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In the late 1970s, the Mexican oil company Pemex

was scouring the Gulf of Mexico for possible sites

to drill. A ring of mountains on the ocean floor

with a diameter of around 70km sparked the

interest of Pemex geologist Glen Penfield. Further

scrutiny of the Yucatán Peninsula revealed another

concentric ring, strongly suggesting some kind of

catastrophic impact, with its centre lying close to

what is now the small coastal town of Chicxulub.

When a young University of Arizona graduate

called Alan Hildebrand got in touch with Penfield,

they teamed up and tracked down cores from

three deep exploration wells that Pemex had

drilled within the region (C1, S1 and Y6 in the

gravity map below). In these rocks, they found

evidence of a cataclysmic event at precisely the

moment the dinosaurs vanished, at the end of the

Cretaceous Period. Now, 25 years on, we’ve drilled

deeper into the crater than ever before (Chicx-03A

below). All eyes will be on the expedition scientists

in September when they begin analysis of the

1,300m-long core.

THE STORY OF

THE CRATER

PHOTOS: GETTY, SCIENCE PHOTO LIBRARY

ore 40. To the untrained eye, this three-metre

section of rock winched up from a borehole

beneath the Gulf of Mexico might not look

like much. But for Sean Gulick, a geologist at the

University of Texas at Austin, it’s a sample that holds

secrets about one of the most catastrophic events in

the history of planet Earth.

For Gulick, the core will tell him the story of the day

the Earth shook. Sixty-six million years ago, a 14km-

wide meteorite slammed into our planet. Wildfires

raged, earthquakes rumbled, and a dusty curtain fell

upon the Earth. It was the beginning of the end for

around 75 per cent of the planet’s species, including

all non-avian dinosaurs.

Travelling at 20km per second when it entered

Earth’s atmosphere, the meteorite left a crater 200km

across when it smashed into the planet. Today, this

geological scar lies buried beneath the Yucatán

Peninsula in southeastern Mexico – and now, for the

first time, we’ve drilled into its heart.

Throughout April and May, Gulick was stationed on

a drilling rig just off the Yucatán Peninsula. He’s the

co-chief scientist on Expedition 364, the joint project

by International Continental Drilling Program and the

International Ocean Discovery Program to drill down

into the Chicxulub impact crater. On this boat-cum-

drilling platform, 30km off the Mexican coast, his team

have worked day and night to bore down to over 1.3km

beneath the seabed to extract precious cores of rock.

When these cores are cracked open in September,

geologists, physicists, chemists and biologists will

be racing to find out what happened in the minutes,

hours, days and years after touchdown. What they

The meteorite left a crater 200km

across when it smashed into the

planet. Today, this geological scar lies

buried beneath the Yucatán Peninsula

C

SCIENCE