HiRISE images

Barely a dune
Published 7/14/2012 in Lori Fenton's Blog Author lfenton
A piece of Mars: What makes a dune different from a random pile of sand? Usually the requirement is that it has a "slipface", a steep avalanching slope. The central dune in the image here has a small one, making it a type of dune called a barchan. The other dunes are called "dome dunes", because they don't have proper slip faces. It is arguable that they aren't really proper dunes at all. (HiRISE ESP_027378_2540) read more ❯

Wrapping around
Published 7/11/2012 in Lori Fenton's Blog Author lfenton
A piece of Mars: Dunes near the north pole of Mars form in a very cold environment. Winter ice continually tries to stop them in their tracks, which makes for unusually rounded dunes like these. (HiRISE ESP_027451_2635) read more ❯

An intriguing mess
Published 7/10/2012 in Lori Fenton's Blog Author lfenton
A piece of Mars: What an intriguing mess this is. These are dunes or ripples, oriented every which way, and mottled with white spots. The different orientations tell us that the winds blow from several different directions, on timescales long enough to seriously influence the dunes. The mottling is a mystery. (HiRISE ESP_025386_1800) read more ❯

Dunes all gone
Published 7/9/2012 in Lori Fenton's Blog Author lfenton
A piece of Mars: Way up in the cold northern plains of Mars, some of the dunes are being blown away slowly by the wind. Here are some that are barely there yet -- dark patches of sand in the shape of their former glory. (HiRISE ESP_027389_2645) read more ❯

Dune bones
Published 6/20/2012 in Lori Fenton's Blog Author lfenton
A piece of Mars: The thin stripes within stripes are the bones of dunes. You're seeing old dunes that have had their tops eroded away so you're seeing into their insides, as if you were dissecting them in a biology class and looking at their skeletons. That's unusual -- on Earth dunes usually get buried or destroyed, so being able to see their interior structure is quite amazing. (HiRISE ESP_026992_2025) read more ❯

The edge of the ice
Published 6/19/2012 in Lori Fenton's Blog Author lfenton
A piece of Mars: This is the edge of the northern polar cap on Mars. At the top is the bright icy surface, which is abruptly cut by a cliff. The wall of the cliff shows many layers of different materials -- the darker ones are old dunes. How cool is it to know that the polar ice cap on another planet is sitting on what used to be an enormous sand sea? It's like looking at limestone and shale on mountains here on Earth an imagining them once being at the bottom of an ocean. It blows my mind.... read more ❯

Generations of erosion
Published 6/18/2012 in Lori Fenton's Blog Author lfenton
A piece of Mars: Sometime in the past, large ripples wandered the dusty lanes of this landscape, sandblasting the hills as they marched on by. Those ripples stopped moving and turned into the fossils you see here. Their bumpy texture indicates that they too are slowly being eroded away. (HiRISE ESP_026462_1740) read more ❯

Enigma
Published 6/17/2012 in Lori Fenton's Blog Author lfenton
A piece of Mars: Here is an example of an aeolian enigma. Dunes are depositional, meaning they are made of stuff that piles up on a surface. But these dunes show the strata of the underlying rock within them, which means these things were made from erosion of this rock. So we don't really know how they form, although a few ideas have been kicked around. (HiRISE PSP_008313_1730) read more ❯

Stretched out
Published 6/6/2012 in Lori Fenton's Blog Author lfenton
A piece of Mars: Dunes near the north pole take on a stretched appearance. It's been proposed that ice in the dunes acts to cement them, which makes them look elongated. (HiRISE PSP_010219_2785) read more ❯

Boulder tracks
Published 6/4/2012 in Lori Fenton's Blog Author lfenton
A piece of Mars: You can't easily tell here, but you're looking at a steep slope that is high at the bottom of the image and flattens out at the top of the image (the small dunes at the top sit at the foot of the wall). What's neat here are the many small boulder tracks, formed as rocks get knocked down. A road through this canyon would need a sign saying "Warning Falling Rocks". (HiRISE ESP_026356_1960) read more ❯

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