Did Two Asteroids colliding in Outer Space seal the Fate of the Dinosaurs?

In 1980 the physicist Luis Alvarez and his son, geologist Walter Alvarez proposed a theory that an asteroid hitting the Earth might have caused the mass extinction that led to the demise of the dinosaurs.  High levels of the rare Earth element iridium had been found in sediments dating from the late Cretaceous and this led the father and son team to postulate that an asteroid impact could have wiped out much of life on Earth 65 million years ago.  Their theory was given further credence with the discovery, in 1990, of a huge impact crater found off the coast of Mexico.  Could this be the “smoking gun” evidence of an asteroid impact that led to the extinction of the dinosaurs?

The impact crater, now known as the Chicxulub crater (a Mayan word that translates to “tail of the devil”) is estimated to have been 112 miles (180 kilometres) across and was made by an object of around 6 miles in diameter (10 kilometres).  Evidence now suggests that there may have been a series of impacts around 65 million years ago.  Such a catastrophic bombardment would have resulted in global environmental damage, huge fires, acid rain and mega tsunamis.  Not surprisingly then that approximately 70% of life was wiped out.  This theory has been largely accepted by the scientific community, but debate has arisen as to where this asteroid object came from.  Now new research by a joint US and Czech team, published in the journal Nature points to an event between 140 mya and 180 mya that set in motion the asteroid collision that would spell doom for the dinos.

A Global Impact – Doom for the Dinosaurs?

Picture courtesy of astro-virginia.edu

A collision between two large asteroids in an orbit between Mars and the outer planets may have sent huge splinters of rock hurtling towards Earth, including the one that hit 65 mya claims the team from the South-west Research Institute of Colorado.

The three researchers, William Bottke, David Vokrouhlicky and David Nesvorny created a computer simulation that plotted the paths and direction of many large objects in what is known as the “Asteroid Belt” between Mars and Jupiter.  The orbit of one large terrestrial object known as (298) Baptistina intrigued them, as it shared the same orbital path with a lot of smaller asteroids.  Using the computer model to study the trajectories of these objects in the past, the team noted that the Baptistina asteroid and these other rocks were once joined together as a giant asteroid over 100 miles across, cruising the innermost region of the asteroid belt.  Their studies showed that between 140 mya and 180 mya (160 mya is the time period stated with most confidence by the researchers), a time when dinosaurs were dominating the Jurassic period – this huge asteroid was “bumped” into by another monster rock some 37 miles across (60 kilometres).

From this soundless collision was born a huge cluster of rocks, including 300 bodies larger than 6 miles in diameter (10km) and 140,000 bodies larger than 1/2 mile in size.  Over the remainder of the Mesozoic these rock pieces found new orbits under the influence of the Yarkovsky effect (named after the Russian engineer who identified this phenomenon), thermal particles from the Sun give objects momentum.  As the group of rocks spread out, at least some of them were captured by the gravitational pull of the inner planets and they began their journey with many impacting on Mars, Earth and Venus.

One such lump ended up colliding with Earth and causing the Cretaceous/Tertiary mass extinction.  The joint US and Czech team identify other celestial craters that may have been caused by debris from the Baptistina collision, a number of craters on Venus may have been as a result of this event and the huge moon crater Tycho estimated to be 108 million years old may also have been caused by an asteroid sent on its course by the initial impact 250 million miles away and approximately 60 million years earlier.

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