Health & Science

Lakes and rivers on ancient Mars

Mars was once a warm and wet planet, with vast lakes, flowing rivers, broad deltas—and, possibly, some form of life. Photos and data from the Mars Reconnaissance Orbiter, now circling the Red Planet, found widespread deposits of mineral-laden clay throughout Mars’ southern hemisphere, from valleys to dunes to the tips of volcanoes. This, say planetary geologists in a new study in Nature, indicates that the entire area was under water early in the planet’s history, about 4 billion years ago. The planet apparently remained wet for about 800,000 years, and was also much warmer than it is today, with surface temperatures of 200 degrees or more. “What does this mean for habitability? It’s very strong,” says planetary geologist Jack Mustard of Brown University. “It was a benign, water-rich environment for a long period of time.” Today’s Mars is a frozen wasteland, with daily temperatures of around minus-60 degrees Fahrenheit. Any water that remains exists as permafrost or is buried far below the surface of the planet, and NASA’s Phoenix Mars Lander is now digging in that permafrost in an attempt to find proof of both water and organic molecules. Scientists are now eager to launch a more ambitious mission to collect direct evidence of Mars’ warm, wet past, and to search for clues that microbes or plants once thrived there. “It’s clear that we need to work together to figure out a way to go to Mars, collect a sample of these rocks, and bring them back to Earth,” astrophysicist Joe Michalski tells National Geographic News. “That’s really going to be the next milestone.”

How menthol helps hook smokers

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Over the years, says a new study, tobacco companies have carefully modulated levels of menthol in their cigarettes to lure young smokers. Brands such as Marlboro make “mild” cigarettes with a slight flavor of menthol because companies found that a minty flavor eased an adolescent’s transition to becoming a smoker. In 1987, an R.J. Reynolds memo noted that “first-time smoker reaction is generally negative,” but that “initial negatives can be alleviated with a low level of menthol.” Menthol, the memo explains, not only mitigates the bitter taste of smoke, it can itself become addictive. “As smokers acclimate to menthol, their demand for menthol increases over time.” Researchers at the Harvard School of Public Health conclude that menthol is one of the tobacco industry’s most potent recruiting tools. “For decades, the tobacco industry has carefully manipulated menthol content not only to lure youth but also to lock in lifelong adult customers,” study author Howard Koh tells the Associated Press.

Why Africans are susceptible to HIV

About 10,000 years ago, people in Africa evolved a way to fight off the malaria parasite. Thanks to a tiny change in their DNA, Africans stopped producing a red blood cell surface protein that allowed the malaria parasite entry into their blood cells. As a result, that species of malaria actually died off, but the DNA quirk remained. Today, people in Africa are facing another threat: the spread of HIV. The very same mutation that allowed ancient Africans to fight malaria is now increasing their vulnerability to the HIV virus. Scientists estimate that people with the mutation—90 percent of Africans, and 60 percent of African-Americans—are up to 40 percent more vulnerable to infection by HIV. “There has always been this myth that people in sub-Saharan Africa were more likely to get HIV because of differences in their sexual behavior, or that they are more promiscuous,” Dr. Ade Fakoya of the International HIV/AIDS Alliance tells BBCnews.com. “This shows that it’s not that simple.”

More painful than a melting iceberg

Global warming has been blamed for everything from species extinctions to the melting of Arctic ice. Now scientists say it may also give people kidney stones. Kidney stones are calcium deposits that tend to form in susceptible people when they’re dehydrated. As America gets warmer, a new study says, more people will develop the stones, which cause excruciating pain when they move into the very narrow and sensitive urinary tract. By 2050, hydrologist Tom Brikowski tells New Scientist, warmer climates will produce about 2.25 million more kidney stones in the U.S. The effect will be especially prominent in the “kidney-stone belt,” in the South and Southwest, where the rate of stone formation is currently double. In the future, as many as 26 percent of men and 14 percent of women in these warm-temperature states will develop kidney stones. As high as those numbers are, says Paul Epstein of Harvard Medical School, they “may be an underestimate based on what we know.”