{"id":769829,"date":"2023-10-17T14:31:22","date_gmt":"2023-10-17T18:31:22","guid":{"rendered":"http:\/\/spaceweekly.com\/?p=769829"},"modified":"2023-10-17T14:31:22","modified_gmt":"2023-10-17T18:31:22","slug":"mercurys-strange-hollows","status":"publish","type":"post","link":"https:\/\/spaceweekly.com\/?p=769829","title":{"rendered":"Mercury\u2019s Strange Hollows"},"content":{"rendered":"
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6 min read<\/p>\n

Mercury\u2019s Strange Hollows<\/h1>\n<\/div>\n<\/div>\n<\/div>\n

Enigmatic depressions on the surface have puzzled scientists since the 1970s<\/strong><\/h3>\n
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NASA\u2019s MESSENGER probe has discovered a surprise on Mercury: Something is digging \u201chollows\u201d\u00a0in the surface of the innermost planet.<\/figcaption><\/figure>\n

NASA\u2019s MESSENGER spacecraft discovered strange hollows on the surface of Mercury. Images taken from orbit revealed thousands of mysterious depressions, pitted and uneven, in areas all across the planet, up to a half-mile (800 meters) across and 120 feet (37 meters) deep. This mosaic view of the Raditladi impact basin includes individual frames capturing areas about 12 miles (20 km) wide, which merged high-resolution monochrome images from MESSENGER\u2019s Narrow Angle Camera with a lower-resolution enhanced-color image from its Wide Angle Camera.<\/p>\n

For decades, scientists have been puzzling over strange hollows on Mercury\u2019s surface, thousands of peculiar depressions at a variety of longitudes and latitudes, ranging in size from 60 feet to more than a half-mile across (18-800 meters), and up to 120 feet deep (37 meters). No one knows how they got there.<\/p>\n

And while none are as spooky as the Sleepy Hollow of Washington Irving\u2019s legend, Mercury\u2019s hollows are just as mysterious and, so far, seen nowhere else in the universe.\u00a0<\/p>\n

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\"Hollows<\/figure>
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NASA\/Johns Hopkins University Applied Physics Laboratory\/Carnegie Institution for Science<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\n

\u201cThere\u2019s essentially no atmosphere on Mercury,\u201d said planetary geologist David Blewett, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. \u201cWith no atmosphere, wind doesn\u2019t blow and rain doesn\u2019t fall, so the hollows weren\u2019t carved by wind or water. Other forces must be at work.\u201d<\/p>\n

Mercury, the smallest planet in the solar system and closest to the Sun, is battered by heat, radiation, and solar wind; its extreme temperatures range from 800\u00b0F (430\u00b0C) on the sunny side, to as low as -290\u00b0F (-180\u00b0C) on the night side. It\u2019s slightly larger, and similar to our Moon \u2013 airless, rocky, and peppered with impact craters large and small \u2013 but Mercury has rarely been visited by spacecraft, and retains many of its secrets.<\/p>\n

Scientists got their first tantalizing glimpses of the hollows when the Mariner 10<\/a> probe flew past Mercury in the 1970s, and captured low-resolution shots of curious bright areas in some craters.\u00a0<\/p>\n

NASA returned to the small planet with the MESSENGER<\/a> mission, which first flew past Mercury in 2008, then settled into orbit in 2011.<\/p>\n

That spacecraft circled the planet more than 4,000 times in four years, collecting hundreds of thousands of images and other data, and giving researchers new insights into this little-explored world. Mariner had cataloged less than half the planet\u2019s surface during its brief visits 40 years earlier.<\/p>\n

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\"A<\/figure>
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A view of hollows on the crater named for author Edgar Allan Poe on Mercury, \u201cThis sinfully scintillant planet.\u201d In this representation, Poe\u2019s raven-colored rim stands out from the tan volcanic plains that surround it. Tiny hollows speckle the dark rim like blue-white stars in the blackness of night. The image was one of hundreds of high-resolution targeted color observations by MESSENGER\u2019s Wide Angle Camera, using filters of red, green, and blue.<\/div>\n
NASA\/Johns Hopkins University Applied Physics Laboratory\/Carnegie Institution for Science<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\n

\u201cA Little Valley\u2026Among High Hills\u201d<\/strong><\/strong><\/h2>\n

MESSENGER (the Mercury Surface, Space Environment, Geochemistry and Ranging mission) finally provided a sharper view of the enigmatic tracts. To differentiate them from other surface features, researchers dubbed them \u201chollows\u201d (akin to Washington Irving\u2019s description of the terrain in \u201cThe Legend of Sleepy Hollow\u201d \u2013 \u201ca little valley or rather lap of land among high hills.\u201d)<\/p>\n

The probe sent back finely detailed, beautiful images of the hollows, looking in some color-enhanced mosaics like sheets of copper corroded with blue-green patina. In others \u2013 such as shots of Sander crater in Mercury\u2019s vast Caloris basin \u2013 the strange landforms, etched and ragged, glow bright blue amid the surrounding crater walls and mounds. And yet the images and other data, from MESSENGER\u2019s X-Ray Spectrometer, Laser Altimeter, and other instruments, gave only hints and no definitive answers about the hollows.<\/p>\n

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\"Measurements<\/figure>
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This enhanced-color image from the MESSENGER mission shows (from left to right) the craters Munch (38 miles, or 61 km, wide), Sander (32 miles, or 52 km), and Poe (50 miles, 81 km), which lie in the northwest portion of Mercury\u2019s Caloris basin. The hollows are the bright blue areas covering the floor of Sander and dotting the rims of Munch and Poe. The hollows are highly reflective and naturally appear bluish; in images like this, the spacecraft\u2019s Wide Angle Camera used its 11 color filters to exaggerate the color spectrum, to highlight the variation among surface materials.<\/div>\n
NASA\/Johns Hopkins University Applied Physics Laboratory\/Carnegie Institution for Science<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\n

\u201dWhen we got high-resolution views back of Sander, the floor of the crater just looked amazing,\u201d said Carolyn Ernst of Johns Hopkins APL, a deputy instrument scientist on the MESSENGER mission. \u201cIt had all these crazy-shaped, irregular depressions, and it had this bright material outside of it. And to this day, we don\u2019t fully know what causes them.\u201d<\/p>\n

Researchers observed that the hollows are among the youngest and brightest features on the planet, especially compared to the impact craters where most reside, which date back as far as 4 billion years. The hollows, on the other hand, are relatively shiny and new \u2013 about 100,000 years old, on average \u2013 and may still be evolving today.<\/p>\n

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