The signatures for the other three planets, WASP-12b, WASP-19b and XO-1b, also are consistent with water, NASA said.
NASA said the five planets are hot Jupiters, massive worlds that orbit close to their host stars. The researchers were initially surprised that all five appeared to be hazy.
"These studies, combined with other Hubble observations, are showing us that there are a surprisingly large number of systems for which the signal of water is either attenuated or completely absent," said Heather Knutson of the California Institute of Technology, a co-author.
"This suggests that cloudy or hazy atmospheres may in fact be rather common for hot Jupiters," he added.
