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DAWN - Bild des Tages - Mai 2012

31.05.2012 - Crater chains on regolith

This Dawn Framing Camera (FC) image of Vesta shows chains of craters on an undulating surface. This undulating surface is probably formed of fine-grained debris, called regolith, which was ejected from large impact craters as they formed nearby. A part of such a large crater is visible in the bottom left of the image. It is possible that the chains of craters were formed by material ejected during the formation of this large crater because they are aligned roughly perpendicular to the rim of the crater. This is the alignment that would be expected for large blocks of material thrown out of the crater. Then as these blocks scoured across Vesta’s surface they may have formed the chains of craters.

30.05.2012 - Chain of craters

31 May 2012
This Dawn Framing Camera (FC) image of Vesta shows a long chain of craters in the right part of the image. This crater chain appears to extend for roughly 10 kilometers (6 miles) and is less than 1 kilometer (0.6 mile) in width. It is made up of several small craters: some are distinct from one another and others appear to partly merge together. This chain of craters was possibly formed by debris ejected from a larger crater scouring the surface of Vesta. It is unlikely that the large crater in the top of the image is the crater from which the debris originated. This because the chain of craters is not aligned roughly perpendicular to the rim of this crater, which is how they would be expected to be aligned if they originated from this crater.

29.05.2012 - Secondary crater chains

This Dawn Framing Camera (FC) image of Vesta shows many secondary crater chains on Vesta’s surface. The secondary crater chains are made up of small craters, which are less than 1 kilometer (0.6 mile) in diameter, usually slightly overlap one another and are collected into linear structures that stretch for up to 10 kilometers (6 miles) in this image. These chains were most likely formed by material ejected from an impact into Vesta skipping across Vesta’s surface and scouring the chains. They are called secondary crater chains because the material that forms them is ejected from a primary impact of material that originated in space. It is possible that the primary impact that formed some of these chains is the large, shadowed crater in the top of the image.

28.05.2012 - Grooved surface

28 May 2012
This Dawn Framing Camera (FC) image of Vesta shows a part of the surface in Vesta’s northern hemisphere, which is scoured by many grooves with different orientations. These grooves are much longer than they are wide: some can be traced nearly all the way across the image but they are less than 1 kilometer (0.6 mile) wide. Grooves on Vesta are thought to form by a number of processes and it is possible that these grooves formed by movement of the regolith on Vesta’s surface. The mechanism for the movement could be a creep-like process. The regolith is formed by repeated impacts into the asteroid, which creates the fine-grained regolith that covers Vesta in a sandy-like layer.

25.05.2012 - Undulating surface and secondary crater chains

This Dawn Framing Camera (FC) image of Vesta shows the characteristic undulating surface of Vesta’s southern hemisphere and many small craters, some of which make up secondary crater chains. Curvilinear grooves and ridges that run diagonally across the image characterize the undulating surface. Most of the craters in this image are less than 1 kilometer (0.6 miles) across. A series of small craters in the bottom right of the image form a secondary crater chain that is roughly 4 kilometers (2.5 miles) long. This secondary crater chain was probably formed by material ejected from an impact into Vesta skipping across Vesta’s surface and scouring the chain. It is called a secondary crater chain because the material is ejected from a primary impact of material that originated in space.

24.05.2012 - Apparent brightness and topography images of Aquilia crater

23 May 2012
The left-hand image is a Dawn FC (framing camera) image, which shows the apparent brightness of Vesta’s surface. The right-hand image is based on this apparent brightness image, which has had a color-coded height representation of the topography overlain onto it. The topography is calculated from a set of images that were observed from different viewing directions, which allows stereo reconstruction. The various colors correspond to the height of the area. The white and red areas in the topography image are the highest areas and the blue areas are the lowest areas. Aquilia crater is the large crater that dominates the top part of both images. The three-dimensional structure of Aquilia is clearer in the topography image: the deepest part of the crater (colored blue) is offset from the crater’s center, the smaller crater on Aquila’s rim is also relatively deep and the top side of Aquila is steeper than the opposite side.

