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| Piú viste - Artistic Views of the Solar System |
Flash-PIA02108.jpgFlash!!!108 visiteThis image shows a flash produced in a laboratory by a high-velocity bead slamming into dust. Though the flash itself can't be resolved, its brilliant effects can be seen in this three-second time exposure. Scientists say that the collision between Deep Impact's Impactor and comet Tempel 1 may produce a similar flash.
This flash occurred when a quarter-inch sphere smashed into powdered dust at a speed of 6,4 Km-per-second (about 4 miles-per-second).
Even though the actual flash lasted less than 50 millionths of a second, the camera recorded the hot debris in the impact crater (center) and the streaking ejecta.
This experiment was performed at NASA's Ames Research Center, Moffett Field, Ca.
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Huygens to Titan-IMG001244-br500.jpgHuygens probe's going to Titan107 visiteAn artist's concept of the European Space Agency's Huygens Probe en route to Titan after release from the NASA Cassini orbiter.
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Titan-PIA11001.jpgEthane Lake on Titan106 visiteNASA scientists have concluded that at least one of the large lakes observed on Saturn's moon Titan contains liquid hydrocarbons, and have positively identified the presence of ethane. This makes Titan the only body in our solar system beyond Earth known to have liquid on its surface.
Scientists made the discovery using data from an instrument aboard the Cassini spacecraft. The instrument identified chemically different materials based on the way they absorb and reflect infrared light. Before Cassini, scientists thought Titan would have global oceans of methane, ethane and other light hydrocarbons. More than 40 close flybys of Titan by Cassini show no such global oceans exist, but hundreds of dark, lake-like features are present. Until now, it was not known whether these features were liquid or simply dark, solid material.
"This is the first observation that really pins down that Titan has a surface lake filled with liquid," said Bob Brown of the University of Arizona, Tucson. Brown is the team leader of Cassini's visual and mapping instrument. The results will be published in the July 31 issue of the journal Nature.
Ethane and several other simple hydrocarbons have been identified in Titan's atmosphere, which consists of 95 percent nitrogen, with methane making up the other fiver percent. Ethane and other hydrocarbons are products from atmospheric chemistry caused by the breakdown of methane by sunlight.
Some of the hydrocarbons react further and form fine aerosol particles. All of these things in Titan's atmosphere make detecting and identifying materials on the surface difficult, because these particles form a ubiquitous hydrocarbon haze that hinders the view. Liquid ethane was identified using a technique that removed the interference from the atmospheric hydrocarbons.
The visual and mapping instrument observed a lake, Ontario Lacus, in Titan's south polar region during a close Cassini flyby in December 2007. The lake is roughly 20,000 square kilometers (7,800 square miles) in area, slightly larger than North America's Lake Ontario.
"Detection of liquid ethane confirms a long-held idea that lakes and seas filled with methane and ethane exist on Titan," said Larry Soderblom, a Cassini interdisciplinary scientist with the U.S. Geological Survey in Flagstaff, Ariz. "The fact we could detect the ethane spectral signatures of the lake even when it was so dimly illuminated, and at a slanted viewing path through Titan's atmosphere, raises expectations for exciting future lake discoveries by our instrument."
The ethane is in a liquid solution with methane, other hydrocarbons and nitrogen. At Titan's surface temperatures, approximately 300 degrees Fahrenheit below zero, these substances can exist as both liquid and gas. Titan shows overwhelming evidence of evaporation, rain, and fluid-carved channels draining into what, in this case, is a liquid hydrocarbon lake.
Earth has a hydrological cycle based on water and Titan has a cycle based on methane. Scientists ruled out the presence of water ice, ammonia, ammonia hydrate and carbon dioxide in Ontario Lacus. The observations also suggest the lake is evaporating. It is ringed by a dark beach, where the black lake merges with the bright shoreline. Cassini also observed a shelf and beach being exposed as the lake evaporates. "During the next few years, the vast array of lakes and seas on Titan's north pole mapped with Cassini's radar instrument will emerge from polar darkness into sunlight, giving the infrared instrument rich opportunities to watch for seasonal changes of Titan's lakes," Soderblom said.
More information is available at: http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and http://wwwvims.lpl.arizona.edu .
MareKromium
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Mars Express-PIA04802_modest.jpgMars Express105 visitenessun commento
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Mars.jpgEarth and Mars, soon closer than ever!103 visiteThe Red Planet is about to be spectacular again. In October and November 2005, Earth is catching up with Mars in an encounter that will culminate in a new close approach between the 2 planets.
The next time Mars may come this close is in AD 2287. Due to the way Jupiter's gravity tugs on Mars and perturbs its orbit, astronomers can only be certain that Mars has not come this close to Earth in the last 5000 years, but it may be as long as 60.000 years before it happens again. The encounter will culminate on October 30th.
By late October, Mars will be a bright star-like object in the sky and therefore very easy to spot.
Nota: le informazioni pubblicate in precedenza erano riferite al "contatto ravvicinato" Terra/Marte dell'AD 2003.
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Titan-IMG001958-br500.jpgHuygens' Landing Site103 visiteThis is an artist's interpretation of the area surrounding the Huygens Landing Site, based on images and data returned on Jan. 14, 2005.
On January 14, 2005, the European Space Agency's (ESA) Huygens Probe reached the upper layer of Titan's atmosphere and landed on the surface after a parachute descent 2 hours and 28 minutes later.
As part of the joint NASA/ESA/ASI mission to Saturn and its Moons, the Huygens Probe was sent from the Cassini spacecraft to explore Titan, Saturn's largest moon. Titan's organic chemistry may be like that of the primitive Earth around 4000 MY ago, and it may hold clues about how life began on our Planet.
