A NASA-funded study presented at the Lunar and Planetary Science Conference last week suggests that big asteroids hit Earth more often than previously thought, based on satellite data. But not everyone agrees with the interpretation, according to the journal Science, which says more fieldwork is needed to confirm the data.
The study was led by James Garvin, chief scientist of NASA's Goddard Space Flight Center in Maryland, and used high-resolution data from several Earth-observing satellites to examine three impact craters. Garvin's team suggests that large rings are visible in the data, showing that the craters are tens of miles wider than previously measured. That size adjustment, in turn, implies that the impacts were far more powerful than previously cataloged.
Generally speaking, researchers estimate that a space rock at least 0.62 miles (1 km) wide hits Earth about every 600,000 or 700,000 years, according to Science. The new study ramps up the rate considerably, suggesting four objects of that size smacked into Earth in the last million years.
Source: www.space.com
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