23.05.2012 - Apparent brightness and topography images of Aelia crater

The left-hand image is a Dawn FC (framing camera) image, which shows the apparent brightness of Vesta’s surface. The right-hand image is based on this apparent brightness image, which has had a color-coded height representation of the topography overlain onto it. The topography is calculated from a set of images that were observed from different viewing directions, which allows stereo reconstruction. The various colors correspond to the height of the area. The white and red areas in the topography image are the highest areas and the blue areas are the lowest areas. Aelia crater is the small crater, with streaks of dark and bright material, near the center of the image. It is clear from the topography image that Aelia crater formed on an area of raised topography. The larger crater above Aelia is also highlighted in the topography image because the extent of its depth becomes clearer.

22.05.2012 - Teia crater

23 May 2012
This Dawn Framing Camera (FC) image of Vesta shows Teia crater, which is the crater with bright and dark material offset to the left of the center of the image. Teia crater is only 6.6 kilometers (4 miles) in diameter but it contains a lot of curious features. Firstly, it has an irregularly shaped rim, which is fresher on one side and partially obscured on the other side. The rim is partially obscured by what appears to be slumped material. There are boulders visible on the top of this slumped material. The boulders can be identified by the dark shadows that they cast and are only a few hundred meters (hundreds of feet) across. There is mostly bright material in Teia crater but there is also a patch of dark material on one side. An older, more degraded crater, on the bottom right side of Teia crater, is partially covered by Teia crater.

21.05.2012 - Sossia and Canuleia craters

This Dawn Framing Camera (FC) image of Vesta shows Sossia and Canuleia craters. Sossia is the crater surrounded by dark material in the bottom left of the image and Canuleia is the larger crater surrounded by bright material in the bottom right of the image. The bright material around Canuleia crater is collected together into broad rays that extend for up to 10 kilometers (6 miles). There are also narrower bands of bright material that originate from just underneath Canuleia’s rim and slump towards its center. A roughly 12 kilometer (7.5 mile) long band of darker material ranges from the wall of Canuleia crater to the area surrounding the crater. This band of darker material appears to be overlying the bright material, so it is likely that it is younger than the bright material.

18.05.2012 - Sossia crater

22 May 2012
This Dawn Framing Camera (FC) image of Vesta shows Sossia crater, which is the crater partially surrounded by dark material near the bottom of the image. Sossia crater has a reasonably fresh rim and patches of dark material cropping out around part of this rim. This dark material spreads away from the rim of the crater and slumps down into the center of the crater. There is also an area of dark material associated with a smaller crater below Sossia’s rim. This smaller crater is almost completely filled by dark material. A much smaller amount of bright material also crops out from Sossia’s rim. Surrounding Sossia crater is the undulating terrain of Vesta’s southern hemisphere, which consists of curvilinear ridges and grooves.

17.05.2012 - Urbinia and Sossia craters

This Dawn Framing Camera (FC) image of Vesta shows Urbinia and Sossia craters. Urbinia is the large crater, which dominates the top left of the image, and Sossia is the small crater surrounded by dark material in the bottom of the image. Urbinia crater is a distinctive crater for many reasons: it has a fresh and very irregularly shaped rim; there is a younger, smaller crater near its center and there are patches of dark and bright material around its rim, which slump towards its center. The quadrangle in which Urbinia is located is named after it because of the individuality of the crater. Sossia crater is much smaller than Urbinia, Sossia is 8 kilometers (5 miles) in diameter and Urbinia is 24 kilometers (15 miles) in diameter. But, it is also an interesting crater because of the dark material associated with it.

