Science: Update

THE PLANNED destruction of the last known stocks of the smallpox virus in June should be postponed, or "important scientific opportunities" could be lost, says the Institute of Medicine in the US. Two centres hold the virus - the Centers for Disease Control in Atlanta, Georgia, and a Russian virology institute in Novosibirsk in Siberia. The World Health Organisation intends to destroy them, but critics say that some countries may have kept smallpox stocks for use as bio-weapons.

THE "WORKING draft" of the human genome's 2 billion or so base pairs should be ready by spring 2000, 18 months ahead of time. It will cover at least 90 per cent of the genome, which contains roughly 100,000 genes. The completion date for the entire sequencing should be 2003, though the three centres doing sequencing work to publish the data are racing Craig Venter's company Celera, which aims to patent human gene sequences in the US.

THE COMET Hale-Bopp, which blazed across the sky in 1997, may be full of primordial material from which the Sun and the planets formed almost 5 billion years ago. Radio telescope data found that the comet's nucleus was spewing a volatile mixture of primordial deuterium (an isotope of hydrogen), the poisonous gas hydrogen cyanide and heavy water (water containing deuterium). The material may be rising from deep within the comet, said Geoffrey Blake, a professor of cosmochemistry and planetary sciences at California Institute of Technology. The images, published in Nature, suggest that 15 to 40 per cent of Hale-Bopp's mass is pristine interstellar material, while the rest has been transformed during the comet's long passages through space.

NEW INSIGHTS into the way the brain analyses visual information is revealed in Nature. Researchers at the Paul Sabatier University in Toulouse report that putting together a three-dimensional picture of an object occurs earlier in the visual pathway - between retina and visual cortex - than was thought. The brain integrates information coming from the retina with information about the direction in which the eyes are pointed. The scientists say that nerve cells in the area of the visual cortex, known as V1, not only react to orientation of a visual stimulus, but also monitor the differences in its position on each retina, which gives information about how far away the stimulus is. It had been thought that this information was adjusted to reflect the direction of gaze at a later stage.