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Earth may have been pommel by large blank rocks more often than antecedently estimate , controversial new research suggests , rear the risk that a mintage - terminate encroachment could come sooner than we think .
The study , presented at the annualLunar and Planetary Science Conferencein The Woodlands , Texas last week , focused on the largest - known wallop crater from the past million age . Using raw high-pitched - resolution imaging , the authors reason that these crater were in the beginning far bigger than they see now . If they ’re ripe , asteroids or comets larger than 0.6 miles ( 1 kilometer ) have hit Earth up to a dozen times in the last million years alone . That ’s a far higher pace than the previous estimates of once every 600,000 to 700,000 years .
Meteor crater in Arizona is one of the most well-preserved impact craters on Earth, with an estimated age of about 50,000 years. A new study of larger, less pristine craters raises new questions about how many large impacts Earth experiences in a given timeframe.
" It would be in the range of serious crap happening,“James Garvin , the study ’s lead author and main scientist atNASA ’s Goddard Space Flight Center , toldScience .
However , other scientist stay on unconvinced that the landscape features Garvin and his team reported are really part of the old crater .
" I ’m skeptical,“Bill Bottke , a planetal dynamicist at the Southwest Research Institute in Boulder , Colorado , told Science .
Unlike on Mars or the moon , Earth ’s impact craters disappear relatively quickly due to wearing away do by water and wind . Scientists estimate the risk of space impact free-base on the history ofimpacts on the moonand by monitoring near - Earth asteroids .
But Garvin and his colleagues used new high - solving satellite data to bet at the remnants of volcanic crater on Earth . This information consisted of lidar ( light detective work and ranging ) , which expend optical maser pulses to exactly evaluate distance , and stereo imaging , which take a artificial satellite taking two trope of the same place from slimly different angles ; a comparison of these images then enables a 3D reconstruction of the scene .
Using this method , the researchers find at least four impact craters with what they argue are far larger outer lip than antecedently measured . For instance , the Pantasma crater in Nicaragua was antecedently estimate to have a diameter of 8.7 miles ( 14 kilometre ) , but Garvin and his colleagues detected an out - out rim with a 21.9 - sea mile ( 35.2 klick ) diameter . The lake - fulfil Bosumtwi volcanic crater in Ghana was estimated at about 6.5 air mile ( 10.5 km ) in diameter , but the new study revealed a ring - similar ridge with a diameter of 16.7 miles ( 26.8 km ) . And the 8.7 - mile - wide Zhamanshin volcanic crater in Kazakhstan may have actually been 18.9 nautical mile ( 30.4 km ) in diameter , accord to the new research .
The investigator also examined the Iturralde Crater in Bolivia . This remote orbitual feature may or may not be an shock volcanic crater . irrespective , the young study revealed a band - like feature 18.9 Admiralty mile ( 30.4 km ) wide , significantly turgid than the 5 - Admiralty mile ( 8 kilometre ) diameter of the main feature film .
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These encroachment would have released the equivalent of 400,000 to 730,000 megatons of TNT — enough to blow part of Earth ’s atmosphere into space and fling fragments of impingement glass across the globe , Garvin and his squad say . And if at least four of these impacts occurred on ground , which covers only one - third of the Earth ’s surface , doubly as many space stone may have fallen in the oceans . The researchers are also still study an additional four young craters on continents .
What is n’t exonerated is whether the ring - like features the researchers discover are actually parts of old crater rims . Brandon Johnson , a planetary scientist at Purdue University , told Science the ridges might be rings of detritus ejected from the impingement . However , he said , the possibility evoke an pressing need for more research .
" We ’ve get to go there , check out the geology , and get more detail , " Johnson tell Science .
