Tag Archives: Cassini

Cassini Discovers Organic Molecules in Newly Released Ice Grains from Enceladus’ Ocean

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Enceladus, Saturn’s moon, constantly emits ice grains and gas plumes from its subterranean seas through fissures near the Antarctic region. A research team from the University of Stuttgart and the University of Berlin Fly utilized data from NASA’s Cassini spacecraft to chemically analyze newly emitted particles originating from Enceladus’ ocean. They successfully identified intermediates of organic molecules that may have biological significance (including aliphatic and (hetero)cyclic esters/alkenes, ethers/ethyl, and tentatively, nitrogen and oxygen-containing compounds), marking the first discovery of such compounds among ice particles in extraterrestrial oceans.

Artist’s impression of NASA’s Cassini spacecraft navigating through the plumes erupting from Enceladus’ Antarctic region. These plumes resemble geysers and release a mix of water vapor, ice grains, salt, methane, and various organic molecules. Image credit: NASA/JPL-Caltech.

Enceladus has a diameter of approximately 500 km, and its surface is covered by ice shells that are about 25-30 km thick on average.

Cassini made the first revelation of a hidden ocean beneath Enceladus’ surface back in 2005.

A current emerges from a fissure near the moon’s Antarctic, sending ice grains into space.

Some ice particles, smaller than grains of sand, settle on the moon’s surface, while others escape, forming a ring that orbits Enceladus around Saturn.

“Cassini consistently detected samples from Enceladus while passing through Saturn’s E ring,” noted Nozail Kawaja, a researcher at the Free University of Berlin and the lead author of the study.

“Many organic molecules have already been identified within these ice grains, including precursors to amino acids.”

The ice grains in the ring may be hundreds of years old and could have undergone changes due to strong cosmic radiation.

Scientists aimed to analyze the recently released grains to enhance their understanding of the dynamics within Enceladus’ seas.

Fortunately, they already had the relevant data. In 2008, Cassini flew directly through the ice sprays. The released primitive particles were emitted just minutes before they interacted with the spacecraft’s Cosmic Dust Analyzer (CDA) at speeds of approximately 18 km/sec. These represented not only the most recent ice grains Cassini has detected but also the fastest.

“Ice grains encompass not just frozen water, but also other molecules containing organic matter,” Dr. Kawaja stated.

“Lower impact speeds can break the ice, leading to signals from water molecule clusters that may obscure signals from certain organic molecules.”

“However, when ice grains strike the CDA at high speeds, the water molecules do not cluster, allowing previously hidden signals to emerge.”

Years of data from previous flybys were necessary to interpret this information.

This time, the authors successfully identified the molecules contained in the freshly released ice grains.

The analysis showed that certain organic molecules known to be present in the E rings were also found in the fresh ice grains, affirming their formation within Enceladus’ seas.

Furthermore, they discovered a completely new molecule that had never before been observed in Enceladus’ ice grains.

Chemical analyses revealed that the newly detected molecular fragments consisted of aliphatic, (hetero)cyclic esters/alkenes, ethers/ethyl, and potentially nitrogen and oxygen-containing compounds.

On Earth, these same compounds participate in a series of chemical reactions that ultimately yield more complex molecules essential for life.

“Numerous pathways from the organic molecules detected in Cassini’s data to potentially biologically relevant compounds exist, enhancing the possibility of habitability on the moon,” Dr. Kawaja mentioned.

“We have more data currently under review, so we anticipate further discoveries soon.”

“The molecules we identified in the newly released materials indicate that the complex organic molecules Cassini detected within Saturn’s E ring are not merely a result of prolonged exposure to space; they are readily found within Enceladus’ ocean,” added co-author Dr. Frank Postberg, also from the Free University of Berlin.

For more details, refer to the study featured in this month’s edition of Natural Astronomy.

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N. Kawaja et al. Detection of organic compounds in newly released ice grains from the Enceladus ocean. Nat Astron Published online on October 1, 2025. doi: 10.1038/s41550-025-02655-y

Source: www.sci.news

Cassini uncovers the properties of Titan’s hydrocarbon sea

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Saturn’s moon Titan was explored by NASA’s Cassini spacecraft between 2004 and 2017. Although Cassini revealed much about this Earth-like world, its radar observations provided limited information about Titan’s liquid hydrocarbon oceans: Kraken, Ligeia, and Punga Mare. New paper In the journal Nature CommunicationsCornell University researcher Valerio Poggiali and his colleagues reported the results of their analysis of data from the Cassini radar experiment on Titan’s polar oceans.

