Cores extracted from Earth's polar ice caps can tell scientists the story of our planet's long-term climatic fluctuations. Now researchers are trying to elicit a comparable tale from the polar regions of Mars.

Using the most detailed images available, Jacques Laskar of the Astronomy and Dynamic Systems in Paris and his colleagues investigated a section of the northern ice cap on Mars. Specifically, they compared the stratigraphy of ice troughs to the amount of incoming radiation calculated to reach the planet, taking into consideration its interactions with other bodies in the solar system and its rotation and tilt. The two matched well for the ice layers in the top 350 meters, the scientists found, which likely accumulated over the last 900,000 years. The results are the first evidence of a specific correlation between the pattern of layered deposits on the Red Planet's poles and climatic oscillations caused by variation in its orbit and inclination.

The researchers caution that their conclusions, published today in the journal Nature, contain a fair bit of uncertainty because, for one thing, "we are very far from being able to core the martian ice caps as was successfully done on earth." But in an accompanying commentary, Alan D. Howard of the University of Virginia concludes that "in the future, missions that land on the planet and drill into the layered deposits may provide definitive interpretations of the climate cycles on Mars."