The windy weather on two inscrutable ice giants Uranus and Neptune can help scientists better understand the atmospheres of exoplanets.

Decades-old data from the Voyager 2 spacecraft has led scientists to conclude that Uranus and Neptune are home to some of the most extreme winds found in our solar system. Most of these winds travel at speeds of over 620 miles per hour and can keep blowing for years.

Though both planets are part of our solar system, scientists have not been able to learn much about their atmospheres and this new discovery could help them understand a bit about the two planets' dynamic atmospheres.

"We know what the winds are doing right at the top, where we see the clouds, because we can watch those clouds blow around and we can track those motions," said study coauthor Adam Showman, a planetary scientist at the University of Arizona in Tucson. "What we have not known is what they're doing in the deep interior or even really at all below the clouds  -- that's very hard to measure."

The Sun's rays penetrate through the Earth's thin atmosphere and so it is easy to detect this atmosphere. But Uranus and Neptune are two planets filled with liquid, which makes it difficult for scientists to detect where their atmospheres begin.

"In an age in which space missions penetrate the far reaches of the solar system, it seems incredible that planetary scientists still argue about the depth of atmospheric circulations inside the ice giants, Uranus and Neptune, and the gas giants, Jupiter and Saturn," Peter Read of the University of Oxford,  wrote in a Nature commentary.

To look into this matter further, scientists analyzed gravity field data collected by the Voyager 2 spacecraft when it flew by Uranus in 1986 and Neptune in 1989.

Gravity is controlled by the amount of mass at the centre. Changes in the distribution of mass of these planets affect the gravitational field. Also the rapid rotations of Uranus and Neptune lead to rapid changes in the atmospheric pressure.

They then created a wind-induced gravity map of Uranus and Neptune and found that the streams of gas observed in the atmosphere of these planets are limited to a "weather layer" of no more than about 620 miles in depth--that makes up only a fraction of a percent of the mass of these planets.

The study was published in the journal Nature.