NASA- We have had satellites able to measure the temperature of the global ocean for decades. But measurements of another important characteristic of ocean water- it’s saltiness- have until now relied on boats. This means that data was only collected where boats went, and the ocean is a very large place. A couple months ago, NASA launched a new satellite that can measure the saltiness (or salinity) of the ocean. Why bother? We don’t full understand how the ocean impacts the water cycle. But, changes in the water cycle affect salinity. For instance, one summer an usually large volume of water might evaporate from the tropical Atlantic. That water could then be transported, in clouds, to Brazil, causing local rains to be unusually heavy. If someone wants to know why rainfall is so heavy, they could look at salinity records- evaporation removes water but leaves salt behind, so ocean areas with lots of evaporation would have higher salinity. Then, next time they see a similar pattern of salinity, they might be able to prepare for heavy rains.