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LLR-Itokawa-Impacts.jpgThe Craters of Itokawa75 visiteBravissimo, come sempre anche lui, il Dr Marco Faccin il quale, attraverso questo splendido e suggestivo collage, ci mostra e dimostra che, in fondo, NON E' VERO che sul piccolo Asteroide Itokawa non ci sono crateri.
Ci sono, eccome: non molti (e difficilmente discernibili), ma ci sono.
E come mai esistono dei crateri su un mondo che, a parere della NASA, dovrebbe avere una "consistenza" (rectius: densità) bassissima; tanto bassa da farlo risultare, alla fine, come un "mucchio di detriti spaziali tenuti gravitazionalmente assieme"? Un mondo che, laddove impattato da un macigno vagante, dovrebbe - semplicemente - andare in pezzi?
Ebbene la risposta è duplice e (relativamente) facile, a nostro avviso:
1) l'impatto fra Itokawa ed un corpo vagante di dimensioni ridottissime e/o avente una densità bassissima si potrebbe risolvere tranquillamente nella creazione di un cratere poco profondo e di piccole dimensioni;
2) le stime NASA sulla densità di Itokawa sono errate e questo piccolo asteroide - al pari di innumerevoli altri - è un grande macigno errante il quale può sopportare con relativa tranquillità gli impatti con altri corpi vaganti rocciosi e compatti, purchè aventi dimensioni (comunque) modeste.
Avete altre idee? Scriveteci! ...E, per adesso, GRANDI complimenti al bravissimo Dr Faccin!MareKromium
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LLR-Itokawa-ST_2485860275_v.jpgItokawa: the First (and, so far, the only) "Space Potato" (MULTISPECTRUM; credits: Lunexit)54 visitenessun commentoMareKromium
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Lutetia-01.jpgAsteroid "Lutetia"65 visiteAsteroid Lutetia will no longer remain a mystery as the European Space Agency's (ESA) Rosetta has captured the first close-up images of this Celestial Body, which will help them gain insights into the composition of the space rock that has long puzzled the scientists.
In what can be termed as the closest encounter with one of the largest asteroid, ever visited ESA led robotic spacecraft mission, Rosetta, raced past Lutetia as close as 3200 Km, with the closest encounter at 18:10 CEST (Central Europe Standard Time), when the spacecraft was just 3162 Km away from the giant asteroid.
Rosetta, which had a first look of Lutetia in January 2007, has this time “triumphed at asteroid” and captured images like never before.MareKromium
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Lutetia-02.jpgAsteroid "Lutetia"61 visiteThough the first look of the giant asteroid, through nearly 400 images, has revealed a lot about the primitive survivor's cratered surface, a lot more needs to be unlocked.
The data collected by Rosetta Spacecraft, with the help of multi-wavelength cameras, spectrometers etc., will unravel the mysteries surrounding the composition of Lutetia. Some asteroids are a broken part of iron-rich cores of proto-planets or they may just be composed of Carbon.MareKromium
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Lutetia-03.jpgAsteroid "Lutetia"54 visiteA closer look at the asteroid that orbits between Mars and Jupiter reveals that Lutetia's Surface is battered with many craters, indicating that during the 4,5 BY (Billion Years) of existence, the primitive survivor has suffered many impacts.
The information gathered also confirm that Lutetia, discovered by French painter turned astronomer Hermann Goldschmidt in 1852, is approx. 100 Km in diameter, has a elongated body, and its longest side measures about 130 Km.
In a statement, David Southwood, ESA Director of Science and Robotic Exploration, said:“It has been a great day for exploration, a great day for European science. The clockwork precision is a great tribute to the scientists and engineers in our Member States in our industry and, not least, in ESA itself”.MareKromium
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Lutetia-04-PCF-LXTT.jpgAsteroid "Lutetia" (possible Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)98 visiteMareKromium
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Lutetia-05-CTX-EDM-PCF-LXTT-IPF.jpgAsteroid 21-Lutetia (CTX Frame and EDM - Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)150 visite21 Lutetia is a relatively large Main-Belt Asteroid, measuring about 100 Km in diameter (approx. 120 km along its Major Axis). It was discovered in the AD 1852 by the French-German Astronomer Hermann Goldschmidt, and is named after Lutetia, such as the Latin name of the city that stood where Paris was later built. The Asteroid 21 Lutetia has an irregular shape and is heavily cratered, with the largest Impact Crater reaching about 45 Km in diameter.
The Surface of this Asteroid is geologically heterogeneous and it is intersected by a system of Grooves and Scarps, which are thought to be the external manifestation of deep, internal, Fractures; it also possess an high Average Density, which could have meant that is (likely) made of Iron and Nickel rich Rock (even though, as we shall better see later on, this - however logical - claim, is still unproven). The ESA - Rosetta Probe passed as close as about 3162 Km (approx. 1965 miles) from 21 Lutetia in July 2010 and, at the time of Rosetta's Fly-By, it was the largest Asteroid ever visited by a Spacecraft (that, until the NASA - Dawn Spaceraft arrived at 4 Vesta, in July 2011).
