Researchers using data from NASA’s Mars Reconnaissance Orbiter have found evidence of an ice age recorded in the Red Planet’s polar caps.

Like our own planet, modern-day Mars experiences annual rotation and seasonal cycles, as well as longer cycles, that influence the distribution of ice. However, these longer cycles might be more pronounced on the Red Planet.

This is because Mars’ tilt changes substantially – by as much as 60 degrees – on timescales of hundreds of thousands to millions of years. By comparison, the Earth’s tilt varies by only about 2 degrees over the same period.

On Mars, this greater variability determines the amount of sunlight reaching a given spot on the surface and thus the stability of ice at all latitudes.

“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 team member Dr. Isaac Smith from the Southwest Research Institute.

“Furthermore, because Mars has no oceans at present, it represents a simplified ‘laboratory’ for understanding climate science on Earth.”

Dr. Smith and his colleagues used radar measurements from NASA’s Mars Reconnaissance Orbiter to probe Mars’ polar ice caps.

Clear layers within the ice allowed them to calculate how much ice was deposited at different times.

The results, published in the journal Science, provide evidence for a recent ice age.

“Detailed measurements of ice thickness show that about 87,000 cubic km of ice have accumulated at the Martian poles since the end of the last ice age about 370,000 years ago,” the scientists explained.

“This volume is equivalent to a global layer of 1.97 feet (60 cm). The majority of the material accumulated at the north pole.”

“We found an accelerated accumulation rate of ice in the uppermost 328 to 984 feet (100 – 300 m) of the polar cap,” they said.

“The volume and thickness of ice matches model predictions from the early 2000s.”

“Radar observations of the ice cap provide a detailed history of ice accumulation and erosion associated with climate change.”

The results will support modeling efforts to understand the Martian climate, looking at the movement of ice from poles to mid-latitudes during climate cycles.

_____

Isaac B. Smith et al. 2016. An ice age recorded in the polar deposits of Mars. Science, vol. 352, no. 6289, pp. 1075-1078; doi: 10.1126/science.aad6968