16.05.2012 - Serena crater

16 May 2012
This Dawn framing camera (FC) image of Vesta shows Serena crater, which is the large crater in the left middle of the image. The left side of the crater’s rim is much more degraded than the right side, which is much fresher. Areas of dark and bright material crop out from slightly under the rim and slump towards the center of the crater. The longest slump streaks are nearly 5 kilometers (3 miles) long in the crater that is approximately 19 kilometer (12 miles) in diameter. There is a mound of material in the center of the crater and many small craters scattered over Serena crater. There are other smaller craters distributed throughout the image, which also have bright and dark material associated with them.

15.05.2012 - Scantia crater

This Dawn framing camera (FC) image of Vesta shows Scantia crater, which is the large crater in the bottom left corner of the image. Scantia is approximately 20 kilometers (12 miles) in diameter and has a reasonably degraded rim. On the left side of Scantia there are two areas of material that are slumping towards the crater’s center. The tops of these slumping areas are rounded, so it is possible that they were originally impact craters that were formed after projectiles hit the slope of Scantia. There are many smaller craters surrounding Scantia, which have different states of preservation and freshness. There are also chains of craters and linear grooves, which are less than 1 kilometer (0.6 mile) wide, running diagonally across the bottom right corner of the image.

14.05.2012 - Rubria crater

14 May 2012
This Dawn framing camera (FC) image of Vesta shows Rubria crater, which is the crater with the dark and bright material, that is offset from the center of the image. Rubria’s bright material mostly crops out of the rim of the crater and slumps towards the center. In contrast, Rubria’s dark material is located outside of the crater rim in long streaks, as well as cropping out of the rim of the crater and slumping towards its center. The longest dark material streak that is still connected to Rubria’s rim is located on the top part of the rim. But it is possible that the other streaks to the top of the rim, the farthest of which is approximately 15 kilometers (9 miles) from the rim, may also be associated with Rubria crater. Rubria is one of the freshest looking, and consequently probably one of the youngest, craters in visible in this image.

11.05.2012 - Octavia crater

This Dawn framing camera (FC) image of Vesta shows Octavia crater, which is the large crater in the right of the image. Octavia crater dominates the landscape of Vesta that is visible in this image: it is approximately 30 kilometers (19 miles) in diameter and the next largest crater is only approximately 4 kilometers (2 miles) in diameter. Octavia’s rim is fresher on the right side and more degraded on the left side. The left side may be more degraded due to slumping of material into the center of the crater. There is a linear build-up of material in the center of the crater, which probably accumulated from slumping. The fresher part of the rim has a scalloped edge and there is no obvious cause visible in the image for this particular morphology. There are patches of dark and bright material throughout the crater, most noticeably below the rim on the right side.

10.05.2012 - Occia crater

8 May 2012
This Dawn framing camera (FC) image of Vesta shows Occia crater in the top left part of the image. This image is located slightly further to the south than the last image of the day, which showed Occia crater and its northern neighbor Rubria crater. The distinctive pattern of Occia’s dark material is clear in this image: there are two main areas of dark material that are on either side of Occia, both inside and outside of the rim. This pattern is similar to the butterfly pattern of ejecta occasionally found on planets such as Mars. Butterfly patterns of ejecta consist of two separate lobes of ejecta on the opposite sides of a crater, which are formed when an impact crater was made by a very shallow impact onto a surface. However, from this image alone it is not clear if these areas of dark material formed in such a way.

09.05.2012 - Rubria and Occia craters

This Dawn framing camera (FC) image of Vesta shows Rubria and Occia craters. Rubria is the crater in the top center of the image and Occia is the crater just below the middle of the image on the right side. Both craters are similar in morphology and size, Rubria is approximately 10 kilometers (6 miles) in diameter and Occia is approximately 7 kilometers (4 miles) in diameter. Both Rubria and Occia contain dark and bright material and both have reasonably sharp, well-defined and regularly shaped rims. The dark material in Rubria and Occia is generally confined into triangular segments of the craters, but the bright material is more evenly distributed. The boundaries between the dark and bright material in Rubria are more distinctly defined than in Occia.

