The last ice age on Earth ended about 11,000 years ago, but that was just a few blurs compared to so-called Snowball Earth scenarios. Scientists believe that the Earth experienced some of these periods when the entire surface was covered with ice and snow. New research from MIT points to a possible mechanism for events on Earth with Snow, and that may help explain the development of complex life. It can also affect the search for explorations around other stars.
An ice age is simply a period during which global temperatures drop enough for polar ice caps and alpine glaciers to expand. A Snowball Land is on a completely different level, and this has made it difficult to identify the causes. Researchers have long speculated that it may be due to reduced incoming sunlight or a drop in stored global warming, but the MIT team specifically points to “scale-induced glaciations” as the main cause.
The findings suggest that all you need for a Snowball Earth is a fairly large drop of solar radiation reaching the planet’s surface. Interestingly, modeling done by graduate student Kostandin Arnscheidt and geophysics professor Daniel Rothman shows that solar radiation does not have to fall on any particular threshold to cause a Snowball Earth. Rather, it simply has to fall quickly over a short period of geological time.
As the ice cover grows, the planet reflects more light and glaciation becomes a “runaway” effect. So you get to a Snowball scenario, but fortunately for us, these periods are temporary. The planet’s carbon cycle is interrupted when ice and snow cover the entire surface, and this causes a build-up of carbon dioxide. Eventually, this leads to a heat trend that explodes the Earth from a period of snow.
Research suggests several ways that solar radiation can go down fast enough to cause global glaciation. For example, volcanic activity can deposit particles in the atmosphere that reflect sunlight before it reaches the surface. It is also possible that biological processes can change the atmosphere, producing more cloud cover to block the sun.
The two suspected periods of Snow Land are likely to have occurred about 700 million years ago, which is an obvious time in the history of the planet. This is also when multicellular life erupted in the oceans. So perhaps, Snowball Earth cleared the way for the development of complex life. It could be the same on other planets. We can finally spot exoplanets around distant stars in the “habitable zone” covered in ice. This does not mean that they will be icy forever, and great things can come if melted.
Top Figure Credit: Stephen Hudson / CC BY 2.5