"Scientists have discovered a huge crater in the Saharan desert, the largest one ever found there.
The crater is about 19 miles (31 kilometers) wide, more than twice as big as the next largest Saharan crater known. It utterly dwarfs Meteor Crater in Arizona, which is about three-fourths of a mile (1.2 kilometers) in diameter.
In fact, the newfound crater, in Egypt, was likely carved by a space rock that was itself roughly 0.75 miles wide in an event that would have been quite a shock, destroying everything for hundreds of miles. For comparison, the Chicxulub crater left by a dinosaur-killing asteroid 65 million years ago is estimated to be 100 to 150 miles (160 to 240 kilometers) wide."
This article interested me because it brings up an important point about the various classes of 'space object' which leave their mark on Earth's surface. 'Meteor Crater', for example, is pretty obviously identified as the impact of a meteor due to its small size (and maybe other characteristics I am not aware of). Obviously this new crater and the Chicxulub crater are a different order altogether - the latter is identified as an asteroid impact but how certain can we be of this? Most readers here, I assume, will be most interested in the evidence for comets and cyclical 'cometary showers' impacting Earth. Is anybody aware of the details of how geologists identify the type of body involved in an impact and how weathering processes complicate this?
The crater is about 19 miles (31 kilometers) wide, more than twice as big as the next largest Saharan crater known. It utterly dwarfs Meteor Crater in Arizona, which is about three-fourths of a mile (1.2 kilometers) in diameter.
In fact, the newfound crater, in Egypt, was likely carved by a space rock that was itself roughly 0.75 miles wide in an event that would have been quite a shock, destroying everything for hundreds of miles. For comparison, the Chicxulub crater left by a dinosaur-killing asteroid 65 million years ago is estimated to be 100 to 150 miles (160 to 240 kilometers) wide."
This article interested me because it brings up an important point about the various classes of 'space object' which leave their mark on Earth's surface. 'Meteor Crater', for example, is pretty obviously identified as the impact of a meteor due to its small size (and maybe other characteristics I am not aware of). Obviously this new crater and the Chicxulub crater are a different order altogether - the latter is identified as an asteroid impact but how certain can we be of this? Most readers here, I assume, will be most interested in the evidence for comets and cyclical 'cometary showers' impacting Earth. Is anybody aware of the details of how geologists identify the type of body involved in an impact and how weathering processes complicate this?
