‘Snowball Earth Was Crushing And Cold. What Animals Could Survive It?

This article originally appeared in Hakai, an online publication about science and society in coastal ecosystems. Read more stories like this at hakaimagazine.com.

Once upon a time, planet Earth was a cross between a freezer and a car shredder. At vast distances in the history of the planet, everything from pole to pole was crushed by a layer of ice a kilometer or more thick. Scientists call this Earth Snowball.

Some primitive animals managed to survive this cold period from about 720 to 580 million years ago, but they did not have enough work. Despite their valiant successes, the constant expansion and contraction of the gigantic ice sheets has destroyed the remains of strong, hardy creatures whose records are almost non-existent, and scientists do not know how they managed to survive.

“It looks like a giant bulldozer,” says Hugh Griffiths of the British Antarctic Survey. "The next expansion of the glacier will erase everything from the face of the earth and turn it into chaos."

While there's no direct evidence from all of these glacial upheavals, Griffiths says it's reasonable to assume that a wide variety of animals bred on Earth. This suggests that this epoch should have preceded the so-called Cambrian explosion, that is, about 540 million years ago, when an unprecedented variety of animals appeared on Earth. “It's not a huge leap of the imagination that there are smaller, simpler things,” says Griffiths.

The full picture of animal life at that time has been lost, but Griffiths and his colleagues are trying to figure out how this could be in a recent paper.

The team considered three different frozen periods. The first was the Sturtovo Snowball Earth, which began about 720 million years ago. This continued for up to 60 million years. This is a staggeringly long period between the end of the dinosaur age and today. Then came Marino Snow Land, which began 650 million years ago and lasted only 15 million years. It was followed by the Gasquière Glacier about 580 million years ago. This third ice age was shorter and is often referred to as Snowball Land rather than Snowball Land because the ice sheet may not have been as extensive.

Although the ice crushed most of the fossils from these periods, scientists have found some remains. These rare fossils depict amazing animals that existed during the Gasquier Ice Age. Among these ancient inhabitants of the Land of Snow were forelimbs, organisms a bit like fern leaves. Frondamorphs lived on the seafloor under the ice and may have extracted nutrients from the water that flowed around them.

Griffiths and colleagues argue that, in the absence of direct evidence for animal survival strategies during previous extreme freezing periods, life is likely to reproduce in the most similar environment on Earth today: Antarctica.

Some modern inhabitants of Antarctica, such as sea anemones, live upside down, attaching themselves to the underside of sea ice. One of the preferred feeding strategies for krill is to feed on microorganisms on this inverted plane. Griffiths and colleagues note that they may have been the first animals to feed and also take refuge in these areas.

It is also possible that the rise and fall of sea ice could cause algae or other ice-dwelling micro-organisms to enter the seawater, allowing them to thrive, which could serve as food for other primitive animals.

One problem faced by the inhabitants of Snowball Earth was a possible lack of oxygen, both due to low levels of oxygen in the air and limited mixing of the atmosphere with water. But oxygenated meltwater higher up in the water column can support animals that depend on it. Some modern inhabitants of the Antarctic seafloor, such as some species of Cinderella, solve this problem by relying on water currents to carry a constant stream of oxygen and nutrients from small patches of open water on the Antarctic surface to the depths. ice Rack. There is no reason to believe that this did not happen during Gasquière's reign.

"We're actually talking about very simple life forms... but for now, that's all you need to be the king of the animals," says Griffiths.

In addition to frontal forms, sponges can also live on the seabed. According to Griffiths, some sponge fossils date back to an era long before Sturtwood's Snowball Country, although this is disputed.

Ashley Hood, a sedimentologist at the University of Melbourne in Australia who was not involved in the study, jokes that "everyone, including us, has the oldest sponge they've ever found and no one believes it."

Some modern sponges live in symbiosis with bacteria, which can help them access nutrients when other foods are in short supply. “It probably depends on the survival strategy they used early in their history,” suggests Hood.

Andrew Stewart, assistant curator at the Te Papa Tongarewa Museum in New Zealand, who also did not contribute to this article, has studied countless species in the harsh Antarctic environment. Many of these creatures live in incredibly dark, cold, or chemically toxic places. For Stewart, the rugged creatures of Antarctica are a reminder of how resilient life on Earth is and may have always been.

“This is the most amazing place,” he says. - Tell me, no, damn it, nothing will survive there! Well, actually it can."