Jupiter not as dry as earlier thought, reveals new NASA probe

The largest planet in our solar system may not be as dry as earlier shown by a NASA probe, according to the first science results revealed by the US space agency's Juno mission on the amount of water in Jupiter's atmosphere.

At the equator, water makes up about 0.25 per cent of the molecules in Jupiter's atmosphere -- almost three times that of the Sun, said the study published in the journal Nature Astronomy.

These are also the first findings on the gas giant's abundance of water since NASA's 1995 Galileo mission suggested Jupiter might be extremely dry compared to the Sun.

The comparison is based not on liquid water but on the presence of its components, oxygen and hydrogen, present in the Sun.

"We found the water in the equator to be greater than what the Galileo probe measured," said Cheng Li, a Juno scientist at the University of California, Berkeley.

"Because the equatorial region is very unique at Jupiter, we need to compare these results with how much water is in other regions," Li said.

An accurate estimate of the total amount of water in Jupiter's atmosphere has been on the wish lists of planetary scientists for decades. The figure in the gas giant represents a critical missing piece to the puzzle of our solar system's formation.

Jupiter was likely the first planet to form, and it contains most of the gas and dust that was not incorporated into the Sun.

The leading theories about its formation rest on the amount of water the planet soaked up.

Water abundance also has important implications for the gas giant's meteorology (how wind currents flow on Jupiter) and internal structure.

While lightning -- a phenomenon typically fuelled by moisture -- detected on Jupiter by Voyager and other spacecraft implied the presence of water, an accurate estimate of the amount of water deep within Jupiter's atmosphere remained elusive.

Before the Galileo probe stopped transmitting 57 minutes into its Jovian descent in December 1995, it radioed out spectrometer measurements of the amount of water in the gas giant's atmosphere down to a depth of about 120 kilometres.

The scientists working on the data were dismayed to find ten times less water than expected.

A rotating, solar-powered spacecraft Juno was launched in 2011. Because of the Galileo probe experience, the mission seeks to obtain water abundance readings across large regions of the immense planet.

The Juno science team used data collected during Juno's first eight science flybys of Jupiter to generate the findings.