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Tehnica LANTERNEI CHINEZESTI ajuta la urmarirea norilor de pe Saturn
(http://img152.imageshack.us/img152/163/saturnih5.jpg)
   In imagine: Planeta Saturn - Se poate observa la poli aurora. (Foto: Hubble/NASA)

O noua imagine a planetei Saturn demonstreaza o tehnica ce creaza efectul "lanternei chinezesti", aratand silueta norilor lui Saturn in contrast cu interiorul cald. Vazut astfel, interiorul lui Saturn arata o activitate surprinzatoare cuprinzand o larga varietate de nori de diferite marimi si forme.

Deoarece norii din nivelele superioare acopera acesti nori in lumina vizibila, redarea de imagini cu norii de pe Saturn nu este posibil cu ajutorul camerelor care au nevoie de lumina pentru a captura imagini. Cateva imagini capturate de Cassini cu ajutorul spectrometrului visual si infrarosu au fost combinate astfel incat sa evidentieze norii mai aproape de suprafata planetei pe fondul radiatei generate de interiorul lui Saturn. Literalmente, acest procedeu "aprinde" planeta din interior spre exterior ca o lanterna.
Norii din emisfera nordica a lui Saturn sunt ceva mai subtiri decat cei din emisfera sudica. Se crede ca acesta este un efect de anotimp; idea va fi testata cand va veni primavera peste cativa ani in emisfera nordica.

Partile colorate in rosu aprins indica zone care nu prezinta nori josi sau particule, in timp ce zonele de un rosu mai inchis sunt mai innorate.

Sursa: NASA/Jet Propulsion Laboratory 

P.S. ce crezi Ciuciulete... am vreo sansa cu telescopul meu sa vad asa ceva???  :roll:

CitatP.S. ce crezi Ciuciulete... am vreo sansa cu telescopul meu sa vad asa ceva??

numai daca telescopul tau este Hubble... :evil:
Eu am vazut si fotografiat ceva similar ca in atasament (nu dispun de pozele originale acum), cu o improvizatie de binoclu, lentile foto, tuburi si camera web cu obiectivul scos (evident si PC) plus scaun si alte obiecte de sprijin plus ceva contorsionistica si muuulta rabdare  :-D (mai ales ca la mariri mari, o sa observi, obiectul vizat fuge repede din vizor....datorita rotatiei Pamantului).
Totusi, inelele lui Saturn, chiar si asa, au fost o experienta deosebita pt mine atunci cand le-am vazut pt prima data (inainte de faza cu web-camul) si nu ma asteptam sa le pot vedea. Si pentru tine va fi la fel. Din pacate, telescopul va trebui folosit .. afara, fie cat de frig, pentru ca prin geamul ferestrei vei distorsiona imaginile. In perioada asta poti incerca sa vezi Saturn dimineata inainte de a se ilumina, Saturn fiind undeva spre sud-est pe la 50..60 grade inaltime fata de orizont.. si luna, restul planetelor fiind cam absente in perioada asta a anului. Poti incerca si petele solare, dar ATENTIE, numai daca stii sa te protejezi de lumina solara. daca nu, las-o balta cu soarele!!, ca poti orbi, mai ales cu telescoapele astea!

chiar vazand poza asta cu Saturn m-am gandit ca si Saturn, Jupiter etc, ar avea un Soare Central care sa le creeze efectul de aurora...de ce nu? ca doar sistemele astea sunt in esenta fractali... :roll:
De ce nu se spune nimic(de "savanti") despre gigantica structura artificiala care orbiteaza in jurul Terei si creeaza efectul de Curcubeu?
Ne tot indoapa cu "explicatii stiintifice" multe fara justificari reale...

Salut Ciuciulete!!

Multam mult pentru toate informatiile pe care mi le-ai dat....iti imaginezi ca deja sunt "abonata" pe situl Observatorului Astronomic...sorb fiecare stire astronomica..
Ce ma surprisns cel mai mult la observatiile facute pana acum prin telescop este viteza uluitoare cu care se invarte Pamantul...ai scris si tu chestia asta undeva pe un topic, incredibil cat de repede dispar astrele din obicetiv si cat de putin percepem cu ochiul liber miscarea de rotatie ...
Cat despre Soare, stiu ca este fff periculos, am observat ca totusi telescopul are dispozitivele necesare de protectie in cazul observatiei solare...inca nu am incercat...nici n-am avut ocazia...dimineata la job cand ajung deja e seara.. :|
Cat despre observatia prin geam...deja sunt racita din cauza geamului deschis :cry:..insa MERITA sacrificiul. :-D
Abia astept sa am ocazia sa-l pun la treaba undeva in afara orasului, unde influentele luminilor din oras nu ajung...poate am ocazia sa prind un fenomen Iridium Flare.
Multumesc inca o data si sigur o sa va tin la curent cu observatiile.
Apropos ai ideepe ce data in Decembrie se vad Perseidele...am auzit ca sunt mult mai spectaculoase decat cele din vara.

Dreamy a spus:

CitatMultumesc inca o data si sigur o sa va tin la curent cu observatiile.

Pentru a nu fi off-topici fata de subiectele curente, poate e bine sa creezi un topic nou, (de exemplu: "astronomie - experiente personale" sau ceva de genul asta)  :wink:

Maya a spus:

CitatDe ce nu se spune nimic(de "savanti") despre gigantica structura artificiala care orbiteaza in jurul Terei si creeaza efectul de Curcubeu?

nu stiam despre asta, e vre-un topic pe aici in acest sens?! (apropo: curcubeu poti crea si tu in camera cu o sursa de lumina si o prizma de sticla)

CitatNe tot indoapa cu "explicatii stiintifice" multe fara justificari reale...

cred ca e destul de departe de a fi astfel. De cele mai multe ori pur si simplu noi, nespecialistii, nu intelegem mare lucru din explicatiile stiintifice, caci nu-i nici unul dintre noi sa le stie pe toate.

legat de topic, omenirea are de vreo 2 ani o sonda automata in misiune pe orbita in jurul lui Saturn, misiunea Cassini-Huygens, care trimite informatii si imagini spectaculoase si in premiera de acolo. (plus ca a si trimis o mini-sonda sa aterizeze pe suprafata inghetata (-170 grade) a satelitului Titan, de unde a transmis imagini in premiera pana sa inghete definitiv in atmosfera inospitaliera (mi se pare ca sonda fiind mai "calduta", a topit metanul solidificat pe care aterizase, si gazele expulzate au defectat-o rapid - oricum nu fusese proiectata sa reziste unor asemenea conditii). Detalii si imagini ale misiunii inca in desfasurare aici: http://saturn.jpl.nasa.gov/home/index.cfm  (iar direct sectiunea de imagini aici: http://saturn.jpl.nasa.gov/multimedia/images/index.cfm)

CitatThe Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.

spuneam in postul anterior de misiunea Cassini-Huygens ..
azi pe "Astronomy Picture of the Day " au dat o imagine (si film!) despre norii de pe Saturn..de fapt un urias ciclon, probabil prezent acolo de milioane de ani, si de o diomensiune mai mare decat TERRA noastra....

CitatExplanation: What's happening at the south pole of Saturn? To find out, scientists sent the robot Cassini probe now orbiting Saturn directly over the lower spin axis of the ringed giant. Cassini found there a spectacular massive swirling storm system with a well developed eye-wall, similar to a hurricane here on Earth. One image of the storm is shown above, while several frames from the overpass have been made into a movie that shows the huge vortex rotating. The storm is slightly larger than the entire Earth and carries winds that reach 550 kilometers per hour, twice the velocity of a Category 5 hurricane. This pole vortex on Saturn might have been raging for billions of years and is not expected to drift off the pole.

poza aici: http://antwrp.gsfc.nasa.gov/apod/ap061113.html
iar mai multe poze distantate in timp si adunate intr-un fiilmulet, aici: http://ciclops.org/media/ir/2006/2313_6310_4.mpg

Primul uragan de pe Saturn
Vineri 10 Noiembrie 2006
Un fenomen neobiºnuit are loc în aceste zile pe planeta Saturn. Este vorba despre o furtunã, prima de acest fel detectatã vreodatã de pe Pãmânt. Furtuna are dimensiuni gigant de 8.000 de km.
Uraganul este foarte diferit de cele care au loc pe planeta noastrã. Rafalele de vânt depãºesc 350 de km pe orã, iar centrul ciclonului este foarte bine definit fiind mãrginit de nori care se desfãºoarã pe o înãlþime de 75 de km, aproximativ de 5 ori mai mult decât norii uraganelor terestre. Se pare cã spirala descrisã de ciclon este cãt douã treimi din suprafaþa totalã a planetei noastre. Cercetãtorii au declarat cã, deºi aratã ca un uragan, se comportã diferit. Furtuna pare sã se fi oprit chiar deasupra polului sud al planetei, acolo unde este cel mai cald ºi unde atmosfera este puternic rarefiatã. Ea nu se deplaseazã aºa cum s-ar întampla pe Terra.
O altã premierã constã în faptul cã furtunile care au loc pe alte planete ale sistemului solar nu au acel ochi specific perturbaþiilor terestre. Prezenþa acelei deschideri reprezintã pentru cercetãtori o fereastrã prin care se pot apropia mai mult de suprafaþa planetei Saturn. E greu sã ne imaginam ce s-ar fi întâmplat dacã un asemenea turbion s-ar fi format în atmosfera terestrã. Pare mai degrabã un scenariu science fiction.
Sursa:http://www.realitatea.net/23337_Primul-uragan-de-pe-Saturn-.html (http://www.realitatea.net/23337_Primul-uragan-de-pe-Saturn-.html)

Misiunea de cercetare Cassini-Huygens a descoperit recent un un masiv lant muntos pe Titan, satelitul natural a lui Saturn!!
Mai multe informatii puteti afla pe:
http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=709

Existenta unor lacuri si oceane de metan lichid pe Titan, luna lui Saturn, a fost prezisa cu 20 de ani in urma. Insa nu s-a reusit confirmarea lor, asta pana pe 22 iulie 2006, cand prin dreptul lui Titan a trecut sonda Cassini.

