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| Piú viste - Saturn: the "Ringed Beauty" and His Moons |
Atlas,_Daphins_and_Pan-PIA21449.jpgAtlas, Daphnis and Pan156 visiteCaption NASA:"This montage of views from NASA's Cassini Spacecraft shows three of Saturn's Small Ring moons: Atlas, Daphnis and Pan at the same scale for ease of comparison.
Two differences between Atlas and Pan are obvious in this montage. Pan's Equatorial Band is much thinner and more sharply defined, and the central mass of Atlas (the part underneath the smooth Equatorial Band) appears to be smaller than that of Pan.
All of these images were taken using the Cassini Spacecraft Narrow-Angle Camera. The images of Atlas were acquired on April 12, 2017, at a distance of about 10.000 miles (approx. 16,0093 Km) and at a Sun-moons-Spacecraft angle (or Phase Angle) of 37°. All three images are oriented so that North is up".MareKromium
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Rhea-PIA12746.jpgRhea's Terminator (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)154 visiteCaption NASA:"The Cassini Spacecraft captured this High-Resolution view of the Cratered Surface of Saturn's moon Rhea as the Spacecraft flew by this Celestial Body on October 17, 2010.
This view is centered on highly Cratered Terrain located at approx. 60° North Lat. and 251° West Long.
The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera. The view was acquired at a distance of approx. 40.000 Km(such as about 25.000 miles) from Rhea and at a Sun-Rhea-Spacecraft, or Phase, Angle of 88°.
Image scale is roughly 238 meters (781 feet) per pixel".MareKromium
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Enceladus-PIA14858-PCF-LXTT.jpgFountains of Light (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team) 153 visiteCaption NASA:"NASA's Cassini Spacecraft successfully completed its Oct. 1st Fly-By of Saturn's moon Enceladus and its Jets of Water Vapor and Ice. At its closest approach, the Spacecraft flew approx. 62 miles (about 100 Km) above the moon's Surface. The close approach was designed to give some of Cassini's instruments, including the Ion and Neutral Mass Spectrometer, the chance to "taste" the Jets themselves.
At a higher vantage point during the encounter, Cassini's high-resolution camera captured pictures of the jets emanating from the moon's South Polar Region. The latest raw images of Enceladus are online at:
http://saturn.jpl.nasa.gov/photos/raw/.
The images of the Surface include previously seen Leading-Hemisphere Terrain. However, during this encounter, multi-spectral imaging of these Terrains extended farther into the UV Region of the Spectrum than had previously been achieved at this resolution.
By looking at the Surface at UV wavelengths, scientists can better detect the difference between surface materials and shadows than they can at visible wavelengths, where icy materials are highly reflective and shadows are washed out. With both UV and Visible Light images of the same Terrain available to them, scientists will better understand how the Surface coverage of icy particles coming from the Vents and Plumes changes with Terrain type and age. Cassini's next pass of this fascinating moon will be Oct. 19, 2011, when the Spacecraft shall fly-by at an altitude of approximately 765 miles (such as about 1231 Km)".MareKromium
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Saturnian_Lightnings-03.jpgSaturnian Lightnings151 visiteNASA's Cassini Spacecraft captured images of lightning at Saturn that allowed scientists to create the first movie showing lightning flashing on another Planet.
"The Visible Light images tell us a lot about the lightning," said Ulyana Dyudina, a Cassini imaging team associate based at the California Institute of Technology (Caltech) in Pasadena, Calif., who was the first to see the flashes. "Now we can begin to measure how powerful these storms are, where they form in the cloud layer and how the optical intensity relates to the total energy of the thunderstorms."
After waiting years for Saturn to dim enough for the Spacecraft's cameras to be able to detect bursts of light, scientists were able to create the movie, complete with an accompanying soundtrack that features the crackle of radio waves emitted when lightning bolts struck.
"This is the first time we have the visible lightning flash together with the radio data," said Georg Fischer, a radio and plasma wave science team associate based at the Space Research Institute in Graz, Austria. "Now that the radio and visible light data line up, we know for sure we are seeing powerful lightning storms."
Cassini, launched in 1997, and NASA's Voyager mission, launched in 1977, had previously captured radio emissions from storms on Saturn.
A belt around the gas giant, where Cassini previously detected radio emissions and bright, conservative clouds, even earned the nickname "storm alley." Cassini's cameras, however, had been unable to obtain pictures of lightning flashing.
Since the Robotic Spacecraft's arrival at Saturn in 2004, it has been difficult for Cassini to see lightning because the planet is very bright and reflective. Sunlight that shines off of Saturn's enormous Rings makes even the night side of Saturn brighter than a full-moon night on Earth.
