"Hot Jupiters" is the name given to Jupiter-like exoplanets. There are three such distant gas giants that astrophysicists recently analyzed for evidence of water vapor in their atmospheres, but they came up dry.

According to the present theory of planet formation, Hot Jupiters are born in areas of the solar system that are rich in water. After their formation, they migrate toward their host stars, which accumulate water much more slowly than the planets.

Yet new findings by the Hubble Space Telescope show that the present theory is wrong. The telescope found that the environments on all three Hot Jupiters are actually drier-much drier-than Jupiter. The planet from which the telescope collected the most precise measurements was 1,000 times drier than Jupiter.

Some scientists believe the Hubble's findings were clouded...literally. They argue that clouds above the exoplanets blocked the view of the water vapor in the planets' atmospheres.

Nikku Madhusudhan, the leader of the study and an astronomer at the University of Cambridge, UK, acknowledged that the arguments are plausible but unlikely. He counters that clouds would not be able to survive so high in the planets' atmospheres and within such wide ranges of temperatures.

"There is just no candidate cloud composition or physics that can do it," Madhusudhan argues.

Astronomer Zachory Berta-Thompson of MIT and his colleagues, who studied another hot rocky planet, believe that clouds can be present so high in the atmosphere, even in thin layers. He says that while the formation of the clouds and of the water vapor is still complex and unclear, it does not mean they do not exist.

"It's a little bit frustrating that these planets are slightly more complicated than we'd like them to be," he says.

Hubble Telescope observes and measures approximate water vapor by watched the planet as it crosses in front of its host star in orbit. By observing the spectrum of infrared light that passes through the atmosphere and translating the measurements into models, Hubble allows Madhusudhan and colleagues to deduce the chemical composition of the planet's atmosphere.

In order to confirm the findings and skirt around the complexities of these planets, higher-resolution data will be needed. Researchers are turning to NASA's developing James Webb Space Telescope in the hopes that it will provide data that will clear the mystery surrounding these planets and their controversially dry atmospheres.