WASHINGTON ? The discovery of a 4.4-million-year-old skeleton, human-kind's oldest known ancestor, was the greatest scientific breakthrough of 2009, the prestigious journal Science said on Thursday.

The fossil, known as Ardi, topped a list of the 10 greatest scientific advances for the year, which also featured the discovery of water on the moon and the use of ultra-thin carbon atom sheets in experimental electronic devices.

Ardi, or Ardipithecus ramidus, was the subject of 15 years of painstaking examination by anthropologists who said the find, in what is now Ethiopia, provided untold insights into human evolution.

At 1.2 million years older than "Lucy", previously the oldest known human ancestor, Ardi helped shatter popular myths about the direct similarity between humans and modern apes.

Many of the traits found in Ardi's skull, teeth, pelvis, hands and feet, showed that African apes have evolved extensively since sharing a common ancestor with humans.

"(Ardi) changes the way we think about early human evolution," said Bruce Alberts, Science's editor.

Among the other developments listed by the journal were the discovery of previously unknown pulsars by NASA's Fermi telescope, including one located 4,600 light-years from Earth.

The observations helped explain how a pulsar -- the rapidly-spinning and highly-magnetized core of a exploded star -- works, and how they contribute to electromagnetic radiation in the universe.

Astrophysics provided two more of the top 10 advances of the year, including NASA's discovery of ice water on the moon.

In October the US space agency slammed a missile into the permanently shadowed Cabeus crater, near the moon's southern pole, at around 5,600 miles (9,000 kilometers) per hour.

It was followed four minutes later by a spacecraft equipped with instruments that detected significant amounts of ice water.

NASA was also praised by Science for astronauts' repairs of the Hubble space telescope, providing unprecedented images of our universe.

Meanwhile physicists working with bizarre crystalline materials managed to create magnetic ripples that could help confirm the existence of monopoles, a theoretical particle with only one magnetic pole.

And physicists operating an X-ray laser at Stanford University got fresh snap-shots of chemical reactions in progress and molecules 10,000 times smaller than a human hair.

The year also saw the advances in the way we use materials, including graphene -- highly conductive sheets of carbon atoms.

Scientists examining the ultra-thin structures were able for the first time to manipulate them into nano-scale electronic devices, raising hopes that the advance could spark an entire industry.

In the biological sciences breakthroughs were made in gene therapy and signal pathways, which offer the hope of extending human life.

While gene therapists developed new ways to treat brain disease, hereditary blindness and some immune disorders, those working on signal pathways developed a drug that extended the life-span of mice by around 10 percent.

It was the first time the drug, rapamycin, had been proven to work on mammals.

As climate change topped the political agenda, scientists grasped a clearer picture of plant molecules that could allow them to develop new ways to protect crops against drought.

In the coming year Science's editors said they expect breakthroughs in stem cell research, cancer cell metabolism and the mapping of the human genome.

With the White House set to decide on funding, the future of human space flight and NASA"s quest to return man to the moon by 2020 and establish lunar bases for further exploration to Mars, may also be decided.