Scientists discovered the cause of an ancient ice age that might help us in our fight against climate change.
When thinking of an ice age, most people probably imagine the one from the popularized films centering around a group of warm-blooded animals migrating south in an attempt to survive the cold. That particular ice age took place in the paleolithic, approximately twenty thousand years ago. Earth has encountered many more ice ages during its lifetime though. One of them took place almost half a billion years ago, far before the age of the dinosaurs.
Image Credit: Lttiz via Wikimedia Commons - HDR tune by Universal-Sci - CC BY-SA 3.0
This ancient ice age set the stage for a boom of new species evolving with the new range of temperatures around the planet. The catalyst of this important ice age though, has eluded scientists for many years, until now. A recent study published in Science Advances asserts that this ice age was caused by global cooling, triggered by increased amounts of dust in the atmosphere of earth originating from a giant asteroid collision in outer space.
It's pretty normal for dust from outer space to float down to Earth. Usually, this dust originates from small bits of asteroids and comets, but it normally counts for only a small portion of all the dust in our atmosphere. Most of the regular dust in our atmosphere originates from volcanic ash, deserts and sea salt. Yet something different was the case 466 million years ago when a titanic (approximately 150 kilometer wide) asteroid between Mars and Jupiter broke apart. It created incredible amounts of space dust that would eventually reach Earth.
According to Phillip Heck, one of the paper's authors, it is normal for Earth to gain about 40.000 tons of dust from space every year. But imagine multiplying that by a factor of a 1000 or even 10.000. To put this in context, Heck stated that the Earth receives about one thousand semi-trucks worth of extraterrestrial dust in an ordinary year. In the two million years after the asteroid collision, it would have been approximately ten million trucks.
The scientists hypothesized that those massive amounts of space dust, flowing down to Earth over a period of 2 million years, played a significant role in the cooling climate. Lead author Birger Schmitz added that their results show for the first time that such dust, at times, has cooled Earth significantly.
To decipher all of this, researchers searched for traces of space dust in 466 million year old rocks and matched it with tiny micrometeorites from Antarctica as a reference. "We studied extraterrestrial matter, meteorites, and micrometeorites, in the sedimentary record of Earth, meaning rocks that were once seafloor," says Heck. "And then we extracted the extraterrestrial matter to discover what it was and where it came from."
This is a 466-million-year-old fossil meteorite, created in the same asteroid collision that caused the dust that led to an ice age. - Image Credit: (c) Field Museum, John Weinstein
Different researchers had already discovered that our planet was experiencing an ice age somewhere around this time. Schmitz and his colleagues are the first to show that this ice age syncs up with extra dust in Earth's atmosphere. The dust would have filtered out the sunlight causing the planet to cool down. Because the dust drifted down to Earth over two million years or more, the lowering of temperature was gradual enough for life to adjust and even benefit from the changes. An outburst of new species evolved as animals adjusted for survival in regions with contrasting temperatures.
According to the researchers, it is essential to note that life on Earth could only adapt because of the slow-paced changes in temperature. A quick change in climate can actually be disastrous. Heck pointed out that the rapid climate change caused by the meteorite that killed the dinosaurs, for example, was catastrophic.
It is attractive to think about adding the mechanics behind this discovery to our toolbox used in the fight against climate change. But according to Heck we should be careful with trying to solve our current global warming problems by looking at dust blocking sunlight. We could very easily make things worse if something goes wrong. Geo-engineering is complicated and should not be considered lightly. Nonetheless, Heck stated that it is a good idea to explore any concept that might help us in our fight against global warming, be it cautiously.
Sources and further reading: Field museum press release, Ice Ages
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