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"  White Sands National Monument is Earth&amp;#039;s largest gypsum dune field, and it may be the product of the same geological processes that created similar landscapes on Mars, NASA researchers say. &amp;quot;They&amp;#039;re studying our dune field to understand the dunes on Mars,&amp;quot; says Rebecca Wiles, the monument&amp;#039;s chief of interpretation. To get there, take U.S. Highway 70 west from Alamogordo, N.M. Drive about 15 miles out of town through the New Mexico desert and you will see white hills of sand glistening in the sun up ahead, hills that reflect the way this country looked millions of years ago.  Rangers guide hikers to Lake Lucero on monthly trips, while the quarter-mile Playa Trail offers easy access to a smaller playa on the eastern edge of the dune field. A 5-mile hiking loop reaches the edge of Alkali Flat. Five miles may not intimidate experienced hikers, but walking a trail is not the same as slogging the distance through sand. About 250 million years ago, much of the southwestern U.S. lay beneath the shallow Permian Sea. As it dried up, gypsum precipitated out of the water and settled on the seafloor. When the Rocky Mountains formed 75 million years ago, the same process raised the mountains that now surround the Tularosa Basin. The gypsum that once sat on the seafloor now covers mountaintops. Rain and melting snow carry gypsum down into the basin, where the water evaporates and leaves selenite, a crystallized form of gypsum. Selenite crystals protrude from the ground in Lake Lucero at the southwest corner of the park, in the expanse of Alkali Flat on its western boundary, and in a handful of smaller playas.  In Lake Lucero, selenite crystals weather and crumble into shards that eventually become small flakes. When the desert wind lifts these gypsum flakes, it drags them along the ground and grinds them into fine grains of white sand that pile up at the eastern edge of the lake. The wind pushes these low mounds of sand up to 30 feet a year at first, but as they advance, they gradually slow. The dunes at the far edge of the dune field move only inches each year. The playas of White Sands may be similar to Martian locations like Gale Crater, where NASA&amp;#039;s Curiosity rover landed in 2012. The 3.5 billion-year-old crater may once have held liquid water, if researchers are correct about a large pile of sediment at its center, which may contain gypsum. Because gypsum is usually formed by the evaporation of water, its presence in Gale Crater could mean that an ancient lake once existed there. The teeming life among the dunes has evolved for this constantly moving environment. Yucca plants grow towering stems to keep their heads above the advancing wave of sand and then collapse under their own weight when a dune drifts past. Sumac digs in, hardening the sand beneath its roots and creating a stable tower for itself amid the shifting grains. Among these stubborn desert plants, animals have adapted to the restless white landscape, making White Sands a &amp;quot;desert Galapagos.&amp;quot; Many species have evolved paler coloring to conceal themselves, along with other adaptations. For example, compare a white dune lizard to a brown scrub lizard, Wiles says. &amp;quot;They live at some points just feet apart from each other, but this one is evolved to the dune field. He&amp;#039;s got longer toes, which allow him to run faster on the sand.&amp;quot; The best place to encounter this unique wildlife is the Dune Life Nature Trail, a 1-mile loop that crosses the desert scrub before taking a wide circuit through the edge of the dune field. Hikers may see beetles, lizards, snakes, grasshoppers, birds, and rabbits, as well as burrows and tracks that signal their presence. Beneath White Sands, a thick layer of clay\u2014once the bottom of Lake Otero, which covered the area 2 million to 11,000 years ago\u2014holds water under the dune field, and that water is like the glue that holds the dunes together. The sand itself stays at around 98 percent humidity, which keeps it fairly cool, so you can give in to the urge to kick off your hiking shoes and dig your toes into the sand. Before you go, check the park&amp;#039;s website for information about upcoming missile tests at adjacent White Sands Missile Range. Wiles told PM, &amp;quot;We&amp;#039;ve had rockets and missiles come down in places where visitors could be,&amp;quot; so to keep visitors safe, both White Sands National Monument and Highway 70 close during missile tests. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/adventure/outdoors/a9472/get-out-there-the-otherworldly-dunes-of-white-sands-15976569/>