The asteroid impact that wiped out the dinosaurs was so powerful it took at least 8 million years for the impact site to cool, during which time microscopic life thrived in the subsurface ecosystem. New research findings have been published in the journal Communications Earth & Environment.
The Chicxulub asteroid, which struck Earth 66 million years ago in what is now Mexico, is believed to have been up to 15 kilometers in diameter. The impact triggered such climatic chaos that it annihilated three-quarters of Earth’s species. All dinosaurs, save for the ancestors of birds, went extinct, and the planet endured a nuclear winter for at least 15 years.
Its effects were also felt deep underground. “The Chicxulub impact was strong enough to cause deformation at least 35 kilometers below the Earth’s surface, which can be detected through geophysical surveys,” states Anja P.C. Peuckert of the University of Glasgow, UK.
According to Peuckert, the impact melted approximately 10,000 cubic kilometers of rock. The combination of molten rock and seawater created a porous material filled with tiny pockets of hot water, known as a hydrothermal system.
Thanks to the presence of minerals that only form where liquid water and heat exist, we know the asteroid created hydrothermal environments several kilometers deep. But the scale and duration of the heating, and consequently the existence of the resulting hydrothermal system, have been greatly underestimated.
Previously, it was thought that it took a mere 2 million years for the impact site to cool. Now, Peuckert and her colleagues suggest it could have taken at least four times longer, providing a much greater window for hydrothermal life to develop.
“One of the biggest unknowns concerning all asteroid impact hydrothermal systems, and Chicxulub in particular, is how long the heat sustains water circulation within the structure,” says Peuckert.
To investigate this, the team drilled a 1-kilometer-deep borehole into the crater to retrieve rock samples. As potassium in the rocks has decayed into argon over time, researchers were able to measure the amount of argon trapped within the samples to determine their age.
“We obtained a range of ages from the time of the impact 66 million years ago to about 58 million years ago,” says Peuckert. “This tells us that hydrothermal activity persisted in at least part of the Chicxulub structure for 8 million years after the impact.”
Sulfur isotopes in the cores indicate that microbial life existed within the hydrothermal system and recovered rapidly after the impact.
The findings imply that the earliest impact craters on the young Earth – and potentially on other worlds – might also have hosted habitable hydrothermal systems for longer than previously believed.
“This provides more opportunities for life to develop, evolve, and spread,” states Peuckert. “It supports the concept that early life on Earth could have found long-term refuges within impact craters, and perhaps even life on other planets where these massive impact craters are dominant landscape features.”
Gavin P. Kirkland of Curtin University in Perth, Australia, comments that while “there isn’t fully definitive data on continuous hydrothermal activity” at Chicxulub, there is strong evidence that the impact site remained hot for millions of years.
“Large impacts don’t just destroy environments,” he says. “They can also create long-lived subsurface systems where hot fluids circulate through fractured rock. These chemically rich environments can provide protected habitats for microbes and perhaps even favorable conditions for some early chemical stages of life’s development.”
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