NASA | How to Cook a Comet. At around 230 million miles away from the sun, solar radiation begins to cook off the frozen water ice directly into gas. This is called sublimation. If it survives this, the intense radiation and pressure closer to the sun could destroy it altogether. Animators at NASA's Goddard Space Flight Center in Greenbelt, Md. created this short movie showing how the sun can cook a comet. Mona Evans, "Comets" http://www.bellaonline.com/articles/art33712.asp
Mysterious cloud spotted on Mars Amateur astronomers are puzzling over a seemingly anomalous cloud that has shown up on images of Mars taken over the past few days. Is it really a cloud, or a trick of the eye? Does it really extend 150 miles up from the surface, as some of the observers suggest? And what churned up all that stuff, anyway? The amateurs and the pros will be trying to resolve those questions before the phenomenon fades away.