Target Earth [antikvár]

ForewordTarget Earth, the title of this book, describes our planet in its cosmic context If one phenomenon has dominated the sculpting of the many planets and moons we have investigated, forming the vast craters that pockmark their surfaces, it is impacts by asteroids and comets.Such hugely energetic events are not only important for geology.They are also of significance for biology. We know only of life on Earth, but rt is thought possible that microbial life could be transferred between the planets - from Earth to Mars, say, or vice-versa - within rocks blasted into space by massive impacts. Certainly many meteorites are_______ proven to have originated on the Moon, and^S. some on Mars. Whether the lattercontain signs of primordial Martian life \ is another matter__________\ Leaving aside the transfer of^^bacteria from planet to planet we---^xX \know that asteroid andf Sun \ 1 comet impacts over the eons have Earth 1 ) / influenced the evolution of ij\j/ terrestrial life. Although there is still^^ Aten_/xi' / much scientific debate on this---/ matten it is widely believed that th^V jijjj^ y^/ extinction of the dinosaurs (along wlihthe majority of other living things) / ---^ 65 million years ago was triggered by su^i animpact.The residual scan a crater around 120 miles (200 kilometers) wide, has been identified on the Yucatán Peninsula in Mexico. Debris from the explosion has been found spread all over the worid.This is not the only impact to be linked to a mass extinction event The southern end of Chesapeake Bay seems to have been shaped by an impact 35 million years ago. just a few months ago it was announced that another large crater had been recognized in Australia, one that may be linked to the biggest extinction of all some 250 million years back^^These were all truly cataclysmic events, releasing equivalent to hundreds of millions of megatons ofmT Although these super-impacts release pherawlmal energies, they occur very infi-equently, at interval^^ tens of millions of years. A more pressing danger is ijpiresented by those smaller impacts that release less enera a/pect hundreds of millions, perhaps billions, of people to,^ Mhe statistical calculations are quite simple.They sho^<

Termékadatok

Cím: Target Earth [antikvár]

Szerző: Duncan Steel

Kiadó: The Reader's Digest Association

Megjelenés: 2000. január 01.

Kötés: Fűzött kemény papírkötés

ISBN: 0762102985

Méret: 230 mm x 230 mm

Duncan Steel művei

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