New evidence from NASA's Mars Reconnaissance Orbiter suggests that Mars is emerging from an ice age that ended approximately 400,000 years ago. The data was obtained from polar deposits on the Red Planet and - much like Earth's ice ages - the period was driven by long-term cyclical changes in the planet's orbit and tilt.
"We found an accelerated accumulation rate of ice in the uppermost 100 to 300 meters of the polar cap," said Isaac Smith of the Southwest Research Institute (SwRI) and lead author of the paper. "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."
Today, Mars experiences annual rotation and season cycles just like Earth. In addition, it also experiences longer cycles that influence its ice distribution just like our planet, although these cycles are likely more pronounced on Mars due to the amount that its tilt changes - as much as 60 degrees - during time periods of hundreds of thousands to millions of years. In comparison, Earth's tilt only changes by about two degrees over the same time period.
The increased variability of Mars' tilt alters the amount of sunlight that hits a given spot on the planet's surface, which, in turn, influences the stability of its ice.
"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," Smith said. "Furthermore, because Mars has no oceans at present, it represents a simplified 'laboratory' for understanding climate science on Earth."
The SwRI team determined that approximately 87,000 cubic kilometers of ice have accumulated on Mars' poles since the end of its last ice age, which took place approximately 370,000 years ago. The findings will help scientists better understand the history of polar deposits on Mars and their relationship to factors such as axial tilt, orbital eccentricity and rotation around the sun.
"Studying ice on Mars also is important to the future of human exploration of the Red Planet," Smith added. "Water will be a critical resource for a martian outpost."
The findings were published in the May 27 issue of the journal Science.