The Equinox period around August 2009 finally brought enough darkness needed for Cassini's cameras. During Equinox, the Sun shone directly over the Planet's Equator, lighting the Rings edge-on only, leaving the bulk of the Rings in shadow.
The movie and radio data collected by the scientists suggest extremely powerful storms, with lightning that flashes as brightly as the brightest super-bolts of lightning on Earth, according to Andrew Ingersoll, a Cassini imaging science subsystem team member at Caltech.
"What's interesting is that the storms are as powerful or even more powerful at Saturn as on Earth," Ingersoll said. "But they occur much less frequently, with usually only one happening on the planet at any given time, though it can last for months."
The first images of lightning on Saturn were captured in August 2009, during a storm that lasted from January to October 2009, longer than any other observed lightning storm in the Solar System.
In order to make a video, scientists needed more pictures with brighter lightning and strong radio signals. Data collected during a shorter subsequent storm, which occurred from November through mid-December 2009, was also used.
The frames in the video were obtained over a period of 16 minutes on Nov. 30, 2009. The flashes lasted less than one second. The images also show a cloud as long as 1900 miles (3057,746 Km) across, with the regions illuminated by the lightning flashes reaching approx. 190 miles (305,7746 Km) in diameter. Scientists used the width of the lightning flashes to gauge the depth of the bolts below the cloud tops.
Lightning that strikes on Earth and Saturn emit radio waves at a frequency that can cause static on an AM radio. The audio in the video approximate that static sound, based on Saturn's electrostatic discharge signals that were detected by Cassini's radio and plasma wave science instrument.
Scientists monitoring the Cassini Orbiter were busy during this Equinox period, having already observed clumps in Saturn's Rings that are as high as the Rocky Mountains.
The Cassini-Huygens mission is a joint project involving NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of Caltech, manages the Cassini-Huygens mission for NASA's Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at the Jet Propulsion Laboratory.MareKromium
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A - Saturn_s sky before the Streak (1).jpgSaturn's Sky just before the "Streak" (1) - N00008768149 visiteOggi, 5 Agosto 2004, inseriamo nella Sezione del Sito Lunar Explorer Italia dedicata a Saturno ed alle sue Lune, una serie di 5 fotogrammi ripresi dalla Sonda Cassini/Huygens che, a nostro parere, rappresenta una prova tangibile della presenza di un Oggetto Volante Non Identificato in transito nello spazio di Saturno.
Si tratta dei frames n. N00008768; N00008769; N00008770; N00008771 ed N00008772.
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Dione-PIA11471.jpgCosmic "Smile"...147 visiteCaption NASA:"Only a sliver of Dione is visible as the Cassini Spacecraft looks at the dark side of the moon. In a high-phase viewing geometry like the one in which this picture was taken, the Sun and the Spacecraft are on nearly opposite sides of the moon. Here, only a narrow crescent reflects light forward toward Cassini's camera. The outline of a crater is just visible in the Southern Hemisphere.
This view looks toward the Leading Hemisphere of Dione. North on Dione is up and rotated 2° to the right. The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera on Feb. 25, 2009.
The view was acquired at a distance of approx. 484.000 Km (such as about 301.000 miles) from Dione and at a Sun-Dione-Spacecraft, or Phase, Angle of 166°.
Image scale is roughly 3 Km (a little less than 2 miles) per pixel".MareKromium
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Enceladus-PIA12762-PCF-LXTT.jpgFountains of Light (Enhanced Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)147 visiteCaption NASA:"A crescent Enceladus, imaged from its night side, shows off spectacular Water Ice Plumes emanating from its South Polar Regions. This image was captured at a Phase, or Sun-Enceladus-Spacecraft, angle of 157° so that Sunlight would reveal the backlit Plumes. Terrain near the South Pole is now dark as Spring has come to the Northern Hemisphere of the Celestial Body. Lit Terrain seen here is on the Trailing Hemisphere of Enceladus. North is up.
The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera on Jan. 30, 2011. The view was obtained at a distance of approx. 228.000 Km(such as 141.588 miles) from Enceladus. Image scale is roghly 1 Km (0,621 miles) per pixel".MareKromium
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Janus-MF-EB-LXTT.jpgJanus (RAW Natural Colors; credits for the additional process. and color.: Elisabetta Bonora and Marco Faccin - Lunexit Team)146 visiteJanus - apparently, and according to our Readers, one of the most interesting Celestial Bodies that we have shown and talked about on our APOD in the past - is one of the so-called "Inner Natural Satellites" of the Giant Gas-Planet Saturn; it is also called and known, sometimes, as Saturn X, and it occupies (better yet: shares) the same orbit as the Saturnian Inner Minor moon Epimetheus. This (now we know NOT infrequent) circumstance, however caused, in the past, some confusion to many astronomers which, at the time of Janus' discovery - and according to their different observations - assumed that there should have been only one Celestial Body in the orbit where Janus was spotted.