08.05.2012 - Lepida crater

8 May 2012
This Dawn framing camera (FC) image of Vesta shows Lepida crater. Lepida is the large crater that dominates the right side of the image. Lepida is 44 kilometers (27 miles) in diameter on average and has an irregularly shaped, fresh rim. A smaller crater is barely visible on the left side of Lepida. Part of the edge of this crater forms the lump in Lepida’s left side rim. It is possible that other parts of Lepida’s irregular rim are formed in a similar manner. The irregular rim may also be caused by slumping or another mechanism. From this image Lepida appears to be a shallow crater, but a cross section of the crater would be necessary to confirm this suggestion. There is some bright material cropping out of Lepida’s rim and slumping towards its center, mostly on the right side.

07.05.2012 - Helena and Laelia craters

This Dawn framing camera (FC) image of Vesta shows Helena crater, which is the crater that resembles the shape of a butterfly’s wings in the center of the image, and Laelia crater, which is the crater in the bottom right corner of the image. Helena is approximately 22 kilometers (14 miles) in diameter and Laelia is approximately 9 kilometers (6 miles) in diameter. There are many areas of dark material in and around Laelia crater. Some of this dark material crops out from the crater’s rim and slumps towards its center, while other patches of dark material, mostly associated with smaller craters, surround Laelia. There is another, similarly sized crater, which appears to be overlapped by Helena crater. Helena looks slightly fresher than this other crater so it is likely Helena that is the younger crater.

04.05.2012 - Laelia crater

4 May 2012
This Dawn framing camera (FC) image of Vesta shows Laelia crater, which is the crater with dark material inside of it and surrounding it in the bottom center of the image. The dark material inside of Laelia crops out from the rim and then slumps towards the crater’s center. The dark material outside of Laelia is dominantly associated with smaller impact craters that are less than 1 kilometer (0.6 mile) in diameter. One spectacular small, dark material crater is located to the bottom right of Laelia and has an impressive pattern of dark material ejecta rays extending from it. More small impact craters with dark material ejecta are located above Laelia crater in this image.

03.05.2012 - Laelia and Sextilia craters

This Dawn framing camera (FC) image of Vesta shows Laelia crater and Sextilia crater. Sextilia crater is the large crater in the top right of the image, which is approximately 20 kilometers (12.4 miles) in diameter. The quadrangle in which these craters are located is named after Sextilia crater. Laelia crater is the smaller crater (approximately 9.2 kilometers (5.7 miles) in diameter) offset from the center of the image that has dark material inside of it and surrounding it. Sextilia crater only contains bright material, which slumps from its rim towards it center, so it is interesting that it is located in such close proximity to Laelia crater, which is dominated by dark material.

02.05.2012 - Justina crater

2 May 2012
This Dawn framing camera (FC) image of Vesta shows Justina crater, which is the crater surrounded by bright material, in the bottom left of the image. Justina crater has a reasonably degraded rim and is roughly 7 kilometers (4.3 miles) in diameter. It is a distinctive crater because of the bright blanket of ejecta material that surrounds it on nearly all sides. There is a gap in this bright material on the right side of Justina. There also appears to be bright material slumping into Justina, which partly obscures its rim in some places. A patch of dark material is located on the right side of the crater. Justina is surrounded by sinuous ridges and grooves, which are characteristic of Vesta’s southern hemisphere.

01.05.2012 - Fabia crater

This Dawn framing camera (FC) image of Vesta shows Fabia crater on the right side of the image. Fabia crater is roughly 12 kilometers (7.5 miles) in diameter and has a large area of bright material originating from its top right rim and slumping towards its center. The top left rim of Fabia is more degraded than the rest of the rim, which is likely due to debris slumping into the crater and covering up this part of the rim. There are many boulders located on the debris and around the top part of Fabia crater. These boulders are much less than 1 kilometer (0.6 mile) wide and are identified by the shadows that they cast to the left. Note that the large dark patches with bright rims in the left of the image are artifacts that result from the processing of the image and are not features on Vesta’s surface.

Mai 2012

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