WATER ON MARS 

The long search for liquid water on Mars may finally be over: Scientists say they've found the first clear signs of water flowing on the Martian surface, in the form of seasonal streams that cascade down crater slopes. Mars is already known to have ice, but life (as we know it) usually shuts down when water freezes. These newly found streams, however, could offer a much more welcoming habitat — if they actually turn out to be streams. The scientists who discovered them say that's the most likely explanation, but they're still not popping the champagne quite yet. "This is the most compelling evidence yet for liquid water on Mars," one of the researchers said Thursday during a news conference. "It's not proof, but it's compelling."

This compelling evidence was obtained by NASA's Mars Reconnaissance Orbiter, which has been circling the red planet for five years and snapping photos with a powerful camera called HiRISE. In going back through some of those photos, scientists recently noticed thousands of dark streaks on the surface that shift with the seasons — the streaks vanish in the Martian winter but reappear every summer, when surface temperatures rise high enough to let water exist in a liquid state. The streaks run though narrow channels called "linae," or lines, that range between 18 inches and 15 feet wide, and at the height of summer they can lengthen by up to 60 feet a day. While the scientists point out that "the sites where these occur are rare," they have nonetheless located more than 1,000 suspected streams at 39 separate locations.

The study offers some other possible explanations for the streaks, suggesting they could be rock falls or the result of strong surface winds. But, as lead investigator Alfred McEwen admits, "We haven't found any good way to explain what we're seeing without water." They likely won't get a chance to test that theory anytime soon, though — NASA is sending a new rover to Mars later this year, but it won't land near any linae, and couldn't drive on such steep slopes, anyway. Until a full study of the streaks can be conducted, scientists will be left to keep studying the images, perform experiments on Earth that mimic conditions on Mars, and wonder if anything might live in those salty streams. According to study co-author Lisa Pratt, it's plausible that life could adapt to such conditions. "If there were to be evolving organisms on Mars, I don't see any reason why they couldn't adapt to that kind of seasonally available, very brief access to resources. You bloom quickly, you do what you need to do, and you go dormant."

(Sources: NASA, Space.com, San Francisco Chronicle, Washington Post, New York Times)

SHELL FREEZES OVER 

The Obama administration has taken a big first step toward opening the Arctic Ocean to offshore oil drilling, the New York Times reports, granting Royal Dutch Shell conditional approval to start drilling exploratory wells there next summer. This suggests Obama is "easing a regulatory clampdown" on offshore drilling that has stood since last year's Gulf oil spill, the Times reports, and may signal that Alaskan waters can't avoid the giant oil rigs that have become common across the Gulf of Mexico.

"We base our decisions regarding energy exploration and development in the Arctic on the best scientific information available," says Michael Bromwich, director of the U.S. Bureau of Ocean Energy Management, Regulation and Enforcement, which regulates offshore drilling. "We will closely review and monitor Shell's proposed activities to ensure that any activities that take place under this plan will be conducted in a safe and environmentally responsible manner." Officials point out that Shell must still obtain some secondary permits before it can actually start drilling into the Arctic seabed, and will be tightly bound to new safety rules and incident-response standards that have been updated since the Gulf spill. Still, executives at Shell — which has spent nearly $4 billion over five years trying to convince the U.S. to let it drill off Alaskan coasts — can barely contain their excitement about the approval, however conditional. "We feel very good about it," Pete Slaiby, Shell's vice president in Alaska, tells the Times. "It's one of the road marks we wanted to see. It makes us very happy."

[skipwords]Environmentalists and Alaskan natives, however, are less enthusiastic. They have long warned that the Arctic is too remote, and conditions there too turbulent, for oil companies to ensure they can handle spills and leaks. "Hard questions need to be asked about any oil company's ability to mount a response to a major oil spill in hurricane-force winds, high seas, broken and shifting sea ice, subzero temperatures, and months of fog and darkness," the director of the Pew Environment Group's Arctic program tells the Times. But, as the Center for Biological Diversity's Brendan Cummings points out, legal challenges could slow down the approval process. "No drill bits are going to hit the Arctic seafloor until at least one and probably several courts have reviewed this plan," he says.[/skipwords]

(Sources: New York Times, Los Angeles Times)

SPIN ZONE 

Tropical Storm Emily petered out Thursday after dumping heavy rain on Hispaniola, and while U.S. forecasters say it has a 60 percent chance of regenerating into a tropical cyclone, they also have bigger cyclone-related news to share. The U.S. Climate Prediction Center updated its outlook for the 2011 Atlantic hurricane season Thursday, raising the number of expected storms and increasing their confidence that this summer will be an active hurricane season for the Atlantic Basin.

