Sand dunes emerge from a winter coat of carbon dioxide frost on a spring day in northern Mars, in a photo taken by the Mars Reconnaissance Orbiter in January.
The south-facing slopes are dark where the ice has melted. Soon the dunes will be completely bare and all signs of spring activity will be gone, NASA's blog explains.
There are four seasons on Mars, as on Earth, but the seasons vary in length and a year lasts for 687 days. The planet is also much warmer when it is closest to the sun, in a state called perihelion, than when it is farthest from the sun, in a state called aphelion.