On the evening of October 9, 1946, members of the Kaibab Trail crew at the Grand Canyon National Park were watching the sky during a meteor shower caused by the trail of Comet Giacobini-Zinner. When they saw a meteorite explode almost overhead with a brilliant flash, leaving a visible glow and smoke cloud.
Seconds later a small object hit the ground with a thud in front of the group. Soon located, it was too hot to handle for an hour – but expert analysis revealed it wasn’t what it seemed.
When space rocks survive the journey to the ground, traveling anywhere between 11 and 45 miles per second, atmospheric friction super-heats their surface. They briefly glow white hot. Small meteors vaporize completely. If grape-sized or larger their surface instantaneously melts then re-solidifies into a thin fusion crust.
Reaching the lower atmosphere, meteorites cease glowing, entering what’s called ‘dark flight.' Newly fallen, they’re never more than warm to the touch. Some are so cold that when picked up, people instantly drop them.
Having spent aeons in outer space, meteors are exposed to temperatures as low as -150 Celsius. Their atmospheric descent of just a few seconds allows no time for entry heat to transfer below that fusion crust.
And the apparent 1946 Grand Canyon meteorite? Two years later a member of the trail crew revealed he’d taken a clinker from the cook-stove and thrown it in front of his crewmates - as a practical joke!
This Earth Note is funded in part by Pink Jeep Tours, written by Diane Hope and produced by KNAU and the Sustainable Communities Program at Northern Arizona University.