Imaginile radar luate de Cassini dovedesc prezenta unor largi mase de lichid. Intensitatea din imaginea colorata este proportionala cu luminozitatea intoarsa de radar. Culorile nu sunt o imagine a ceea ce ar vedea ochiul uman.

Lacurile, care apar mai intunecate decat terenul din jur, sunt accentuate de regiunile slab colorate din jurul lor. Regiunile care apar luminoase pe radar sunt de culoare cafenie in imagine. Aceasta imagine a fost facuta de instrumentele sondei Cassini pe 22 iulie, 2006. Imaginea este centrata la aproximativ 80 de grade nord, 35 de grade vest si cuprinde o arie de 140 de kilometri.

Sursa: NASA/Jet Propulsion Laboratory

nu e o imagine surprinsa de SPITZER sau HUBBLE, ci de Cassini, insa ramane  la fel de frumoasa...



"The Cassini probe has imaged a huge cloud system covering the north pole of Titan, Saturn's largest moon. Is it from such clouds that methane "rain" falls on to the surface of Titan? Cassini has already spotted lakes that appear to be filled with liquid hydrocarbons like methane and ethane."

nu e despre saturn.....

Martian moon 'could be key test'

(fig 1   Image: Esa/DLR/FU Berlin/G.Neukum)

Mars' moon Phobos could be the target for a technology trial that would seek to return rock samples to Earth.
A UK team is developing a concept mission that aims to land a spacecraft on the potato-shaped object and grab material off its surface.
These small rock fragments would then be despatched to Earth in a capsule.
"It is being seen as a technological demonstrator for an eventual Mars sample return," said Dr Andrew Ball from the Open University.
Those aspects of the mission that worked well could be incorporated into a full-scale assault on the Red Planet.
Both Europe and the US have made the objective of bringing back Martian rocks to Earth laboratories a top priority for their space programmes. A joint venture is likely to occur within the next 15-20 years.
But getting on and off a large planet will be extremely difficult, and the British satellite manufacturer Astrium is proposing to test the required technologies on the low-gravity target of Phobos first.
"It would be a three-year mission. We're looking at a 2016 launch," said Marie-Claire Perkinson, a principal mission systems engineer at the Stevenage company.

Many links

Even so, the Phobos concept has a number of challenging steps, all of them capable of killing the mission if a single element goes wrong.
It is envisaged that a "mothership", powered by an ion engine, would fly into orbit around Mars where it would release a lander craft down on to the surface of the moon.
This robot vehicle might do some in-situ experiments but its main task would be to core, drill, or scoop up surface "soil" into a sealed vessel.
Then, it would lift off from Phobos using chemical thrusters to attempt to dock with, or be captured by, the passing mothership. If that succeeds, the sample vessel would be transferred across and packaged inside an additional bio-secure sealed-container ready for the trip home.
Close to Earth, this capsule would be jettisoned into the atmosphere to make a hard landing; it would need no parachute assistance.
"It's really the sample transfer chain which is the critical issue - right from landing on Phobos and taking the sample, and then passing it through the various vehicles to return to Earth," explained Ms Perkinson.
"It's challenging because it requires a lot of new technology development, and it's reliant on a lot of mechanisms, which is something we usually try to avoid."  ( fig 2 )



The concept is being considered by the European Space Agency (Esa) under its Aurora programme for Solar System exploration.

Already approved and in development is a robot rover that will trundle across the surface of the Red Planet to look for signs of past or present life; and Astrium is working on the vehicle's chassis. (The Aurora programme is committed to a rover project)
A precursor Mars-sample-return mission could get the go-ahead from Esa in the next couple of years. French industry is interested in leading this project and is preparing its own, competing concept.
Whoever is chosen may well have to watch the Russians give it a go first. They are currently working on a project known as Phobos-Grunt, which could fly as early as 2009.
But leading out of the box is not a guarantee of success. Getting down on to a small low-gravity body has its own difficulties. The wrong approach could crush landing legs or even result in the vehicle bouncing straight back off into space.
Such problems were amply demonstrated by the recent Japanese attempts to grab samples off the surface of an asteroid.
It is still not clear whether the Hayabusa spacecraft managed to capture any material and the probe's return to Earth is still haunted by uncertainty.

Moon 'death' ( fig 3)

For Dr Ball, a consultant on the Astrium proposal, Phobos represents a fascinating subject for study in its own right, over and above any eventual objective of getting down to the surface of the Red Planet.
The moon, like its sister Deimos, is asteroid-like in appearance - in fact, these two satellites are very probably "primitive" asteroids that were captured into Mars' orbit by its gravity.

Close study should also refine estimates for the expected "death" of Phobos. Its orbit around Mars is shrinking and in a few tens of millions of years it will either fall on to the planet or, more likely, shatter under tidal forces into countless pieces and form a ring.

One of the moon's most notable features is the system of grooves that cross its surface. These are assumed to be the result of collisions with rocks blasted off the surface of Mars by space impacts.

This raises the intriguing prospect that Phobos may actually be littered with Martian material.
"So, with this mission, you could get two for one," said Dr Ball.
"When there's a large impact on Mars, ejecta-debris gets thrown up, and some of that can hit Phobos. Over billions of years, Phobos should have accumulated some fraction of Martian soil in its surface.

"In doing this mission, we'd not only be demonstrating many of the technologies required for a Mars sample return, but we may even get some Martian material itself."

The size of the Phobos sample would not need to be very large.
Some 200g would be enough to keep current astro-labs busy and have a portion in reserve for future analysis using yet-to-be developed techniques - a standard approach when dealing with scarce extra-terrestrial material.


pt fig 2:
(1) The spacecraft could leave in 2016 when Earth and Mars are in a favourable alignment, reducing the mission length to three years
(2) Cruise phase would use a solar-electric engine. This relies on solar power to accelerate xenon ions to produce forward thrust
(3) The mothership would go into orbit around Mars; the lander would be ejected to make its own way down to the surface of Phobos
(4) The lander could do some in-situ experiments, but its primary objective would be to package away surface material
(5) After lift-off, the lander would dock with, or be captured by, the mothership - a key test for Mars sample return technology
(6) The Phobos samples will be transferred to a sealed and bio-secure re-entry capsule for the journey home:
(7) After ejection and Earth re-entry, the capsule would crash-land; no parachute would be used to slow its fall

pt fig 3
Measures 27 x 22 x 18km; could be a captured asteroid
Orbits less than 6,000km above Mars; slowly falling inwards
First high-res probe images taken by Mariner 7 in 1971
Dedicated Soviet probes, Phobos 1 & 2, failed en route
10km-wide Stickney crater (above) records huge impact


sursa : http://news.bbc.co.uk/

Saturn moon's cosmic graffiti art


Saturn's moon Enceladus is a "cosmic graffiti artist", with geysers which spray out material that eventually settles over other satellites.
Hubble Space Telescope observations show how material from Enceladus alters the appearance of its neighbours.
One of Saturn's rings - the E ring - is largely made up of icy material from Enceladus' volcanic plumes.
These particles then collide with other moons that orbit within the E ring, coating their surfaces with material.
Anne Verbiscer from the University of Virginia and colleagues measured the reflectivity, or "albedo" of the saturnian satellites.
They concluded that interactions with E ring particles, ultimately from Enceladus' plumes, produced high albedos on the moons Tethys, Mimas, Dione and Rhea.
With a diameter of 500km (310 miles), Enceladus is a relatively small moon.
"Inevitably, material from Enceladus impacts all satellites orbiting within the E ring, enhancing their albedos at the hands of a diminutive giant," the researchers write in Science.
Enceladus is thought to have reservoirs of near-surface liquid water that erupt to form geysers.
These jets have been observed erupting from a "hot spot" in the moon's south polar region.
"We knew the E ring had a considerable extent from Mimas to beyond Tethys. So naturally, satellites orbiting within there are going to get coatings of this icy material," said Professor Carl Murray, from Queen Mary in London, who was not an author on the Science paper.
Prof Murray, who is a co-investigator on the Cassini-Huygens mission, added: "Anything more we can find out about the E ring is important because it is the material that came from under the surface of Enceladus. We believe there is a source of liquid water under the surface."

The Cassini spacecraft reached Saturn in July 2004 to study the planet, its rings and its moons.
On a flyby of Enceladus, it was able to sample and analyse material ejected by the south polar volcanic plume.

