Dating terrestrial impact structures
This gives a 3 to 1 chance that any incoming impactor will, if it doesn't explode a few miles up like whatever happenned at Tunguska in 1908, impact one of the oceans and leave no easily visible trace.
Secondly, any crater on dry land would be at the mercy of the elements, and should there have been collisions with cometary debris, or asteroids, in the Amazon Basin, say, then vegetation would without doubt obscure them in a very short time indeed.
There for all to see with the naked eye, and in even greater detail using a pair of good binoculars or a small telescope, are impact craters galore.
There doesn't appear to be one square mile of the lunar surface that is not pockmarked with impact craters, and while some are undoubtedly very ancient they also contain within their crater rims a multitude of newer craters from much more recent impacts.
This was a wake-up call even for those who understood what was going on, and resulted in more funding being requested by astronomers to research the frequency of impacts throughout the solar system, but also to search for any evidence of past impacts on Earth.
Here, these anthropic considerations are diversified in a host of new ways to identify the most sensitive features of biochemistry and astrobiology. Henderson, The Fitness of the Environment for Life, this book looks at the delicate balance between chemistry and the ambient conditions in the universe that permit complex chemical networks and structures to exist." "Astrobiology: A Multidisciplinary Approach is the most comprehensive textbook available for emerging upper-level courses in astrobiology.
Internationally renowned authority Jonathan Lunine gives students with a variety of backgrounds a solid foundation in the essential concepts of physics, chemistry, biology, and other relevant sciences to help them achieve a well-rounded understanding of the fascinating study of the origin of life, planetary evolution, and life in the cosmos." "Asteroids and comets: Every year, millions of these 'stray bullets' streak through the skies, and tons of small meteorites strike our planet!
Over the following decade interest began to rise in the idea of 'terrestrial impacts', and by 1990 most scientists at least accepted that the craters on our Moon were caused by impacts of cometary debris and asteroids of varying sizes, and not the volcanoes they had previously thought responsible.
As space exploration continued, the images sent back to Earth, especially by the Voyager spacecraft, allowed astronomers to build a picture of the sort of dynamic solar system first suggested by Victor Clube and Bill Napier in their groundbreaking books "Cosmic Serpent", published 1982, and developed further in "Cosmic Winter" published 1990. One where regular influxes of comets from the various areas of space transitted by our solar system in its orbit through the galaxy suggested inevitable, and multiple, collisions with all the planetary bodies and their respective moons.