| Piú viste - Asteroids and Comets |
Eros-NP-PIA02498.jpgThe North Pole of Eros58 visiteCaption NASA originale:"For a long time, imaging activities on the NEAR Shoemaker spacecraft have focused on the high northern latitudes of Eros. The point at which the Sun is directly overhead - known as the "subsolar point" - has been steadily moving from Eros' Northern Regions toward the equator as the asteroid's seasons progress. As this happens, the Northern Hemisphere is illuminated less and less and previously dark southern latitudes progressively come into view. In this image, taken March 19, 2000, from a range of 205 Km (approx. 127 miles), the asteroid's North Pole is in the upper right of the frame. The whole scene is 7,4 Km (approx. 4,6 miles) across".
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Eros-PIA02499.jpgA deep impact on Eros means short daylight hours...58 visiteCaption NASA originale:"For people who live in mountain valleys, daylight can be a short-lived experience. Mountains to the east make the Sun rise later in the morning, while mountains to the west make the Sun set earlier in the evening. The brevity of daytime in a valley is accentuated during the shortened days of winter. The floor of the 5,5-Km (3,4-mile) diameter impact crater that dominates one face of Eros experiences the ultimate in short daylight hours. Three factors conspire to make this true. Firstly, Eros rotates rapidly, once every 5,27 hours. Secondly, the crater's 0,9-Km (0,56-mile) high walls tend to block direct sunlight from the floor, even while the outside of the crater is illuminated. Thirdly, during the current season on Eros, the Sun never makes it high in the sky in this location".
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Asteroids_from_HST-01.jpgAsteroids, from HST (2)58 visite"Many asteroids remain undiscovered. In fact, 1 was discovered in 1998 as the long blue streak in the above archival image taken by the Hubble Space Telescope. In 2002 June, the small 100-mt asteroid 2002 MN was discovered only after it whizzed by the Earth, passing well within the orbit of the Moon. 2002 MN passed closer than any asteroid since 1994 XM1 but not as close as 2004 MN4 will pass in 2029. A collision with a large asteroid would not affect Earth's orbit so much as raise dust that would affect Earth's climate. One likely result is a global extinction of many species of life, possibly dwarfing the ongoing extinction occurring now".
Dopo aver letto questi commenti la nostra memoria ritorna allo tsunami del Dicembre 2004 ed al paventato spostamento dell'asse terrestre: l'ipotesi più plausibile per spiegare l'accaduto sembra essere proprio quella che la NASA stessa ci suggerisce commentando questi frames HST: un asteroide di circa 100 metri potrebbe aver impattato l'Oceano Indiano.
C'è da riflettere.
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Tempel1-r-ImpactConfirmation.jpgDeep-impact...58 visiteTime of Impact: July 4, 05:52:15.0 +/- 17 sec UT as seen from Earth (1-sigma uncertainty)
Impact successfully occurred on July 4 at 05:52:24 UT as seen from Earth
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Tempel1-W.jpgDeep-impact...13 seconds after collision!58 visiteCaption NASA originale:"This image shows the initial ejecta that resulted when NASA's Deep Impact probe collided with comet Tempel-1 at 10:52 p.m. Pacific Time, July 3 (1:52 a.m. Eastern time, July 4). It was taken by the spacecraft's high-resolution camera 13 seconds after impact. The image has been digitally processed to better show the comet's nucleus".
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Tempel1-XX-HRI_937_1.jpgDeep-impact...67 seconds after collision!58 visitecaption NASA originale:"This spectacular image of comet Tempel 1 was taken 67 seconds after it obliterated Deep Impact's impactor spacecraft. The image was taken by the HR camera on the mission's flyby craft. Scattered light from the collision saturated the camera's detector, creating the bright splash seen here. Linear spokes of light radiate away from the impact site, while reflected sunlight illuminates most of the comet surface. The image reveals topographic features, including ridges, scalloped edges and possibly impact craters formed long ago".
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Tenth_Planet-00.jpgThe 10th Planet? (1)58 visiteDa "NASA - Picture of the Day", del 31 Luglio 2005:"Is that a Tenth Planet? A faint, slowly moving dot discovered by computer shows clear signs of being a deep Solar System object at least as large as Pluto. The object, designated 2003 UB313, is currently situated nearly 100 times the Earth-Sun distance - over twice the average Pluto-Sun distance. That far out, the only way a single round object could be as bright as 2003 UB313 would be if it is at least as large as Pluto and completely reflective.
Since 2003 UB313 is surely not completely reflective, it could be substantially larger. One of the discovery frames is shown above digitally expanded and artificially brightened. 2003 UB313 was identified initially on frames taken by the automated 1.2-meter Samuel Oschin Telescope at Palomar Observatory in California, USA".