-The heat emission is associated with the tiger stripe features which mark the southern pole. The temperatures are in Kelvin (zero K equals -273C)

sursa:  http://news.bbc.co.uk/
mai multe si aici :   http://news.bbc.co.uk/2/shared/spl/hi/sci_nat/04/cassini/html/introduction.stm

Nava spaþialã Cassini a descoperit un nou inel în jurul planetei Saturn. Cercul este subtil ºi are ca marcã distinctã o cruce neagrã. Se pare cã noul inel a apãrut în urma impactului unui meteorit care a lovit suprafaþa a douã luni saturniene. Lunile Janus ºi Epimetheus sunt prea mici pentru a putea susþine praful produs de explozia meteoritului, de aceea particulele au fost dislocate în spaþiu. Subtilul inel coincide cu orbita celor douã luni, de aceea specialiºtii cred cã ele sunt responsabile de apariþia noului cerc.

Cercetãtorii au fãcut descoperirea în urma unui eveniment destul de neobiºnuit: o eclipsã solarã a lãsat nava spaþialã Cassini în umbra lui Saturn pentru 12 ore. În acest interval au putut vedea foarte clar toate cercurile din jurul planetei-gigant, Saturn.
Sursa - Antena 3

Daca ati vazut filmul: "Masina timpului"...in care se presupunea ca luna daca ar exploda s-ar  transforma in inel al terrei! O buna ipoteza de luat in calcul si in cazul: Saturn

The Cassini space probe pictures three of Saturn's small moons in conjunction with its immense ring system. Prometheus and Pandora, on the right, are "shepherd moons" whose gravity keeps the edge of the F-ring sharp. Janus is the third moon pictured. (Image: Nasa/JPL/Space Science Institute)

The New Horizons probe pictures a 290km-high (180 miles) plume from the volcano Tvashtar, which is situated near the north pole of the Jovian moon Io. The probe continues to return stored data from its recent flyby of Jupiter.

Major space missions move ahead

The European and US space agencies are moving ahead on their next major missions to explore the Solar System.
Nasa has begun choosing a destination for a "flagship" robotic venture along the lines of Cassini-Huygens, which has been exploring Saturn and its moons.
It is considering four targets: the Jupiter system, Jupiter's moon Europa, and Saturn's moons Enceladus and Titan.
The European Space Agency has called for proposals for one flagship mission and another medium-sized mission.
Europa, Titan and Enceladus are also among the destinations expected to be proposed under the European Space Agency's (Esa) "Cosmic Visions" programme of exploration.
Other proposals likely to be submitted include a mission to return soil from a near-Earth asteroid.
Titan resembles a primordial Earth, and it can serve as a laboratory to show us how unusual and complex organic chemistry takes place

Curt Niebur, Nasa
"There are some ambitious projects being proposed," said John Zarnecki, director of the Centre for Earth, Planetary Space and Astronomical Research (Cepsar) at the Open University, UK.
"We've been talking about them for months or even years. Teams are together and proposals are being prepared."
And many of the issues are topics of discussion here in Texas this week at the 38th Lunar and Planetary Science Conference.


Life lessons

Professor Zarnecki is part of an international consortium behind a mission to Europa proposal being prepared for submission to the European Space Agency.

He is also involved with a team hoping to mount a European return to Titan. This time, a probe might survey the saturnian moon's surface by balloon.

The American and European agencies are developing their space exploration programmes separately, but both say co-operation further down the line is a distinct possibility.
Some scientists would like to go back to Titan
Nasa and Esa are looking at similar timescales for the launch of their respective missions. Nasa is planning for a launch date sometime after 2015; Esa plans its missions for the period between 2015 and 2018.
The US space agency (Nasa) has drawn together four science definition teams to investigate one target each. They will scope out how the missions might be performed.
Curt Niebur, discipline scientist at Nasa's headquarters in Washington DC, told the BBC News website: "All three of these worlds hold our interest because of their unusual similarities to Earth and the knowledge they can give us about how life does, or does not, start.
"Chemically, Titan resembles a primordial Earth, and it can serve as a laboratory to show us how unusual and complex organic chemistry takes place."


Under the ice

A probe to Europa has been on the wish lists of planetary scientists for a decade.
Thought to host an ocean of water under its icy shell, this Jupiter moon is considered to be one of the best places in the Solar System to search for extraterrestrial life.

"It has the three ingredients that life needs: liquid water, energy and nutrients," said Dr Niebur.
Europa may have oceans and micro-organisms under its ice
Professor Ron Greeley, a planetary scientist at Arizona State University, has been appointed to co-chair the Nasa science definition team for a Europa mission. He told BBC News: "We fly one flagship roughly every decade; it takes a lot of resources to do that category of mission.
"We will determine what the major science goals are and how to do them. These include what instruments could do the job, what orbits are required, how we could operate in the harsh radiation environment of Europa."
Scientists have long wanted to burrow through Europa's ice to the ocean beneath, but John Zarnecki says that, for now, this may be too ambitious.
He favours a two-stage approach, in which an orbiter is sent first, possibly with ground-penetrating radar, followed later by a lander capable of penetrating the ice.
"Others say we should go for a lander and a penetrator straight away, but I don't know how feasible that is, financially and technically. Landing on Europa is very demanding, you have to brake very hard on approach," he said.

Fast riser

Saturn's moon Enceladus has recently surged up the list of priority targets for exploration.
When the Cassini-Huygens probe arrived at the Saturn system in 2004, it observed water vapour erupting in huge geysers from an active volcanic region at Enceladus' south pole.
This combination of heat and liquid water close to the surface makes it interesting to astrobiologists, scientists who study the origin and evolution of life in the Universe.
Nasa's science definition teams will report back in August.

An independent evaluation will take place over the following few months with a view to choosing a target for the flagship mission.
Scientists have to submit their letters of intent to the European Space Agency by 30 March. They will then need to submit fuller mission proposals by the end of June.
A previous joint Esa-Nasa mission to Europa was dropped following budgetary changes at the US space agency in 2006.


sursa:   http://news.bbc.co.uk/2/hi/science/nature/default.stm

Hot start explains moon's geysers

The plumes of water that erupt from Saturn's icy satellite Enceladus can be traced back to a radioactive "meltdown" shortly after the moon formed.
The discovery, in 2005, of water vapour spewing from geysers at Enceladus' south pole took scientists by surprise.
How this tiny, ice-covered moon generated the amounts of heat needed to fuel these eruptions was a puzzle.
Now scientists say a short-lived burst of radioactivity early in its history kicked off a slow cooking of its core.
The new model for Enceladus' evolution was presented at the Lunar and Planetary Sciences Conference here in Houston, Texas.


Pocket dynamo

When the Voyager 2 probe visited Saturn in the 1980s, it found that Enceladus was unlike many of the other moons in its neighbourhood, whose pockmarked surfaces bore testament to billions of years of heavy bombardment.
By contrast, Enceladus had a relatively smooth, young surface that must have been renewed by some recently active process.
In 2005, Nasa's Cassini orbiter discovered an active region near the moon's south pole marked by tiger stripe-like features. Geysers were seen at this location to hurl water vapour and ice crystals into space.
Since then, the challenge for researchers has been to figure out how this diminutive ball of ice and rock produced the heat necessary to power these eruptions.

The answer, say Dennis Matson and Julie Castillo-Rogez of Nasa's Jet Propulsion Laboratory in California, probably lies in a brief period of radioactive heating when the moon was a youngster.
The model supports the recent finding that Enceladus' plumes contain molecules that require searing temperatures in order to form.
Dr Castillo-Rogez said the "only way" to achieve such high temperatures was "through the rapid decay of some radioactive species".

Dr Matson said that temperatures in Enceladus' interior could have reached as high as 1,000 Kelvin (727C).
"I don't know if it is that hot today, but it certainly got up that high," he said.


Rapid decay

Enceladus started off 4.5 billion years ago as a jumbled-up ball of ice and rock containing the rapidly decaying radioactive isotopes aluminium-26 and iron-60.
The moon probably acquired these radioactive species from minerals called calcium-aluminium-rich inclusions (CAIs), which formed early in Solar System history and are found today in meteorites.
According to the new model, the decay of these isotopes over a period of about seven million years would have generated enormous amounts of heat.

This heat melted the moon's ice, causing the rocky material to sink to the moon's centre, where it consolidated to form a core.
Once this intense, but short-lived period of heating was over, other effects may have taken over the warming of the moon's interior.
More slowly decaying radioactivity in the core along with the tidal forces exerted on Enceladus by Saturn's gravity may be responsible for the heating which continues today.


Gas detection
[/b]
The researchers say their model neatly explains the detection of gaseous nitrogen in the plume expelled from geysers.
Nitrogen is not thought to have been part of Enceladus' original make-up. Instead, Dr Matson and Dr Castillo-Rogez believe it is formed via the breakdown of ammonia, where the warm core and the surrounding liquid water meet.
However, the decomposition of ammonia to form gaseous nitrogen requires temperatures of about 577C (1,070F).
Slowly decaying radioactivity and tidal forces cannot account for such high temperatures alone, but they can when combined with the "hot start" model.
Since the discovery of Enceladus' plume by Cassini, the moon has become a high priority target for future exploration.
With a brew of organic chemicals in the interior, a heat source and liquid water, the moon has all the key ingredients needed for life.



fig 1: The heat emission is associated with the tiger stripe features which mark the southern pole. The temperatures are in Kelvin (zero K equals -273C)

fig 2 :Cassini has seen plumes of material head into space

fig 3 :enceladus  "cold geyser" model

Probe reveals seas on Saturn moon



Nasa's Cassini probe has found evidence for seas, probably filled with liquid hydrocarbons, at the high northern latitudes of Saturn's moon Titan.
The dark features, detected by Cassini's radar, are much bigger than any lakes already detected on Titan.
The largest is some 100,000 sq km (39,000 sq miles) - greater in extent than North America's Lake Superior.
It covers a greater fraction of Titan than the proportion of Earth covered by the Black Sea.
The Black Sea is the Earth's largest inland sea and covers about 0.085% of our planet's surface.

