New studies look at the planet's upper atmosphere

Mar 22, 2010 15:10 GMT  ·  By
A photo of Jupiter's upper atmosphere, which appears to be lacking in neon and helium
   A photo of Jupiter's upper atmosphere, which appears to be lacking in neon and helium

Over the past 15 years, astronomers have been puzzled at a seemingly-inexplicable mystery. When the Galileo space probe first arrived at the gas giant Jupiter, back in 1995, it revealed the fact that the upper atmosphere of the planet was poorer in the noble gases helium and neon than anyone anticipated. These are the lightest noble gases in the Periodic Table of Elements, and experts could not find the reason for which they were lost from Jupiter's atmosphere. Now, thanks to modern computers and simulations, experts are able to identify the reason underlying this phenomenon.

Because sending a sample-return mission to any gas giant is a financial and technical impossibility at this point, researchers need to assess the internal composition of planets such as Jupiter and Saturn using nothing more than comparisons with the Sun. They scan for the planets' constituent elements, and then look at how abundant these chemicals are in the celestial bodies as compared to the Sun. Through this method, a research team discovered that Jupiter had a lot less neon gas, and also less helium than models had predicted. Details of the work are reported in the current issue of esteemed scientific publication Physical Review Letters.

After Galileo first presented its findings, a group of experts proposed that the neon gas was slipping away from the upper atmosphere, and further within the gas giant. However, up until now, no one knew what mechanism could possibly be driving this. The new models suggest that a layer must exist within the atmosphere, where helium condenses into droplets, rather than mixing smoothly with the hydrogen gas. As the helium rain falls, it also strips neon from the upper atmosphere, taking it further towards the planet's core.

The new investigation was conducted by investigators at the University of California in Berkeley (UCB). They developed a computer model that was capable of taking into account the interactions of the hot gases that make up Jupiter's core, and this approach led them to the conclusion that the condensation layer must exist somewhere in the atmosphere. The same could hold true for Saturn as well, the investigators say, although atmospheric missions to these two locations are needed before a clear conclusion can be drawn from the models.