Jupiter's atmosphere may contain water

Chemical signatures of water detected during observations of the Great Red Spot.
By Laurel Kornfeld | Dec 05, 2018
Researchers led by Gordon L. Bjoraker, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, detected the chemical signatures of water during spectroscopic observations of Jupiter's Great Red Spot with ground-based telescopes.

Scientists have long questioned whether water is present in Jupiter's atmosphere, especially given the high water content of the giant planet's largest moons.

Previous searches for atmospheric water, including a probe dropped into the giant planet's atmosphere by NASA's Galileo spacecraft in 1995, did not discover any, partly due to landing in a dry area.

For a long time, Jupiter was thought to have a composition very much like that of the Sun--almost all hydrogen and helium, with no solid core.

However, several probes that visited the planet have found chemical evidence for a core made of rock and water that could be 10 times as massive as the Earth.

Bjoraker and his team observed the Great Red Spot using the most sensitive infrared telescope at the W.M. Keck Observatory in Hawaii and a new instrument at the NASA Infrared Telescope Facility (IRTF). They looked in wavelengths sensitive to the leak of thermal radiation from the lower part of the large storm. In addition to detecting the chemical signatures of water, they measured the pressure of the water and confirmed the presence of carbon monoxide.

These data suggest Jupiter has between two and nine times more oxygen than the Sun and that computer models that predicted a large amount of water on the planet are correct.

In spite of the Great Red Spot being made up of dense clouds, the researchers successfully used new spectroscopic technology to look thousands of miles deep into it.

"Jupiter's water abundance will tell us a lot about how the giant planet formed, but only if we can figure out how much water there is in the entire planet," said Juno project scientist Steven M. Levin of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

Bjoraker's data will be combined with that collected by NASA's Juno spacecraft, which is using an infrared spectrometer and a microwave radiometer that can probe as far as 100 times Earth's surface pressure in its own search for water on Jupiter.

Some planetary scientists theorize that Jupiter's atmosphere contains three layers of clouds--the lowest composed of water ice and liquid water, the middle composed of ammonia and sulfur, and the top composed solely of ammonia. Bjoraker's findings include some evidence for these layers.

As a next step, Bjoraker and his team will use the same technique to study other regions of the giant planet.

If water is present on Jupiter, it may also exist on the solar system's other gas giants--Saturn, Uranus, and Neptune, noted planetary atmospheres expert Amy Simon, also at Goddard.

Findings of the study have been published in The Astronomical Journal.


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