The newly observed body on Titan covers at least 0.12% of that world's surface. Cassini team members argue that this gives them reason to call it a sea.

Since Cassini's radar has caught only a portion of each of the new features, only their minimum size is known.



Methane and ethane

Titan is the second largest moon in the Solar System and has a diameter that is almost twice that of Earth's Moon.
While there is no definitive proof that these seas contain liquid, their shape, their dark appearance in radar that indicates smoothness, along with other properties, point to the presence of liquids.
The liquids are probably a combination of methane and ethane, given the conditions on Titan and the abundance of methane and ethane gases and clouds in Titan's atmosphere.
"Carl Sagan [the astronomer] said that Titan must be covered with oceans, and that these replenished the atmosphere with methane," explained Charles Wood, chair of space studies at the University of North Dakota, US.
But that vision of hydrocarbon oceans had to be scrapped when Cassini peered through Titan's organic haze and found a chaotic, geologically active surface, but no large bodies of liquid.

Recently, the orbiter started to spot lake-like features at Titan's northerly regions.

"They are limited to about 65 degrees latitude," said Charles Wood, although he added that river-like channels seemed to be everywhere on Titan.
The discovery of these even larger bodies might hold the solution to the problem of replenishment of the atmosphere with methane.
After making these findings, Cassini team members plan to re-point the orbiter's radar instrument during a May flyby so that it can pass directly over the large dark features imaged by the cameras.
The Cassini-Huygens mission is a cooperative project of the US space agency (Nasa), the European Space Agency (Esa) and the Italian Space Agency (Asi).

Icy map to probe Europa's secrets


Scientists have produced a global geological map of Jupiter's moon Europa, which has been proposed as a destination for a future space mission.
Interest in Europa has been fuelled by indications that a liquid water ocean lurks beneath its outer shell of ice.
The mapping effort will help build a geological history of the enigmatic moon and target future explorations.

Galileo explored the Jupiter system from 1995 to 2003.
The work was presented here at the Lunar and Planetary Science Conference in Houston.
The maps have allowed the scientists to identify several distinct geological units on Europa. Understanding the distribution and age relationships of these units can assist the reconstruction of a geological history for the moon.
Europa's surface is young, active and smooth with few craters. But it is criss-crossed by a network of fractures, thought to be where the icy shell has been prised apart by the tidal forces of Jupiter.

We're trying to figure out what's what on the surface so we can go and explore further - Ron Greeley, Arizona State University

"When we make planetary maps, we're pretty limited by fieldwork, so 'ground truth-ing' is difficult - but not impossible, as we've found with the Mars Rovers," said Professor Ron Greeley, director of planetary geology at Arizona State University (ASU) in Tempe, US.

"We have to rely on remote sensing information. On Earth, this is conventionally done in exploration for oil or mineral deposits. The data is used to make maps to figure out the best places to go and explore.

"That's what we're doing with Europa. We're trying to figure out what's what on the surface so we can go and explore further."



Salty ocean

Voyager 2, launched in 1977, was the first spacecraft to fly past Europa, sending back snatched glimpses of the surface at a resolution of about 2km (1.2 miles) per pixel.
Galileo made multiple flybys of the moon, building up a collection of images at different resolutions, ranging from 12.6 to 0.23km (7.8-0.14 miles) per pixel.
Compiling these pictures into a global map has required painstaking work by Ron Greeley, Thomas Doggett and their colleagues at ASU.

"We do not have global coverage, even at the lowest resolution. It is very non-uniform. Also, the illumination of the surface differs widely from one dataset to another," explained Professor Greeley.

Europa, the fourth largest of Jupiter's satellites, is a high priority for future exploration. Study of its magnetic field by the Galileo probe provided strong evidence for a salty ocean beneath the ice.
The moon contains all the ingredients needed for the emergence of life: liquid water, an energy source (provided by the tidal pull exerted by Jupiter's gravity) and organic chemicals.

If life ever emerged on Europa, researchers believe it could exist in an environment similar to terrestrial deep ocean hydrothermal vents or Antarctica's Lake Vostok.



Mission proposals

Nasa has drawn up science definition teams to assess four potential targets for a "flagship" robotic mission to launch after 2015. These targets are the Jupiter system, Europa and Saturn's moons Enceladus and Titan.
The agency has appointed Ron Greeley and Robert Pappalardo from Nasa's Jet Propulsion Laboratory in California to co-chair a team of about a dozen experts who will set out the major science objectives for a Europa mission.

Europa's distinctive icy shell could be 20km thick

Their work will look at what instruments a spacecraft should take, what orbits would be required for the mission and how the probe might operate in the Jovian moon's harsh radiation environment.
After the four teams report back in the summer, officials at Nasa HQ in Washington DC will evaluate the case for a mission and decide which to carry forward.

In addition, an international consortium is preparing a Europa mission proposal to be submitted under the European Space Agency's (Esa) Cosmic Visions programme of space exploration. This consortium is exploring a potential link-up with Japanese partners.
A "dream" concept for the exploration of Europa would be a robotic probe, perhaps powered by radioactive decay, that could melt through the ice and explore the ocean beneath.

But this would pose formidable technical challenges: the ice shell could be about 20km (12 miles) thick, according to one model.
"Is the technology there to do that? Possibly. My own personal feeling is that it is fantastically ambitious," said Professor John Zarnecki, from the UK's Open University, who is a member of the consortium hoping to mount a European mission to the Jovian moon.
"I think there should be a two-stage approach, beginning with an orbiter, perhaps with ground-penetrating radar and perhaps a way of measuring the gravity field - which is another way to tell what's beneath the surface. Then we go for a lander and a penetrator."

Just getting to Europa is tough, a spacecraft would have to pick up lots of speed and then break hard to reach it. In addition, the harsh radiation environment gives a spacecraft orbiting the moon a lifetime of just 66 days, according to an Esa feasibility study.



fig 1 : On the map, blue represents different plains, green is for chaotic terrain. Also shown are impact craters (yellow), crater ejecta (brown), wide bands (pink), major ridges (blue lines), pits and domes (green dots). Areas with worse than 1.7km/px resolution or no coverage at all are shown in white.

fig 2: Geological features on the surface of Europa could be explained by the existence of a warm, convecting layer of ice several kilometres below a brittle ice crust (A). An alternative model (B) proposes an underlying layer of liquid water with a depth of more than 100km (60 miles).

Big Auroras on Jupiter


So you thought Northern Lights were big in Alaska? "That's nothing," says Randy Gladstone of the Southwest Research Institute in San Antonio, Texas. "Jupiter has auroras bigger than our entire planet."

Last month, Gladstone and colleagues used NASA's Chandra X-ray Observatory to capture this picture:FIG 1 si FIG 2  ( in raze x)
The purple ring traces Jupiter's X-ray auroras. Gladstone calls them "Northern Lights on steroids. They're hundreds of times more energetic than auroras on Earth."
Chandra has observed Jupiter's auroras many times before, but this recent dataset is exceptional both in length and quality. Gladstone hopes it will help him solve some mysteries lingering for almost 30 years.

Jupiter's auroras were discovered by the Voyager 1 spacecraft in 1979. A thin ring of light on Jupiter's nightside looked like a stretched-out version of our own auroras on Earth. But those early photos merely hinted at the power involved. The real action, astronomers soon learned, was taking place at high-energy wavelengths invisible to the human eye. In the 1990s, ultraviolet cameras on the Hubble Space Telescope photographed raging lights thousands of times more intense than anything ever seen on Earth, while X-ray observatories saw auroral bands and curtains bigger than Earth itself.

Jupiter's hyper-auroras never stop. "We see them every time we look," says Gladstone. You don't see auroras in Alaska every time you look, yet on Jupiter the Northern Lights always seem to be "on."

Gladstone explains the difference: On Earth, the most intense auroras are caused by solar storms. An explosion on the sun hurls a billion-ton cloud of gas in our direction, and a few days later, it hits. Charged particles rain down on the upper atmosphere, causing the air to glow red, green and purple. On Jupiter, however, the sun is not required. "Jupiter is able to generate its own lights," says Gladstone.

The process begins with Jupiter's spin: The giant planet turns on it axis once every 10 hours and drags its planetary magnetic field around with it. As any science hobbyist knows, spinning a magnet is a great way to generate a few volts—it's the basic principle of DC motors. Jupiter's spin produces 10 million volts around its poles.

"Jupiter's polar regions are crackling with electricity," says Gladstone, "and this sets the stage for non-stop auroras."

The polar electric fields grab any charged particles they can find and slam them into the atmosphere. Particles for slamming can come from the sun, but Jupiter has another, more abundant source nearby: the volcanic moon Io, which spews oxygen and sulfur ions (O+ and S+) into Jupiter's spinning magnetic field. ( fig 3 )

Somehow, these ions make their way to Jupiter's poles where electric fields send them hurtling toward the planet below. Upon entering the atmosphere, "their electrons are first stripped away by molecules they run into, but as they slow down they start grabbing electrons back. The 'charge exchange reaction' produces intense X-ray auroras," he explains.