Artistic depiction of Kraken Mare, a giant ocean of liquid methane on Titan. Image courtesy of NASA John Glenn Research Center.

“The Cassini spacecraft explored Saturn’s largest moon, Titan, between 2004 and 2017, revealing an Earth-like world with a strange yet very familiar diversity of surface morphologies formed by a methane-based hydrological system operating in a dense nitrogen atmosphere,” said Dr Poggiali and his co-authors.

“Winds in the lower atmosphere move the sediments, forming the vast sand dunes that encircle Titan’s equator.”

“At mid-latitudes, flat, relatively featureless plains form the transition between the eolianite-dominated equator and the lacustrine-dominated poles.”

“In the polar regions, large oceans and small lakes of liquid hydrocarbons dominate the landscape.”

“The channels created by precipitation drain into the ocean, forming estuaries and sometimes deltas and other familiar coastal deposits.”

“Cassini has revealed much about Titan, but this discovery raises even more questions.”

For the study, scientists used data from four bistatic radar observations collected by Cassini during four flybys in 2014 (May 17, June 18, and October 24) and 2016 (November 14).

For each, surface reflections were observed when the probe was closest to Titan (approach) and when it was moving away (exit).

The authors analyzed data from outflow observations of Titan’s three large polar oceans: Kraken Mare, Ligeia Mare, and Punga Mare.

“In a bistatic radar experiment, a spacecraft directs a radio beam towards a target, in this case Titan, where the beam is reflected towards a receiving antenna on Earth,” the researchers explained.

“This surface reflection is polarized, which means it provides information gathered from two independent perspectives, as opposed to the perspective provided by monostatic radar data, where the reflected signal is sent back to the spacecraft.”

“The main difference is that the bistatic information is a more complete data set and is sensitive to both the composition of the reflective surface and its roughness.”

The team found that the composition of the ocean’s surface layers of hydrocarbons varies depending on latitude and location (for example, near rivers or estuaries).

Specifically, the southernmost parts of Kraken Mare exhibit the highest dielectric constant, a measure of a material’s ability to reflect radio signals.

For example, water on Earth is highly reflective and has a dielectric constant of about 80, while Titan’s ethane and methane oceans have a dielectric constant of about 1.7.

The researchers also determined that ocean conditions in all three areas were fairly calm during the flyby, with surface waves measuring less than 3.3 mm.

Slightly higher levels of roughness, up to 5.2 mm, were found in coastal areas, near estuaries and straits, which could be an indication of tidal currents.

“There are also indications that the rivers that feed the oceans are pure methane until they flow into the open ocean liquid, which is rich in ethane,” Dr Poggiali said.

“It’s the same as when freshwater rivers flow into the saltwater of the ocean on Earth and mix together.”

“This fits well with weather models of Titan, which predict that the ‘rain’ falling from Titan’s skies is almost pure methane, with traces of ethane and other hydrocarbons,” said Professor Philip Nicholson of Cornell University.

“Further studies of the data Cassini has collected during its 13-year exploration of Titan are already underway.”

“There’s still a mountain of data waiting to be fully analyzed in a way that will lead to further discoveries. This is just the first step.”

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V. Poggiali others2024. Surface characteristics of Titan’s ocean as revealed by the Cassini bistatic radar experiment. Nat Community 15, 5454; doi: 10.1038/s41467-024-49837-2

This article is a version of a press release provided by Cornell University.

Source: www.sci.news

New study suggests Jupiter’s Great Red Spot may not be the permanent feature reported by Cassini

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Jupiter’s Great Red Spot is perhaps the best-known atmospheric feature and a popular icon among the solar system’s objects. Its large oval shape, contrasting red color, and long lifespan make it easily visible with a small telescope. A new study led by scientists from the University of the Basque Country, based on historical measurements of its size and motion, shows that the present-day Great Red Spot was probably first reported in 1831 and is not a permanent spot observed by Giovanni Domenico Cassini and others between 1665 and 1713.