For a long time, in fact, the Astronomical Community struggled to figure out what was going on, until they realized that what they were trying to solve, was (let us use this expression) an "impossible equation": in other words, they were trying to reconcile (so-called "reductio ad unum") different observations of different and distinct Objects, on the wrong assumption that what they all were looking at, was just a single Celestial Body.
The discovery of Janus is attributed to its first observer, such as the French Astronomer Audouin Dollfus, who spotted Janus on December 15, 1966. The newly discovered Object was given the temporary designation of "S/1966 S 2". Previously, though, another Astronomer (Jean Texereau) had also photographed the very same Celestial Body (to be exact, on October 29, 1966), but without realizing the discovery! On December 18 of the same year, then, Richard Walker made a similar observation which is now credited as the discovery of Epimetheus.
Twelve years later, in October 1978, Stephen M. Larson and John W. Fountain finally realized that the 1966 observations would have been better explained by assuming that they were relative NOT to one, BUT to two distinct Objects (as we said, Janus and Epimetheus), sharing very similar (or perhaps the same, as we know now) orbits. Finally, in the AD 1980, the NASA - Voyager 1 Spacecraft confirmed that this "controversial moon" was, in fact, a couple of co-orbital Celestial Bodies.
Afterwards, Janus was observed on other occasions and given different provisional designations. It was observed, for instance, by the NASA - Pioneer 11 Probe when it passed near Saturn on September 1st, 1979. Janus was also observed by Dan Pascu on February 19, 1980 (and then provisionally designed as "S/1980 S 1") and then by John W. Fountain (once again), Stephen M. Larson (again), Harold J. Reitsema and Bradford A. Smith on the 23rd (and, this time, the observed object was, always provisionally, recorded as "S/1980 S 2").
All these Scientists, in a way and in the end, should therefore share, to various degrees, the title of Discoverer of Janus, but this "fair dispute", so far (and as far as we know), has not been solved.
As far as the physical characteristics of Janus are concerned, we can say that this relatively small moon (whose dimensions are approx. 203 × 185 × 153 Km) is extensively cratered, and a few of these craters are more than 30 Km across. The Janian Surface, as we already wrote in the past, appears to be older than Prometheus' one, but younger than Pandora's. Furthermore, if you consideri its oval (or, if you prefer, its "non-spherical") shape, its (very) low Density and relatively high Albedo, it seems logic to conclude, for the time being, that Janus should just be a porous and icy "rubble pile" (such as the final result of a cloud of Cosmic Debris that have coalesced under the influence of gravity).
The so-called Rubble Piles-type Celestial Bodies have a low density because there are, we believe, large cavities between the various "chunks" - such as fragments - of rocky material that made them up; Rubble Piles may also form when an Asteroid or a moon (which may originally be monolithic - such as "one single piece of rock") is smashed by an impact, and the shattered pieces left over by the impact, in time, fall back together, primarily due to self-gravitation (---> mutual attraction). In other words: a Celestial Body like Janus is formed, in our opinion, by a mass of different materials that cohered over time (we repeat: something like a "cloud" of Cosmic Debris - rocks, boulders, dust etc. - which, in time, due to a mutual gravitational attraction, got together until they became one - yet extremely fragile - Celestial Body).
In the light of the above considerations and assumptions, we, as IPF, believe that Janus can reasonably be assimilated, for instance (and among others), to Asteroid 25143 Itokawa or 433 Eros.MareKromium
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Saturn-PIA21895.jpgFarewell Cassini...145 visiteCaption NASA:"This Natural Color view view is the last image taken by the imaging cameras on NASA's Cassini Spacecraft. It looks toward the planet's night side, lit by reflected light from the Rings, and shows the location at which the Spacecraft would enter the Planet's Atmosphere a few hours later.
ThE view was created by using images taken with red, green and blue spectral filters. The imaging cameras obtained the view at approximately the same time that Cassini's Vsual and InfraRed Mapping Spectrometer made its own observations of the impact area in the thermal infrared.
