Smoke and Mirrors: The Legacy of a Veteran Cosmic Rock
Imagine life as a rock the size of an average suburban house, hurtling through the lonely void of the inner solar system. Every 293 days you lap the Sun, ranging between the orbits of Venus and Earth. It is June 1, 2004, and you have just passed a comfortable 33 million kilometers behind cloud-shrouded Venus, a planet baking in a runaway natural greenhouse.
Earth is the second brightest planet in your sky. It grows slightly more luminous with each passing day as you travel outward. By early July, the blue dot of Earth exceeds Venus in spectacle. You aren't alarmed; your orbit has been travelled countless thousands of times before. However, on this passage around the Sun, things are different. As fate would have it, on September 3rd, that blue dot will sneak up from behind and run you down!
That fateful time has arrived. Looking towards the Earth, you see the icy wilderness at the edge of the Antarctic coast, clearly outlined amongst broken cloud late in the afternoon. You start to feel the outer fringes of Earth's atmosphere about 120 km from the surface. It is now too late. Travelling at a relative speed of 13 km per second, it's all going to be over before you can nervously count the Sun's planets. Friction with gases in Earth's atmosphere turns you into a rapidly brightening 'shooting star', decelerating and shedding your mass at an increasing rate. Passing through 56 km altitude, a thermal shockwave starts to race through you. At 32 km from the surface, the shockwave literally breaks you apart, shedding several large pieces which are almost completely turned to dust in less than a second. All that remains is a smoke trail in the sky, and a few stones on the sea ice.
So was the demise of one of the largest meteoroids to have collided with the Earth in the past decade. Read how this visitor came to be detected in one of the remotest corners of the planet using a powerful laser, a stroke of good luck, and a global network of sensors in Cosmic Hole-in-One and Dodging Armageddon, articles in the Autumn 2005 issue of the Australian Antarctic Magazine. And what has this event told us about the workings of our atmosphere and primitive material in our own solar neighbourhood…
Written by Andrew Klekociuk – Ice, Oceans, Atmosphere and Climate program
Lidar video clip – Footage: P Nink and A Cunningham
Simulated view of the Earth (without clouds) as seen from the meteoroid 10 minutes before impact.
Image created by Earth and Moon Viewer, by John Walker