The last ice age on Earth ended about 11,000 years ago, but compared to the Snowball Earth scenarios, it was only a few climbs. Scientists believe that the Earth experienced several of these periods, when the entire surface was covered with ice and snow. New research from MIT points to a potential mechanism for events in Snowball Earth, which could help explain the evolution of complex life. It can also affect the search for exoplanets around other stars.
The ice age is simply a period during which global temperatures are falling enough for polar ice caps and alpine glaciers to expand. The snowball is on a completely different level, so it is difficult to identify the causes. Scientists have long assumed that it had something to do with a reduction in incoming sunlight or a decrease in retained global heat, but the MIT team specifically points to “peace-induced icing” as the primary cause.
Findings suggest that all you need for a snowball is a large enough drop in sunlight to reach the planet’s surface. Interestingly, modeling by graduate student Constantin Arnscheidt and geophysics professor Daniel Rothman shows that sunlight does not have to drop to any specific threshold to trigger Earth Bullets. Rather, it must decline rapidly over a geologically short period of time.
As the ice sheet increases, the planet reflects more light and icing becomes an “escape”. This is how you get to the snowball scene, but fortunately for us these periods are temporary. The planet’s carbon cycle is interrupted when ice and snow cover the entire surface, causing carbon dioxide to accumulate. Eventually, this leads to a warming trend that will break the Earth from the snowball season.
Research suggests that several ways in which sunlight could be reduced quickly enough to cause global icing. For example, volcanic activity could deposit particles in the atmosphere that reflect sunlight before they reach the surface. It is also possible that biological processes could change the atmosphere, creating more turbidity that would block the sun.
Two periods of suspicion of a snowball on Earth most likely occurred about 700 million years ago, a remarkable time in the planet’s history. This is also the case when multicellular life has exploded in the oceans. So maybe Snowball Earth cleared the way for the development of a complex life. It can be the same on other planets. Finally, we can notice exoplanets around distant stars in a “living area” covered with ice. That doesn’t mean they will be icy forever, and when they melt, big things could happen.
Top credit: Stephen Hudson / CC BY 2.5