So Jupiter's Northern Lights are, in a sense, volcano powered. Mystery solved? Not quite.

No one knows exactly how volcanic exhaust meanders from Io out through Jupiter's magnetosphere and back to Jupiter's poles. "We're still trying to figure it out," says Gladstone.

But that is a minor detail compared to another, even bigger puzzle: There is an X-ray "pulsar" inside Jupiter's northern auroras. Sometimes Chandra sees it, sometimes not. When it's on, the pulsar emits gigawatt bursts of X-rays with a regular beat of 45 minutes.
Gladstone suspects the pulsar has nothing to do with Io's volcanoes, but instead is caused by the sun. "Maybe Jupiter's magnetic field, when it gets hit by a solar wind gust, rings like a bell with a 45-minute period," he speculates. "There are many other possibilities as well."

The February 2007 dataset may hold important clues. "Chandra observed the auroras for 15 hours, and we weren't the only ones watching," he says. The Hubble Space Telescope, the FUSE satellite, XMM-Newton (a European X-ray observatory), the New Horizons spacecraft and many ground-based observatories were all taking data at the same time. The campaign was timed to coincide with New Horizons flyby of Jupiter—a slingshot maneuver designed to increase its velocity en route to Pluto.

"Jupiter's auroras have never been observed by so many telescopes at once," says Gladstone. "I'm really excited by these data, and the analysis is just beginning."

Cassini Views Titan from Bottom to Top

Cassini's science instruments studied Titan during the May 28, 2007, flyby. As seen from Earth, Cassini dipped behind Titan near the south pole and re-emerged near the north pole. From this unique vantage point, Cassini's radio science instrument used a radio signal to study the properties of Titan's atmosphere, and the infrared and visible-light cameras imaged a bright surface feature on Titan named Dilmun

Neon Saturn

In this false-color image, the Cassini spacecraft captures Saturn's glow, represented in brilliant shades of electric blue, sapphire and mint green, while the planet's shadow casts a wide net on the rings.  The colors represent different wavelengths: red is thermal heat originating within the planet; in blue, icy ring particles shimmer in sunlight scattered through the rings; in green, a thick covering of high-altitude hazes strongly reflect sunlight.

This striking false-color mosaic was created from 25 images taken by Cassini's visual and infrared mapping spectrometer over a period of 13 hours, and captures Saturn in nighttime and daytime conditions. The visual and infrared mapping spectrometer acquires data simultaneously at 352 different wavelengths, or spectral channels. Data at wavelengths of 2.3, 3.0 and 5.1 microns were combined in the blue, green and red channels of a standard color image, respectively, to make this false-color mosaic.


On the night side (right side of image), with no sunlight, Saturn's own thermal radiation lights things up. This light at 5.1 microns wavelength (some seven times the longest wavelength visible to the human eye) is generated deep within Saturn, and works its way upward, eventually escaping into space. Thick clouds deep in the atmosphere block that light. An amazing array of dark streaks, spots, and globe-encircling bands is visible instead. Saturn's strong thermal glow at 5.1 microns even allows these deep clouds to be seen on portions of the dayside (left side), especially where overlying hazes are thin and the glint of the sun off of them is minimal. These deep clouds are likely made of ammonium hydrosulfide and cannot be seen in reflected light on the dayside, since the glint of the sun on overlying hazes and ammonia clouds blocks the view of this level.

A pronounced difference in the brightness between the northern and southern hemispheres is apparent. The northern hemisphere is about twice as bright as the southern hemisphere. This is because high-level, fine particles are about half as prevalent in the northern hemisphere as in the south. These particles block Saturn's glow more strongly, making Saturn look brighter in the north.

   Egal ce spun toti ,eu inclin sa pledez pentru "lampa Chinezeasca"

Two more active moons around Saturn


Saturn's moons Tethys and Dione are flinging great streams of particles into space, according to data from the NASA/ESA/ASI Cassini mission to Saturn. The discovery suggests the possibility of some sort of geological activity, perhaps even volcanic, on these icy worlds.

The particles were traced to the two moons because of the dramatic movement of electrically charged gas in the magnetic environs of Saturn. Known as plasma, the gas is composed of negatively charged electrons and positively charged ions, which are atoms with one or more electrons missing. Because they are charged, the electrons and ions can get trapped inside a magnetic field.
Saturn rotates around itself in just 10 hours and 46 minutes. This sweeps the magnetic field and the trapped plasma through space. Just like a child on a fast-spinning merry-go-round, the trapped gas feels a force trying to throw it outwards, away from the centre of rotation. 

Soon after Cassini reached Saturn, in June 2004, it revealed that the planet's hurried rotation squashes the plasma into a disc and that great fingers of gas are indeed being thrown out into space from the disc's outer edges. Hotter, more tenuous plasma then rushes in to fill the gaps.
Now, Jim Burch of the Southwest Research Institute, USA, and colleagues have made a careful study of these events using the Cassini Plasma Spectrometer (CAPS). They have shown that the direction of the ejected electrons points back towards Tethys and Dione. "It establishes Tethys and Dione as important sources of plasma in Saturn's magnetosphere," says Burch.

UUntil this result, among Saturn's inner moons only Enceladus was known to be an active world, with huge geysers spraying gases hundreds of kilometres above the moon's surface. "This new result seems to be a strong indication that there is activity on Tethys and Dione as well," says Andrew Coates from the Mullard Space Science Laboratory, University College London, and a collaborator on this latest work.

Hydrocarbons, Necessary For Life, Found On Saturn's Moon Hyperion



NASA's Cassini spacecraft has revealed for the first time surface details of Saturn's moon Hyperion, including cup-like craters filled with hydrocarbons that may indicate more widespread presence in our solar system of basic chemicals necessary for life.
Te up-close view of Hyperion shows a low-density body blasted by impacts over eons. Scientists believe that the spongy appearance of Hyperion is caused by a phenomenon called thermal erosion, in which dark materials accumulating on crater floors are warmed by sunlight and melt deeper into the surface, allowing surrounding ice to vaporize away. (Credit: NASA/JPL/Space Science Institute)Hyperion yielded some of its secrets to the battery of instruments aboard Cassini as the spacecraft flew close by in September 2005. Water and carbon dioxide ices were found, as well as dark material that fits the spectral profile of hydrocarbons.

A paper appearing in the July 5 issue of Nature reports details of Hyperion's surface craters and composition observed during this flyby, including keys to understanding the moon's origin and evolution over 4.5 billion years. This is the first time scientists were able to map the surface material on Hyperion.

"Of special interest is the presence on Hyperion of hydrocarbons – combinations of carbon and hydrogen atoms that are found in comets, meteorites, and the dust in our galaxy," said Dale Cruikshank, a planetary scientist at NASA's Ames Research Center, Moffett Field, Calif., and the paper's lead author. "These molecules, when embedded in ice and exposed to ultraviolet light, form new molecules of biological significance. This doesn't mean that we have found life, but it is a further indication that the basic chemistry needed for life is widespread in the universe."

Cassini's ultraviolet imaging spectrograph and visual and infrared mapping spectrometer captured compositional variations in Hyperion's surface. These instruments, capable of mapping mineral and chemical features of the moon, sent back data confirming the presence of frozen water found by earlier ground-based observations, but also discovered solid carbon dioxide (dry ice) mixed in unexpected ways with the ordinary ice.

Images of the brightest regions of Hyperion's surface show frozen water that is crystalline in form, like that found on Earth.

"Most of Hyperion's surface ice is a mix of frozen water and organic dust, but carbon dioxide ice is also prominent. The carbon dioxide is not pure, but is somehow chemically attached to other molecules," explained Cruikshank.

Prior spacecraft data from other moons of Saturn, as well as Jupiter's moons Ganymede and Callisto, suggest that the carbon dioxide molecule is "complexed," or attached with other surface material in multiple ways. "We think that ordinary carbon dioxide will evaporate from Saturn's moons over long periods of time," said Cruikshank, "but it appears to be much more stable when it is attached to other molecules."

"The Hyperion flyby was a fine example of Cassini's multi-wavelength capabilities. In this first-ever ultraviolet observation of Hyperion, the detection of water ice tells us about compositional differences of this bizarre body," said Amanda Hendrix, Cassini scientist on the ultraviolet imaging spectrograph at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Hyperion, Saturn's eighth largest moon, has a chaotic spin and orbits Saturn every 21 days. The July 5 issue of Nature also includes new findings from the imaging team about Hyperion's strange, spongy-looking appearance.

Saturn's Old Moon Iapetus Retains Its Youthful Figure



Saturn's distinctive moon Iapetus (eye-APP-eh-tuss) is cryogenically frozen in the equivalent of its teenage years. The moon has retained the youthful figure and bulging waistline it sported more than three billion years ago, scientists report.



"Iapetus spun fast, froze young, and left behind a body with lasting curves," said Julie Castillo, Cassini scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Unlike any other moon in the solar system, Iapetus is the same shape today as it was when it was just a few hundred million years old; a well-preserved relic from the time when the solar system was young.

Cassini flew by Iapetus in early 2005 and discovered the moon had a walnut shape, bulging at its midsection. On top of that it has a chain of mountains located exactly along its equator.

Scientists now think the moon's bulging midriff and slow spin rate point to heating from long-extinct radioactive elements present when the solar system was born.