The Permanent Spot (PS) and the early Great Red Spot (GRS): (a) drawing of the PS by GD Cassini on 19 January 1672, (b) drawing by S. Swave on 10 May 1851, showing the GRS area as a clear ellipse bounded by a depression (depicted by a dashed red line). (c) photograph taken by AA Common on 3 September 1879 using a 91 cm reflecting telescope at Ealing (London). The GRS appears as a clear "dark" ellipse because it is red and the photographic plate is sensitive to violet-blue wavelengths. (d) photograph taken at Lick Observatory on 14 October 1890 using a yellow filter. All figures show astronomical images of Jupiter (south at top, east at left) to preserve the notes on the drawings. Image courtesy of Sánchez-Lavega others., doi: 10.1029/2024GL108993.

Jupiter’s Great Red Spot is the largest and longest-lasting known vortex of any planet in the solar system.

The formation mechanism that produced this feature is unknown, and its longevity is controversial.

It was also unclear whether the Great Red Spot was the dark oval nicknamed the “Eternal Spot” that astronomer Giovanni Domenico Cassini and others reported between 1665 and 1713.

“Speculation about the origin of the Great Red Spot dates back to the first telescopic observations by Giovanni Domenico Cassini, who in 1665 discovered a dark oval at the same latitude as the Great Red Spot, which he named a permanent spot, because it was observed by Cassini and other astronomers until 1713,” said Professor Agustin Sánchez Lavega from the University of the Basque Country.

“For the next 118 years, traces of it were lost, and it was only after 1831 that S. Schwabe again observed a clear, almost elliptical structure at the same latitude as the GRS. This can be considered the first observation of the present-day GRS, possibly of the infant GRS.”

“Since then, the Great Red Spot has been regularly observed by telescopes and by various space probes that have visited the planet up to the present day.”

In their study, the authors analysed the change in the size of the Great Red Spot over time, its structure, and the behaviour of two meteorological structures, the former permanent spot and the Great Red Spot.

To do so, they used historical sources dating back to the mid-17th century, shortly after the telescope was invented.

“Based on our measurements of its size and motion, we infer that it is highly unlikely that the current Great Red Spot is the permanent spot observed by Cassini,” Professor Sanchez LaVega said.

“The permanent spot probably disappeared sometime between the mid-18th and 19th centuries, which would put the lifespan of the red spot at least 190 years.”

“The Red Spot, which in 1879 measured 39,000 kilometres along its longest axis, has now shrunk to about 14,000 kilometres and is becoming rounder at the same time.”

“Furthermore, since the 1970s, several space missions have studied this weather phenomenon in detail.”

“Recently, various instruments on the Juno spacecraft in orbit around Jupiter have shown that the Great Red Spot is shallow and thin compared to its horizontal length. Its vertical length is about 500 km.”

To understand how this giant whirlpool formed, the astronomers ran numerical simulations using two complementary models of the behavior of thin vortices in Jupiter’s atmosphere.

Powerful winds prevail on this giant planet, flowing along parallels that alternate in direction and latitude.

To the north of the Great Red Spot, winds blow westward at 180 km/h, while to the south, winds blow in the opposite direction, eastward at 150 km/h.

This creates huge north-south shear in the wind speed, which is the fundamental element that allows vortices to grow internally.

The study explored a variety of mechanisms to explain the formation of the Great Red Spot, including the eruption of a giant superstorm like those rarely observed around its twin planet Saturn, or the merging of several smaller vortices caused by sheared winds.

The results show that although anticyclones form in both cases, their shapes and dynamic characteristics are different from those of the present-day Great Red Spot.

“We believe that if one of these anomalies had occurred, it, or its effects in the atmosphere, would have been observed and reported by astronomers at the time,” Prof Sanchez Lavega said.

In a third set of numerical experiments, the researchers investigated how the GRS may arise from known instabilities in the winds that they believe could produce elongated cells that surround and trap the GRS.

Such cells were early red spots, the proto-Great Red Spot, whose subsequent shrinkage would give rise to the compact, rapidly rotating Great Red Spot observed in the late 19th century.

