Asteroids, like this giant studied by Japanese researchers, are big chunks of early solar system rock moving at very high speeds in eccentric orbits around the Sun. This one is much larger than our recent gadfly, Asteroid 2009 DD45.
Asteroid 2009 DD45 unexpectedly whizzed close by Earth a couple of days ago, giving just a couple of days warning. Closest approach came less than five Earth diameters away. The lump of rock was between 19 and 43 meters across--more than big enough to equal the Tunguska Event, a massive air blast over Siberia which leveled 800 square miles of ancient Siberian forest in 1908. Most investigators think the Tunguska Event resulted from the explosion of a similar size asteroid as it entered the atmosphere.
Today, the impact of an asteroid of this size would result in human and economic, and natural catastrophe, wherever it occurred, whether or not we saw it coming.
The time scale of human life, even that of human civilization, is small compared to the frequency of catastrophic impacts of all sorts, both terrestrial and extra-terrestrial. The geological record is punctuated by countless catastrophes.
Even as we reflect on the occasions of the 200 year anniversary of Charles Darwin's birth, and the 150 year anniversary of the publishing of his On the Origin of Species; do we fail to fully encompass the stochastic nature of change that resulted in today's diversity and distribution of life?
Charles Lyell, geologist, proponent of "uniformitarianism," published his influential three volume Principles of Geology in 1830-1833. He gave Darwin deep time in which to operate his slow agents of change. And, he gave us all the next best thing to no change at all--gradualism, slow change we can live with comfortably.
If our lives spanned millennia rather than decades, maybe we'd have a better grasp of the importance of the sudden hiccups that shake things up and change outcomes globally. Maybe then we would encompass the meteoric speed of change Homo sapiens has brought, and the Earth-changing impact of that collision.
Asteroid 2009 DD45 details can be found at Tom's Asteroid Flybys Webpage.
See goodSchist for a discussion of asteroids and cosmic precursors for life: Cerces, Dawn and (no) Panspermia.