The last ice age on Earth ended about 11,000 years ago, but that was just a few flurries compared to the so-called Earth Snowball scenarios. Scientists believe the Earth experienced many of these periods when the entire surface was covered in ice and snow. New research from MIT indicates a potential mechanism for Snowball World events, and that may help explain the development of complex life. It can also impact the search for exoplanets around other stars.
Ice age is simply a period during which the global temperature drops enough for polar ice caps and alpine glaciers to expand. Snowball World is on a completely different level, making it difficult to identify the causes. Researchers have long assumed it has to do with incoming sunburns or retained global warming, but the MIT team specifically refers to “rate-induced glaciations” as the primary cause.
The findings suggest that all you need for Snowball Earth is a large enough drop in solar radiation to reach the surface of the planet. Interestingly, the modeling done by graduate student Constantin Arnscheidt and geophysics professor Daniel Rothman show that solar radiation should not drop to any particular limit to trigger a Snowball World. Rather, it only needs to drop rapidly over a geologically short period of time.
When ice cover increases, the planet reflects more light and glaciation becomes a “runaway” effect. This is how you can 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, causing the accumulation of carbon dioxide. Eventually, this leads to a warming trend that breaks the Earth out of a snowball period.
Research suggests a few ways solar radiation can decrease fast enough to lead to 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 Earth bubble occurred probably about 700 million years ago, which is a remarkable time in the history of the planet. That’s also when multicellular life exploded in the oceans. So perhaps, Snowball Earth has cleared the way for the development of a complex life. It could be the same on other planets. We could eventually look at exoplanets around distant stars in the snow-covered “habitable zone.” That doesn’t mean they will be icy forever, and big things can come as soon as they dissolve.
Top image credit: Stephen Hudson / CC BY 2.5