[X] My Assistant

[alan]

At least three massive asteroids smashed into the Earth more than 3.2 billion years ago, and caused such destruction, they dramatically changed the structure and composition of the Earth's surface. This is according to new research from scientists at the Australian National University. The team uncovered evidence of major earthquakes, faulting, and volcanic eruptions that were so violent they dramatically changed the way the Earth's surface was forming. This happened during a period that the Moon also suffered heavy bombardment.

“Our findings are further evidence that the seismic aftershocks of these massive impacts resulted in the abrupt termination of an over 300 million years-long evolutionary stage dominated by basaltic volcanic activity and protracted accretion of granitic plutons,” Dr Glikson said.

“The precise coincidence of the faulting and igneous activity with the impact deposits, coupled with the sharp break between basaltic crust and continental formations, throws a new light on the role of asteroid impacts in terrestrial evolution,” Dr Glikson said.

http://www.universetoday.com/am/publish/ea...ids.html?582005

Could one of the geologist interpret this please.

[Guest_Richard Trigaux_*]

I do not see any reason so that secondary impact may gather in the antipodes. But I cannot say definitively no, this would deserve a study, for instance about Tycho. But the antipodes of Tycho are out of reach of amateurs telescopes, they are in the databases of images... Where?



A common phenomena is that there are often secondary impactors. For instance the 20kms Ries crater in Germany has a secondary 1km crater with the same date. The Chixculub too has a secondary in the USA, although there is no evidence it was simultaneous. There is a Moon crater (Copernic, I guess, but I am not sure) surrounded by a hundred of small craters all around, as if the main impactor was followed by a swarm of debris.

[tty]

I do not see any reason so that secondary impact may gather in the antipodes. But I cannot say definitively no, this would deserve a study, for instance about Tycho. But the antipodes of Tycho are out of reach of amateurs telescopes, they are in the databases of images... Where?

Actually this is a well-known and well-documented phenomenon, and actually rather obvious if you consider the trajectories. For more details see e. g.

http://www.lpi.usra.edu/meetings/lpsc97/pdf/1252.PDF

http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1447.pdf

However I'm not sure how it would work on the Moon where the escape velocity is only 2.3 kms-1. Most of the high-energy ejecta would probably escape altogether or be greatly perturbed by the Earth. Mars would be a better place to look.

tty