The streams are about 12 to 15 feet wide and 300 feet or more long, scientists said. "What we're dealing with is wet soil, thin layers of wet soil, not standing water," said Aifred  McEwen of the University of Arizona at Tueson! the principal scientist for the Mars Reconnaissance Orbiter's high-resolution imaging experiment,

     Because liquid water is essential to life, the findings could have major implications for the possibility of Martianlife, There searchers said further exploration is needed to determine whether microscopic life exists on the planet.

    The presence of liquid water could also make life easier for astronauts visiting or living on Mars. Watercould be used for drinking and for creating oxygen and rocket fuel. NASA's goal is to send humans there inthe 2030s.

    The evidence of flowing water consistslargely of dark, narrow streaks(条痕) on the surface that tend to appear and growd uring the warmest Martian months and fade the rest of the year.

    Mars is extremely cold even in summer,and the streaks are in places where the temperature is as low as minus 10 degrees Fahrenheit. But salt can lower the freezing point of water and melt ice.

    The source of the water is a mystery. Scientists noted it could be melting ice. It could be an underground a quifer, which is rock or sand that can hold water. It is possibly water vapor from the thin Martian atmosphere, Or it may be a combination Michael Meyer, lead scientistfor NASA's Mars exploration program, said the only definitive way for now to determine whether there's life on Mars is to collect rocks and soil foranalysis on Earth - something a U.S. lander set for lift-off in 2020 will do.

    Denali National Park, Alaska

    History

    Within Denali National Park, the Toklat River will always have a special significance, as it was the location where naturalist Charles Sheldon built a cabin and was so moved that he fought to preserve the land. He moved back east and spent nine years lobbying (游说）to create Alaska's first national park.

    When to Visit

    To avoid the crowds, visit in June, but keep in mind that there are up to 21 hours of sunlight in Alaska in summer. If it seems like a bit much for your taste, try visiting in late August or September.

    If you visit to climb Mount McKinley, May and early June are the best times to climb.

    Major Attractions

    It is difficult not to see Denali's largest attraction towering 20,320 feet high. Mount McKinley can even be seen up to 70 miles away on a clear day. If you brave the climb to the top, you will be rewarded with charming views of the Alaska Range.

    Sable Pass is a prime spot to view grizzly bears. Closed to off-road foot traffic, the area is popular for bears feeding on berries, roots, and even occasionally on other mammals.

    Beginning at just below the summit of Mount McKinley, Muldrow Glacier flows 35 miles through a gorge and across the tundra. Twice in the last hundred years, the Muldrow has surged (涌动）, most recently in the winter of 1956-1957.

Accommodation

    Five campgrounds are located within the park, and many are open from late spring to early fall.Note: reservations are strongly recommended during summer. Riley Creek campground is open all year round, and all but two (Sanctuary and Wonder Lake) offer RV (可供居住的大篷车）sites.

    Also within the park are a few lodges (旅馆）—North Face Lodge, Denali Backcountry Lodge and Kentishna Roadhouse.

    Some people will do just about anything to save money．And I am one of them．Take my family's last vacation．It was my six­year­old son's winter break from school, and we were heading home from Fort Lauderdale after a week long trip．The flight was overbooked, and Delta, the airline, offered us $400 per person in credits to give up our seats and leave the next day．I had meetings in New York, so I had to get back．But that didn't mean my husband and my son couldn't stay．I took my nine­month­old and took off for home．

    The next day, my husband and son were offered more credits to take an even later flight．Yes, I encouraged — okay, ordered — them to wait it out at the airport, to “earn” more Delta Dollars．Our total take: $1,600．Not bad, huh?

