Water ice clouds have been detected on Jupiter

Researchers using ground-based telescopes have detected the chemical signatures of water deep beneath the surface of Jupiter’s Great Red Spot.

Jupiter is a gas giant that contains more than twice the mass of all of our other planets combined. And though 99% of Jupiter’s atmosphere is composed of hydrogen and helium, even small fractions of percent of the atmosphere having water would add up to a lot of water.

They detected water ice cloud at seven bar. Seven times the pressure on earth atmosphere at sea level.

The team focused its sights on the Great Red Spot, a hurricane-like storm more than twice as wide as Earth that has been blustering in Jupiter’s skies for more than 150 years. The team searched for water by using radiation data collected by two instruments on ground-based telescopes: iSHELL on the NASA Infrared Telescope Facility and the Near Infrared Spectograph on the Keck 2 telescope, both of which are located on the remote summit of Maunakea in Hawaii. iShell is a high-resolution instrument that can detect a wide range of gases across the color spectrum. Keck 2 is the most sensitive infrared telescope on Earth.

The team found evidence of three cloud layers in the Great Red Spot, with the deepest cloud layer at 5-7 bars. A bar is a metric unit of pressure that approximates the average atmospheric pressure on Earth at sea level. Altitude on Jupiter is measured in bars because the planet doesn’t have an Earth-like surface from which to measure elevation. At about 5-7 bars – or about 100 miles below the cloud tops – is where the scientists believed the temperature would reach the freezing point for water. The deepest of the three cloud layers identified by the team was believed to be composed of frozen water.

The Astronomical Journal – The Gas Composition and Deep Cloud Structure of Jupiter’s Great Red Spot

“The discovery of water on Jupiter using our technique is important in many ways. Our current study focused on the red spot, but future projects will be able to estimate how much water exists on the entire planet,” Ádámkovics said. “Water may play a critical role in Jupiter’s dynamic weather patterns, so this will help advance our understanding of what makes the planet’s atmosphere so turbulent. And, finally, where there’s the potential for liquid water, the possibility of life cannot be completely ruled out. So, though it appears very unlikely, life on Jupiter is not beyond the range of our imaginations.”

Clemson’s main role in the research was to use specially designed software to transform raw data into science-quality data that could be more easily analyzed and also shared with scientists at Clemson and around the world. This type of work was performed this past spring by Rachel Conway, an undergraduate student in physics and astronomy who became involved in the project via Clemson’s Creative Inquiry program.

“When I initially began, I started by running the data through. The code was already written and I was just plugging in new data sets and generating output files,” said Conway, a native of Watertown, Connecticut. “But then I began fixing errors and learning more about what was actually going on. I’m interested in everything and anything that’s out there, so learning more about what we don’t know is always cool.”

Researchers have obtained high-resolution spectra of Jupiter’s Great Red Spot (GRS) between 4.6–5.4 μm using telescopes on Mauna Kea to derive gas abundances and to constrain its cloud structure between 0.5–5 bars. They used line profiles of deuterated methane (CH3D) at 4.66 μm to infer the presence of an opaque cloud at 5 ± 1 bars. From thermochemical models, this is almost certainly a water cloud. They also used the strength of Fraunhofer lines in the GRS to obtain the ratio of reflected sunlight to thermal emission. The level of the reflecting layer was constrained to be at 570 ± 30 mbar based on fitting strong NH3 lines at 5.32 μm. They identified this layer as an ammonia cloud based on the temperature where gaseous NH3 condenses. They found evidence for a strongly absorbing but not totally opaque cloud layer at pressures deeper than 1.3 bars by combining Cassini/CIRS spectra of the GRS at 7.18 μm with ground-based spectra at 5 μm. This is consistent with the predicted level of an NH4SH cloud. They also constrained the vertical profile of H2O and NH3. The GRS spectrum is matched by a saturated H2O profile above an opaque water cloud at 5 bars. The pressure of the water cloud constrains Jupiter’s O/H ratio to be at least 1.1 times solar. The NH3 mole fraction is 200 ± 50 ppm for pressures between 0.7–5 bars. Its abundance is 40 ppm at the estimated pressure of the reflecting layer. They obtained 0.8 ± 0.2 ppm for PH3, which is a factor of 2 higher than in the warm collar surrounding the GRS. They detected all five naturally occurring isotopes of germanium in GeH4 in the GRS. They obtained an average value of 0.35 ± 0.05 ppb for GeH4. Finally, they measured 0.8 ± 0.2 ppb for CO in the deep atmosphere.

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