<P> Alluvial fans have been observed by the Cassini - Huygens mission on Titan using the Cassini orbiter's synthetic aperture radar (SAR) instrument . These fans are more common in the drier mid-latitudes at the end of methane / ethane rivers where it is thought that frequent wetting and drying occur due to precipitation, much like arid fans on Earth . Radar imaging suggests that fan material is most likely composed of round grains of water ice or solid organic compounds about two centimetres in diameter . </P> <Ul> <Li> Ground - level view of a large alluvial fan in Death Valley </Li> <Li> Small alluvial fan, Death Valley </Li> <Li> Alluvial Fan in southern Iran . Image from NASA's Terra satellite </Li> <Li> <P> Alluvial fan in Death Valley, California, seen from source area of Black Mountains at Dante's View . </P> </Li> </Ul> <Li> Ground - level view of a large alluvial fan in Death Valley </Li> <Li> Small alluvial fan, Death Valley </Li>

When do alluvial fans develop in arid desert environments