Nota: permetteteci un piccolo commento su questo "grande successo". Di dati significativi sull'ambiente di Titano (p.e.: temperature medie nel ciclo giorno/notte; presenza o meno di venti; presenza o meno di polveri in sospensione; componenti primari dell'atmosfera a varie altitudini etc.), ad oggi, non ci pare ne sìano emersi. A parte qualche "sembra" e qualche "si sta ancora studiando" non c'è ancora nulla di solido su cui lavorare (o almeno speculare). E questo per non dire delle fotografie di Titano al suolo: dovevano dirci tanto. Alla fine, quelle poche (ed orrende) immagini ricevute non ci hanno detto assolutamente niente.
La "Discesa dell'Europa su Titano" (come si scrisse in tono trionfalistico un anno fa - per poi dimenticare tutto in 24 ore...) fu dunque vera gloria?
Ai posteri l'ardua sentenza...
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Toutatis.jpgEarth from the asteroid "Toutatis"102 visiteOn September 29, 2004, the Earth came within 1 million miles of the asteroid Toutatis - the closest predicted approach of our fair planet to a sizable asteroid or comet in this century. Coming within 1 million miles (or about 4 times the Earth-Moon distance), Earth would appear to be nearly the size of the full moon in the asteroid's sky, as suggested in this illustration. In Earth's sky, Toutatis appeared only as a faint object rapidly moving against a background of stars. Also known as Earth-Crossing Asteroid (ECA) 4179, Toutatis is in an eccentric 4 year orbit which moves it from the asteroid belt between Mars and Jupiter to just inside Earth's orbit. When the Earth passed near it in 1992 Toutatis was imaged by radar and seen to be 2 irregularly shaped lumps, perhaps joined by a narrow neck. This bizarre object is about 3 Km wide, 5,5 Km long and is tumbling through space. Studies of Toutatis and other ECA's help reveal connections between the Solar System's meteorites main-belt asteroids and comets.
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Voyagers-Heliosphere3b.jpgThe "Voyagers" at the Final Frontier100 visiteVoyager 1 and 2 are still going strong and are returning valuable science data. Each Voyagers' Cosmic Ray Detector, Magnetometer, Plasma Wave Detector and Low-Energy Charged Particle Detector all still operational. In addition, the Ultraviolet Spectrometer on Voyager 1 and the Plasma Science instrument on Voyager 2 continue to return data. Both spacecraft are expected to continue to operate and send back valuable data until at least the year 2020.
The mission currently employs the equivalent of about 10 full-time people at JPL, significantly less than the approximately 300 during the height of its famed "Grand Tour" of the planets through 1989. Only two veterans of the Voyager launches still work on the flight team. Some of the summer interns the team has employed were not even born when the spacecraft were launched. The project scientist, Dr. Ed Stone of the California Institute of Technology has been with the mission since inception and two original principal investigators - Dr. Stamatios Krimigis of the Applied Physics Laboratory and Dr. Norman Ness of the University of Delaware - remain.
During the journey, the Voyagers flew by Jupiter, Saturn, Uranus and Neptune and returned nearly 80 thousand images and more than 5 trillion bits of data. After traveling through space for more than 27 years, Voyager 1 is now more than 14 billion kilometers (94 AU) from the Sun, heading in a northerly direction toward interstellar space. Voyager 2, closer at about 11 billion kilometers (75 AU), is headed on a southerly path toward interstellar space. Voyager 1 is now the furthest human-made object from the Sun, having surpassed Pioneer 10 on February 17, 1998.
Since the beginning of the Interstellar Mission in 1990, the two spacecraft have returned well more than 65 billion bits of data, though at lower data rates than during the Grand Tour. The data continue to reveal new characteristics of the effects of the sun in the distant solar wind. As an example, a Coronal Mass Ejection (CME) shock wave from the October 2003 solar storms was detected at Voyager 2 in mid-April 2004. Some of the most powerful flares in recorded history hurled billion-ton clouds of gas, called coronal mass ejections (CMEs), into the solar system. By the time the resulting shocks reached Voyager 2, about 6 months later, they had combined into Merged Interaction Regions and had slowed considerably. Traveling at 600 km/sec, it had slowed considerably from the 1500-2000 km/sec detected last Fall as the storms left the Sun. Voyager 2 measured the speed of the shock, its composition, temperature and magnetism. When combined with measurements from SOHO, Mars Odyssey, Ulysses, Cassini and other spacecraft, the Voyager data show how far-ranging CMEs evolve and dissipate.
For the past two years or so, Voyager 1 has detected phenomena unlike any encountered before in all its years of exploration. These observations and what they may infer about the approach to the termination shock have been the subject of on-going scientific debates. While some of the scientist believed that the passage past the termination shock had already begun, some of the phenomena observed were not what would have been expected. So the debate continues while even more data are being returned and analyzed. However, it is certain that the spacecraft are in a new regime of space. The observed plasma wave oscillations and increased energetic particle activity may only be the long-awaited precursor to the termination shock. If we have indeed encountered the termination shock, Voyager 1 would be the first spacecraft to enter the solar system's final frontier, a vast expanse where wind from the Sun blows hot against thin gas between the stars: interstellar space.
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Mars-B.jpgMars, SOME time ago...100 visitenessun commento
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Mars~1.jpgNot too close, not too far...98 visitenessun commento
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Titan-IMG001293-br500.jpgHuygens is landed on Titan!97 visitenessun commento
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Titan - artwork.jpgHuygens on Titan96 visiteThin methane clouds dot the horizon and a narrow methane spring or "methanefall" flows from the cliff at left and drifts mostly into vapor. Smooth ice features rise out of the methane/ethane lake, and crater walls can be seen far in the distance.
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