This location - the site of Cassini's atmospheric entry - was at this time on the night side of the Planet, but would rotate into daylight by the time Cassini made its final dive into Saturn's Upper Atmosphere, ending its remarkable 13-year exploration of Saturn.
The view was acquired on Sept. 14, 2017 at 19:59 UTC (spacecraft event time). The view was taken in Visible Light using the Cassini Spacecraft Wide-Angle Camera at a distance of about 394.000 miles (such as roughly 634.081 Km) from Saturn. Image scale is about 11 miles (about 17,7 Km). The original image has a size of 512 x 512 pixels".MareKromium
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Dione-N00165580-82-EB-LXTT.jpgPossible Transient Luminous Phenomenon on the "Dark Side" of Dione144 visiteLa Natura del piccolo "flash" individuato nelle Regioni Equatoriali di Dione, è bene dirlo a chiare lettere, non può essere in alcun modo stabilita con certezza.
Dall'analisi di dettaglio del frame, comunque, possiamo estrapolare alcune ipotesi, che Vi elenchiamo in ordine di fondatezza/verosimiglianza (a nostro parere, come ovvio):
1) Bagliore da Impatto Meteorico - Meteor Strike's related/caused Flash;
2) Fiaccola di origine ignota (magari un outgassing?) - Flare of unknown origin (l'equivalente Dioniano di un TLP);
3) Artefatto Fotografico da perdita di segnale - image artifact due to lack of signal;
4) Artefatto Fotografico a causa indeterminata - image artifact due to an undetermined cause .MareKromium
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Rhea-PIA10246.jpgThe "IMPOSSIBLE" Rings of Rhea143 visiteLa notizia è di quelle che suscitano clamore e che hanno il "profumo" della Scoperta Epocale: dunque una luna di Saturno - Rhea - avrebbe un debole sistema di anelli che ruota attorno ad essa!
Meraviglia, ovviamente, alla prima lettura. ma poi...Poi subentra la riflessione. Una riflessione che ho condiviso con gli Amici del Forum di UFO-ONLINE e che vorrei riproporre a tutti gli Amici di Lunar Explorer Italia.
Ecco quello che ho scritto per UFO-ONLINE:"...Oggi mi permetto questa intrusione per segnalare un particolare che, a quanto pare, è "sfuggito" alla NASA ed a tutti gli Astronomi che si occupano di Scienze Planetarie.
Rhea, si diceva, così come lo suggeriscono degli elementi "indiretti" raccolti dalla Sonda Cassini durante i suoi fly-byes nelle prossimità di questa luna, potrebbe avere dei deboli anelli.
Parlo di elementi indiretti poichè l'unico elemento diretto di cui potremmo davvero disporre (ossìa l'osservazione "remota" di particelle o corpuscoli aggregati a formare anche delle mere "sezioni di anello" - come accade per Urano e Nettuno - intorno a Rhea), in vero, ci manca.
Ma pure ammettendo che le riflessioni NASA sulle evidenze indirette (quote:"...Due to a decrease in the number of electrons detected by NASA's Cassini spacecraft on either side of the moon, scientists suggest that rings are the likeliest cause of these electrons being blocked before they reach Cassini...") della presenza di "anelli" (o forse sarebbe meglio parlare di "detriti orbitali") intorno a Rhea fossero corrette, ebbene sapete qual'è la cosa veramente curiosa?
E' che questi "anelli" (o "detriti", se sposate la terminologia che suggerisco) NON POTREBBERO/ NON POSSONO ESISTERE.
Ed il perchè è questo (cerco di spiegarmi in maniera lineare, e scusate se oversemplifico): pensate alla Luna. Alla nostra Luna.
Perchè essa non può avere anelli?
Perchè, ci insegnano le Scienze Planetarie, essa in primo luogo possiede solo una "micro-attrazione gravitazionale" (o micro-gravità) la quale NON BASTA a tenere in equilibrio perpetuo corpi orbitali anche di dimensioni ridottissime.
E questo è il motivo per cui le Sonde terrestri che studiano la Luna - tipo SMART-1 o KAGUYA o CLEM in passato - necessitano di mini-propulsori: perchè, una volte entrate in orbita, esse restano in equilibrio stabile per pochissimo tempo e poi, senza "correzioni di rotta", finirebbero inevitabilmente con il precipitare sulla Luna.
D'altro canto, se la spinta fornita dai propulsori fosse anche solo in minima parte "eccessiva", ecco che la Sonda sfuggirebbe all'attrazione lunare, perdendosi nello Spazio. Chiaro, quindi: queste sono due evidenti implicazioni/conseguenze della micro-gravità.
