I thought this was quite interesting about the wild times of the heavy bombardment period during rhe early days of earth, the moon and Mars. Things were apparently 3x or more crazier than we knew about!
Prior to a few years ago, it was thought there were only about 45 large (300km+) craters on the moon. In the paper below from the NS article about an upcoming presentation to the Lunar and Planetary Science Conference , Frey has increased the crater count to over 150 craters 300 km+ in size. I'd like to see a copy of this paper, if anyone has a copy.
If you want to read more on the subject, here is a reference to an earlier paper by Frey describing 92 additional 300km+ craters uncovered on the moon, complete with a map. The moon looks like one highly damaged target with huge basins on opposing parts of the globe! http://www.docstoc.com/docs/1084042...ar-Impact-Basins-Revealed-by-Topographic-Data
If you have more interest, Frey has also studied the large crater impacts on Mars too. Here is one interesting paper, with a map, of some of the previously unknown large buried Martian craters: http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2018.pdf Frey also believes that the Mars suffered a huge double-strike of 3000 km craters just prior to the formation of Hellas (another big hit): http://www.lpi.usra.edu/meetings/lpsc2008/pdf/1342.pdf
The possible short (~56 MY) period of
time between two very large impacts that produced 3000 km
wide basins of very different central crustal thicknesses in the
highlands (Ares, 37 km) and lowlands (Utopia, 15 km) may
require that crust was “pre-thinned” prior to the formation of
large lowland basins.
http://www.newscientist.com/article/mg20126993.500-moon-hides-scars-of-a-violent-past.html
Moon hides scars of a violent past
13 March 2009
THE moon has been hiding the scars of its violent, asteroid-filled past.
Most surveys of lunar impact craters have used photos, but Herbert Frey of NASA's Goddard Space Flight Center in Greenbelt, Maryland, wanted to know if there were any old craters buried beneath younger ones. So he studied elevation mapping data from the Clementine mission in the 1990s. He also used simulations to identify impact signatures, such as a roughly circular crater with a thin crust and a thicker rim. This approach uncovered 150 craters more than 300 kilometres wide instead of 45.
Frey is now trying to work out the age of the newly found craters. If they are the same age as the others, this would support the idea that asteroids bombarded the inner solar system for a particularly intense period about 4 billion years ago. Some researchers think that life may have existed before this bombardment, but if so, its survival now seems less likely, says Andrew Valley of the University of Wisconsin, Madison. "The probability that early primitive life, if it existed, could find refuge, even in sediments beneath the ocean would be reduced," he says.
Frey, who will present the work at the Lunar and Planetary Science Conference in Woodlands, Texas, later this month, expects more subtle features to be discovered when the Asian lunar probes release further data and NASA's Lunar Rover Orbiter launches in May
Prior to a few years ago, it was thought there were only about 45 large (300km+) craters on the moon. In the paper below from the NS article about an upcoming presentation to the Lunar and Planetary Science Conference , Frey has increased the crater count to over 150 craters 300 km+ in size. I'd like to see a copy of this paper, if anyone has a copy.
If you want to read more on the subject, here is a reference to an earlier paper by Frey describing 92 additional 300km+ craters uncovered on the moon, complete with a map. The moon looks like one highly damaged target with huge basins on opposing parts of the globe! http://www.docstoc.com/docs/1084042...ar-Impact-Basins-Revealed-by-Topographic-Data
If you have more interest, Frey has also studied the large crater impacts on Mars too. Here is one interesting paper, with a map, of some of the previously unknown large buried Martian craters: http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2018.pdf Frey also believes that the Mars suffered a huge double-strike of 3000 km craters just prior to the formation of Hellas (another big hit): http://www.lpi.usra.edu/meetings/lpsc2008/pdf/1342.pdf
The possible short (~56 MY) period of
time between two very large impacts that produced 3000 km
wide basins of very different central crustal thicknesses in the
highlands (Ares, 37 km) and lowlands (Utopia, 15 km) may
require that crust was “pre-thinned” prior to the formation of
large lowland basins.
http://www.newscientist.com/article/mg20126993.500-moon-hides-scars-of-a-violent-past.html
Moon hides scars of a violent past
13 March 2009
THE moon has been hiding the scars of its violent, asteroid-filled past.
Most surveys of lunar impact craters have used photos, but Herbert Frey of NASA's Goddard Space Flight Center in Greenbelt, Maryland, wanted to know if there were any old craters buried beneath younger ones. So he studied elevation mapping data from the Clementine mission in the 1990s. He also used simulations to identify impact signatures, such as a roughly circular crater with a thin crust and a thicker rim. This approach uncovered 150 craters more than 300 kilometres wide instead of 45.
Frey is now trying to work out the age of the newly found craters. If they are the same age as the others, this would support the idea that asteroids bombarded the inner solar system for a particularly intense period about 4 billion years ago. Some researchers think that life may have existed before this bombardment, but if so, its survival now seems less likely, says Andrew Valley of the University of Wisconsin, Madison. "The probability that early primitive life, if it existed, could find refuge, even in sediments beneath the ocean would be reduced," he says.
Frey, who will present the work at the Lunar and Planetary Science Conference in Woodlands, Texas, later this month, expects more subtle features to be discovered when the Asian lunar probes release further data and NASA's Lunar Rover Orbiter launches in May
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