"We've modeled how Iapetus formed its big, spin-generated bulge and why its rotation slowed down to its present nearly 80-day period. As an unexpected bonus, Iapetus also told us how old it was," said Dennis Matson, Cassini project scientist at JPL. "You would expect a very fast-spinning moon to have this bulge, but not a slow-spinning moon, because the bulge would have been much flatter."

Scientists calculate Iapetus originally rotated much faster--at least five hours, but less than 16 hours per revolution. The fast spin gave the moon an oblate shape that increased the surface area (in the same way the surface area of a round balloon stretches when the balloon is pressed into an oblate shape). By the time the rotation slowed down to a period of 16 hours, the outer shell of the moon had frozen. Furthermore, the surface area of the cold moon was now smaller. The excess surface material was too rigid to go back smoothly into the moon. Instead, it piled up in a chain of mountains at the equator.

"Iapetus' development literally stopped in its tracks," said Castillo. "In order for tidal forces to slow Iapetus to its current spin rate, its interior had to be much warmer, close to the melting point for water ice." The challenge in developing a model of how Iapetus came to be "frozen in time" has been in deducing how it ever became warm enough to form a bulge in the first place, and figuring out what caused the heat source to turn off, leaving Iapetus to freeze.

The heat source had to have a limited life span, to allow the moon's crust to rapidly become cold and retain its immature shape. After looking at several models, scientists concluded that the heat came from its rocks, which contain short-lived radioactive isotopes aluminum-26 and iron-60 (which decay very rapidly on a geologic timescale). Since these elements decay at a known rate, this allowed scientists to "carbon date" Iapetus by using aluminum-26 instead of carbon. Scientists calculate the age of Iapetus to be roughly 4.564 billion years old.

Evidence for these same isotopes (aluminum-26 and iron-60) has been found in meteorites formed in the inner solar system. Therefore, there is a possibility of comparing the early chronology of the outer solar system with other objects in the inner solar system, such as Earth, Earth's moon and asteroids.

"This is the first direct evidence of the early spin history for a satellite in the outer solar system. It teaches us more about how the speed of a body's rotation influenced its evolution, and broadens our knowledge of the early history of outer planet satellites," said Matson.

Credit: NASA/JPL/Space Science Institute)

Intrucat vad ca degeaba scrie: "Sectiunea de limba romana" ca apar mesaje in engleza atunci pun si eu un articol interesant despre norii lui Saturn in limba straina pe care o stiu cel mai bine daca tot nu conteaza ca aici e sectiunea in limba romana:


Сатурн - шестая по удаленности от Солнца и вторая после Юпитера по размеру планета Солнечной системы. Известен больше всего опоясывающими его яркими кольцами. Легко различим невооруженным глазом; планета известна с доисторических времен.

Сатурн - самая дальняя планета, которую можно увидеть невооруженным глазом - Галилей в 1610 году впервые наблюдал ее с помощью подзорной трубы и обнаружил по обеим сторонам диска 2 меньших по размеру "тела". И только в 1656 году Христиан Гюйгенс объяснил истинную природу этих тел, выдвинув гипотезу о существовании вокруг планеты кольца.

В 1675 году Кассини удалось разглядеть внутри кольца разделительную полосу, получившую в честь итальянского астронома название; щель Кассини. Все тот же Кассини открыл, кроме того, пересекающие планету параллельные полосы, похожие на полосы Юпитера, только менее явные.

В конце XVIII века Уильям Гершель впервые вычислил период вращения Сатурна на основе изучения ряда характеристик этих полос - 10 ч 16 мин, что почти совпадает с истинным периодом - 10 ч 13 мин.

Вблизи Сатурна побывало три зонда. Первым был "Пионер-1", который после исследования Юпитера пролетел недалеко от Сатурна в сентябре 1979 года. Фотографии, сделанные зондом, позволили познакомиться с невидимыми с Земли кольцами и маленьким спутником.

Вторым прибывшим к планете зондом был "Вояджер-1", приблизившийся к ней в ноябре 1980 года на расстояние 64 000 км. Он передал данные об основных спутниках. "Вояджер-2" подлетел к Сатурну в августе 1981 года и должен был проследовать к Урану и Нептуну, имея совершенно иную орбиту, чем у его зонда-собрата.

Орбитальная и физическая характеристика. Сатурн - вторая от Солнца из четырех газообразных планет Солнечной системы. У него такая же структура, как и у Юпитера, и даже одинаковый элементный состав: водород и гелий.

По модели внутренней структуры у Сатурна имеется каменистое ядро, вокруг которого находится слой металлического водорода, а выше - слой молекулярных водорода и гелия, смыкающийся с нижними слоями атмосферы. Одна из особенностей планеты - очень низкая, наименьшая из всех планет Солнечной системы плотность - она ниже плотности воды. Одним из подтверждений этого факта является форма планеты, кажущейся приплюснутой на полюсах и очень сильно раздутой на экваторе. Полярный диаметр почти на 10% меньше экваториального.

Сатурну требуется 29,5 лет для полного оборота вокруг Солнца. Он находится на среднем расстоянии от нашей звезды в 9,5 АЕ, то есть в 9,5 раз дальше от Солнца, чем Земля. На такое расстояние доходит очень малое количество солнечного света - в 90 раз меньше, чем количество света, доходящего до нашей планеты.

Iata traducerea in engleza a textului expus de Curiosul in limba rusa:


"Saturn - sixth on the distance from the Sun and second in size after Jupiter planet solar system. Known most surrounding its bright rings. Easy to discern the naked eye; planet known since prehistoric times.

Saturn - the long-distance planet, which can be seen naked eye - Galileo in 1610 for the first time saw it through pipes and podzornoy found on both sides of the disc 2 smaller "body". I only Christian Huygens in 1656 explained the true nature of the bodies, making the hypothesis of the existence of rings around the planet.

In Cassini in 1675 managed to discern the dividing strip inside the ring, which has received the honour in the name of the Italian astronomer; crack Cassini. All the same Cassini opened, in addition, parallel bands crossing the planet similar to the bands of Jupiter, just less obvious.

At the end of the XVIII century William Herschel first rotation period of Saturn calculated on the basis of examination of a number of characteristics of these bands - 10 hours 16 minutes, almost the same as the genuine period - 10 h 13 min.

Near the three visited Saturn probe. The first was the Pioneer-1, which, after a study of Jupiter flew close to Saturn in September 1979. Photos made probe allowed to get acquainted with invisible from the Earth rings and small satellite.

The second arrived to the planet probe was Voyager-1, draws near to it in November 1980, at a distance of 64000 km. He conveyed the major satellites. Voyager-2 "flew to Saturn in August 1981 and had to go to Uranus and Neptune, with an entirely different orbit than that of his fellow-probe.

Orbital and physical characteristics. Saturn - the second of four from the Sun gaseous planets of the solar system. He has the same structure as that of Jupiter, and even the same elemental composition: hydrogen and helium.

According to the model of the internal structure of Saturn has a rocky nucleus around which is a layer of metallic hydrogen, and above - a layer of molecular hydrogen and helium, with the lower layers smykayuschiysya atmosphere. One of the features of the planet - is very low, the lowest of all the planets of the solar system density - less than the density of water. One of the confirmation of this fact is in the world, seemingly priplyusnutoy at the poles and is highly inflated at the equator. Polar diameter of almost 10% less than the equatorial.

Saturn is required 29.5 years for a full traffic around the Sun. He is on the average distance from the star in our AE 9.5, that is, 9.5 times further from the Sun than the Earth. At a distance comes a very small amount of sunlight - in 90 times less than the number of light before reaching the planet."


Intrucat engleza este o limba cu influente mult mai mari decat limba rusa, am sa va rog sa incercati sa o folositi.
Pentru texte scrise in alte limbi, va invit sa folositi cu incredere GOOGLE TRANSLATE http://www.google.com/translate_t .
Are 2 optiuni interesante: 1. traducerea integrala a unui text dintr-o alta limba in engleza
                                   2. traducerea completa a unui site dintr-o alta limba in engleza.

Ark

Saturn îºi ascunde inelele!


Saturn, ,,bijuteria sistemului solar", la a cãrui vedere pânã ºi astronomii veterani nu se pot opri sã nu suspine, pare sã-ºi piardã inelele, tendinþa fiind observatã de experþi din întreaga lume.

Ampla sa reþea de inele se concentreazã rapid într-o linie subþire. ,,Inelele s-au îngustat considerabil în cursul anului trecut", explicã Efrain Morales Rivera, un astronom amator din Aguadilla, Puerto Rico. ,,Diviziunea Cassini (o ,,pauzã" neagrã între inele) a devenit foarte greu de vãzut", a adãugat el. Acum aproximativ 400 de ani, acelaºi fenomen l-a uimit ºi pe Galileo.

Privind printr-o lunetã primitivã, el a descoperit inelele lui Saturn în 1610, anunþând imediat lumea despre existenþa unei ,,minuni foarte stranii". Un an mai târziu, el a observat cu o uimire ºi mai mare cã inelele tind sã disparã. În 1612 ele pãreau sã fi dispãrut cu totul, iar Galileo a renunþat sã mai priveascã spre Saturn. De fapt, spun specialiºtii NASA, inelele nu dispar, ci se aºazã într-un plan aproape perpendicular pe cel al observatorilor de pe Terra, fiind deci mai greu de vãzut.

