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Wired.com's Space Photos of the Week: Perfectly Safe Celestial Coronas includes radar images of the surface of Venus taken from spacecraft in orbit around it. One of them shown below.

What causes this peculiar cracking? It reminds me of ice somehow.

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In 1991 NASA’s Magellan spacecraft captured the cracks and corona on the surface of Venus. You can see some younger impact craters, as well as cracks from plate tectonics; that main circular feature is a corona created by past volcanic activity.PHOTOGRAPH: NASA/JPL

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    $\begingroup$ The other major rocky bodies of the solar system have cracks too, it's just that their surfaces are covered with regolith and/or water or ice & we do see it as much. From what we have interpreted, Venus has no regolith, or minimal regolith so it's easier to notice. What intrigues me is the different styles of cracking & what causes that difference. One set is thin gently curved cracks with large distances between the cracks. The other are wide interlaced cracks in the upper right of the main photo. The third set being the ring of cracks around the main crater & the fish scale one in the crater $\endgroup$ – Fred Mar 8 at 4:28
  • $\begingroup$ @Fred while I don't have the science words to express myself, these look so familiar somehow because I grew up where ice on puddles, lakes, windows and everywhere else was common. Maybe I can change the title to "Why is Venus so intriguingly cracked?" :-) $\endgroup$ – uhoh Mar 8 at 4:50
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    $\begingroup$ Either title is fine. :-) The other thing I've noticed is that some of the long gently curved cracks are a continuation of wider cracks. See the long crack in the middle of the photo. The wide crack ends at the edge of the main crater & the thin crack goes through the crater. Because that set of cracks goes through all the other features & they're not offset at any of the junctures they would be the youngest cracks in view. Their gentle curvature & wide spacing makes me wonder if there might be a huge impact crater somewhere to the right of the photo, at a great distance. $\endgroup$ – Fred Mar 8 at 5:02
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I found the picture with a small write up on a JPL site.

It's a picture of the Aine Corona with pancake domes.

P-38340 MGN-48 5/21/91

This Magellan radar image shows a region approximately 300 kilometers (180 miles) across, centered on 59 degrees south latitude, 164 degrees east longitude and located in a vast plain to the south of Aphrodite Terra. The data for this image were obtained in January 1991.The large circular structure near the center of the image is a corona, approximately 200 kilometers in diameter and provisionally named Aine Corona. Just north of Aine Corona is one of the flat-topped volcanic constructs known as "pancake" domes for their shape and flap-jack appearance. This pancake dome is about 35 kilometer (21 miles) in diameter and is thought to have formed by the eruption of an extremely viscous lava. Another pancake dome is located inside the western part of the annulus of the corona fractures. Complex fracture patterns like the one in the upper right of the image are often observed in association with coronae and various volcanic features. They are thought to form because magma beneath the surface follows pre-existing fracture patterns. When eruptions or other movements of the magma occur, the magma drains from the fractures and the overlying surface rock collapses. Other volcanic features associated with Aine Corona include a set of small domes, each less than 10 kilometers (6 miles) across, located along the southern portion of the annulus of fractures, and a smooth, flat region in the center of the corona, probably a relatively young lava flow. The range of volcanic features associated with coronae suggests that volcanism plays a significant role in the formation of coronae.

Apparently, pan cake domes are on found on Venus.

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  • $\begingroup$ So the fracture pattern seen is thought to follow pre-exiting fracture patterns? $\endgroup$ – uhoh Mar 9 at 11:59
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    $\begingroup$ Cracks occurs due to solidification of magma and stresses within the rock, but if the explanation given is true, there are some weird geological fracture patterns. It is possible that the cracks in the photo represent a series of cracking over time. $\endgroup$ – Fred Mar 9 at 12:20
  • $\begingroup$ Since I have no real understanding of these processes on Earth I can't really understand yet. Does "...solidification of magma..." refer to the original formation of the planet, or do some supervolcano eruption or to an impact event, or something else, or just don't know and not ready to venture a guess? $\endgroup$ – uhoh Mar 9 at 13:47
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    $\begingroup$ Magna is naturally occurring molten rock, beneath the surface, irrespective of when it was molten - 4.5 billion years ago or now. Once it reaches the surface it gets renamed lava. Volcanoes erupt lava on the surface, but the lava is sourced from a magma chamber underground. Only Earth has plate tectonics at some plate boundaries where one plate subducts beneath the other one. In doing so it gets heated a melts, forming "new" magma. This is how the Japanese islands formed - it's a phenomenon known as an island arc chain. ... $\endgroup$ – Fred Mar 9 at 18:46
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    $\begingroup$ ... Another source of magma is a magma plume. Solidification of magma, on Earth has occurred throughout its 4.5 billion years history. Venus is thought to not have plate tectonics. It apparently is volcanically active, with magma chambers beneath the surface. It would appears that like Earth, Venus has had magma solidify throughout its history. $\endgroup$ – Fred Mar 9 at 18:57

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