From: LARRY KLAES (ljk4_at_msn.com)
Date: Tue Oct 23 2007 - 12:43:44 PDT
>From: Centauri Dreams <gilster_at_mindspring.com>
>Reply-To: Centauri Dreams <gilster_at_mindspring.com>
>To: ljk4_at_msn.com
>Subject: Centauri Dreams
>Date: Tue, 23 Oct 2007 14:04:46 -0500 (CDT)
>
>Centauri Dreams
>
>///////////////////////////////////////////
>Finding the Dino Killer
>
>Posted: 23 Oct 2007 01:00 PM CDT
>http://www.centauri-dreams.org/?p=1531
>
>
>By Larry Klaes
>
>Tau Zero journalist Larry Klaes now returns with a look at the impact that
>evidently killed the dinosaurs, and the unusual family of planetoids now
>thought responsible. Is Chicxulub an event that could only have happened in
>the distant past, or a warning of possible danger ahead?
>
>About 65 million years ago, a large planetoid at least six miles in
>diameter struck our planet at what is now the Yucatan Peninsula in Mexico,
>leaving a crater over 100 miles across. The force of the impact, which was
>two million times more powerful than the greatest nuclear bomb ever
>detonated, instantly killed every living thing within a one thousand mile
>radius.
>
>Many other creatures suffered similar fates when debris from the planetoid
>impact flung high into the air came plunging back to the ground, setting
>off firestorms that spread across the globe. The clouds of smoke and dust
>from this event hung in our atmosphere for several years, blocking out the
>Sun and terminating many plants that relied on solar energy for
>photosynthesis. As a result, many plant eating creatures died from the loss
>of their food source, which in turn affected the animals that preyed on
>them.
>
>The dinosaurs, having existed on Earth for over 160 million years, were
>among those victims who disappeared from our planet. The mammals, which
>until then had been little more than groups of rodents, came to prominence
>and are among the dominant species today, with humanity being among their
>members.
>
>One major factor that remained unknown was what made what is now called the
>Chicxulub crater. Scientists assumed it was either a planetoid or comet,
>but the Dino Killer’s exact nature and place of origin seemed lost in
>time and space.
>
>Now a team of team of researchers from the Southwest Research Institute
>(SwRI) and Charles University in Prague think they may know where the space
>rock in question came from. They have described their ideas in an article
>titled, An asteroid breakup 160 Myr ago as the probable source of the K/T
>impactor, published in the September 6 issue of the science periodical
>Nature.
>
>According to the theory developed by the international team, which includes
>Dr. William Bottke (SwRI), Dr. David Vokrouhlicky (Charles University,
>Prague), and Dr. David Nesvorny (SwRI), about 160 million years ago –
>give or take 20 million years – a large planetoid residing deep within
>the planetoid belt between the planets Mars and Jupiter was struck by a
>smaller but still significantly sized planetoid. The resulting debris
>became what is known today as the Baptistina planetoid family.
>
>Some of the many pieces from this family eventually drifted from the
>planetoid belt and became Earth-crossing objects. One space rock from the
>Baptistina family may have struck our Moon some 108 million years ago,
>creating the prominent ray crater Tycho in the lunar southern hemisphere.
>Another family member went on to form our planet’s Chicxulub crater,
>significantly changing the types of creatures on Earth 65 million years
>ago.
>
>Support for these conclusions comes from the impact history of Earth and
>Moon. Both worlds bear the scars of a two-fold increase in the formation
>rate of large craters over the last 100 to 150 million years.
>
>The Baptistina bombardment produced a prolonged surge in the impact flux
>that peaked roughly 100 million years ago, explained Nesvorny. This matches
>up pretty well with what is known about the impact record.
>
>For those who might think that the threat to our world from space has
>passed, Bottke warns that we are in the tail end of this shower now. Our
>simulations suggest that about 20 percent of the present-day, near-Earth
>asteroid population can be traced back to the Baptistina family. This means
>there is still a chance that a Near Earth Object (NEO) could strike our
>planet, causing destruction and death on a level equivalent to the one
>experienced by the dinosaurs.
>
>Ever since humanity became aware of this celestial danger, some scientists
>and others have been devising means to keep our species from going the way
>of the dinosaurs. As they planned methods to deflect and destroy NEOs that
>could strike Earth, they also realized that a detailed knowledge about the
>types of bodies that threaten our world needed to be made. Otherwise, an
>incorrect technique to protect our planet could make a bad situation worse.
>
>One method scientists have deployed to learn more about NEOs is with
>powerful radar beams from Earth, which determine not only the shape of such
>planetoids but also their makeup. Radar helps researchers learn if a
>planetoid is a solid or porous body. Such information is critical when
>determining how best to deflect or destroy a space rock headed for our
>world.
>
>The best tool for this task has been the Arecibo Radio Observatory on the
>island of Puerto Rico. The 1,000 foot wide dish is 25 times better than any
>other existing similar instrument for peering into the nature of these
>potentially deadly objects in space.
>
>Unfortunately for this branch of science, budget constraints imposed upon
>Arecibo by the National Science Foundation (NSF) have curtailed much of the
>planetary radar operations from that facility. The very existence of
>Arecibo itself is in jeopardy through the year 2011. With no other
>comparable facilities being built for at least a decade or more, it is
>hoped that those who control the finances in these areas will see the
>wisdom in continuing the study and search for planetoids that could cause
>irreversible harm to our civilization and all life on Earth.
>
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