A creation story provides unique insight into the values a culture holds and the relationship it finds between God, humanity, and the natural world. While more limited, scientific explanations for the formation of the solar system and the development of life can also shed light on the interconnectedness of our species, our civilization, and our place in the universe. The history of the Earth begins with the formation of the sun approximately four and one half billion years ago, from a cold molecular cloud in interstellar space that began to collapse. As the cloud collapsed, a disk of debris encircled the newly-forming sun. Within the disk, small clumps began to grow by sweeping up nearby debris. Eventually the largest clumps cleared a path within the disk and became a planet. While much of the material within the disk fell into the center to become part of the sun, or collided with an orbiting clump to be incorporated into a planet, or was ejected from solar system entirely, a very small fraction remains to this day in orbit around the sun. Meteors, asteroids, and comets remain, ranging in size from small dust particles to minor planets the mass of Mt. Everest.
Because the planets of our solar system formed from collisions with smaller objects, some near misses and collisions continue to this day. At 2:25pm on Friday, February 15, 2013 Asteroid 2012 DA14 will pass approximately 17,000 miles above the Earth’s surface (too faint to see with the unaided eye but visible using a binoculars or a small telescope over Australia and Indonesia). Asteroid 2012 DA14 is a rocky body about fifty yards in diameter with a mass of more than 180,000 tons. While this is the closest observed approach of an asteroid this size, we know that a similar-size object struck the Earth in 1908. Luckily in 1908 that asteroid exploded in the atmosphere above an unpopulated region in Siberia leveling over 800 square miles of trees. The dust in the atmosphere from the explosion caused the night sky to glow and blocked sunlight measurability for several days. Newspapers at the time reported being able to read by the glow in London. Seismographs also recorded the explosion. However, because of the tumult of world events and the remote location of the impact site, scientists did not explore the site until 1927. Astronomers estimate that collisions like the 1908 Tunguska event occur once every 1,200 years.
Luckily, Asteroid 2012 DA14 will not strike the Earth and will likely not cause any disturbance at all. However, its close approach reminds us of the potential threats posed by the remaining debris from the formation of the solar system. In general, the larger the object, the less frequently a collision occurs. A mile-wide asteroid or comet did strike the Earth near the Yucatan Peninsula sixty-five millions years ago. That impact altered the climate enough to cause the extinction of a significant fraction of life on earth, including all species of dinosaurs. Thanks to that collision, placental mammals evolved and radiated to fill many of the environmental niches previously occupied by dinosaurs. Scientist studying molecular and morphological evolution extrapolated what the common ancestor to all the species of placental mammals might have looked like. Their work was published last week. Pictured to the left, the animal is estimated to be a bit smaller than a squirrel. This hairy, long-tailed ancestor of all non-marsupial mammals lived with the dinosaurs and somehow survived the mass extinction after the devastating collision. So, this week as Asteroid 2012 DA14 passes overhead it serves as a reminder of the processes that formed and continue to shape the Earth and its inhabitants.