The composition of 21 Lutetia has puzzled astronomers for some time, and that is because, while classified among the M-type Asteroids, most of which are Metallic (better yet: rich of Metallic Minerals/Elements), 21 Lutetia must be one of the so-called Anomalous Members of this classification, since it does not display much evidence of Metallic Minerals on its Surface. As a matter of fact, after most part of the data received from the Rosetta Probe were analyzed, several indications of a NON-Metallic Surface of this Asteroid were found, like, for instance, a flat, Low Frequency Spectrum (similar to that of Carbonaceous Chondrites and C-type Asteroids - which is, of course, deeply different from the one of the so-called Metallic Meteorites, such as those Meteorites which are logically believed to derive from a Metallic - such as, we repeat, Iron and Nickel-rich - Celestial Body), a low Radar Albedo (unlike the high Albedoes of Strongly Metallic Asteroids, like 16 Psyche), evidence of Hydrated Materials on its Surface, abundant Silicates, and a thicker layer of Regolith than most of the other known (as far as their composition is concerned) Asteroids.MareKromium
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MATHILDE_FLY-BY.gifMathilde (NEAR Probe Fly-By)55 visiteGuardate bene: osservate il "main crater" di Mathilde, così (enorme-mente) simile allo Stickney Crater di Phobos e poi, se volete, provate a pensare...Crateri troppo grandi, per mondi troppo piccoli!
Che ne dite?MareKromium
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Man-Made_Nebula.gifMan-Made Nebula, such as: a warning sign of the Kessler Syndrome (GIF Movie)76 visiteCaption NASA:"What's that cloud drifting in space? It's not an astronomical nebula because...those appear to stay put.
Atmospheric clouds don't look like this.
The answer to last week's sky mystery turned out to be orbiting and expanding debris from the upper stage of a failed Russian rocket that exploded unexpectedly. The cloud became visible to unaided southern hemisphere observers, and its cause was initially unknown. The above time lapse movie shows the cloud drifting as seen from Australia. Streaks in and near the cloud are likely large pieces of debris. The debris cloud is more than an astronomical curiosity -- particles from this cloud and others could become projectiles damaging existing satellites. As the cloud disperses, many particles will fall to Earth, but many more may help make low Earth orbit an increasingly hostile environment".MareKromium
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Mathilde-PIA02479.jpgMathilde69 visiteCaption NASA originale:"Two different views of asteroid 253 Mathilde were obtained by the NEAR spacecraft on June 27, 1997. The image at left was obtained as the spacecraft approached Mathilde with its camera pointed near the direction of the Sun; only a few of the prominent ridges on Mathilde are illuminated. The visible area at left is 29 Km (approx. 18 miles) high and the phase angle (the angle from Sun-Mathilde spacecraft) is 136°. As the spacecraft receded from Mathilde, it observed the asteroid (about 60 Km - or 38 miles across) almost fully lit by the Sun at a phase angle of 43° (right image). Mathilde's irregular shape results from a long history of severe collisions with smaller asteroids. The largest visible crater is about 30 Km (19 miles) in diameter".
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Mathilde-PIA02494.jpgMathilde and Eros: C-Type and S-Type57 visiteCaption NASA originale:"In this montage, Mathilde (at left) and Eros (at right) are shown at the same scale, as they were imaged by NEAR Shoemaker from about 1.800 Km on June 27, 1997, and February 12, 2000, respectively. Mathilde is 56 Km across and Eros is 33 Km long and 13 Km wide. However, Mathilde's brightness is greatly exaggerated for viewing purposes - it's actually 6 times darker than Eros, with about the same reflectivity as soot! In a scheme that reflects how asteroids have historically been a topic for astronomy, not geology, they are classified into groups based on their colors as observed through telescopes. The 2 major classes of asteroids are called S-Types and C-Types. S-Types, whose colors are consistent with "stony" or rocky compositions, prevail among asteroids that orbit closer to the Sun than the mid-point of the asteroid belt. Eros and the 2 asteroids encountered briefly by the Galileo spacecraft on its way to Jupiter - Gaspra and Ida - are all S-Types. C-Types like Mathilde have a dark gray color consistent with a "carbonaceous" composition, rich in carbon compounds and other dark materials. They prevail in the outer part of the asteroid belt".
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McNaught-00.jpgComet McNaught (1)54 visiteCaption NASA:"Early morning risers with a clear and unobstructed eastern horizon can enjoy the sight of Comet McNaught (C/2006 P1) in dawn skies over the next few days. Discovered in August by R. H. McNaught (Siding Spring Survey) the comet has grown bright enough to see with the unaided eye but will soon be lost in the glare of the Sun. Still, by January 11 sun-staring spacecraft SOHO should be able to offer web-based views as the comet heads toward a perihelion passage inside the orbit of Mercury. This image captures the new naked-eye comet at about 2nd magnitude in twilight skies near sunset on January 3rd. After rounding the Sun and emerging from the solar glare later this month, Comet McNaught could be even brighter".
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