What Springtime Looks Like On Mars

The above image taken by the Mars Reconnaissance Orbiter in January shows northern spring beginning on Mars, where dark sand dunes are seen emerging from a winter coat of carbon dioxide ice.

Mars, like Earth, has four seasons. On Earth, the seasons are similar in length, about 90 days, because of the nearly circular orbit of the Earth around the sun. The changes in season - fall, winter, spring, and summer- are mostly caused by Earth's axial tilt.

The seasons on Mars are not similar in length, and much longer, because a Martian year is almost double the length of an Earth year and the planet's distance from the sun varies widely during its orbit. The entire planet is much warmer when its close to the sun, called perihelion, than when its far from the sun, called aphelion.

A description of the photo, released by NASA in early March reads: "The steep lee sides of the dunes are also ice-free along the crest, allowing sand to slide down the dune. Dark splotches are places where ice cracked earlier in spring, releasing sand. Soon the dunes will be completely bare and all signs of spring activity will be gone."