Les planètes du système solaire: Mercure

MERCURE P.125 Masse: 3,3E23 kg Diamètre 4878 km Densité: 5,42 kg/dm3 Distance au soleil: 58 millions km Jour: 58.6 Jours T. Année: 87.9 jours Inclinaison de l’axe: 0 T. moy. surface: 179C Atmosphère: Traces Pas de satellites P.125

Mercure et la Terre, à l’échelle P.125

MERCURE Masse: 5,5% Terre Rayon: 38% Terre Distance au soleil: 39% Terre

MERCURE Particularités: 1ère planète à partir du soleil Champ magnétique 1%T Mercure fait un tour et demi sur lui-même durant son orbite Gros noyau métallique Température de surface variant de 427C le jour à -173 C la nuit Plus petite que les plus grosses lunes de Jupiter et Saturne

L’INTÉRIEUR DE MERCURE Manteau et surface de roche et/ou de silicates Noyau métallique de fer et de Nickel P.125

100 km

Surface grandement cratérisée. 25 km

Bassin Caloris P.127

Fosses à la surface: signe de rétrécissement

signe de rétrécissement Fosses à la surface: signe de rétrécissement As the MESSENGER team continues to study the high-resolution images taken during the Mercury flyby encounter on January 14, 2008, scarps (cliffs) that extend for long distances are discovered. This frame, taken by the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS), shows a region of Mercury's surface previously unseen by spacecraft and a large scarp crossing vertically through the scene, on the far right of the image. This scarp is the northern continuation of the one seen in the NAC image released on January 16. The width of this image is about 200 kilometers (about 125 miles), showing that these scarps can be hundreds of kilometers long on Mercury. The presence of many long and high scarps, as discovered from pictures from the Mariner 10 mission in 1974 and 1975, suggests a history for Mercury that is unlike that of any of the other planets in the solar system. These giant scarps are believed to have formed when Mercury’s interior cooled and the entire planet shrank slightly as a result. However, Mariner 10 was able to view less than half the planet, so the global extent of these scarps has been unknown. MESSENGER images, like this one, are providing the first high-resolution looks at many areas on Mercury's surface, and science team members are busy mapping these newly discovered scarps to see whether they are common everywhere on the planet. Mission Elapsed Time (MET) of image: 108826206 Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Départ de la sonde Mariner 10: 10 novembre 1973 EXPLORATION: Départ de la sonde Mariner 10: 10 novembre 1973 Résultats: 12000 photos de Vénus et de Mercure

Sonde Mariner 10: construction P.126

Mariner 10

MErcury Surface, Space ENvironment, GEochemistry and Ranging MESSENGER MErcury Surface, Space ENvironment, GEochemistry and Ranging http://messenger.jhuapl.edu/

Lancement de la sonde MESSENGER, 3 août 2004 http://www.youtube.com/watch?v=7ykx1S9wZGg

