They form in large sand seas (deserts) where there is ample sediment supply AND the wind directions are very variable. These can be amongst the largest dunes on Earth, exceeding 1000 ft in height. If wind directions are stable, then longitudinal dunes result. If sand supply is less and wind is stable, then Barchans occur. If there is little sand, and irregular winds, small and poorly-formed dunes result.
None of these are like the "Spiders" on Mars.
(Oh, and it helps if you look at that Google Maps image from a different angle - those are radiating ridges, not grooves.
[img src="http://www.cartage.org.lb/en/themes/sciences/earthscience/Geology/Deserts/Deserts/TypesofDunes/stardunes.gif"]
Space/Science » in reply to Earth analogs of the Mars "spiders"?
They're called Star Dunes
