Life returned to asteroid crater “within years”
Chicxulub ecosystem recovered remarkably quickly, astounding researchers. Andrew Masterson reports.
“Life, uh, finds a way,” said the character of Ian Malcolm (Jeff Goldblum) in the 1993 movie Jurassic Park.
It’s a line that was quite possibly echoed by a large international team of scientists when it discovered that a very short time after a massive asteroid smacked into the Gulf of Mexico 66 million years ago – triggering the Cretaceous/Palaeogene mass extinction that wiped out three-quarters of species on Earth – life was thriving in waters of the crater created.
The finding, made by researchers led by Christopher Lowery of the University of Texas at Austin, US, is surprising, and effectively torpedoes an existing theory that suggested the recovery of some marine ecosystems after the disaster was delayed because the asteroid delivered a cargo of toxins into the ocean.
The bolide plunged into shallow water on what is known as the Yucatán carbonate platform, setting off a catastrophic series of events that ended the age of the dinosaurs – and very nearly everything else, as well. The crater left behind is known as Chicxulub.
Studies examining the fossilised remains of single-celled shelled creatures known as foraminifera have previously shown that marine recovery around the world got underway at various times following the impact.
Some areas showed foraminifera numbers and diversity were increasing again around 100,000 years after the event. Other regions, however, including parts of the Gulf of Mexico, did not start to recover for 300,000 years.
The geographical spread of the variations in recovery rates bore a possible relationship to their distance from the Chicxulub, and to the assumed northward direction of the impact shockwave.
This led some researchers to suggest that slower foraminifera recovery in the northern ocean regions could be explained by metal toxins released from the asteroid when it broke up on impact.
A powerful piece of evidence to support the theory would be if recovery at the impact site itself – the place most saturated by toxins if the hypothesis is supported – took a very long time indeed.
To discover if this was in fact the case, Lowery and his colleagues analysed drill cores obtained from the Chicxulub crater by a research project called the International Ocean Discovery Program (IODP).
The cores contained rock and foraminifera deposited during the first 200,000 years after the impact. What they revealed was astounding.
The fossil evidence, the scientists write in the journal Nature, provides “unequivocal evidence for benthic life in the crater within years of the impact”.
From perhaps sparsely populated beginnings, things moved very fast. The researchers found that a “high-productivity ecosystem” was fully established at ground-zero within just 30,000 years of the catastrophe.
The recovery inside the crater was thus much faster than that experienced in other areas – and 10 times more rapid than that experienced in other sections of the Gulf of Mexico.
The speed and size of life’s return, the researchers say, “indicates that proximity to the impact did not delay recovery and that there was therefore no impact-related environmental control on recovery”.
The long lag-times in other areas, they suggest, can be explained without exogenous elements, and possibly involve complex interactions between food supplies and “competitive exclusion by opportunists”.