City Creek Nature Notes – Salt Lake City

February 21, 2017

February 21st

Filed under: Astronomy, Geology — canopus56 @ 10:20 am

Star Dust

8:30 a.m. It is another clear, sunny, warm day, and the morning sun climbs down the east facing canyon walls. Dust can be seen in the air of the canyon and now as an orange brown tinge on the last remnants of snow banks at the side of the road. A few dust molecules in the canyon have fallen on the road from outer space or as I jog, I have inhaled some of them into my lungs. In 2014, Gardner at the University of Illinois and colleagues, using a laser to measure the upper atmosphere, made an improved estimate of the number of tonnes of space dust that falls on the Earth each day: about 60 tonnes (Gardner). The dust consists of particles emitted by the Sun, contained in the interplanetary dust ring in the plane of our solar system, grains from the collisions of asteroids, the remnants of comet tails, and to a lesser extent, interstellar dust particles from other solar systems (Gardner; Westphal). Doing some rough, simple estimating, there are 907,185 grams in a ton and 510.1 trillion square meters on the surface of the Earth, including the oceans. Thus, there are 1.76 x 10^-8 grams of space dust falling on each square meter of the Earth everyday. There are 19.2 square miles in the canyon and the canyon first began to form 11 million years ago (Hintze). Thus, between its formation and the present, about a 1.76 square meter of star dust has fallen on the canyon; a cube whose one side is about the height of a man. That dust is spread on the canyon’s surface, is embedded in its rocks, or has washed away and or eroded out to the Great Salt Lake. Every day, I jog about 4 miles or 6,500 meters. During that jog, I estimate that the 6,500 square meters that I run over contain a total of approximately 0.0001 grams of star dust. In a sense, as Joni Mitchell reminded us, I am also star dust because the Earth and everything on it was formed from the dust left over by an Archean nova. That I am running each day through a few molecules of new space and interstellar star dust gives me a sense of a connection to wider universe outside of my daily life.


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