Gros plan pris par la sonde MESSENGER As MESSENGER sped by Mercury on January 14, 2008, the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) captured this image before its closest approach with the planet. The scene is near Mercury's terminator (the line between the sunlit day side and dark night side of the planet), where shadows are long and height differences accentuated, revealing rising crater walls that tower over the floors below. The large crater situated on the right side in the bottom half of the image is Sullivan crater, a structure about 135 kilometers (84 miles) in diameter also seen during the Mariner 10 mission. An influential American architect, Louis Sullivan and his work are often associated with the rise of modern skyscrapers, and this crater named in his honor finds a fitting home in Mercury's ancient geological architecture. Mission Elapsed Time (MET) of image: 108821402 Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Gros plan pris par la sonde MESSENGER Two weeks ago, on January 14, 2008, MESSENGER became the first spacecraft to see the side of Mercury shown in this image. The first image transmitted back to Earth following the flyby of Mercury, and then released to the web within hours, shows the historic first look at the previously unseen side. This image, taken by the Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS), shows a closer view of much of that territory. Just above and to the left of center of this image is a small crater with a pronounced set of bright rays extending across Mercury's surface away from the crater. Bright rays are commonly made in a crater-forming explosion when an asteroid strikes the surface of an airless body like the Moon or Mercury. But rays fade with time as tiny meteoroids and particles from the solar wind strike the surface and darken the rays. The prominence of these rays implies that the small crater at the center of the ray pattern formed comparatively recently. This image is one in a planned set of 99. Nine different views of Mercury were snapped in this set to create a mosaic pattern with images in 3 rows and 3 columns. The WAC is equipped with 11 narrow-band color filters, and each of the 9 different views was acquired through all 11 filters. This image was taken in filter 7, which is sensitive to light near the red end of the visible spectrum (750 nm), and shows features as small as about 6 kilometers (4 miles) in size. The MESSENGER team is studying this previously unseen side of Mercury in detail to map and identify new geologic features and to construct the planet’s geological history. Mission Elapsed Time (MET) of image: 108827618 Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Le nord de Mercure est moins cratérisé que le sud… As MESSENGER sped by Mercury on January 14, 2008, the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) captured this shot looking toward Mercury's north pole. The surface shown in this image is from the side of Mercury not previously seen by spacecraft. The top right of this image shows the limb of the planet, which transitions into the terminator (the line between the sunlit, day side and the dark, night side) on the top left of the image. Near the terminator, the Sun illuminates surface features at a low angle, casting long shadows and causing height differences of the surface to appear more prominent in this region. It is interesting to compare MESSENGER's view to the north with the image looking toward the south pole, released on January 21. Comparing these two images, it can be seen that the terrain near the south pole is more heavily cratered while some of the region near the north pole shows less cratered, smooth plains material, consistent with the general observations of the poles made by Mariner 10. MESSENGER acquired over 1200 images of Mercury's surface during its flyby, and the MESSENGER team is busy examining all of those images in detail, to understand the geologic history of the planet as a whole, from pole to pole. This image was acquired about 94 minutes after MESSENGER's closest approach to Mercury, when the spacecraft was at a distance of about 32,000 kilometers (20,000 miles). Mission Elapsed Time (MET) of image: 108830513>br /> Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Gros plan pris par la sonde MESSENGER During MESSENGER's flyby of Mercury on January 14, 2008, part of the planned sequence of observations included taking images of the same portion of Mercury's surface from five different viewing angles. The first view from this sequence was taken just after MESSENGER made its closest approach to Mercury, from a low viewing angle; an image of the first view was released on January 19. The image released here, acquired with the Wide Angle Camera (WAC) on the Mercury Dual Imaging System (MDIS), was snapped 13 minutes after MESSENGER's closest approach with Mercury. The lower two-thirds of this image shows much of the same terrain seen in the first view, but from a much higher viewing angle, as the spacecraft began to pass nearly overhead. At the time of this image, MESSENGER was at a distance of about 3000 kilometers (about 2000 miles) from Mercury. A comparison of the images taken at different viewing angles provides important information about the properties of the materials that make up Mercury's surface. In addition, each view was taken through all 11 of the WAC's narrow-band color filters. The image shown here is from filter 7, which is sensitive to light near the red end of the visible spectrum (750 nm). The MESSENGER team is working to compare these images taken from different perspectives and in different colors to understand surface properties on Mercury. In addition, knowledge of the variation of image properties with viewing angle in this region will permit a more confident comparison of images of other portions of the surface taken at different illumination and viewing angles. This image is about 1000 kilometers (about 600 miles) across. Image Mission Elapsed Time (MET): 108825632 Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Gros plan pris par la sonde MESSENGER: Cratère Matisse 208 km dia. As NASA’s MESSENGER spacecraft approached Mercury on January 14, 2008, the spacecraft took this image of the crater Matisse. Named for the French artist Henri Matisse, Matisse crater was imaged during the Mariner 10 mission and is about 130 miles in diameter. Matisse crater is in the southern hemisphere and can be seen near the terminator of the planet (the line between the sunlit, day side and the dark, night side). On Mercury, craters are named for people, now deceased, who have made contributions to the humanities, such as artists, musicians, painters, and authors. The International Astronomical Union (IAU) oversees the official process of naming new craters and other new features discovered on bodies throughout the solar system. Scientists studying and mapping unnamed features can suggest names for consideration by the IAU. The 1,213 images taken by MESSENGER during its first flyby encounter with Mercury cover a large region of Mercury's surface previously unseen by spacecraft, revealing many new craters and other features that will need to be named. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Première image à haute résolution prise par la sonde MESSENGER One week ago, the MESSENGER spacecraft transmitted to Earth the first high-resolution image of Mercury by a spacecraft in over 30 years, since the three Mercury flybys of Mariner 10 in 1974 and 1975. MESSENGER's Wide Angle Camera (WAC), part of the Mercury Dual Imaging System (MDIS), is equipped with 11 narrow-band color filters, in contrast to the two visible-light filters and one ultraviolet filter that were on Mariner 10's vidicon camera. By combining images taken through different filters in the visible and infrared, the MESSENGER data allow Mercury to be seen in a variety of high-resolution color views not previously possible. MESSENGER’s eyes can see far beyond the color range of the human eye, and the colors seen in the accompanying image are somewhat different from what a human would see. The color image was generated by combining three separate images taken through WAC filters sensitive to light in different wavelengths; filters that transmit light with wavelengths of 1000, 700, and 430 nanometers (infrared, far red, and violet, respectively) were placed in the red, green, and blue channels, respectively, to create this image. The human eye is sensitive across only the wavelength range 400 to 700 nanometers. Creating a false-color image in this way accentuates color differences on Mercury's surface that cannot be seen in the single-filter, black-and-white images released last week. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Effondrement potentiellement signe d’activité volcanique MESSENGER's Narrow Angle Camera (NAC) on the Mercury Dual Imaging System (MDIS) acquired this view of Mercury’s surface illuminated obliquely from the right by the Sun. The unnamed crater (52 kilometers, or 31 miles, in diameter) in the center of the image displays a telephone-shaped collapse feature on its floor. Such a collapse feature, not seen on the floors of other craters in this image, could reflect past volcanic activity at and just below the surface of this particular crater. MESSENGER team members are examining closely the more than 1200 images returned from this flyby for other surface features that can provide clues to the geological history of the innermost planet. The crater is located in the southern hemisphere of Mercury, on the side that was not viewed by Mariner 10 during any of its three flybys (1974-1975). This scene was imaged while MESSENGER was departing from Mercury from a distance of about 19,300 kilometers (12,000 miles), about 1 hour after the spacecraft's closest encounter with Mercury. The image is of a region approximately 236 kilometers (147 miles) across, and craters as small as 1.6 kilometers (1 mile) can be seen. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Évolution géologique complexe A complex history of geological evolution is recorded in this frame from the Narrow Angle Camera (NAC), part of the Mercury Dual Imaging System (MDIS) instrument, taken during MESSENGER’s close flyby of Mercury on January 14, 2008. Part of an old, large crater occupies most of the lower left portion of the frame. An arrangement of ridges and cliffs in the shape of a "Y" crosses the crater’s floor. The shadows defining the ridges are cast on the floor of the crater by the Sun shining from the right, indicating a descending stair-step of plains. The main, right-hand branch of the "Y" crosses the crater floor, the crater rim, and continues off the top edge of the picture; it appears to be a classic “lobate scarp” (irregularly shaped cliff) common in all areas of Mercury imaged so far. These lobate scarps were formed during a period when Mercury’s crust was contracting as the planet cooled. In contrast, the branch of the Y to the left ends at the crater rim and is restricted to the floor of the crater. Both it and the lighter-colored ridge that extends downward from it resemble “wrinkle ridges” that are common on the large volcanic plains, or "maria," on the Moon. The MESSENGER science team is studying what features like these reveal about the interior cooling history of Mercury. Ghostly remnants of a few craters are seen on the right side of this image, possibly indicating that once-pristine, bowl-shaped craters (like those on the large crater’s floor) have been subsequently flooded by volcanism or some other plains-forming process. This image was taken 18 minutes after close approach, when MESSENGER was about 5,000 kilometers (about 3,000 miles) away from Mercury. The image is about 200 kilometers (about 125 miles) across, and features as small as about 400 meters (about 400 yards) can be resolved. Mission Elapsed Time (MET) of image: 108825904 Credit: Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Just nine minutes after MESSENGER passed 200 kilometers (124 miles) above the surface of Mercury – its closest distance to the planet during the January 14, 2008, flyby – the probe’s Wide Angle Camera (WAC) on the Mercury Dual Imaging System (MDIS) snapped this image. The WAC is equipped with 11 different narrow-band filters, and this image was taken in filter 7, which is sensitive to light near the red end of the visible spectrum (750 nm). This view, also imaged through the remaining 10 WAC filters, is from the first set of images taken following MESSENGER's closest approach with Mercury. The image shows Mercury's surface as seen from a low viewing angle, looking over the surface and off the limb of the planet on the right side of the image. The cratered terrain in the image is on the side of Mercury unseen by spacecraft prior to this MESSENGER flyby. This scene was imaged at multiple viewing angles as MESSENGER sped away from Mercury, and these multiple views of the same surface features from different perspectives and in different colors will be used to help understand the properties of Mercury's surface.

