It came from outer space
by Mary Aegerter | © Washington State University
The dust on your mantelpiece may be more interesting than it appears at first swipe. Some of it may be from outer space. While that may not make much difference to your dust rag, some feel that extraterrestrial dust might help explain the cyclical nature of the Earth’s climate, says Ed Brook, assistant professor of geology and environmental science at Washington State University's Vancouver campus.
Brook and his collaborators have developed a method to measure the extraterrestrial dust found in the ice cores taken at Vostok, Antarctica. It involves filtering the dust out of the ice core, a process that takes four days per sample, then assaying the dust for an isotope of helium that’s prevalent in outer space but rare on earth. Brook and his colleagues are using it to construct a record of the dust flux from the Vostok ice cores over the past 100,000 years.
The Vostok ice cores hold a well studied record of climate over that time, says Brook. “We know the rates of accumulation of the ice, and we know very well how the ice record relates to changes in climate.” If the extraterrestrial dust is responsible for cyclical change, the pattern of its accumulation should track with the climate change.
Brook doesn’t think it’s likely that extraterrestrial dust is responsible for the 100,000-year climate cycles characteristic of the last million years. “There’s not enough extraterrestrial dust,” he says—at least not to influence climate directly. The link could be more obscure. The dust might have changed the upper atmospheric chemistry. “Or maybe,” he says, “the dust is rich in iron, a limiting nutrient for phytoplankton.” Increased numbers of phytoplankton presumably would reduce atmospheric CO2 and cause climate change.
But even if large changes in the amount of extraterrestrial dust don’t track with climate change, they would be of interest.
If there’s no variation in the amount of extraterrestrial dust over time, glaciologists will be happy. An even dust fall would mean a higher concentration of dust in years of little snow fall, a lower concentration in years of high snow fall—a means of determining rates of ice accumulation in the past.
Any data will be useful to scientists working to understand how dust moves in the solar system, as well as to those who study the origin of the atmosphere and oceans—for it’s believed that most of our volatile elements such as hydrogen, oxygen, nitrogen, and carbon came here in meteorites.
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