Secondo punto: si dice (anzi: si studia) che la Luna non può avere anelli (o micro-corpi in orbita stabile attorno ad essa) a causa degli influssi mareali della Terra, la quale, ora avvicinandosi ed ora allontanandosi, "turba" i già precari equilibri gravitazionali che caratterizzano lo spazio circum-lunare.
Giustissimo: le "Onde di Marea" (Gravitazionale) fanno proprio questo: interagiscono con altre onde ed equilibri e si disturbano vicendevolmente.
Il Corpo Maggiore (che emana le Onde Maggiori), come ovvio, disturba di più il Corpo Minore (che emana le Onde Minori).
Morale numero 1: la Luna non ha, non ha avuto nè avrà mai "anelli" o cose simili. Non stabilmente, comunque.
Ora trasportate questo ragionamento ed i due principii che ho cercato di esprimere nel contesto Rhea/Saturno, laddove le proporzioni CAMBIANO in maniera sfavorevolissima per Rhea, la quale non solo possiede una micro-gravità anch'essa, ma è pure soggetta a perturbazioni mareali - a causa di Saturno - enormemente più grandi di quelle che la nostra Terra cagiona alla nostra Luna.
Morale numero 2: ma se la nostra Luna, date le circostanze di cui sopra, non può avere anelli nè corpi orbitali stabili intorno ad essa (neppure artificiali e quindi piazzati in orbita da noi e con precisione millimetrica), come potrà mai averli Rhea la quale si trova in una situazione enormemente MENO FAVOREVOLE???
Conclusioni. Mi permetto due ipotesi e poi, se vorrete, se ne potrà discutere.
Ipotesi 1: l'evidenza indiretta della presenza di corpuscoli orbitali intorno a Rhea (anelli o sezioni di anelli o detriti) in equilibrio gravitazionale stabile è errata, poichè poggia su basi assurde (per la nostra Scienza);
Ipotesi 2: L'evidenza indiretta di cui sopra è ESATTA, ma i "corpuscoli" rilevati da Cassini sono l'evidenza di un fenomeno MERAMENTE TRANSITORIO, il quale svanirà nel giro di pochissimo tempo (settimane, al massimo). Quindi no anelli ma, al limite, una temporanea aggregazione di detriti erranti i quali, forse, sono il prodotto della disintegrazione di un mini-asteroide che non ha felicemente superato il Limite di Roche e si è quindi frantumato nei pressi di Rhea.
Spero che questa piccola annotazione Vi interessi e Vi faccia pensare a come, tantissime volte, i nostri Amici Scienziati (quelli famosi e "certificati", come gli Scienziati NASA), dicono delle cose che, onestamente, sono molto discutibili.
Le differenze fra noi, Liberi Ricercatori, e loro? Beh, mezzi e competenze a parte, ne evidenzio una: se una teoria come quella degli Anelli di Rhea l'avessi tirata fuori io, o il mio Caro Amico e Collega Dr Barca, o qualsiasi altro Ricercatore "free", ci saremmo beccati al volo - molto probabilmente - degli incompetenti.
Ma se una storia come questa la esprime chi lavora alla NASA, allora, per quanto IMPROBABILE (a dire poco), diventa un qualcosa di (forse) epocale.
O mi sbaglio?..."
Pensateci anche Voi e poi, se vorrete, scriveteci/mi!
Dr Paolo C. FiengaMareKromium
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Phoebe-PIA07795.jpgPhoebe: Cartographic Projections (Mercator Projection)140 visiteCaption NASA:"This Map is part of a group release of Mercator and Polar Stereographic Projections of Saturn's moon Phoebe.
A "Mercator Projection" is a map that preserves directions on a body, but distorts sizes, especially near the Poles. This Global Digital Map of Phoebe was created using data taken during Cassini's close Fly-By of the small moon that occurred in June 2004.
The mosaic is projected into the Mercator Projection within the Latitude range from 57° South to 57° North; the Stereographic Projections represent Latitudes greater and lower than + or - 55°. Thus, this map meets the standard scale of 1:1.000.000, as recommended by the U.S.G.S.
The projections are conformal, the quadrangles overlap and the scale of the Poles was chosen such that the circumference of the Stereographic Projection is identical to the width of the Mercator Projection.
The nomenclature was proposed by the Cassini imaging team and has yet to be validated by the International Astronomical Union. Resolution of the digital mosaic is 233 meters (764 feet) per pixel, although the highest resolution images have resolutions of 70 meters (230 feet) per pixel. The Mean Radius of Phoebe is approx. 107 Km (such as 66,447 miles)".MareKromium
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