Nearly 1 in 20 Americans older than 50 have artificial knees, or more than 4 million people, according to the first national estimate showing how common these replacement joints have become in an aging population. Doctors know the number of knee replacement operations has surged in the past decade, especially in baby boomers.

Scientists say NASA is about to propose major cuts in its exploration of other planets, especially Mars. And NASA's former science chief is calling it irrational. With limited money for science and an over-budget new space telescope, the space agency essentially had to make a choice in where it wanted to explore: the neighboring planet or the far-off cosmos.

FBI background interviews of some people who knew Apple co-founder Steve Jobs reveal a man driven by power and alienating some of the people who worked with him. In the FBI documents released Thursday, many of those who knew Jobs praised him, speaking highly of Jobs' character and integrity and asserting that he always conducted his business dealings in a reputable manner.

Federal weather forecasters say the La Nina weather phenomenon that contributed to the southwestern U.S. drought is winding down. The National Weather Service's Climate Prediction Center says La Nina is showing signs that it will be over by summer.

Federal weather forecasters say the La Nina weather phenomenon that contributed to the southwestern U.S. drought is winding down. The National Weather Service's Climate Prediction Center says La Nina is showing signs that it will be over by summer.

If scientists find microbes in a frigid lake two miles beneath the thick ice of Antarctica, it will illustrate once again that somehow life finds a way to survive in the strangest and harshest places. And it will offer hope that life exists beyond Earth.

The ruins aren't particularly impressive, just some stone and clay footings for houses that probably supported walls of wood or clay wattle. And it's that very ordinariness that has experts excited. The remnants being uncovered in the hills east of Mexico City at a spot known as Amecameca are from an ancient neighborhood — a home to regular folks.

A federal grand jury has indicted a Romanian citizen on charges he hacked into 25 climate-research computers at NASA's Jet Propulsion Laboratory in Pasadena. Tuesday's indictment charges Robert Butyka, 25, with one count of unauthorized impairment of a protected computer, according to the U.

An ocean experiment that was accidentally conducted amid the shipping silence after Sept. 11 has shown the first link between underwater noise and stress in whales, researchers reported Wednesday. The analysis indicated that a drop in a stress-related hormone found in the right whales was tied to a dip in ocean noise that followed a near-standstill in ship traffic, due to security concerns following the attacks.

Opening a scientific frontier miles under the Antarctic ice, Russian experts drilled down and finally reached the surface of a gigantic freshwater lake, an achievement the mission chief likened to placing a man on the moon. Lake Vostok could hold living organisms that have been locked in icy darkness for some 20 million years, as well as clues to the search for life elsewhere in the solar system.

Hackers affiliated with the group Anonymous obtained personal information for more than 150 police officers from an old website of the West Virginia Chiefs of Police Association and posted the data online. The FBI is investigating, said William Roper, the association's president and the police chief of Ranson, W.

NASA astronaut Janice Voss, who first worked for the space agency as a teenager and flew five shuttle missions in seven years, has died. She was 55. The agency said in a statement Tuesday that Voss died overnight after a battle with cancer. A native of South Bend, Ind.

Roger Boisjoly, a NASA contractor who repeatedly voiced concerns about the space shuttle Challenger before it exploded, has died. He was 73. Boisjoly died of cancer on Jan. 6 in Nephi, about 40 miles south of Provo, his wife Roberta Boisjoly said.

President Barack Obama called on Tuesday for millions of dollars in new funding to improve math and science education, an effort he said would be crucial to the nation's long-term success. Obama said his upcoming budget proposal, set to be released next week, would include a request for $80 million from Congress for a new Education Department competition to support math and science teacher preparation programs.

A developing Senate plan that would bolster the government's ability to regulate the computer security of companies that run critical industries is drawing strong opposition from businesses that say it goes too far and security experts who believe it should have even more teeth.

The head of memory chip maker Micron, long known for taking risks in stunt piloting, died Friday when a small experimental plane he was piloting steeply banked, stalled and crashed near an Idaho runway. Steve Appleton, who survived a similar crash eight years ago and had a reputation as a hard-driving daredevil, was the only person aboard the plane when witnesses said it crashed shortly after its second take-off attempt in Boise, according to safety investigators.

Researchers who spent three years dragging sheets of fabric through the woods to snag ticks have created a detailed map they claim could improve prevention, diagnosis and treatment of Lyme disease. The map, which pinpoints areas of the eastern United States where people have the highest risk of contracting Lyme disease, is part of a study published in the February issue of the American Journal of Tropical Medicine and Hygiene.

NASA says it still has confidence in the quality of Russia's manned rockets, despite an embarrassing series of glitches and failures in the Russian space program. A leak developed recently during a test of the next Soyuz capsule scheduled to launch astronauts to the International Space Station, so Russian space officials have decided not to use it.

Facebook is baring its business soul. The unveiling came late Wednesday when the company that depends on people to share their lives online filed its plans to raise $5 billion in an initial public offering of stock. It's a revelatory moment that prospective investors, curious competitors and nosy reporters have been awaiting for two years.

Snow has been missing in action for much of the U.S. the last couple months. But it's not just snow. It's practically the season that's gone AWOL. "What winter?" asked Mike Halpert, deputy director of the National Weather Service's Climate Prediction Center.

FB? That's the best they could do? The company that changed how politicians raise money, dissidents start revolutions and parents keep tabs on their kids announced its stock ticker symbol Wednesday. And it used about as much creativity as liking someone else's status.

A bullet that directs itself like a tiny guided missile and can hit a target more than a mile away has the potential to change the battlefield for soldiers without costing too much, engineers at Sandia National Laboratories said Wednesday.

Republican presidential candidate Newt Gingrich wants to create a lunar colony that he says could become a U.S. state. There's his grand research plan to figure out what makes the human brain tick. And he's warned about electromagnetic pulse attacks leaving America without electricity.

A glimpse beyond our solar system reveals the neighborhood just outside the sun's influence is different and stranger than expected, scientists reported Tuesday. One oddity is the amount of oxygen. There are more oxygen atoms floating freely in the solar system than in the immediate interstellar space, or the vast region between stars.

Romanian authorities are investigating a 20-year-old who is suspected of hacking into several Pentagon and NASA servers and posting confidential data he retrieved from those servers on his blog, officials said Tuesday. The suspect was identified as Razvan Manole Cernaianu, reportedly an information technology student known online as TinKode.