Is There Water on Jupiter?

by Jerry Coffey on June 18, 2008

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Jupiter and its moons. Image credit: NASA/JPLOne of the first things that many people ask about a planet is whether there is water or not. So, naturally, the question ”is there water on Jupiter?” has been asked many times. The answer is yes, there is a small amount of water, but it is not ”on” Jupiter. It is in the form of water vapor in the cloud tops.

Scientists were surprised to find only trace amounts of water on Jupiter. After all, they had reasoned that Jupiter should have more oxygen than the Sun. The oxygen would have combined with the more than abundant hydrogen in the Jovian atmosphere, thus making water a significant component. The trouble is that the Galileo space craft found that Jupiter’s atmosphere contains less oxygen than the Sun; therefore, water is a minor trace element in the atmosphere.

That does not mean that there is not significant amounts of water elsewhere in the Jovian system. A few of Jupiter’s moons have been found to have water or water ice in their atmosphere or on their surface. Europa is the most important source of water in the system. Europa is thought to have an iron core, a rocky mantle and a surface ocean of salty water. Unlike oceans on Earth, this ocean is deep enough to cover the whole surface of Europa, and being far from the sun, the ocean surface is globally frozen over. Europa’s orbit is eccentric, so when it is close to Jupiter the tide is much higher than when it is at aphelion. Tidal forces raise and lower the sea beneath the ice, most likely causing the cracks seen in images of Europa’s surface. The tidal forces cause Europa to be warmer than it would otherwise be. The warmth of Europa’s liquid ocean could prove critical to the survival of simple organisms within the ocean, if they exist.

Some scientists at NASA believe that the ocean under Europa’s surface does not consist of water, but say light reflected from the moon’s icy surface bears the spectral fingerprints of hydrogen peroxide and strong acids, perhaps close to pH 0. They are not sure whether this is just a thin surface dusting or whether the chemicals come from the ocean below. The hydrogen peroxide certainly seems to be confined to the surface, as it is formed when charged particles trapped in Jupiter’s magnetosphere strike water molecules on Europa. On the other hand, parts of the surface are rich in water ice containing what appears to be an acidic compound. Robert Carlson of NASA’s Jet Propulsion Laboratory thinks this is sulfuric acid. He believes that up to 80 per cent of the surface ice on Europa may be concentrated sulfuric acid. He goes on to suggest that this may be confined to a layer formed by surface bombardment with sulfur atoms emitted by volcanoes on Io. Tom McCord of the Planetary Science Institute in Winthrop, Washington and Jeff Kargel of the US Geological Survey in Flagstaff, Arizona point out that the greatest concentrations of acid seem to be in areas where the surface has been broken by tidal forces. They believe that ocean liquid has gushed up through those cracks and the ocean is actually the source of all of the acid. This theory holds that the acid on the surface began as salts(mainly magnesium and sodium sulphates), but the intense surface radiation caused chemical reactions which left an icy crust containing a high concentration of sulfuric acid as well as other sulfur compounds. That means that the ocean is an acidic brine that would be destructive to life as we know it.

Giving the answer to ”is there water on Jupiter” is probably the simplest piece of information about the planet. Nearly everything else is open a lot of interpretation until more space craft are sent for additional exploration.

Here’s an article about how the water on Europa might actually be corrosive to life, and the discovery of an extrasolar planet that does have evidence of water.

The Nine Planets site has a great description of Jupiter, including its lack of water, and an old article about Galileo’s search for water on Jupiter.

We’ve also recorded an entire show just on Jupiter for Astronomy Cast. Listen to it here, Episode 56: Jupiter, and Episode 57: Jupiter’s Moons.

Sources:
NASA: Jupiter
NASA: Europa

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