Apart from humanity’s apparent determination to destroy our planet via climate change, the greatest threat to Earth’s survival is whether or not an asteroid will crash land on its surface. Historically, scientists have believed that species-ending asteroid impacts —like the one that took out the dinosaurs— have been extremely rare. Now, a new study is suggesting that might not be true.
Using extremely high-resolution satellite data and techniques used to uncover asteroid craters on Mars, a team of researchers led by NASA Goddard’s Chief Scientist, James Garvin, have reported that four of Earth’s asteroid impact craters may be more than twice the diameter of established measurements. This finding would suggest that serious impacts occur more frequently—and more recently—than we realized.
“If these four known features…are all around 30 kilometers in diameter and not 10 or 12 kilometers, then the energies that were released would become 400- 500,000 megaton explosions,” Garvin told Motherboard. “Bigger than all the volcanic activity in the last million years.”
To form this hypothesis, Garvin and colleagues used high resolution satellite data from the company Planet and height data measured by NASA’s laser satellites, GEDI and IceSat-2, to look through tree cover at sites like Pantasma in Nicaragua and create four-meter resolution maps of the crater area. An algorithm originally designed to find craters on Mars then analyzed the maps for circular patterns that may represent the edge of the impact crater.
For four of the sites they analyzed, the algorithm predicted larger diameters for the impact craters than established numbers.
The findings were presented by Garvin at the Lunar and Planetary Science Conference in Texas but he anticipates a longer paper on the work may be coming down the pipeline sometime closer to the end of 2023.
These explosions wouldn’t necessarily be on the level of dinosaur extinction, but they’d be enough to affect the climate after their impact and even cause small scale extinctions, Garvin told Science. This would be a big upset to how we understand Earth’s resilience to energetic explosions like these impacts and studying those dynamics would be an important precursor to better understanding “the sustainability of aspects of life on Earth,” Garvin said.
However, both Garvin and other experts in the field of near Earth object impacts and planetary science agree that this whole scenario is a big “if.”
Masatoshi Hirabayashi is an associate professor of aerospace engineering at Auburn University and worked on NASA’s recent DART mission to explore planetary defense techniques against potential asteroids. He told Motherboard in an email that Earth’s history of erosion makes these types of measurements very difficult.
“I want to be cautious about the results,” Hirabayashi said. “I also count craters on planetary bodies; it is challenging to identify craters on high confidence levels, particularly when they are highly eroded. I may suggest more data to support this claim.”
A number of other planetary scientists have also voiced skepticism about these results, which Garvin welcomes with open arms.
“I appreciate the skepticism because I’m [also] skeptical,” Garvin said. “I think this work is worthy as a catalyst… to get the community to think about this and compare it to other planets.”
In short, the jury is very much still out and Garvin agrees that further study, including field work to visit these new predicted boundaries and studies of the climate record to see if these big energy events appear, will be necessary to come to more confident conclusions.
As for what these predictions could mean for Earth’s future risk from similar high-energy impacts, Garvin and Hirabayashi agree that it’s not going to change much.
“This study does not affect Earth's future risk of being hit by an asteroid making similar sized craters,” Hirabayashi said. “Small bodies larger than 100 m in diameter are well cataloged [and] the craters argued by Garvin et al. were likely formed by hypervelocity impacts of small bodies much larger than that size. By this, the impact risk in the near future is very low.”