Scientists believe that icy planets are too cold to support life as we know it on Earth. However, new research suggests that frozen exoplanets could be more favorable for life as we know it on Earth, despite their frigid temperatures.
Snowball planets – Earth-like planets with frozen oceans to the equator – are not favorable for life because it’s extremely cold. But the research published in the AGU Journal of Geophysical Research: Planets suggests that snowball planets might have areas favorable for life near their equators where they could reach livable temperatures.
“You have these planets that traditionally you might consider not habitable and this suggests that maybe they can be,” Adiv Paradise, an astronomer and physicist at the University of Toronto and lead author of the new study said in a statement.
“We know that Earth was habitable through its own snowball episodes, because life emerged before our snowball episodes and life remained long past it,” Paradise said. “But all of our life was in our oceans at that time. There’s nothing about the land.”
Planets turn into frozen exoplanets when the atmospheric carbon dioxide declines too much to sustain warmth from the sun. It is a result of the combination of rainfall and erosion. Water then absorbs carbon dioxide which results in carbonic acid, reacting with rocks causing erosion. The interaction causes the carbonic acid to break down, binding it with minerals that are carried to the oceans and are stored on the seafloor.
Scientists have believed that carbon dioxide removal stopped once the planet would become frozen enough to become a snowball, as the surface of the planet was frozen. However, the new study found there are snowball planets that continue losing carbon dioxide despite being frozen. That means that there is still non-frozen ground remaining, and that there is occasional rainfall to continue to remove carbon dioxide.
Scientists also simulated some of the warmer snowball planets conditions, to see whether the land areas were warm enough to host liquid water and life despite the frozen oceans. They found that the land areas located in the center of the continents could reach temperatures above 50 degrees Fahrenheit, which is much warmer compared to the lowest temperature at which life can reproduce, -4 degrees Fahrenheit.
The team also suggests that frozen exoplanets with Earth-like properties can enter the snowball state because of certain situations. Scientists used to believe that planets were exiting the snowball state due to the gradual buildup of carbon dioxide that came from volcanoes, although the weathering could cause enough carbon dioxide to get kicked out to the atmosphere which would balance the volcanic output.
“What we find is actually that line is a bit fuzzy,” Paradise said.