elizabeth Catlos and published in Meteoritics and Planetary Science in July 2026, relocates the strike to approximately 370 million years ago, in the Late Devonian. A hundred million year correction to a well catalogued crater is the kind of revision that reorders more than one filing cabinet.

The flaw in the old figure was not carelessness but a reasonable method applied to compromised material. Previous ages derived from conodont teeth, the durable microfossils of small eel like animals recovered from the site. The difficulty is that those teeth were already millions of years old when the meteorite arrived, and the explosion then shuffled fragments of many different ages into a single chaotic deposit. Dating such a mixture tells you when the rocks formed, not when the sky fell on them, and in a structure assembled by violence that distinction is easy to lose.

Catlos and her colleagues instead went to zircon, the mineral geochronologists trust most, measuring the steady decay of uranium into lead inside individual crystals. Crucially, they worked with NASA to image those grains with cathodoluminescence and electron backscatter diffraction, methods that reveal internal recrystallisation textures diagnostic of shock. That allowed the team to distinguish crystals genuinely reset by the impact from inherited older grains, which is the step that converts a scatter of numbers into an argument. Her summary of the result was characteristically flat: no matter what technique they used, it kept coming back to this younger signal.

Two consequences follow. The first is subtractive. Ames had been counted among a proposed family of Ordovician impacts across North America, a cluster sometimes explained by a temporary ring of asteroid debris orbiting the Earth much as Saturn's rings orbit Saturn, and removing a member weakens the statistical basis for that picture. The second is additive, and more provocative. Roughly 372 million years ago the Frasnian and Famennian extinction erased a large share of marine life, and a crater of this size dated to 370 million years ago now belongs in the discussion of plausible contributors, though a single impact of this scale is far from sufficient to explain a global crisis. The crater that oil crews have been drilling through for years has quietly changed which chapter of Earth history it illustrates.

compromised

Damaged or made unreliable for its intended use.

microfossil

A fossil so small that it must be studied under a microscope.

deposit

A layer of material laid down by natural processes.