Feature

Health & Science

The shifting sands of Mars; Words count for counting; A flea’s mighty genome; The disappearing wild oyster

The shifting sands of MarsMars has weather. A new analysis of NASA photos has revealed that the dramatic sand dunes around the Martian North Pole, long considered static remnants of the Red Planet’s stormy past, change shape from season to season as a result of surprisingly dynamic forces of nature. Researchers at the University of Arizona examined hundreds of high-quality photos of the dark basalt undulations, some of them 100 feet tall, taken by the Mars Reconnaissance Orbiter over the course of two Martian years, the equivalent of four years on Earth. The images revealed that the Texas-sized dune zone is one of the planet’s most active regions. The researchers discovered that in the Martian winter, the sand is coated with a blanket of dry ice, which turns into a gas in the spring, destabilizing the dunes and triggering avalanches. The new images also provide evidence that winds in Mars’ thin atmosphere, previously thought to be too weak to lift even a grain of basalt, actually blow hard enough to fill ravines and gullies with sand in just a single Martian year. Understanding the dunes’ seasonal shifts will be “a key first step” toward understanding “how Mars changed over time,” study co-author Alfred McEwen tells ScienceDaily.com. “The level of erosion in just one Mars year was really astonishing,” says co-author Candice Hansen. “This is a very un-Earthly process.”

Words count for countingIs our understanding of numbers innate or cultural? New research provides stronger evidence than ever that humans must be taught to count, and that without language, math doesn’t exist. Previous studies showed that Amazon tribal people who lacked words for numbers beyond “one, two, and many” were unable to understand precise quantities. But it was never clear whether this inability simply resulted from their not needing numbers to negotiate the world they inhabited. The new study meets that objection by focusing on deaf Nicaraguans, called “homesigners,” who live and work in a society that runs on exact values yet communicate with a system of gestures that doesn’t include signs for numbers. The study found that the homesigners couldn’t accurately count above four. Shown a picture of 10 sheep, for instance, they seemed to estimate the amount—often holding up nine fingers. By comparison, deaf users of American Sign Language, which does have words for numbers, and Spanish-speaking Nicaraguans who weren’t deaf aced the same tests—proving that the missing link for counting was not hearing or culture but language. The study proves that the ability to count “isn’t something you just get for free because you’re human,” author and University of Chicago psychologist Elizabet Spaepen tells Wired.com. “If you’re not getting it in your language, you’re not going to just come up with it on your own.”

A flea’s mighty genomeIt takes about 23,000 genes to hold all the information necessary to create the complex human organism. So how many genes does it take to make the lowly water flea, a tiny crustacean that inhabits freshwater ponds around the world? Ten years of study has yielded an astounding answer: almost 31,000, more than any organism to date. Researchers have long known that Daphnia pulex can shift its shape to adjust to specific predators and is extremely sensitive to changes in its environment. Now they hope that through further study of the water flea’s newly sequenced genome, they can learn which of its genes react to which substances, making the water flea a far more versatile indicator of environmental danger than, say, a canary in a coal mine. “You don’t have to wait for the whole ecosystem to show that there’s something wrong,” study author John Colbourne, a biology professor at Indiana University, tells LiveScience.com. “You simply ask a vitally important component of that ecosystem, ‘Hey, how are you doing?’” While about one third of Daphnia’s genes are new to science, researchers say it shares many others with humans, making it a viable “surrogate model” for examining the impact toxins have on us.

The disappearing wild oysterOysters, once a bountiful food throughout the world, are now rare and expensive delicacies. According to a Nature Conservancy survey, oyster reefs have all but disappeared since the late 19th century due to overharvesting, pollution, and disease. Researchers found roughly 85 percent of wild oyster beds, once the dominant ecosystem in the world’s temperate bays, to be “functionally extinct,” meaning that the bivalves are too few to have a significant impact on their habitat, including through their crucial function of filtering water. Three quarters of the world’s surviving wild oysters now live in just five regions of North America, and the researchers found that only one of them was healthy. “The Gulf of Mexico is likely the last best place where there’s a chance” to preserve the reefs as sustainable fisheries, lead author Mike Beck tells The New York Times. Fortunately, the BP oil spill did not do irreparable damage to the gulf’s oyster beds, still the most productive anywhere. But Beck is pessimistic that the rapacious exploitation of the reefs can be slowed in time to save the wild oyster. “Anywhere where there are oysters in abundance,” he says, “we’re doing the job to take every last one, it seems.”

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