    Now some people may think I'm a bad mother and not such a great wife either．But as a big­time bargain hunter, I know the value of a dollar．And these days, a good deal is something few of us can afford to pass up．

    I've made a living looking for the best deals and exposing（揭露）the worst tricks．I have been the consumer reporter of NBC's Today show for over a decade．I have written a couple of books including one titled Tricks of the Trade: A Consumer Survival Guide．And I really do what I believe in．

    I tell you this because there is no shame in getting your money's worth．I'm also tightfisted when it comes to shoes, clothes for my children, and expensive restaurants．But I wouldn't hesitate to spend on a good haircut．It keeps its shape longer, and it's the first thing people notice．And I will also spend on a classic piece of furniture．Quality lasts．

    Elizabeth Blackwell was born in England in 1821, and moved to New York City when she was ten years old. One day she decided that she wanted to become a doctor. Thai was nearly impossible for n woman in the middle of the nineteenth century. After writing many tellers asking for admission (录取) to medical schools, she was finally accepted by a doctor in Philadelphia. She was so determined that she taught school and gave music lessons to get money for the cost of schooling.

    In 1849, after graduation from medical school. She decided to further her education in Paris. She wanted to be a surgeon (外科医生), but a serious eye problem forced her to give up the idea.

    Upon returning to the United States, she found it difficult to start her own practice because she was a woman. By 1857 Elizabeth and her sister, also n doctor, along with another woman doctor, managed to open a new hospital, the first for women and children. Besides being the first woman physician and founding her own hospital, she also set up the first medical school for women.

    Chinese high school students have the longest study hours compared to their peers (同龄人) in Japan, the US and the Republic of Korea, a survey conducted by the four countries said.

    The survey, released by the China Youth and Children Research Center (CYCRC) on Monday, was jointly conducted with institutions in the four countries in September—October of 2008. It covers nearly 4, 000 students in senior high schools and vocational high schools in the four countries.

    About 78.3 percent of Chinese students said they spend more than eight hours at school and 56.7 percent said they study at least two more hours each day at home. By contrast, only 24.7 percent of their peers in the US, 20.5 percent in Japan and 15.4 percent in Korea study more than two hours after school.

    Around 60 percent of all students surveyed said their burden for studies was the heaviest; however, the Japanese felt their burden was the worst with respondents (应答者) reaching 79.2 percent.

    Among the five biggest headaches for young people in the four countries were: over—scheduling ranked first, followed by a boring leisure life, unsatisfied appearance, little time for exercise and making friends, and no spare money.

    "Moderate (适度的) study pressure can better drive students to develop, however, too much will squeeze (挤) their development space, and can even cause harm to their physical and psychological health," the survey said.

    "Balancing their studies and all-round development is a very important task," it said.

    If you want to spark a heated debate at a dinner party, bring up the topic of genetically modified foods. For many people, the concept of genetically altered, high-tech crop production raises all kinds of environmental, healthy, safety and ethical questions. Particularly in countries with long a grain traditions—and vocal green lobbies—the idea seems against nature.

    In fact, genetically modified foods are already very much apart of our lives. A third of corn and more than half the soybeans and cotton grown in the U. S. last year were the product of biotechnology, according to the Department of Agriculture. More than 65 million acres of genetically modified crops will be planted in the U. S. this year. The genetic genie(鬼怪) is out of the bottle.

    Yet there are clearly some very real issues that need to be resolved. Like any new product entering the food chain, genetically modified foods must be subjected to rigorous testing. In wealthy countries, the debate about biotech is tempered by the fact that we have a rich array of foods to choose from and a supply that far exceeds our needs. In developing countries desperate to feed fast-growing and underfed populations, the issue is simpler and much more urgent: Do the benefits of biotech outweigh the risks？

    The statistics on population growth and hunger are disturbing. Last year the world's population reached 6 billion. The U. N. estimates that nearly 800 million people around the world are undernourished. The effects are devastating. About 400 million women of child-bearing age are iron deficient, which means their babies are exposed to various birth defects. As many as 100 million children suffer from vitamin A deficiency, a leading cause of blindness.

    How can biotech help? Biotechnologists have developed genetically modified rice that is fortified with beta-carotene—which the body converts into vitamin A—and additional iron, and they are working on other kinds of nutritionally improved crops. Biotech can also improve farming productivity in places where food shortages are caused by crop damage attributable to pests, drought, poor soil and crop viruses, bacteria or fungi.