The origin of life and the habitability of worlds other than Earth are two of the biggest mysteries facing science today. Much research has been dedicated to these topics, but there is still a lack of definite answers.

Jan Hendrik Bredehöft from the UK's Open University has been considering habitability on other worlds. "I'm one of those guys who takes a piece of meteorite, grinds it up and finds out what the organic chemistry is in there," said Bredehöft.

Based on these types of studies, he has come to believe that habitable worlds can be split into four categories, each with varying likelihoods of being home to extraterrestrial organisms. This has great potential for assisting the search for life in the universe, particularly as technology is now progressing to the stage where direct imaging of extrasolar planets is possible. Bredehöft presented his ideas at Europlanet's latest Planetary Science Congress.

Evidence of a key mineral on Mars has been found at several locations on the planet's surface, suggesting that any microbial life that might have been there back when the planet was wetter could have lived comfortably.

The findings offer up intriguing new sites for future missions to probe, researchers said.

Observations made by NASA's Mars Reconnaissance Orbiter (MRO), which just completed its primary mission and started a second two-year shift, found evidence of carbonates, which don't survive in conditions hostile to life, indicating that not all of the planet's ancient watery environments were as harsh as previously thought.

Earth's location in the Universe is utterly unremarkable, despite recent theories that propose toppling a foundation of modern cosmology, according to a team of University of British Columbia researchers.

Polish astronomer Nicolaus Copernicus's 1543 book, On the Revolutions of the Heavenly Spheres, moved Earth from being the centre of the Universe to just another planet orbiting the Sun. Since then, astronomers have extended the idea and formed the Copernican Principle, which says that our place in the Universe as a whole is completely ordinary. Although the Copernican Principle has become a pillar of modern cosmology, finding conclusive evidence that our neighbourhood of the Universe really isn't special has proven difficult.

More than 10,000 graves containing ancient amphorae, "baby bottles," and the bodies of soldiers who fought the Carthaginians were found near the ancient Greek colony of Himera, in Italy, archaeologists announced recently. (See photos.)

"It's probably the largest Greek necropolis in Sicily," said Stefano Vassallo, the lead archaeologist of the team that made the discoveries, in September.

Lima - Researchers digging at the Cerro Patapo archeological site in northern Peru have discovered the ruins of an entire city, which may provide the "missing link" between two ancient cultures, investigators said on Tuesday.

Mosquitoes are like Typhoid Mary. They can spread viruses which cause West Nile fever, dengue fever, or yellow fever without themselves getting sick. Scientists long thought that the mosquito didn't care whether it had a virus hitchhiker, but have now discovered, "There is a war going on," said Zach Adelman, assistant professor of entomology at Virginia Tech.

The war is at the cellular level, between the host and invading RNA - the strands of code that produce different kinds of viral proteins.

The mediators that balance the interactions between mosquito and virus are virus-derived short-interfering RNAs (viRNAs), which are generated by the mosquito's immune response to infection. "If the mosquito is not able to cut up the virus genome into viRNAs, an otherwise invisible infection becomes fatal-- for both the mosquito and the virus. In other words, to complete the circle and be transmitted back to a vertebrate host, the virus must submit, to some extent, to the mosquito's antiviral response," said Kevin M. Myles, assistant professor of entomology at Virginia Tech.

Scientists have shown that tiny crystals found inside bacteria provide a magnetic compass to help them navigate through sediment to find the best food.

Researchers say their study could provide fresh clues to explain biomagnetism - a phenomenon in which some birds, insects and marine life navigate using the magnetic field that encompasses the Earth.

The study focuses on magnetotactic bacteria, which contain chains of magnetic crystals, called magnetosomes. They exist all over the globe, living in lake and pond sediments and in ocean coastal regions.

Since the discovery of magnetotactic bacteria in the 1970s, it has not been clear exactly what magnetosomes were for. Previous research suggested that some magnetosome chains would not be useful for navigation because their crystal sizes did not possess the right magnetic qualities.

Venus Express has made the first detection of an atmospheric loss process on Venus's day-side. Last year, the spacecraft revealed that most of the lost atmosphere escapes from the night-side. Together, these discoveries bring planetary scientists closer to understanding what happened to the water on Venus, which is suspected to have once been as abundant as on Earth.

The spacecraft's magnetometer instrument (MAG) detected the unmistakable signature of hydrogen gas being stripped from the day-side. "This is a process that was believed to be happening at Venus but this is the first time we measured it," says Magda Delva, Austrian Academy of Sciences, Graz, who leads the investigation.

Thanks to its carefully chosen orbit, Venus Express is strategically positioned to investigate this process; the spacecraft travels in a highly elliptical path sweeping over the poles of the planet.

Water is a key molecule on Earth because it makes life possible. With Earth and Venus approximately the same size, and having formed at the same time, astronomers believe that both planets likely began with similar amounts of the precious liquid. Today, however, the proportions on each planet are extremely different. Earth's atmosphere and oceans contain 100 000 times the total amount of water on Venus. In spite of the low concentration of water on Venus Delva and colleagues found that some 2x1024 hydrogen nuclei, a constituent atom of the water molecule, were being lost every second from Venus's day-side.

The mystery over what happened to the Beagle 2 spacecraft may have been solved, five years after contact with it was lost as it entered the Martian atmosphere on Christmas Day 2003. An Australian team of hypersonics engineers say a flawed calculation probably resulted in Beagle 2 tumbling out of control as it descended.

Until now, the loss of the probe has been attributed to the general failings of a poorly funded mission: despite an exhaustive enquiry by the European Space Agency, no single cause for the loss of the £50 million spacecraft has been identified.

Beagle 2 was designed to self-stabilise during its descent through the Martian atmosphere. This was to be achieved through careful design of the spacecraft's aerodynamics and centre of gravity, and by spinning the craft as it was released from the European Space Agency's Mars Express orbiter. This generated a gyroscopic force for correcting wobbles as it descended.

The ideal spin rate was difficult to determine because the forces on a spacecraft change sharply as it plunges from the thin upper atmosphere to the denser gas closer to the surface. The Beagle 2 team simulated the forces in both these regimes but could not afford to simulate the way the forces change during the transition between the two. Instead, they estimated the forces using a mathematical process called a bridging function, and settled on a rate of 14 revolutions per minute.

It may sound like a superstitious excuse for a poor day's swimming, but it is not uncommon for triathletes to complain that the water is behaving badly - even that it is "evil". Now a study suggests what they are feeling is real.

Leo Maas, a fluid dynamicist at the Royal Netherlands Institute for Sea Research, and colleagues found that "dead water" - an obstructive effect encountered by ships at sea - can strike swimmers too.

As ships sail over a layer of warm water sitting over saltier, or colder, layers, waves form in the boundary between the two layers. As these waves grow, they form a gulf beneath the ship, sucking away its speed. This effect can stall boats at sea, reducing their speed by up to 80%.

Maas and his colleagues ran two experiments see if dead water could strike swimmers too.