A survey of 10 hot, Jupiter-sized exoplanets conducted with NASA's Hubble and Spitzer space telescopes has led a team to solve a long-standing mystery — why some of these worlds seem to have less water than expected. The findings offer new insights into the wide range of planetary atmospheres in our galaxy and how planets are assembled.Of the nearly 2,000 planets confirmed to be orbiting other stars, a subset of them are gaseous planets with characteristics similar to those of Jupiter. However, they orbit very close to their stars, making them blistering hot.Their close proximity to the star makes them difficult to observe in the glare of starlight. Due to this difficulty, Hubble has only explored a handful of hot Jupiters in the past. These initial studies have found several planets to hold less water than predicted by atmospheric models.