Previous studies have suggested that so-called ‘planet killer’ asteroids only have a chance of striking the Earth once every 600,000 to 700,000 years.
But calculations by James Garvin, chief scientist of NASA’s Goddard Space Flight Centre, hint that this may no longer be the case.
His research suggests that impacts of falling fire rocks measuring over half a mile in width could be three times more frequent than previous estimates.
Apart from causing mass devastation at a local level, an asteroid that size would send a considerable chunk of the Earth’s atmosphere into space.
Analysing data from several Earth-observing satellites to examine four impact craters, also identifying larger rinds around the sites, Garvin found that at least four asteroids strong enough to slice the atmosphere off have hit in the last million years.
As a result, Garvin suggested scientists may previously have misread their findings and previous impacts could well have led to mass extinctions given asteroid collisions would have been up to 10 times more powerful than the largest nuclear bomb dropped in history.
As part of planetary defence research, the study used new high-resolution imagery of four craters where the team could map them in 3D. The sites observed from included Pantasma in Nicaragua, Bosumtwi in Ghana, Iturralde in Bolivia and Zhamanshin in Kazakhstan.
Presenting the findings earlier this year, Garvin said the impacts “would be in the range of serious crap happening”.
He continued: “We have focused attention on four complex impact craters that span the past ~1.0 Ma [one million] of Earth history, mostly within tropical regions, with differing target rock characteristics.”
Early analysis of Pantasma recorded a nine-mile-wide crater left by an asteroid over 800,000 years ago.
The new research, however, suggests that the crater is actually 21 miles wide and the impact equivalent to 727,000 megatons – enough to “blow off part of the Earth’s atmosphere and distribute impact glasses globally”.
The original analysis said the asteroid’s impact was somewhere in the region of 660,000 megatons when it fell to Earth.
Garvin’s new findings recorded Bosumtwi’s crater as having an “outermost rim of 26.8 km with an inner peak ring (with a deep cavity within) of six miles”.
In their notes, the team said: “The perhaps more bizarre Zhamanshin impact feature in Kazakhstan reveals an outer putative rim at 18 miles” — after initial research said the outer rim was only seven miles.
At the final site, Iturralde, new data found that the impact was in fact three times longer than initially thought, the crater spanning over 18 miles compared to the original six.
While the findings could prove to be a breakthrough, some scientists are sceptical. Anna Łosiak — a crater researcher at the Polish Academy of Sciences — doubted the sizes of the crater rims in the new findings.
She told Science: “That would be very scary because it would mean we really don’t understand what’s going on at all—and that there are a lot of space rocks that may come and make a mess.”
