Asteroid created huge hydrothermal system

Mexico’s 66-million-year-old Chicxulub crater continues to reveal its secrets.

Just three days ago researchers suggested the famous asteroid that created it ended up destroying 75% of life and Earth, and probably wiping out the dinosaurs, because it struck at the worst possible angle.

Now a paper in the journal Science Advances offers evidence that the impact not only released huge amounts of climate-changing gases, it also created a hydrothermal system nine times the size of the Yellowstone Caldera system in the US.

This may have persisted for more than a hundred thousand years, permanently altering the chemical and mineralogical makeup of a large chunk of the Earth’s crust, says an international team led by David A Kring from Universities Space Research Association in the US.

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Hydrothermal minerals (analcime and dachiardite) in a one-centimetre cavity within impact rocks. Credit: David A Kring

These findings could support the hypothesis that large meteor impacts earlier in Earth’s history produced hydrothermal clays that catalysed RNA synthesis, they say, sparking the origin of life on Earth.

Chicxulub is one of our largest and best-preserved craters, with a 240-kilometre basin stretching beneath Mexico’s Yucatan Peninsula.

Data has shown that the impact that formed it generated ideal conditions for a hydrothermal system, but until now the details of such a system have not been fully documented.

A previous expedition by Mexican researchers found evidence of hydrothermal alterations 100 metres thick, but Kring and colleagues suggest the impact-induced hydrothermal system circulated hot fluid at least 700 metres below the surface.

They analysed hydrothermally altered rocks recovered from 617 to 1335 metres below the sea floor during Expedition 364 by the International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP), which drilled a borehole into the crater basin.

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A portion of Expedition 364 rock core. Credit: Kring@ECORD_IODP

They found mineral evidence that the hydrothermal system was initially hotter than 300 degrees Celsius, cooling to below 90 degrees within about two million years.

They also observed a network of porous, permeable niches that could have provided habitats for microorganisms within the crater, suggesting that similar niches created by ancient impacts could have provided ideal conditions for the origin and evolution of life much earlier in Earth’s history.

“The hydrothermally altered Expedition 364 core demonstrates that impact cratering is a fundamentally important heat engine in emerging planetary systems and that the geologically young Chicxulub crater is a suitable analogue for terrestrial impact basins created almost 4 Ga [giga-annum] ago,” the authors write.

“Impact-generated hydrothermal systems were prominent features on early Earth and wherever water exists in a planetary crust. This model is transferrable to an early Mars… and any exoplanetary system with similar conditions.”

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