It occurred roughly 370,000 years ago.
Using radar data collected by NASA’s Mars Reconnaissance Orbiter, a Southwest Research Institute (SwRI) team looking into the polar deposits on Mars found evidence that the planet has experienced an ice age.
Ice ages on Mars are driven by similar processes responsible for ice ages on Earth, including changes in the planet’s orbit and tilt, which affects the amount of solar radiation each latitude receives. However, there are significant differences in what defines an ice age on each planet.
“On Earth, when the poles cool they will attract snow, enlarging the ice caps. Eventually they will spread out over the continents, making an ice age. This is because Earth has a lot of free water in the oceans,” Isaac Smith, a postdoctoral researcher at SwRI and lead author of a paper, told The Science Explorer.
Since Mars’ water is already frozen at the poles, if the poles get colder, the ice remains locked within the ice caps — the status quo. Interestingly, ice ages on Mars occur when the poles warm up. “The ice there becomes unstable, and it sublimes. That moisture eventually finds its way to the mid-latitudes, where it will cover from 30° - 60° in both hemispheres,” Smith continued.
Just like Earth, Mars experiences annual rotation and seasonal cycles that influence the amount of sunlight reaching a given spot on its surface, which affects the distribution and stability of the ice. However, these cycles may be more pronounced on Mars.
Why? Mars’s tilt changes dramatically — by as much as 60 degrees on timescales of hundreds of thousands to millions of years. In comparison, Earth’s tilt varies by only 2 degrees over the same amount of time.
“Because the climate on Mars fluctuates with larger swings in axial tilt, and ice will distribute differently for each swing, Mars would look substantially different in the past than it does now,” said Smith in an SwRI press release. In fact, Smith told The Science Explorer that one result of red Mars being covered with white ice is it would give “the planet a pinkish hue.”
Smith and his team used radar observations of the thickness and volume of the Martian ice and compared them to predictions made by climate models. “It turns out that two models were pretty good and predicted the volume and thickness very well. This gives us confidence that our observed ice age corresponds to their modeled one,” Smith explained. “One consequence is that those models give us an age!”
The results of the study, published today (May 27) in the journal Science, revealed that about 20,870 cubic miles (87,000 cubic kilometers) of ice have accumulated at the Martian poles since the end of the last ice age roughly 370,000 years ago — with the majority at the north pole. This is equivalent to a layer 24 inches (60 centimeters) thick spread uniformly across the entire Martian surface.
The results will be used in models to more accurately simulate the Red Planet’s climate, as well as the movement of ice from poles to mid-latitudes during climate cycles. “Studying ice on Mars also is important to the future of human exploration of the Red Planet,” said Smith in the press release. “Water will be a critical resource for a martian outpost.”
This research was funded by NASA’s Mars Reconnaissance Orbiter project.
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