Images Dated 4th March 2004

North America at night

North America at night, satellite image. North is at top. Yellow lights mark the major cities. The western coast of the USA is the most brightly lit area, with the urban area of Los Angeles, San Francisco, Seattle and Vancouver (in Canada), all seen. The eastern USA is densely populated and has many major cities. The American Mid-West, which lies between these other two areas, is sparsely populated, with large stretches of plains, deserts and mountains seen as dark areas. The far north is uninhabited, apart from the lights of Alaska (top left). The Pacific Ocean is also dark. Dawn is breaking over the eastern coast of the USA

© PLANETARY VISIONS LTD/SCIENCE PHOTO LIBRARY

Atherosclerosis

Atherosclerosis. Artwork of a human heart showing narrowing of the coronary arteries due to atherosclerosis, a build up of fatty deposits (atheroma, yellow) on the artery wall. The large red vessel is the aorta, the main artery carrying blood from the heart to the body. Two coronary arteries arise from the aorta and supply the heart muscle with oxygen. The left coronary artery (on the right) divides into the anterior descending and circumflex branches. Coronary artery disease is the most common cause of death in developed countries. The narrowing causes abnormal clotting, which blocks the vessel and starves the heart's muscle of blood, causing a heart attack

© JOHN BAVOSI/SCIENCE PHOTO LIBRARY

DNA in space

DNA in space. Computer artwork of a DNA double helix in space above Earth. This may represent the possible uniqueness of Earth as a cradle of life in the universe, or the ubiquity of DNA and the related RNA in life on Earth. A molecule of DNA (deoxyribonucleic acid) consists of two helical chains coiled around the same axis, each chain consisting of alternate phosphate and sugar groups. The chains are held together in a double helix by the hydrogen bonds formed between nucleotide bases attached to the two chains. There are four bases; adenine (A), cytosine (C), guanine (G) and thymine (T). The sequence of the bases in the molecule forms the genetic code

© CHRISTIAN DARKIN/SCIENCE PHOTO LIBRARY