From NOVA: “In the Past 24 Hours, 60 Tons of Cosmic Dust Have Fallen to Earth”

PBS NOVA

NOVA

13 Mar 2015
Allison Eck

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Sunlight reflecting off cosmic dust particles creates an effect known as “zodiacal light.”

Every day, bits of outer space rain down on the Earth.

Leftover from our solar system’s birth 4.6 billion years ago, cosmic dust is pulled into our atmosphere as the planet passes through decayed comet tails and other regions of chunky space rock. Occasionally, it arrives on Earth in the form of visible shooting stars.

But the amount of space dust that Earth accumulates is maddeningly difficult to determine. Some measures taken from spacecraft solar panels, polar ice cores, and meteoric smoke have attempted an answer, but the estimates vary widely, from 0.4 to 110 tons per day.

But a new paper claims to have narrowed that range. Here’s Mary Beth Griggs, writing for Popular Science:

[A] recent paper took a closer look at the levels of sodium and iron in the atmosphere using Doppler Lidar, an instrument that can measure changes in the composition of the atmosphere. Because the amount of sodium in the atmosphere is proportional to the amount of cosmic dust in the atmosphere, the researchers figured out that the actual amount of dust falling to the earth is along the lines of 60 tons per day.

The scientists published their results in the Journal of Geophysical Research.

It may sound like an academic exercise, but determining how much cosmic dust falls on the Earth can help us better understand a number of critical processes, such as cloud formation in the upper atmosphere and the fertilization of plankton in Antarctica. It also suggests that we may gain a better answer as to whether the Earth is gaining mass each year or losing it. (Our planet constantly leaks gases into space.)

Some of that cosmic dust is probably in you and me. While many of the elements that rain down from the heavens settle to the ground, it’s likely that we consume it in our food or inhale a tiny fraction of it. “We are made of star stuff”—Carl Sagan’s famous quote—rings truer than ever.

See the full article here.

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