As far as current scientific theory understands it, high-temperature planets appear to be the most likely candidates for having water vapor in their atmospheres. After a recent study of three “hot Jupiters,” however, that theory might be bunk: The Hubble Space Telescope was used to examine the atmosphere of three planets orbiting stars similar to the Sun, believed to have water in their atmospheres – and they came up dry.

Well, not totally dry – just much dryer than they thought.

“Our water measurement in one of the planets, HD 209458b, is the highest-precision measurement of any chemical compound in a planet outside the solar system, and we can now say with much greater certainty than ever before that we’ve found water in an exoplanet,” said Dr Nikku Madhusudhan of the Institute of Astronomy at the University of Cambridge, who led the research. “However, the low water abundance we are finding is quite astonishing.”

Altogether, they examined three such exoplanets – HD 189733b, HD 209458b, and WASP-12b. They’re all between 60 and 900 light-years away. They’re mind-bendingly hot, with temperatures recorded between 1,500 and 4,000 degrees Fahrenheit. Those conditions, say scientists, are typically ideal for holding water vapor in the atmosphere. The fact that these three don’t have researchers scratching their heads.

“It basically opens a whole can of worms in planet formation. We expected all these planets to have lots of water in them. We have to revisit planet formation and migration models of giant planets, especially ‘hot Jupiters’, and investigate how they’re formed,” said Madhusudhan.

For the study, the researchers used the near-infrared spectra tool on Hubble to estimate the amount of water vapor in the planetary atmospheres based on sophisticated computer models. With these unexpected results, they say that finding Earth-like (and possibly hospitable) planets will be challenging moving forward, even with such sophisticated measurements.

“We should be prepared for much lower water abundances than predicted when looking at super-Earths (rocky planets that are several times the mass of Earth),” Madhusudhan said.

Future instruments, the researchers say, may need to be designed with even higher sensitivity if there’s ever hope of finding life elsewhere in the universe, or even a planet where life could exist.