SPACE/COSMOS
Citizen science reveals that Jupiter’s colorful clouds are not made of ammonia ice
University of Oxford
Collaborative work by amateur and professional astronomers has helped to resolve a long-standing misunderstanding about the composition of Jupiter’s clouds. Instead of being formed of ammonia ice – the conventional view – it now appears they are likely to be composed of ammonium hydrosulphide mixed with smog.
The findings have been published in the Journal of Geophysical Research – Planets.
The new discovery was triggered by amateur astronomer, Dr Steven Hill, based in Colorado. Recently, he demonstrated that the abundance of ammonia and cloud-top pressure in Jupiter’s atmosphere could be mapped using commercially-available telescopes and a few specially coloured filters. Remarkably, these initial results not only showed that the abundance of ammonia in Jupiter’s atmosphere could be mapped by amateur astronomers, they also showed that the clouds reside too deeply within Jupiter’s warm atmosphere to be consistent with the clouds being ammonia ice.
In this new study, Professor Patrick Irwin from the University of Oxford’s Department of Physics applied Dr Steven Hill’s analytical method to observations of Jupiter made with the Multi Unit Spectroscopic Explorer (MUSE) instrument at the European Southern Observatory’s Very Large Telescope (VLT) in Chile. MUSE uses the power of spectroscopy, where Jupiter’s gases create telltale fingerprints in visible light at different wavelengths, to map the ammonia and cloud heights in the gas giant’s atmosphere.
By simulating how the light interacts with the gases and clouds in a computer model, Professor Irwin and his team found that the primary clouds of Jupiter – the ones we can see when looking through backyard telescopes – had to be much deeper than previously thought, in a region of higher pressure and higher temperature. Too warm, in fact, for the condensation of ammonia. Instead, those clouds have to be made of something different: ammonium hydrosulphide.
Previous analyses of MUSE observations had hinted at a similar result. However, since these analyses were made with sophisticated, extremely complex methods that can only be conducted by a few groups around the world, this result was difficult to corroborate. In this new work, Irwin’s team found that Dr Hill’s method of simply comparing the brightnesses in adjacent, narrow coloured filters gave the identical results. And since this new method is much faster and very simple, it is far easier to verify. Hence, the team conclude that the clouds of Jupiter really are at deeper pressures than the expected ammonia clouds at 700 mb and so cannot be composed of pure ammonia ice.
Professor Irwin said: “I am astonished that such a simple method is able to probe so deep in the atmosphere and demonstrate so clearly that the main clouds cannot be pure ammonia ice! These results show that an innovative amateur using a modern camera and special filters can open a new window on Jupiter’s atmosphere and contribute to understanding the nature of Jupiter’s long-mysterious clouds and how the atmosphere circulates.”
Dr Steven Hill, who has a PhD in Astrophysics from the University of Colorado and works in space weather forecasting, said, “I always like to push my observations to see what physical measurements I can make with modest, commercial equipment. The hope is that I can find new ways for amateurs to make useful contributions to professional work. But I certainly did not expect an outcome as productive as this project has been!”
The ammonia maps resulting from this simple analytical technique can be determined at a fraction of the computational cost of more sophisticated methods. This means they could be used by citizen scientists to track ammonia and cloud-top pressure variations across features in Jupiter’s atmosphere including Jupiter’s bands, small storms, and large vortices like the Great Red Spot.
John Rogers (British Astronomical Association), one of the study’s co-authors adds: “A special advantage of this technique is that it could be used frequently by amateurs to link visible weather changes on Jupiter to ammonia variations, which could be important ingredients in the weather.”
So why doesn’t ammonia condense to form a thick cloud? Photochemistry (chemical reactions induced by sunlight) is very active in Jupiter’s atmosphere and Professor Irwin and his colleagues suggest that in regions where moist, ammonia-rich air is raised upwards, the ammonia is destroyed and/or mixed with photochemical products faster than ammonia ice can form. Thus, the main cloud deck may actually be composed of ammonium hydrosulphide mixed with photochemical, smoggy products, which produce the red and brown colours seen in Jupiter images.
In small regions, where convection is especially strong, the updrafts may be fast enough to form fresh ammonia ice, and such regions have occasionally been seen by spacecraft such as NASA’s Galileo, and more recently by NASA’s Juno, where a few small high white clouds have been seen, casting their shadows down on the main cloud deck below.
Professor Irwin and his team also applied the method to VLT/MUSE observations of Saturn and have found similar agreement in the derived ammonia maps with other studies, including one determined from James Webb Space Telescope observations. Similarly, they have found the main level of reflection to be well below the expected ammonia condensation level, suggesting that similar photochemical processes are occurring in Saturn’s atmosphere.
Notes for editors:
For media enquiries and interview requests contact Professor Patrick Irwin, University of Oxford. Images available on request.
patrick.irwin@physics.ox.ac.uk
Tel: +44 (0)1865 272083
Mob: +44 (0) 7960752607
The new study “Clouds and ammonia in the atmospheres of Jupiter and Saturn determined from a band-depth analysis of VLT/MUSE observations”, Patrick G.J. Irwin et al., has been published in the Journal of Geophysical Research – Planets: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024JE008622
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Journal
Journal of Geophysical Research Planets
Article Title
Clouds and Ammonia in the Atmospheres of Jupiter and Saturn Determined From a Band-Depth Analysis of VLT/MUSE Observations
How astronomers used gravitational lensing
to discover 44 new stars in distant galaxy
JULIA JACOBO
Mon, January 6, 2025 at 11:43 AM MST
The most powerful telescope to be launched into space has made history by detecting a record number of new stars in a distant galaxy.
