A "Gate to Hell" has emerged from ruins in southwestern Turkey, Italian archaeologists have announced. Known as Pluto's Gate -- Ploutonion in Greek, Plutonium in Latin -- the cave was celebrated as the portal to the underworld in Greco-Roman mythology and tradition. Historic sources located the site in the ancient Phrygian city of Hierapolis, now called Pamukkale, and described the opening as filled with lethal mephitic vapors.

"This space is full of a vapor so misty and dense that one can scarcely see the ground. Any animal that passes inside meets instant death," the Greek geographer Strabo (64/63 BC -- about 24 A.D.) wrote.  "I threw in sparrows and they immediately breathed their last and fell," he added.

Almost three quarters of the earth's surface is covered in water and around 90% of all the living space on Earth is contained in the oceans. These vast reserves cradled early life and continue to be home to a wealth of extraordinary creatures.

At least 230,000 unique species have been documented, although as humans have only explored a small fraction of the depths, there may be as many as two million.

The UK's national synchrotron facility - the Diamond Light Source near Oxford - is to become a world centre for studying the structure of viruses and bacteria that cause serious disease.

Diamond uses intense X-rays to reveal the molecular and atomic make-up of objects and materials.  It will now use this capability to image Containment Level 3 pathogens. These are responsible for illnesses such as Aids, hepatitis and some types of flu. Level 3 is one step down from the most dangerous types of infectious agent, such as Ebola, which can only be handled in the most secure government facilities.

The enduring image in the public mind of the mysterious heads on Easter Island is simply that they are heads. So it comes as quite a shock to discover that they have full bodies, extending down many, many feet into the ground of the island.

The Easter Island Statue Project has been carefully excavating two of 1,000-plus statues on the islands - doing their best to uncover the secrets of the mysterious stones, and the people who built them. Inside the Easter Island statues: Experts have known about the bodies before, but when these images started circulating readers doubted their authenticity.

New research from the Spanish National Research Council provides more information about how our arms and legs developed from fins. Basically, tetrapods like humans and cows have a gene, called the hoxd13 gene, that produces a protein that leads to the growth of limbs, something they proved by using not guinea pigs, but zebrafish embryos.

Perhaps the little fish embryo shown here is dancing a jig because it has just discovered that it has legs instead of fins. Fossils show that limbs evolved from fins, but a new study shows how it may have happened, live in the lab.Fernando Casares of the Spanish National Research Council and his colleagues injected zebrafish with the hoxd13 gene from a mouse.  Casares and his colleagues hoped that by injecting extra copies of the gene into the zebrafish embryos, some of their cells would make more of the protein.