One popular theory for dinosaur extinction suggests that a 10 kilometer diameter asteroid impacted 65
million years ago in the northwestern part of the Yucatan Peninsula in Mexico.  The impact of this
extraterrestrial object threw up enough dust into the upper atmosphere to cause a climate change
resulting in a breakdown of the food chain and ultimately the death of the dinosaurs.  Molten rock, ejected
from the impact, started massive firestorms which raged across the planet pumping huge amounts of
smoke and ash into the air and blocking out sunlight.   Geological evidence for this theory is present
worldwide in a very thin layer of clay in the rock strata corresponding in time to dinosaur extinction.  It is
called the "K-T boundary" and dinosaur fossils are found in the layers below the "K-T boundary" but not
above it.  The K-T clay contains soot from fires and is rich in the rare earth element of Iridium which is
plentiful in asteroid material.  The impact of this size meteorite would have started a catastrophic chain
reaction of events, firstly, a shock wave of hot high speed winds from the blast, followed by earthquakes,
tidal waves, volcanic eruptions and global fires.  Winds would have spread the cloud of debris causing
worldwide darkness and a drop in temperatures.  After a few months of darkness, carbon dioxide from the
global fires would have caused an increase in temperature and acid rain.  Only a few small, rugged
species of life, such as crocodiles and turtles, were able to survive this event.- (see below)  The Yucatan
impact, Tunguska fireball and
the Barringer meteor crater in Arizona USA, prove that earth is impacted by
large objects from time to time.  It's not a question "IF" such an object will collide with earth again, only
the question of "WHEN" it will hit.  If this doomsday object is detected early enough, perhaps the power of
space science can nudge it off course and save life on earth from another dinosaur type of extinction.  If
successful, this space mission alone would be worth every penny that has been spent on space research.
Meet Tripod, a three legged box shell turtle who once lived in my garden.  Tripod enjoyed
earthworms, crickets, bananas, dog food and kitchen scraps.  A rugged species, changing
little over 65 million years, her type once walked with, and was stepped on, by dinosaurs.  
Unfortunately, turtles don't do well in modern times because many are killed on roadways.   I
rescued Tripod after she lost her left rear foot due to a passing car.  Fully recovered from her
injury, I recently set her free within a wildlife refuge, far away from any roads.  I'm protective
of all wildlife and I always move turtles off roads when it can be safely done.  The Box Shell
turtle (more correctly called tortoise) is a land dweller, a gentle, timid creature that will usually
draw up into its shell when approached.  I was lucky to have captured the photo above.  Note-
Box Shells, like Tripod, are safe to handle and will not bite, even if they are provoked.  
However, some species of water turtle are very aggressive, like the snapping turtle which
strikes at you fast and it has a long reach with neck length equal to shell length.  So, BE
WARNED, know in advance what you're handling !!!  Check the WWW for more information.