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Asteroids-Sylvia_compo680.jpg87 Sylvia and the Founders of Rome58 visiteDa "NASA - Picture of the Day" del 17 Agosto 2005:"Discovered in 1866, Main Belt Asteroid 87 Sylvia lies 3.5 AU from the Sun, between the orbits of Mars and Jupiter. Also shown in recent years to be one in a growing list of double asteroids, new observations during August and October 2004 made at the Paranal Observatory convincingly demonstrate that 87 Sylvia in fact has two moonlets - the first known triple asteroid system. At the center of this composite of the image data, potato-shaped 87 Sylvia itself is about 380 Km wide. The data show inner moon, Remus, orbiting Sylvia at a distance of about 710 Km once every 33 hours, while outer moon Romulus orbits at 1360 Km in 87,6 hours. Tiny Remus and Romulus are 7 and 18 Km across respectively. Because 87 Sylvia was named after Rhea Silvia, the mythical mother of the Founders of Rome, the discoverers proposed Romulus and Remus as fitting names for the two moonlets (...)".
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Itokawa.gifAsteroid "Itokawa": a new "shooting" against a Celestial Body58 visiteJapan's JAXA Space Agency launched the Hayabusa Mission to rendezvous with asteroid Itokawa. Last week, the small robotic Hayabusa spacecraft arrived at asteroid Itokawa and stationed only 20 Km away. Although a long term goal is to find out how much ice, rock and trace elements reside on the asteroid's surface, a shorter term goal is to determine the mass of the asteroid by measuring the attraction of the drifting Hayabusa spacecraft. During the next few months, Hayabusa will also image and map asteroid Itokawa. The above time-lapse image sequence was taken by Hayabusa upon final approach, showing the general oblong shape of the asteroid. In November, a small coffee-can sized robot dubbed MINERVA is scheduled for release and is expected to hop around the asteroid taking pictures. Also in November, Hayabusa will fire pellets into asteroid Itokawa and collect some of the debris in a return capsule. In December, Hayabusa will fire its rockets toward Earth and drop the return capsule in June 2007.
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Itokawa~0.jpgClosing on Itokawa58 visiteItokawa: un asteroide che sembra contraddire tutto quanto viene dato per acquisito nel campo delle forme esteriori e dei rilievi superficiali dei corpi (teoricamente) esposti a pesantissimi azioni di impatto sin dagli albori della loro esistenza. Pensate a 433-Eros, oppure a Ceres, o Dactyl o a qualsiasi altro corpo similare che abbiamo avuto occasione di vedere da distanza ravvicinata. Forse il solo asteroide AnneFrank non sembra presentare una particolare craterizzazione (ma le immagini, di cattiva qualità, non possono essere considerate definitorie) e quindi si viene a porre nel novero delle rarità. Tuttavia, quello che vediamo adesso, è ben più che un'eccezione e molto di più di un'Anomalìa: Itokawa NON ha alcun cratere superficiale visibile e le sue forme, spigolose ed a tratti aguzze, costituiscono una novità assoluta per i Ricercatori e gli Studiosi di Scienze Planetarie.
Original caption:"Where are the craters on asteroid Itokawa? No one knows. The Japanese robot probe Hayabusa recently approached the Earth-crossing asteroid and is returning pictures showing a surface unlike any other Solar System body yet photographed -- a surface possibly devoid of craters. One possibility for the lack of common circular indentations is that asteroid Itokawa is a rubble pile -- a bunch of rocks and ice chunks only loosely held together by a small amount of gravity. If so, craters might be filled in whenever the asteroid gets jiggled by a passing planet -- Earth in this case. Alternatively, surface particles may become electrically charged by the Sun, levitate in the microgravity field, and move to fill in craters. Over the weekend, Hayabusa lowered itself to the surface of the strange asteroid in an effort to study the unusual body and collect surface samples that could be returned to Earth in 2007".
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Itokawa-04.jpgOrbiting around Itokawa (1)58 visiteHayabusa arrived at its exploration target, near Earth asteroid Itokawa, on Sept., 12th, 2005 after having been propelled there via ion engines and an Earth swing-by. Since then, it has successfully performed orbital maneuvers, precisely keeping its position relative to Itokawa. The Hayabusa Project Team has made many discoveries while carrying out their ambitious scientific observations of Itokawa. This release summarizes and reports the major scientific and engineering achievements in advance of Hayabusa’s unprecedented and historic descent to the surfaceof Itokawa for sample collection middle to later this month (November 2005).
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Itokawa-06.jpgOrbiting around Itokawa (3)58 visiteSpecifically, at the time of arrival at Itokawa, Hayabusa had driven its proprietary new ion engines for 26.000 hours, including their operation during an Earth flyby.
It has also perfectly completed a period of hybrid optical navigation followed by
precise guidance and navigation of the spacecraft during its station keeping period around Itokawa.
These engineering achievements are the primary mission of Hayabusa and their successful completion is a great achievement.
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