NASA's James Webb Space Telescope, history's largest and most complex space observatory that serves thousands of astronomers around the world, has captured a unique image that revealed 44 individual stars in a galaxy 6.5 billion light-years away from the Milky Way, according to a paper published Monday in Nature Astronomy.
MORE: This is how close NASA's Parker Solar Probe got to the sun
Astronomers used Webb's high-resolution optics and distortion in space to reveal the existence of dozens of previously unknown stars, the researchers said. The detection of a "treasure trove" of stars was only possible because the light from the 44 new stars was magnified by a large cluster of galaxies, called Abell 370, in front of it, according to the Center for Astrophysics.
The technique is known as gravitational lensing, which is when a massive amount of matter -- like a cluster of galaxies -- creates a gravitational field that distorts and magnifies the light from distant galaxies that are behind it but in the same line of sight, according to NASA. The effect is essentially like looking through a giant magnifying glass.
PHOTO: Abell 370 galaxy cluster. (NASA)
The strong gravitational magnification enabled astronomers to detect faint background sources and study their internal structures, which can lead to identifying individual stars in distant galaxies, according to the paper.
Gravitational lensing is also known as the "Einstein Ring" because renowned physicist Albert Einstein predicted the possibility in his theory of general relativity.
A visible arc created by gravitational lensing and the bending of light beyond Abell 370 was dubbed the "Dragon Arc." After carefully analyzing the colors of each of the stars inside the Dragon Arc, the researchers found many are red supergiants, which are stars in their final stages of life.
The discovery contrasts with earlier findings, which predominantly identified blue supergiants, which are among the brightest stars in the night sky, according to the Center for Astrophysics.
In the Milky Way and nearby galaxies, such as the Andromeda Galaxy, astronomers can observe stars one by one. But for galaxies billions of light-years away, the stars appear blended together due to the distance.
Newly discovered 'kiss and capture' mechanism explains the formation of Pluto and its largest moon
image:
Snapshot of Pluto and Charon during kiss-and-capture.
view moreCredit: Robert Melikyan and Adeene Denton.
Billions of years ago, in the frigid outer reaches of our solar system, two icy worlds collided. Rather than destroying each other in a cosmic catastrophe, they spun together like a celestial snowman, finally separating while remaining forever linked in orbit. This is how Pluto and its largest moon, Charon, originated, according to a new University of Arizona study that challenges decades of scientific assumptions.
A study led by Adeene Denton, a NASA postdoctoral fellow who conducted the research at the U of A Lunar and Planetary Laboratory, has revealed this unexpected "kiss and capture" mechanism, which could help scientists better understand how planetary bodies form and evolve. By considering something planetary scientists had overlooked over decades – the structural strength of cold, icy worlds – researchers have discovered an entirely new type of cosmic collision.
The findings were published in the journal Nature Geoscience.
For decades, scientists have theorized that Pluto's unusually large moon Charon formed through a process similar to Earth's moon – a massive collision followed by the stretching and deformation of fluid-like bodies, Denton said. This model worked well for the Earth-moon system, where the intense heat and larger masses involved meant the colliding bodies behaved more like fluids. However, when applied to the smaller, colder Pluto-Charon system, this approach overlooked a crucial factor: the structural integrity of rock and ice.
"Pluto and Charon are different – they're smaller, colder and made primarily of rock and ice. When we accounted for the actual strength of these materials, we discovered something completely unexpected," Denton said.
Using advanced impact simulations on the U of A's high-performance computing cluster, the research team found that instead of stretching like silly putty during the collision, Pluto and the proto-Charon actually became temporarily stuck together, rotating as a single snowman-shaped object before separating into the binary system we observe today. A binary system occurs when two celestial bodies orbit around a common center of mass, much like two figure skaters spinning while holding hands.
"Most planetary collision scenarios are classified as 'hit and run' or 'graze and merge.' What we've discovered is something entirely different – a 'kiss and capture' scenario where the bodies collide, stick together briefly and then separate while remaining gravitationally bound," said Denton.
"The compelling thing about this study, is that the model parameters that work to capture Charon, end up putting it in the right orbit. You get two things right for the price of one," said senior study author Erik Asphaug, a professor in the Lunar and Planetary Laboratory.
The study also suggests that both Pluto and Charon remained largely intact during their collision, with much of their original composition preserved. This challenges previous models that suggested extensive deformation and mixing during the impact, Denton said. Additionally, the collision process, including tidal friction as the bodies separated, deposited considerable internal heat into both bodies, which may provide a mechanism for Pluto to develop a subsurface ocean without requiring formation in the more radioactive very early solar system – a timing constraint that has troubled planetary scientists.
The research team is already planning follow-up studies to explore several key areas. The team wants to investigate how tidal forces influenced Pluto and Charon's early evolution when they were much closer together, analyze how this formation scenario aligns with Pluto's current geological features, and examine whether similar processes could explain the formation of other binary systems.
"We're particularly interested in understanding how this initial configuration affects Pluto's geological evolution," Denton said. "The heat from the impact and subsequent tidal forces could have played a crucial role in shaping the features we see on Pluto's surface today."
Journal
Nature Geoscience
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
Capture of an ancient Charon around Pluto
Article Publication Date
6-Jan-2025
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