The formation of large elongated cells has already been observed during the emergence of other major vortices on Jupiter.

“In our simulations, thanks to supercomputers, we were able to find that elongated cells are stable when they rotate around the Great Red Spot at the speed of Jupiter’s winds, which is what you would expect to form due to this instability,” said Dr Enrique García Melendo, an astronomer at the Polytechnic University of Catalonia.

Using two different numerical models, the scientists concluded that if the GRS rotated slower than the surrounding winds, it would break up and the formation of a stable vortex would be impossible.

And if it were very high, the properties of the primordial Great Red Spot would be different from those of the current Great Red Spot.

“Future studies will aim to reconstruct the Great Red Spot’s shrinkage over time and elucidate in more detail the physical mechanisms underlying its persistence,” the authors wrote.

“At the same time, we try to predict whether the Great Red Spot will collapse and disappear when it reaches its size limit, as happened with Cassini’s permanent spot, or whether it will remain stable at its size limit and persist for many years.”

of result Published in a journal Geophysical Research Letters.

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Agustin Sanchez Lavega others2024. Origin of Jupiter’s Great Red Spot. Geophysical Research Letters 51(12):e2024GL108993; doi:10.1029/2024GL108993

Source: www.sci.news

Titan’s underground ocean revealed by Cassini observations

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Titan, Saturn’s largest moon, harbors an ocean of low-density water or ammonia inside, according to an analysis of archival data from NASA’s Cassini mission.

A representation of Cassini’s orbit used to calculate Titan’s gravity. The colored part of the orbit shows the distance from Cassini to Titan, with the minimum distance shown in red. A cross-section of Titan shows the moon’s different layers and blue oceans. In the background you can see Saturn with its rings and ring shadows. Image credit: Britt Griswold, NASA Goddard Space Flight Center.

“Liquid water is one of the prerequisites for life,” said Dr. Sander Goossens of NASA’s Goddard Space Flight Center and colleagues.

“Water is rarely liquid on the surfaces of planets, but many moons of the solar system, such as Titan, have underground oceans.”

“These probably formed a long time ago, which begs the question why they haven’t already frozen in a cold environment far from the sun.”

“Our study supports the explanation that ammonia extended the life of Titan’s liquid oceans. Additionally, it also provides insight into Titan’s deeper layers.”

NASA’s Cassini mission explored Saturn and its icy moons for more than a decade.

Among its many instruments, Cassini carried a radio science subsystem that enabled radiation tracking of Earth-based spacecraft by the Deep Space Network.

These data were used to determine the gravitational field and internal structure of some of Saturn’s moons and Saturn itself. Cassini data was also used to determine Titan’s tidal response.

“The Cassini space probe flew around Saturn from 2005 to 2017,” the researchers said.

“Probes have been sent close to the moon many times to accurately measure Titan’s gravity.”

“Cassini needed to skim past Titan at exactly the right time to properly map the changes in gravity.”

“This is because Titan’s deformation is due to Saturn’s tidal forces, and the tidal forces depend on the distance between Titan and Saturn.”

“Measurements taken when Titan was close to Saturn and when it was far away maximized the difference in Titan’s deformation, and therefore its impact on gravity.”

Scientists calculated Cassini’s speed from precise radar measurements and calculated changes in gravity and the resulting deformation of Titan.

They carefully examined the tidal effects on Titan at each location on the spacecraft’s orbit and concluded that the deformation was smaller than previously calculated.

According to numerical simulations of the moon’s deformation for different internal structures, the most likely scenario is that the ocean has a density similar to water and contains small amounts of ammonia.

“The subsurface ocean may help transport organic matter from the moon’s rocky core to the surface,” the authors said.

“It was thought that Titan’s thick layer of ice between its ocean and its core made this difficult.”

“Our analysis suggests that the ice layer may be thinner than previously thought, and that material exchange between the rock and the ocean is more likely.”

“The organic molecules this produces are considered important ingredients for the emergence of life.”

of study It was published in the magazine natural astronomy.

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S. Goossens other. A low-density ocean inside Titan estimated from Cassini data. Nat Astron, published online March 21, 2024. doi: 10.1038/s41550-024-02253-4

Source: www.sci.news