Explicaþia stã în miºcarea de revoluþie a planetei Saturn în jurul Soarelui, fenomenul repetându-se la fiecare 14-15 ani. În clipa de faþã, inelele saturniene continuã sã se ,,subþieze", urmând ca pe 4 septembrie 2009 ele sã fie aproape invizibile. Momentul este ideal, spun astronomii, pentru mai buna observare a sateliþilor lui Saturn, precum ºi a inelelor exterioare mai subþiri, greu de distins în condiþii ,,normale".


sursa: evenimentul zilei

Titan, luna planetei Saturn, ar putea adãposti viaþã


Imaginile radar din timpul misiunii Cassini-Huygens întãresc predicþiile cã sub crusta groasã de gheaþã de pe Titan, satelitul planetei Saturn, ar exista rezerve de apã lichidã.
Dacã acest lucru este confirmat, atunci Titan deþine sursa vieþii - apa ºi moleculele organice.
Anul 2004 a reprezentat începutul misiunii Cassini, când la o primã observaþie s-a crezut cã suprafaþa era acoperitã în totalitate de un strat gros de hidrocarburi. În momentul în care naveta a schimbat poziþia radarului cãtre lunã, în 2004, ºi când sonda Huygens a fost lansatã un an mai târziu, a fost descoperitã o nouã imagine. S-a constatat cã suprafaþa era tare, cu forme geologice sub formã de dune, canale ºi cratere traversate de "râuri" vaste.
Ultimele cercetãri pe Titan aruncã o nouã privire asupra acestor elemente, iar spre surprinderea cercetãtorilor de la NASA, formele geologice nu se mai aflã unde ar fi trebuit.
Datele sugereazã cã modificãrile sezonale ale rotirii satelitului nu pot exista decât dacã sub crusta solidã ar exista un ocean lichid.
Cercetãtorii, conduºi de Dr. Ralph Lorenz de la Johns Hopkins University Applied Physics Laboratory, SUA, spun cã aceste predicþii pot fi verificate în misiuni ulterioare pe Titan.
"Nu ar fi imposibil de crezut cã pe Titan ar putea exista surse de energie, poate energie geotermalã, cum avem pe Pãmânt la fundul oceanelor", a declarat John Zarnecki, profesor de ªtiinþa Spaþiului, la Open University, din Marea Britanie.
Titan este a doua lunã ca mãrime din Sistemul Solar, dupã satelitul lui Jupiter, Ganymede.
Observaþiile din trecut subliniau cã Titan se aseamãnã Pãmântului, în perioada sa de la început, mai ales în ceea ce priveºte componenþa atmosferei. Singura diferenþã este reprezentatã de temperaturile extrem de scãzute de lângã Saturn.

Sursa: bbc.co.uk

Ocean may exist beneath Titan's crust


Cassini has discovered evidence that points to the existence of an underground ocean of water and ammonia on Saturn's moon Titan. The findings were made using radar measurements of Titan's rotation.
"With its organic dunes, lakes, channels and mountains, Titan has one of the most varied, active and Earth-like surfaces in the solar system," said Ralph Lorenz, lead author of the paper and Cassini radar scientist at the Johns Hopkins Applied Physics Laboratory in Maryland, USA. "Now we see changes in the way Titan rotates, giving us a window into Titan's interior beneath the surface."
Members of the mission's science team used Cassini's Synthetic Aperture Radar to collect imaging data during 19 separate passes over Titan between October 2005 and May 2007. The radar can see through Titan's dense, methane-rich atmospheric haze, detailing never-before-seen surface features and establishing their locations on the moon's surface.
Using data from the radar's early observations, the scientists and radar engineers established the locations of 50 unique landmarks on Titan's surface. They then searched for these same lakes, canyons and mountains in the reams of data returned by Cassini in its later flybys of Titan.
They found that prominent surface features had shifted from their expected positions by up to 30 km. A systematic displacement of surface features would be difficult to explain unless the moon's icy crust was decoupled from its core by an internal ocean, making it easier for the crust to move. 

 
Possible liquid ocean beneath Titan's surface
"We believe that about 100 km beneath the ice and organic-rich surface is an internal ocean of liquid water mixed with ammonia," said Bryan Stiles of NASA's Jet Propulsion Laboratory, California, USA. Stiles is a contributing author to the paper reporting the findings.
The study of Titan is a major goal of the Cassini-Huygens mission because it may preserve, in deep-freeze, many of the chemical compounds that preceded life on Earth. Titan is the only moon in the solar system that possesses a dense atmosphere. The moon's atmosphere is 1.5 times denser than Earth's. It is also the largest of Saturn's moons, bigger than the planet Mercury.
"The combination of an organic-rich environment and liquid water is very appealing to astrobiologists," Lorenz said. "Further study of Titan's rotation will let us understand the watery interior better, and because the spin of the crust and the winds in the atmosphere are linked, we might see seasonal variation in the spin in the next few years."
Cassini scientists will not have long to wait before another go at Titan. On March 25, just prior to its closest approach at an altitude of 1000 km, Cassini will employ its Ion and Neutral Mass Spectrometer to examine Titan's upper atmosphere. Immediately after closest approach, the spacecraft's Visual and Infrared Mapping Spectrometer will capture high-resolution images of Titan's southeast quadrant

Notes for editors:

These findings appear in 'Titan's Rotation Reveals an Internal Ocean and Changing Zonal Winds' by R. Lorenz et al. in the March 21 issue of the journal Science.
The Cassini-Huygens mission is a cooperative project of NASA, the ESA and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, USA, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington.
The Cassini orbiter was designed, developed and assembled at JPL. ESA developed the Huygens lander, while ASI managed the development of the high-gain antenna and other instruments of its participation. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.



Cassini 'tastes' organic brew at Saturn's geyser moon

The Cassini spacecraft tasted and sampled a surprising organic brew erupting in geyser-like fashion from Saturn's moon Enceladus during a close flyby on 12 March. Scientists are amazed that this tiny moon is so active, 'hot' and brimming with water vapour and organic chemicals.
New heat maps of the surface show higher temperatures than previously known in the south polar region, with hot tracks running the length of giant fissures. Additionally, scientists say the organics 'taste and smell' like some of those found in a comet. The jets themselves harmlessly peppered Cassini, exerting measurable torque on the spacecraft, and providing an indirect measure of the plume density.
 
Gas and dust jets match up
"A completely unexpected surprise is that the chemistry of Enceladus, what's coming out from inside, resembles that of a comet," said Hunter Waite, principal investigator for the Cassini Ion and Neutral Mass Spectrometer at the Southwest Research Institute in San Antonio. "To have primordial material coming out from inside a Saturn moon raises many questions on the formation of the Saturn system."
"Enceladus is by no means a comet. Comets have tails and orbit the sun, and Enceladus's activity is powered by internal heat while comet activity is powered by sunlight. Enceladus's brew is like carbonated water with an essence of natural gas," said Waite.
The Ion and Neutral Mass Spectrometer saw a much higher density of volatile gases, water vapour, carbon dioxide and carbon monoxide, as well as organic materials, some 20 times denser than expected. This dramatic increase in density was evident as the spacecraft flew over the area of the plumes.
New high-resolution heat maps of the south pole by Cassini's Composite Infrared Spectrometer show that the so-called tiger stripes, giant fissures that are the source of the geysers, are warm along almost their entire lengths, and reveal other warm fissures nearby. These more precise new measurements reveal temperatures of at least minus 93º Celsius. That is 17º warmer than previously seen and 93º Celsius warmer than other regions of the moon. The warmest regions along the tiger stripes correspond to two of the jet locations seen in Cassini images.

"These spectacular new data will really help us understand what powers the geysers. The surprisingly high temperatures make it more likely that there's liquid water not far below the surface," said John Spencer, Cassini scientist on the Composite Infrared Spectrometer team at the Southwest Research Institute in Colorado, USA.
Previous ultraviolet observations showed four jet sources, matching the locations of the plumes seen in previous images. This indicates that gas in the plume blasts off the surface into space, blending to form the larger plume.
Images from previous observations show individual jets and mark places from which they emanate. New images show how hot spot fractures are related to other surface features. In future imaging observations, scientists hope to see individual plume sources and investigate differences among fractures.
"Enceladus has got warmth, water and organic chemicals, some of the essential building blocks needed for life," said Dennis Matson, Cassini project scientist at NASA's Jet Propulsion Laboratory in California, USA. "We have quite a recipe for life on our hands, but we have yet to find the final ingredient, liquid water, but Enceladus is only whetting our appetites for more."
At closest approach, Cassini was only about 48 km from Enceladus. When it flew through the plumes it was about 193 km from the moon's surface. Cassini's next flyby of Enceladus is in August.
Notes for editors:

The Cassini-Huygens mission is a cooperative project of NASA, the ESA and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, USA, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington.
The Cassini orbiter was designed, developed and assembled at JPL. ESA developed the Huygens lander, while ASI managed the development of the high-gain antenna and other instruments of its participation. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.



