seagirlreed writes "Rocket traffic may be adding water to the Earth's mesosphere, leading to more very high clouds in this layer of thin air on the edge of space. From the article: 'A team of researchers looking for an expected decrease in the number of clouds in this layer, as solar activity and heating have ramped up, were instead surprised to find an increase in the number and brightness of clouds in this near-outer-space region over the last two years. ... The source of the water to make the clouds is a puzzle, Siskind explained, because there is not much sign of it coming up into the mesosphere. On the other hand, rockets and, until recently, shuttles roaming in space could rain water exhaust down into the mesosphere.'"