Could a salt crust turn the entire planet into an ice cube?

Space · Published 27 October 2026 Swipe more like this →

In short: Earth has faced 'Snowball' events where ice reached from pole to equator. While we often blame greenhouse gases, new research suggests a more startling culprit: ordinary salt crystals might have acted as a planetary mirror, reflecting away enough sunlight to trigger a runaway global freeze.

The 'Snowball Earth' hypothesis describes periods between 2.4 billion and 580 million years ago when the planet was nearly entirely encased in ice. One of the most dramatic instances occurred during the Neoproterozoic era, roughly 720 to 635 million years ago. Scientists have long understood the 'runaway' feedback loop involved: as white ice replaces dark ocean water, it reflects more sunlight back into space, cooling the planet further and allowing even more ice to form.

Recent modeling from researchers at Yale, the University of Chicago, and the University of Vienna explores a specific mechanism for this transition. They suggest that salt crystals accumulating on sea ice could have amplified the cooling. As seawater freezes, salt is left behind in the liquid; at extreme temperatures, these salts crystallize. Through sublimation—where ice turns directly into vapor—these crystals can form a thin layer on the surface. Laboratory experiments show such a salt crust can reflect about 93% of incoming sunlight, significantly higher than fresh snow (83%) or melting bare sea ice (67%).

While some scientists propose that large asteroid impacts could have triggered these abrupt freezes, others argue for atmospheric shifts in greenhouse gases. To end the freeze, massive volcanic outgassing likely released enough carbon dioxide to create a warming effect, especially since frozen landscapes would have dampened natural carbon sinks like photosynthesis and rock weathering. If Earth were to face such an event again, temperatures at the equator could plummet to -50°C, potentially leaving only hot springs or deep-sea vents as refugia for life.

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