Astronomers Come up Dry in the Hunt for Water on Jupiter-like Exoplanets

Astronomers may have come up dry when it comes to searching for water on other planets. They've made the most precise measurements to date of water vapor in the atmospheres of Jupiter-like planets and have found that they're much drier worlds than previously expected.

"The low water vapor levels are surprising," said Nicolas Crouzet, one of the researchers, in a news release. "Our models predict a much higher abundance of water vapor, and so these results challenge our current understanding of planet formation. And they raise questions about our ability to identify water in an Earth-like exoplanet."

The core accretion theory of planet formation states that planetary systems form from a huge disk of hydrogen gas and dust around a star. Over a period of a million years or more, the dust particles stick together, forming larger and larger grains. Eventually the grains collect together enough to form into a planet. At the same time, the gravity of the planet attracts an atmosphere of gas from the disk.

While this theory predicts that a planet's most abundant element would be oxygen, which would take the form of water vapor, findings seem to indicate that this isn't the case. Scientists analyzed three exoplanets between 60 and 900 light-years away and found that there's far less water vapor than predicted.

"These very hot planets with large atmospheres, orbiting nearby stars, are the best possible candidates for measuring water levels," said Nikku Madhusudhan, one of the researchers. "And yet the levels we found were much lower than expected. This shows just how challenging it could be to detect water on Earth-like exoplanets in our search for potential life elsewhere."

The findings reveal a bit more about these Jupiter-like planets, which could influence the hunt for extraterrestrial life in the future. More specifically, it shows that models aren't necessarily correct, which means that they need to be revised.

The findings are published in Astrophysical Journal Letters.