Impact majeur récent, avec impacts secondaires On January 14, 2008, NASA’s MESSENGER spacecraft observed about half of the hemisphere not seen by Mariner 10. This image shows part of a large, fresh crater with secondary crater chains located near Mercury’s equator on the side of the planet newly imaged by MESSENGER. Large, flat-floored craters show terraced rims from post-impact collapse of their newly formed walls. The hundreds of secondary impactors that are excavated from the planet’s surface by an incoming object, create long, linear crater chains radial to the main crater. These chains, in addition to the rest of the ejecta blanket, create the complicated, hilly terrain surrounding the primary crater in the image. By counting craters that have formed since the impact event, the age of the crater can be estimated. This count can then be compared with a similar count for the crater floor to determine whether any material has partially filled the crater since its formation. With their large size and production of abundant secondary craters, these flat-floored craters both illuminate and confound the study of the geological history of Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Cratères et plaines As NASA’s MESSENGER spacecraft drew closer to Mercury for its historic first flyby, the spacecraft acquired this image showing a variety of surface textures, including smooth plains at the center of the image, numerous impact craters and rough material that appears to have been ejected from the large crater to the lower right. MESSENGER has acquired over 1200 images of Mercury. These types of images will assist scientists to study, as never before, details to help them learn about the history and evolution of the innermost planet. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Le bassin d’impact Rembrandt Diamètre: 715 km

Le bassin d’impact Rembrandt Diamètre: 715 km