"The atmosphere and Atlantic Ocean are primed for high hurricane activity during August through October," says Gerry Bell, lead seasonal hurricane forecaster for the CPC. "Storms through October will form more frequently and become more intense than we've seen so far this season." Several climate factors point to an intensifying hurricane season, according to the U.S. National Oceanic and Atmospheric Administration, including "exceptionally warm Atlantic Ocean temperatures" that are the third-warmest on record, and the possible redevelopment of La Niña in the Pacific Ocean. Something called the "tropical multidecadal signal," which has been linked to favorable hurricane conditions since 1995, also supports this projection, NOAA reports.

According to NOAA's updated forecast, the entire Atlantic hurricane season — which lasts from June 1 to Nov. 30 — has a 70 percent probability of including the following: 14 to 19 named storms (with top winds of 39 mph or higher), seven to 10 hurricanes (top winds of 74 mph or higher) and three to five major hurricanes (top winds of at least 111 mph). These estimates "are indicative of an active season," NOAA warns, and are well above the long-term seasonal average of 11 named storms, six hurricanes and two major hurricanes. So far in 2011, there have been five tropical storms in the Atlantic Basin — Arlene, Bret, Cindy, Don and Emily — but the hurricane season typically doesn't reach its peak until August through October.

(Sources: NOAA, Houston Chronicle, USA Today)

RICH FOOD 

Eating a balanced diet may help you cut down on health-care costs in the long run, but it can also gobble up your money in the short term, according to a new study published in the journal Health Affairs. This makes it difficult for many Americans to meet the country's recently updated nutritional guidelines, warn the study's authors, who suggest the government should do more to help low-income Americans afford high-quality and nutritious food.

"We know more than ever about the science of nutrition, and yet we have not yet been able to move the needle on healthful eating," lead author Pablo Monsivais tells the AP. The U.S. government recently replaced its well-known food pyramid guidelines with a program called MyPlate, which — among other recommendations — advises Americans to eat more foods that contain potassium, dietary fiber, vitamin D and calcium. But doing that could add hundreds of dollars to a consumer's annual grocery bill, say the study's authors, who found that just introducing the recommended amount of potassium to a diet can increase someone's yearly food costs by $380. They also criticized marketing materials for healthful eating that show foods like salmon and leafy greens, arguing such meals are beyond the means of many Americans. "Almost 15 percent of households in America say they don't have enough money to eat the way they want to eat," one expert who wasn't involved in the study tells the AP. "Right now, a huge chunk of America just isn't able to adhere to these guidelines."

While many nutrition-packed foods are more expensive, other experts argue that Monsivais and his colleagues oversimplify the problem. And TIME's Meredith Melnick, reporting on the Health Affairs study, highlights a few tips about how to make a healthy diet more affordable. As the study's authors themselves point out, for example, "consumers could get potassium from bananas more cheaply than from nectarines, even though nectarines contain more potassium per calorie than bananas do." Bananas are also a "double duty" food, Melnick writes, since they're rich in both potassium and dietary fiber; many other foods also fit into this category, such as white beans, which provide lots of fiber as well as calcium. 

(Sources: Associated Press, TIME)

THIS DAY IN HISTORY

An earthquake flattens a village in Ecuador, the U.S. declares the gray wolf endangered, and more.

Russell McLendon

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Photo (suspected seasonal water flows on Mars): NASA

Photo (Beaufort Sea in Alaska): U.S. Geological Survey

Photo (tropical storm surge and winds in Texas): NOAA

Photo (health-food store displays): Robert Banh/Flickr

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