Planet in Progress? Evidence Of A Huge Planet Forming In Star System

Astrophysicists have a new window into the formation of planets. Ben R. Oppenheimer, Assistant Curator in the Department of Astrophysics at the American Museum of Natural History, and colleagues have imaged a structure within the disk of material coalescing from the gas and dust cloud surrounding a well-studied star, AB Aurigae. Within that structure, it appears that an object is forming, either a small body currently accreting dust or a brown dwarf (a body intermediate between stars and planets) between 5 and 37 times the mass of Jupiter. The observations, accepted for publication in the Astrophysical Journal, represent a significant step toward direct imaging and study of exoplanets (planets orbiting stars other than the Sun), and may bear on theories of planet and brown dwarf formation.
Young stars generally have material widely spread around them that organizes itself into a disk over time. Astronomers believe that this is where planets form. The new image, which is sensitive to the dust around the star but not starlight, shows a horseshoe-shaped structure orbiting AB Aurigae with two denser, brighter clumps of material in a ring around the star next to a darker area. This darker area, a structure relatively depleted of widespread material previously predicted in models of planet formation but never seen before, is thought to be the point at which material is coalescing into a planet or brown dwarf.
Further imaging of this area shows a barely visible spot dead center, a spot too bright to be light reflected off a formed planet but consistent with an object in the process of development that is accreting new material. The two brighter clumps, equidistant from the hole and presumably trailing and leading it in its orbit around the star, seem similar to the Trojan objects that orbit the Sun along with Jupiter. Such a structure has been predicted to form in disks where a planet is present, because of the gravitational interaction between the planet and the star it orbits.
"The deficit of material could be due to a planet forming and sucking material onto it, coalescing into a small point in the image and clearing material in the immediate surroundings. This would look like a hole in the disk," says Oppenheimer. "We are seeing something happening in the disk that seems to be indicative of the formation of a small body, either a planet or a brown dwarf."
Finding planets outside of our solar system is a new phenomenon. It is only in the last 15 years that nearly 300 extrasolar planets have been identified around distant stars. Most of these objects are more massive than Jupiter, orbit very close to their stars, and are identified by indirect methods such as the wobble created by the gravitational pull. None of the known exoplanets have yet been imaged or seen directly, because the light of a star overwhelms the faint glow of a nearby planet.
Oppenheimer and his colleagues circumvented this glare by attaching a coronagraph to a unique U.S. Air Force telescope on Maui, Hawaii. The telescope compensates for turbulence in the Earth's atmosphere, permitting extremely high image quality from the ground. The Lyot Project coronagraph, built on a floating table in a clean-room optics lab at the Rose Center for Earth and Space at the Museum and named for the French astronomer who invented solar coronagraphy, blocks light from the center of the image of a nearby star to reveal faint objects around it. Stellar coronagraphs have been routinely used for several decades, but the Lyot Project's is more precise and exceeds the resolution of the Hubble Space Telescope.
Oppenheimer's team used additional polarization filters to detect even fainter objects much closer to the star than previously possible. Polarization selects light scattered off the disk, distinguishing it from the light of the star, which is not generally polarized. The technology enabled the team to see the disk of material around AB Aurigae with unprecedented sensitivity. Objects up to 100,000 times fainter than and just half an arcsecond from the star (an angle about 100 times finer than the human eye can discern) could be imaged. This is thousands of times better than other instruments.
AB Aurigae is well-studied because it is young, between one and three million years old, and can therefore provide information on how stars and objects that orbit them form. One unresolved question about planet formation is how the initial thick, gas-rich debris disk evolves into a thin, dusty region with planets. The observation of stars slightly older than AB Aurigae shows that at some point the gas is removed, but no one knows how this happens. AB Aurigae could be in an intermediate stage, where the gas is being cleared out from the center, leaving mainly dust behind.

"More detailed observations of this star can help solve questions about how some planets form, and can possibly test competing theories," says Oppenheimer. "And if this object is a brown dwarf, our understanding of them must be revamped."  Brown dwarfs have been found orbiting stars since a team (which included Oppenheimer) first discovered one in 1995, but they are not believed to form in circumstellar material.
The team contributing to this research included Douglas Brenner, Anand Sivaramakrishnan, and Remi Soummer of the Department of Astrophysics, AMNH; Sasha Hinkley and Neil Zimmerman of the Department of Astronomy, Columbia University; Jeffrey Kuhn and David Harrington of the Institute for Astronomy, University of Hawaii; James Graham and Marshall Perrin of the Department of Astronomy, University of California at Berkeley; James Lloyd of the Department of Astronomy, Cornell University; and Lewis Roberts of the Boeing Company, now at NASA's Jet Propulsion Laboratory.
The research was funded in part by the National Science Foundation, NASA's Terrestrial Planet Finder Program, and individual donors. The U.S. Air Force provided access to the AEOS telescope and significant financial support for the project.
This depleted region and the denser clumps near the ends of the white guide lines seem to indicate the formation of a small body within the depleted region. The scale of the image is indicated by the arrow, which corresponds to about 300 times the distance between the Earth and Sun. The orbit of a planet like Neptune, if it were orbiting this star, would be at the edge of the black circle on this scale.



Oamenii de ºtiinþã au descoperit cel mai mare meteorit care a lovit Marea Britanie

S-a izbit de pãmânt cu o vitezã de 61142 km/h ºi a explodat la impact cu forþa a 1000 de bombe nucleare.
Meteoritul a cãzut în nord-vestul Scoþiei în urmã cu 1,2 miliarde de ani. Totuºi, abia de curând, oamenii de ºtiinþã au descoperit punctul de impact, care mãsura aproape un kilometru în diametru ºi unde s-a format un crater de peste 12 kilometri lãrgime.
Ken Amor, de la Departamentul de Studii ale Pãmântului al Universitãþii Oxford, a declarat: "Este cea mai spectaculoasã dovadã a impactului unui meteorit în Insulele Britanice".


Un meteorit cãzut în Peru dã peste cap teoriile cercetãtorilor
Cercetãtorii au anunþat cã un meteorit care a cãzut în luna septembrie în Peru se deplasa mai repede ºi a lovit pamântul mai puternic decât se aºteptau.
Meteoritul, care a fãcut un crater de 15 metri, avea o structurã din rocã ºi ar fi trebuit sã se dezintegreze cu mult înainte de a atinge Pamântul, a declarat Peter Schultz, profesor la Universitatea Brown din Rhode Island.
În general, doar meteoriþii din metal ating suprafaþa Pamântului intacþi, sãpând un crater. Cei din rocã intrã în atmosferã, încetinesc ºi explodeazã, ceea ce poate forma o gaurã în sol, ca un puþ, dar nu un crater.
Acest meteorit s-a deplasat cu o vitezã de 40-50 de ori mai mare faþã de cea normalã ºi a aterizat pe terenul unui râu secat, gaura formatã umplându-se de apã subteranã.
Dupã Schultz, în urma cercetãrilor fãcute de echipa sa, ar trebui rediscutatã teoria lovirii planetelor de cãtre obiecte strãine.


În Spania au fost descoperite fosile umane vechi de 1,2 milioane de ani

Omul a apãrut pe continentul european cu mult mai mult timp înainte decât se credea pânã acum. Dovada în acest sens au adus-o paleoantropologii spanioli, care au publicat date privind descoperirea unor fosile umane vechi de aproximativ 1,2 milioane de ani.
Savanþii au descoperit într-o peºterã situatã în apropiere de oraºul Burgos, din nordul Spaniei, o mandibulã, câþiva dinþi ºi câteva unelte rudimentare din cremene. Aceste fosile au fost datate ca fiind mai vechi cu 400.000 de ani decât cele descoperite în apropiere cu 14 ani în urmã.
Ele sunt similare celor descoperite la Atapuerca în 1994 ºi aduc noi argumente în sprijinul ipotezei potrivit cãreia fiinþele umane apãrute în Africa au venit în Europa nu prin strâmtoarea Gibraltar, ci prin Orientul Mijlociu.
Mandibula descoperitã lângã Burgos seamãnã cu un fragment fosil similar din Georgia, datat cu circa 1,7 milioane de ani în urmã. Mai mult, ele duc la o nouã teorie: cãlãtoria strãmoºilor omului dinspre continentul negru spre celelalte regiuni ale lumii a început cu aproape douã milioane de ani în urmã, ºi nu cu doar 50.000, cum se credea.




Un craniu gãsit în România ar putea schimba teoriile despre omul de Neanderthal

Un craniu cu o vechime de 40.000 de ani, gãsit în Peºtera cu Oase din sud-vestul României, are atât trãsãturile omului modern, cât ºi pe cele ale unui om de Neanderthal. Craniul ar putea demonstra cã aceºtia ar fi putut interacþiona, înainte ca ultimul sã disparã, potrivit Reuters.
Dacã descoperirile vor fi confirmate, craniul va reprezenta cea mai veche descoperire a rãmãºiþelor unui om modern, în Europa.
Craniul are multe din trãsãturile unui om modern, dar este ºi un pic mai îndesat decât cei mai mulþi dintre aceºtia ºi are molarii superiori foarte mari, trãsãturã specificã mai ales celor de Neanderthal.
Studiul despre descoperire, publicat de revista "Proceedings of the National Academy of Sciences" (PNAS), vine în contextul unei dezbateri legate de douã ipoteze: Homo sapiens, omul modern, ºi-a omorât pur ºi simplu "verii" de Neanderthal sau Ei au interacþionat mai întâi.
Mulþi cercetãtori cred cã neanderthalienii au dispãrut din cauza schimbãrilor climatice sau din cauza competiþiei cu humanoizii moderni. Dar alþii considerã cã aceºtia s-au încruciºat cu nou-veniþii ºi au contribuit la tezaurul genetic al omului modern.


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