Science - AP

WASHINGTON - Roads and canals connected walled cities and villages. The communities were laid out around central plazas. Nearby, smaller settlements focused on agriculture and fish farming.

WASHINGTON - More ominous signs Wednesday have scientists saying that a global warming "tipping point" in the Arctic seems to be happening before their eyes: Sea ice in the Arctic Ocean is at its second lowest level in about 30 years.

WEST LAFAYETTE, Ind. - Purdue University on Wednesday reprimanded a scientist who has been accused of falsifying claims he produced nuclear fusion in tabletop experiments.

WEST PALM BEACH, Fla. - Tropical Storm Fay brought some good news to the state's parched Everglades and its liquid heart, Lake Okeechobee — lots and lots of water.

NEW YORK - Talk about an extreme makeover: Scientists have transformed one type of cell into another in living mice, a big step toward the goal of growing replacement tissues to treat a variety of diseases.

PASADENA, Calif. - The plucky Mars rover Opportunity is driving out of a giant crater nearly a year after a dangerous descent to examine exposed bedrock.

HAZLETON, Pa. - Nearly a year after federal epidemiologists first sounded the alarm over a cluster of rare blood cancers in northeastern Pennsylvania, their research has zeroed in on a hardscrabble region 80 miles northwest of Philadelphia that is home to several Superfund sites and a power plant fired by waste coal.

WASHINGTON - Talk about animal magnetism, cows seem to have a built-in compass. No bull: Somehow, cattle seem to know how to find north and south, say researchers who studied satellite photos of thousands of cows around the world.

WASHINGTON - For capuchin monkeys, it seems, it's better to both give and receive, than just to receive. At least, that's what researchers at the Yerkes National Primate Research Center at Emory University in Atlanta have found.

WALLOPS ISLAND, Va. - NASA destroyed an unmanned experimental rocket carrying a pair of research satellites Friday when it veered off course shortly after an early morning liftoff.

WASHINGTON - In northern Greenland, a part of the Arctic that had seemed immune from global warming, new satellite images show a growing giant crack and an 11-square-mile chunk of ice hemorrhaging off a major glacier, scientists said Thursday.

ANCHORAGE, Alaska - Nine polar bears were observed in one day swimming in open ocean off Alaska's northwest coast, an increase from previous surveys that may indicate warming conditions are forcing bears to make riskier, long-distance swims to stable sea ice or land.

CARACAS, Venezuela - An ancient tar pit exposed when Venezuelan oil workers laid a pipeline has yielded a rich trove of fossils, including a type of saber-toothed cat that paleontologists had never found before in South America. Scientists say the find holds the promise of many discoveries to come.

HOUSTON - Powerful acoustic devices used by oil companies searching for new sources of hydrocarbons in the Gulf of Mexico have had no discernible effect on endangered sperm whales living in those waters, according to a federally funded study released Thursday.

TEHRAN, Iran - State TV says Iran's space agency aims to send an astronaut to space within 10 years.

ENSENADA, Mexico - Mexico said Wednesday it will invest 163 million pesos ($16 million) to save a highly endangered species of porpoise in the upper Gulf of California, asking reluctant fishermen to adopt safer methods or give up their trade entirely.

ACCRA, Ghana - Negotiators meet in Ghana this week to resume work on a new climate change treaty and discuss ways to prod developing countries to join the fight against global warming.

WASHINGTON - A space-age version of the rusty springs under old pickup trucks will help NASA fix the most pressing technical problem with its high-tech new rocket to send astronauts back to the moon.

WELLINGTON, New Zealand - Australian Prime Minister Kevin Rudd urged the United States on Tuesday to take more action on climate change and become more involved in the global debate on the issue.

WASHINGTON - Answer this without counting: Are there more X's here XXXXXX, or here XXXXX? That's a problem facing people whose languages don't include words for more than one or two. Yet researchers say children who speak those languages are still able to compare quantities.

WASHINGTON - The world's poorest countries have one thing in ever greater abundance — people.

TEHRAN, Iran - Iran has test launched a rocket it plans to use to carry a research satellite into orbit, state television reported Sunday.

BERLIN - Germans have been treated to the rare sight of a lone and wayward humpback whale swimming in the Baltic Sea, but marine biologists said it may be doomed because the waterway lacks the conditions such mammals need to survive.

TORONTO - For more than 160 years, the fate of British explorer Sir John Franklin and his men has remained locked in the frozen Arctic, but warming temperatures are threatening to change that.

LOS ANGELES - Here's a mind-bending idea: The U.S. military is paying scientists to study ways to read people's thoughts. The hope is that the research could someday lead to a gadget capable of translating the thoughts of soldiers who suffered brain injuries in combat or even stroke patients in hospitals.

CHAMPAIGN, Ill. - Scientists worry that a rapidly reproducing, tiny invasive snail recently found in Lake Michigan could hurt the lake's ecosystem.

WASHINGTON - A tiny woman and two children were laid to rest on a bed of flowers 5,000 years ago in what is now the barren Sahara Desert. The slender arms of the youngsters were still extended to the woman in perpetual embrace when researchers discovered their skeletons in a remarkable cemetery that is providing clues to two civilizations who lived there, a thousand years apart, when the region was moist and green.

LOS ANGELES - NASA has delayed the launch of an unmanned spacecraft to the moon to scout for potential landing sites for astronauts.