ROCKET exhaust is revealing the secrets of a part of the atmosphere so neglected that it has been nicknamed the 鈥渋gnorosphere鈥�. The region extends from 90 to 120 kilometres above the Earth.
鈥淏alloons don鈥檛 go that high and satellites don鈥檛 dip down that low,鈥� says James Russell, from Hampton University in Virginia.
Now Russell and his team have found they can measure wind speeds at these high altitudes by tracking the trails of water vapour left by rockets as they shoot into space. Using a remote sensing satellite orbiting 625 kilometres above the Earth, they are able to detect the infrared radiation emitted by the water. The motion of the rockets鈥� contrails suggests that wind speeds average around 50 metres per second, far faster than expected (Geographical Research Letters, vol 30, p 1819).
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