How the collision of two asteroids caused an ice age on Earth

Jose Vicencio Veloso Jose Vicencio Veloso 7 minutes
Glaciers are currently located mostly in the polar areas and highlands of the planet. But in glacial times, they advance and cover much larger areas at the expense of seawater and therefore, reducing the sea level.

Changes, everything changes. Even the weather. We humans know this very well. Today, our planet is warming very quickly due to the emission of greenhouse gases. But before us, the climate has changed many times, sometimes slowly and sometimes very violently.

The direct impact of a meteorite on planet Earth is not only an inexhaustible source for natural disaster movies, but also, partially explains some of the mass extinctions that have occurred in the past. The extinction of the dinosaurs—around 60 million years ago—is one of them.

But scientists have just discovered that asteroids could affect the planet’s climate in a much more indirect way and, in fact, promote the development of life on Earth. How is that possible?

The Ordovician glaciation

About 466 million years ago, the Earth was very different from what we know today. The day lasted about 21 hours —our planet was spinning on its own axis faster then— and there is no evidence of wildlife on the land surface. Instead, all life developed below the sea surface.

But very abruptly, the hot, high-temperature climate was replaced by low temperatures, completely frozen polar oceans and a drop in sea level.

Using different techniques, scientists have managed to rebuild “the weather” of the planet in the last 500 million years, as can be seen in the following figure.

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Approximate variation of the temperature of the Earth with respect to the current temperature, through a reconstruction made with stable isotopes of oxygen-18 (O18). The blue curve is the fine variation and the black curve the smooth variation. Light blue colors indicate glacial periods. Graph adapted from Velzer et al. (1999).

The decrease in the temperature of the Earth suffered about 460 million years ago is known as the Ordovician glaciationand implied that Earth will cool by about 5 degrees in a “few” million years.

The origin of this ice age—which lasted several tens of millions of years—has been the subject of debate in the geological community. But a recent study seems to solve this mystery.

Interstellar dust delivery

The rock analysis of what used to be shallow sea beds in the ordovician epoch show a marked presence of granite material known as L-Chondrite (in English, L-Chondritic).

What is special about L-Chondrite? It turns out that this type of material comes directly from space. L-Chondrite is one of the most common meteorites on our planetso the abundance of such material shortly before and also during the glaciation period caught the researchers’ attention.

East interstellar dust it accumulated at the bottom of the shallow oceans, leaving a very marked imprint on the rocks. Somehow, meteorite material became more and more prevalent in the airin such a way that after millions of years it managed to cross the different layers of the atmosphere, and was over depositing on the ocean floor.

How can this interstellar dust get into the ocean?

The hypothesis is the following: a few million years before the start of the ice age, there was a huge collision between two asteroids (between the orbits of Mars and Jupiter).

This collision disintegrated the asteroids (which were originally between 100 and 200 km in diameter) into small pieces that were scattered throughout the solar system. After several million years, this material slowly began to surround our planet.accumulating first in the upper parts of the atmosphere, to later reach the Earth’s surface.

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Schematic figure of the processes that led to the Ordovician glaciation, according to Schmitz et al. (2019).

It is quite common for stellar material to enter our atmosphere.. In fact, each year about 40 thousand tons enter. But during the period before the ice age, thanks to the debris from the collision of asteroids, that number increased ten thousandfold.

The effect on the climate was slow and gradual.. These small particles suspended in the upper part of the atmosphere began to block solar radiationjust like a curtain does on a window.

This layer of dust caused the decrease in the Sun’s radiation, which in turn resulted in the generalized cooling of the planet observed about 460 million years ago and would explain the existence of this glacial period.

Because the decrease in temperatures was gradual and slow, the marine fauna managed to adapt in a good way to this process. Furthermore, there was a biodiversity explosion that helped the development of new species.

In this sense, the studies concluded that the entry of space material into the atmosphere due to the collision of meteorites was rather positive for life on earth, because the process was gradual.

The Article Is In Spanish🡽

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