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March 21, 2012 | 9
In March 2011 MESSENGER became the first spacecraft to orbit Mercury. NASA's satellite has been taking measurements since then, and has collected nearly 100,000 images of the solar system's smallest planet, and the one closest to the sun.
The image above was created using laser radar to measure surface elevation. It depicts a 1,200-kilometer-long swath of the planet’s northern plains, falsely colored so that darker colors represent lower regions and lighter areas represent higher elevations. The sinuous ridges, cracked craters and an odd bulge (the large whitish area shown on the left) indicate that the four-billion-year-old plains underwent significant distortion after they formed.
Until now many scientists thought Mercury became a geologically dead world soon after its formation. Instead, MESSENGER found several topographic features that appear to have tilted over time, suggesting that Mercury was geodynamically active for a longer period than expected. It may even be active today.
Scientists do not understand the forces that guided the topographic tilting and bulge formation. On other planets, a viscous molten mantle is responsible. But because Mercury has an extremely thin mantle, it is difficult to imagine how it could have transported such vast geologic expanses, researchers say.
Understanding Mercury's unusual dynamics could help scientists learn more about the formation and evolution of rocky planets.
—By Sarah Fecht
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9 Comments
Add CommentAs the iron core of Mercury is surrounded by a mantle of Iron sulfide and the melting point of iron sulfide is much lower than iron, wouldn't the tidal effects of the sun at only 35 million miles away be sufficient to partially melt the iron sulfide in random areas creating the topographic tilting and bulge formation?
Reply | Report Abuse | Link to thisUnless the wall of the crater in the lower right is lower than it's internal central plain, I'd say that the darker colors (red) are higher than lighter colors (yellow) instead of the opposite (as described in the article). Or am I missing something? Nonetheless, fascinating photograph.
Reply | Report Abuse | Link to thisMaybe being so close to the Sun (DUH). It may well be affected by the 11 year cycle, solar flares, near misses with incoming asteroids. It lives in a very tough neighborhood and we have not mapped the gravity on the Sun but I would imagine that intense magnetic fields may do some weird things and I remember hearing that Mercury was made mostly of metallic elements. So again, blame it on the biggest thing near it. Also perhaps it has some weird resonance with Venus that sits pretty close to it on occasion also.
Reply | Report Abuse | Link to thisMy guess is that it's a sloppy description. From the image, clearly the blue end of the spectrum = lower and the red end = higher (with white/grey being even higher than red).
Reply | Report Abuse | Link to thisBest practice would be to include a colour <--> altitude scale but it's been left out for visual appeal.
I didn't see anything here about the possible swelling of the planet.
Reply | Report Abuse | Link to thisThe sinuous ridges, cracked craters and an odd bulge (the large whitish area shown on the left) indicate that the four-billion-year-old plains underwent significant distortion after they formed.
Reply | Report Abuse | Link to thisI am talking about gravity deformations. You have the sun HUGE and Venus Big that are each about 30 million miles away from Mercury. There may be some weird resonance going on or it may be inflicted by Solar Flares and other Solar events that. Mercury has been shown to have a weak but interesting magnetic field and the map shows some distortions.
We really don't know much about this little planet and hopefully more and more knowledge will come from this expedition but it is really the first attention we have given the planet and already it is presenting surprises.
Pink is highest.Red is high. Then yellow, green, turquoise.Purple is lowest.
Reply | Report Abuse | Link to thisNot mentioned in the article: Does Mercury keep the same face towards the Sun?
I'm color blind. This photo is rather useless to me. Pretty, tho.
Reply | Report Abuse | Link to thisMercury is so close to the Sun that astronomers thought that there would probably be orbital coupling, like the Earth-Moon system (a tidally locked system). They expected the rotation period to be the same as the orbital period, so that one side of Mercury would always face the Sun, just like one side of the Moon always faces the Earth. Does the orbital period equal the rotation period for Mercury? It is a small planet and difficult to observe, so astronomers were not sure of its rotation period. They had to wait for the invention of radar to check it out. By bouncing a radar signal off the planet, they could measure the speed of its rotation and therefore determine the period of rotation (sort of the same way a highway patrol officer can get you clocked on the radar for being slightly over the speed limit on the highway). Are the orbital period and rotation period the same? No. The period for one orbit is about 88 days, while the period for one rotation is 59 days (pretty slow spinner, eh?). At first glance this doesn't seem to be very significant, but if you were to take the ratio of the periods, 59/88, you get a number close to 2/3. What's so great about that?
Reply | Report Abuse | Link to thisThe basic upshot is that there is a kind of coupling between the orbit and rotation, but not the one that was expected. For every two orbits around the Sun, Mercury rotates three times on its axis. Figure 1 shows how the orientation of an astronaut would change over time as Mercury went about the Sun. By the time the planet had made one orbit, Mercury would have made 1.5 (or 3/2) rotations; one more orbit, and there would be a total of three rotations - sort of unusual.
Source www.uni.edu/morgans/astro/course/Notes/section4/new18.html