PASADENA -- Mars used to have seasons, researchers at the California Institute of Technology in Pasadena announced Thursday.
NASA's Mars Reconnaissance Orbiter photographed rock outcroppings that revealed a record of cyclical climate fluctuations within their many stony layers, Caltech researchers said.
"This study gives us a hint of how the ancient climate of Mars operated, and shows a much more predictable and regular environment than you would guess from other geological features that indicate catastrophic floods, volcanic eruptions and impact events," said Caltech graduate student Kevin Lewis, a leading researcher on the project.
The climate changes were likely driven by small variations in Mars'orbit, similar to the way orbital variations that cause certain changes in Earth's climate, Lewis said.
As the tilt of the Earth's axis varies between 22.1 and 24.5 degrees over a 41,000-year period -- tilting the poles closer or farther away from the sun -- the poles experience varying amounts of glaciation.
The tilt of Mars' axis changes by tens of degrees over a 100,000-year period, resulting in a more dramatic variation.