MESSENGER captures image of curious "hollows" around a crater peak

More “Hollowed Ground” on Mercury

5 Jan , 2012 by

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The latest featured image from NASA’s MESSENGER spacecraft, soon to complete its first year in orbit around Mercury, shows the central peak of the 78-mile (138-km) – wide crater Eminescu surrounded by more of those brightly-colored surface features dubbed “hollows”. Actually tinted a light blue color, hollows may be signs of an erosion process unique to Mercury because of its composition and close proximity to the Sun.

First noted in September of last year, hollows have now been identified in many areas across Mercury. They showed up in previous images as only bright spots, but once MESSENGER established orbit in March of 2011 and began high-resolution imaging of Mercury’s surface it became clear that these features were something totally new.

The lack of craters within hollows seems to indicate that they are relatively young features. In fact, they may be part of a process that continues even now.

“Analysis of the images and estimates of the rate at which the hollows may be growing led to the conclusion that they could be actively forming today,” said David Blewett of the Johns Hopkins University Applied Physics Laboratory (APL).

One hypothesis is that the hollows are formed by the sublimation of subsurface material exposed during the creation of craters, around which they are most commonly seen. Being so close to the Sun (29 million miles/46 million km at closest) and lacking a protective atmosphere like Earth’s, Mercury is constantly being scoured by the powerful solar wind. This relentless stream of charged particles may literally be “sandblasting” exposed volatile materials off the planet’s surface!

The image above shows an area approximately 41 miles (66 km) across. It has been rotated to enhance perspective; see the original image and caption here.

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

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Anonymous
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Anonymous
January 5, 2012 11:31 AM
For those not well informed about this recently discovered feature of the quicksilver planet: ________________________________________________________________________________ “Images taken from orbit reveal thousands of peculiar depressions at a variety of longitudes and latitudes, ranging in size from 60 feet to over a mile across and 60 to 120 feet deep. No one knows how they got there. …. “Mars Reconnaissance Orbiter spotted similar depressions in the carbon dioxide ice at Mars’ south pole, giving that surface a ‘swiss cheese’ appearance. But on Mercury they’re found in rock and often have bright interiors and halos. [ A similar process, and/or mechanism, but in a different medium? ] …. “As the planet closest to the Sun, Mercury is exposed to fierce heat… Read more »
Dennis Ray Wingo
Guest
January 5, 2012 3:16 PM

This is interesting!

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
January 5, 2012 6:25 PM

To clear this up a bit, sublimation is a thermodynamical phase transition from thermal vaporization. There can be several processes at work here, and mass ejection by sputtering (say, in the solar wind) is not considered sublimation.

That said, the luminescence, if that is what it is, looks a lot like the sputter glow from sputtered material when you look into a sputter chamber or the air glow around atmospheres demonstrated in many ISS images. Even metals, and alkali metals are known to be emitted by Mercury, have efficient emission. (Hence the use of only minute amounts of mercury in luminescent lighting.)

Lights in the Dark
Guest
January 5, 2012 9:56 PM

So you’re suggesting it may be a geo-fluorescence of some sort?

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
January 6, 2012 5:07 PM
Certainly fluorescence, “lights in the light”, could be part of what I suggest. But at a guess the likelihood for ionization is much higher, so I would assume the most part could be emission from electron recombination. Note that the article claims only “tint”, and image processing with more or less artificially reproduced colors introduces artifacts that looks like emission and “bleeding over” effects. I was just wondering if for once there was something more going on, based on my physics intuition and no more. I thought about it some more, triggered by your response, and considering the intensity of ambient light so close to the Sun, I realize a) secondary emission effects would be difficult to make… Read more »
Torbjorn Larsson OM
Member
Torbjorn Larsson OM
January 6, 2012 5:07 PM
Certainly fluorescence, “lights in the light”, could be part of what I suggest. But at a guess the likelihood for ionization is much higher, so I would assume the most part could be emission from electron recombination. Note that the article claims only “tint”, and image processing with more or less artificially reproduced colors introduces artifacts that looks like emission and “bleeding over” effects. I was just wondering if for once there was something more going on, based on my physics intuition and no more. I thought about it some more, triggered by your response, and considering the intensity of ambient light so close to the Sun, I realize a) secondary emission effects would be difficult to make… Read more »
Torbjorn Larsson OM
Member
Torbjorn Larsson OM
January 6, 2012 5:07 PM
Certainly fluorescence, “lights in the light”, could be part of what I suggest. But at a guess the likelihood for ionization is much higher, so I would assume the most part could be emission from electron recombination. Note that the article claims only “tint”, and image processing with more or less artificially reproduced colors introduces artifacts that looks like emission and “bleeding over” effects. I was just wondering if for once there was something more going on, based on my physics intuition and no more. I thought about it some more, triggered by your response, and considering the intensity of ambient light so close to the Sun, I realize a) secondary emission effects would be difficult to make… Read more »
Torbjorn Larsson OM
Member
Torbjorn Larsson OM
January 6, 2012 5:07 PM
Certainly fluorescence, “lights in the light”, could be part of what I suggest. But at a guess the likelihood for ionization is much higher, so I would assume the most part could be emission from electron recombination. Note that the article claims only “tint”, and image processing with more or less artificially reproduced colors introduces artifacts that looks like emission and “bleeding over” effects. I was just wondering if for once there was something more going on, based on my physics intuition and no more. I thought about it some more, triggered by your response, and considering the intensity of ambient light so close to the Sun, I realize a) secondary emission effects would be difficult to make… Read more »
Torbjorn Larsson OM
Member
Torbjorn Larsson OM
January 5, 2012 6:25 PM

To clear this up a bit, sublimation is a thermodynamical phase transition from thermal vaporization. There can be several processes at work here, and mass ejection by sputtering (say, in the solar wind) is not considered sublimation.

That said, the luminescence, if that is what it is, looks a lot like the sputter glow from sputtered material when you look into a sputter chamber or the air glow around atmospheres demonstrated in many ISS images. Even metals, and alkali metals are known to be emitted by Mercury, have efficient emission. (Hence the use of only minute amounts of mercury in luminescent lighting.)

Wayne
Guest
Wayne
January 6, 2012 2:36 AM

I’m going to go out on a limb here and make a prediction that these features are related to the trail of sodium ions that Mercury leaves in it’s wake…

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