Growing danger

ESA Space in Images This may resemble an alien landscape, but it is actually a microscopic view of tin used to solder electronic components. The long shard rising from the surface is a 'tin whisker' - a spontaneous outgrowth representing a clear and present danger to space missions. The phenomenon was first identified within terrestrial electronics, but these whiskers are known to grow rapidly out of pure tin in the weightlessness, vacuum and temperature extremes of space. Typically, these crystalline filaments are just a few thousands of a millimetre thick, though may extend more than a thousand times further in length. They are electrically conductive and so can threaten catastrophic short circuits: the US Galaxy IV telecommunications satellite was lost due to this issue in 1998 . The traditional method of preventing tin whiskers was to add lead - but lead is toxic, so its use in solder has been phased out through the EU's Reduction of Hazardous Substances directive. ESA and European space industry have been granted a waiver to continue using tin-lead alloy for solder, but not an indefinite one.