A piece of Mars: Blueish and yellowish ripples wind their way around a bright hill. The yellowish ones are probably not moving anymore, but the blueish ones are likely still active from time to time. (HiRISE ESP_020889_1320) read more ❯

A piece of Mars: When the wind erodes layered rocks, it can create a dramatic swirly pattern like this. It looks like ribbon ice cream to me. Mmm, rocks. (HiRISE ESP_011582_1730) read more ❯

A piece of Mars: In nature most dunes pile on one another or strongly influence each other. But occasionally, like a perfect flower or crystal, you find a perfectly shaped dune. Here is a crescentic dune, called a "barchan", formed by winds moving from right to left. (HiRISE PSP_007676_1385, NASA/JPL/Univ. of Arizona) read more ❯

A piece of Mars: The dunes can be so beautiful on Mars. What a lovely vacation spot this would be, provided you brought a large supply of oxygen, food, and a heat source to keep you warm. (HiRISE ESP_026416_1620) read more ❯

A piece of Mars: This is what dunes look like in the deepest part of Mars, where the air is full of bright dust that constantly settles out onto everything. The wind helps to clear off the sand dunes (blue in this image) in two ways: one is by dust devils that leave crooked tracks like drunk vacuum cleaners, and the other is by sand avalanches down steep dune slip faces (HiRISE ESP_025278_1345). read more ❯

A piece of Mars: Patterns within patterns (metapatterns?).  These small martian dunes shown an unusual complexity in their crossing lines, indicating that they were formed by winds from several directions (and it is likely that those winds changed over time). What do you think, should it be the next thing in tweed fashion after houndstooth and herringbone? read more ❯

A piece of Mars: We are looking way up high on Arsia Mons, one of the tallest mountains in the Solar System (its summit is ~19 km high -- Mt. Everest tops out at 8.848 km; the location of this image is at ~10 km). Up here the winds come screaming down the mountain at night, and over time nothing can withstand it. Here a volcanic crater has been slowly blurred by such wind scour. (HiRISE ESP_011677_1655) Can you tell which direction the wind blows? read more ❯

A piece of Mars: It's high summer in the northern hemisphere of Mars. Here, dark dunes near the north pole have finally lost the seasonal ice that blankets them and turns them white for most of the year. For a brief time we can see the true contrast between the dark dunes and the bright terrain they are slowly crawling over. (HiRISE ESP_026598_2650) read more ❯

A piece of Mars: Here are some lovely ripples on Mars. In the same field of ripples, there are large wavy white ones and small complex blue ones. Why are there two different types, made distinct by their color, size, and shape? Nobody knows, but it's a good bet the sand grains that they're made of have different sizes and composition. Regardless of why they look the way they do, they're still quite pretty. (HiRISE ESP_026388_2300) read more ❯

                    A piece of Mars: Today's image comes courtesy of my postdoc, Simone Silvestro. He's studying migrating dunes and has made a 3 image movie of a dune moving across the surface of Mars. This one crawls at a rate of ~0.5 m/year, and it isn't far from where the Curiosity rover will pass when it lands later this year. read more ❯