Upper Atmosphere Research Satellite Upper Atmosphere Research Satellite The Upper Atmosphere Research Satellite (UARS) was a NASA-operated orbital observatory whose mission was to study the Earth’s atmosphere, particularly the protective ozone layer. The satellite was deployed from Space Shuttle "Discovery" during the STS-48 mission on 15 September 1991. It entered Earth orbit at an operational altitude of , with an orbital inclination of 57 degrees. The original mission duration was to be only three years, but was extended several times. When the mission finally ended in June 2005 due to funding cuts, 14 years after the satellite's launch, six of its ten instruments were
Atmosphere of Mercury pushes neutral atoms away from Mercury, creating a comet-like tail behind it. The main component in the tail is sodium, which has been detected beyond 24 million km (1000 R) from the planet. This sodium tail expands rapidly to a diameter of about 20,000 km at a distance of 17,500 km. In 2009, "MESSENGER" also detected calcium and magnesium in the tail, although these elements were only observed at distances less than 8 R. Atmosphere of Mercury Mercury has a very tenuous and highly variable atmosphere (surface-bound exosphere) containing hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor, with a