by Chris Peterson » Sun Jan 01, 2017 6:29 pm
Sam Brewster wrote:Given how battered the moon, might we infer that planet earth has received that many more hits in its 5 billion years? And given the wealth of these moon hits, what might be the best estimate of measurable frequency for both locations....once per century? More? Less?
Impact cratering follows a power law- the larger the impact, the less frequent. Most of the cratering on the Moon was formed during the Late Heavy Bombardment, when the entire inner solar system was being impacted. But since this happened about 4 billion years ago, virtually all geological evidence of those impacts on the Earth have been removed. After that, the impact rate declined significantly.
On the Moon, the rate of readily detectable impacts is several per day. Impacts large enough to create craters visible from Earth with careful telescopic observation might occur every few years. Impacts large enough to create craters visible to the naked eye probably only occur on a scale of thousands of years or longer. Some bodies (in the 10 m diameter range) will create small craters on the Moon but would not be capable of cratering the Earth, because they'd break up in the atmosphere. 50-100 m bodies that can create small (km scale) craters on Earth occur every few tens of thousands of years, similar to the lunar frequency.
[quote="Sam Brewster"]Given how battered the moon, might we infer that planet earth has received that many more hits in its 5 billion years? And given the wealth of these moon hits, what might be the best estimate of measurable frequency for both locations....once per century? More? Less?[/quote]
Impact cratering follows a power law- the larger the impact, the less frequent. Most of the cratering on the Moon was formed during the Late Heavy Bombardment, when the entire inner solar system was being impacted. But since this happened about 4 billion years ago, virtually all geological evidence of those impacts on the Earth have been removed. After that, the impact rate declined significantly.
On the Moon, the rate of readily detectable impacts is several per day. Impacts large enough to create craters visible from Earth with careful telescopic observation might occur every few years. Impacts large enough to create craters visible to the naked eye probably only occur on a scale of thousands of years or longer. Some bodies (in the 10 m diameter range) will create small craters on the Moon but would not be capable of cratering the Earth, because they'd break up in the atmosphere. 50-100 m bodies that can create small (km scale) craters on Earth occur every few tens of thousands of years, similar to the lunar frequency.