Mimantean Crater Herschel Reveals Dark Areas in Close Flyby View

Summary: Mimantean crater Herschel reveals dark areas in a close flyby view captured Feb. 13, 2010, by Cassini Orbiter’s narrow angle camera.

Mosaic of eight images reveals the bright walls and dark areas of Herschel Crater and its environs; red arrows = dark streaks near rim of crater walls, green arrows = dark areas on lower portions of crater walls; mosaic created from eight images obtained during close flyby Feb. 13, 2010, by the Cassini-Huygens spacecraft’s Cassini orbiter, from an approximate distance of 30,000 kilometers (19,000 miles); sun-Mimas-spacecraft (phase) angle at 27 degrees; image scale of 180 meters (600 feet) per pixel; NASA ID PIA12568; image addition date 2010-03-29; image credit NASA/JPL/Space Science Institute (SSI): May be used for any purpose without prior permission, via NASA JPL Photojournal

Mimantean crater Herschel reveals dark areas in a close flyby view captured during the Cassini-Huygens spacecraft’s closest-ever flyby Feb. 13, 2010.

“Bright-walled craters, with floors and surroundings about 20 percent darker than the steep crater walls, are notable in this view,” observes California Institute of Technology’s (Caltech) Rebecca Whatmore in her March 29, 2010, multimedia feature, “Examining Herschel Crater,” for the National Aeronautics and Space Administration (NASA) website’s Cassini-Huygens Mission page.

The image looks almost directly at Mimantean crater Herschel in Mimas’ leading hemisphere, the hemisphere that leads the icy satellite’s orbit around its primary, Saturn. The view’s center point is identified as terrain at 10 degrees south latitude, 125 degrees west longitude.

Herschel Crater is centered at minus 1.38 degrees south latitude, 111.76 degrees west longitude, according to the International Astronomical Union’s (IAU) Gazetteer of Planetary Nomenclature. The large impact crater’s northernmost and southernmost latitudes spread to 18.14 degrees north and minus 21.5 degrees south, respectively. Herschel marks its easternmost and westernmost longitudes at 90.91 degrees west and 131.1 degrees west, respectively. Its diameter spans 139 kilometers.

Herschel Crater’s bright walls exhibit dark streaks below the rim and “. . . relatively dark markings along the lower portion . . .” Cassini-Huygens mission scientists attribute the darkening to the gradually concentrated residue of dark impurities from evaporated icy solvents.

The image’s annotated version indicates dark streaks below the rim with a red arrow. A dark streak below Herschel Crater’s northern rim is highlighted. To the crater’s west, a trio of red arrows, in a north-south alignment, point to dark streaks on the west walls of variously sized craters.

A green arrow indicates darkened regions on lower walls. Two examples of darkened lower walls in Herschel Crater are highlighted. One, which marks the lower portion of Herschel’s north-northeastern wall, lies to the near southeast of the crater’s red arrow-highlighted, upper wall dark streak. The second is located along Herschel’s west-northwest wall. Two green arrows to the west of Herschel’s southwestern rim point to craters with dark markings on the lower portions of their western walls.

A hummocky area extensively interrupts the edge of contact between Herschel’s floor and the darker regions on the lower portions of the crater’s walls. Mission scientists associate the hummocky appearance to the occurrence of melted ice flows during the meteor collision that massively gouged Mimas’ leading hemisphere. “That melt filled the bottom of the crater around the central peak,” explains Whatmore.

Herschel Crater’s fairly smooth floor contrasts dramatically with the densely cratered terrain that characterizes Mimas. Pulverized debris and gigantic ice chunks that were ejected by the meteor’s impact scarred the newly-formed crater’s environs with secondary craters and a thick blanket of debris. A probable explanation for “the relative absence of craters on Herschel’s floor” is that the solidification of the floor’s melt pool occurred after the fallback of ejected debris onto the surrounding terrain.

“These are common processes that should occur on bodies without atmospheres throughout the solar system,” Whatmore considers. “They may be accentuated on Mimas because of the large size of Herschel in comparison to Mimas’ size.”

The image that shows the bright walls and dark areas in and around Herschel Crater was obtained during the Cassini-Huygens spacecraft’s flyby on Saturday, Feb. 13, 2010. The flyby achieved the closest-ever approach to Mimas, logging a distance of only approximately 9,500 kilometers (5,900 miles).

This particular image comprises eight images that were obtained at an approximate distance of 30,000 kilometers (19,000 miles) from Mimas. The sun-Mimas-spacecraft, or phase, angle measured 27 degrees.

The Cassini-Huygens spacecraft’s Cassini orbiter obtained seven images in visible light with its narrow-angle camera (NAC). An image taken by the orbiter’s wide-angle camera (WAC) was combined with the mosaic of seven images as a fill for the mosaic’s lower right.

The takeaways for Mimantean crater Herschel’s dark areas are that the Cassini-Huygens spacecraft’s close flyby on Feb. 13, 2010, obtained eight images centered on Herschel Crater; that the mosaic created from the images reveals the dark-streaked, bright walls of Herschel Crater and its environs; and that the darkening on the upper and lower portions of the walls of Herschel Crater and its surrounding craters are attributed to concentrated residues of dark impurities from evaporating icy solvents.

The Cassini-Huygens spacecraft’s (upper center) narrow-angle and (lower center) wide-angle cameras are contained in the Cassini orbiter’s Imaging Science Subsystem (ISS): courtesy National Aeronautics and Space Administration (NASA), via NASA Cassini at Saturn mission pages

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Mosaic of eight images reveals the bright walls and dark areas of Herschel Crater and its environs; red arrows = dark streaks near rim of crater walls, green arrows = dark areas on lower portions of crater walls; mosaic created from eight images obtained during close flyby Feb. 13, 2010, by the Cassini-Huygens spacecraft’s Cassini orbiter, from an approximate distance of 30,000 kilometers (19,000 miles); sun-Mimas-spacecraft (phase) angle at 27 degrees; image scale of 180 meters (600 feet) per pixel; NASA ID PIA12568; image addition date 2010-03-29; image credit NASA/JPL/Space Science Institute (SSI): May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA12568; Generally not subject to copyright in the United States; may use this material for educational or informational purposes, including photo collections, textbooks, public exhibits, computer graphical simulations and Internet Web pages; general permission extends to personal Web pages, via NASA Image and Video Library @ https://images.nasa.gov/details/PIA12568; via NASA Cassini-Huygens mission pages @ https://www.nasa.gov/mission_pages/cassini/multimedia/pia12568.html

The Cassini-Huygens spacecraft’s (upper center) narrow-angle and (lower center) wide-angle cameras are contained in the Cassini orbiter’s Imaging Science Subsystem (ISS): courtesy National Aeronautics and Space Administration (NASA), via NASA Cassini at Saturn mission pages @ https://solarsystem.nasa.gov/missions/cassini/the-journey/the-spacecraft/

For further information:

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Available via Biodiversity Heritage Library @ https://biodiversitylibrary.org/page/51828893

Herschel, William. “Description of a Forty-Feet Reflecting Telescope. Read June 11, 1795.” Philosophical Transactions of the Royal Society of London for the Year MDCCXCV, vol. LXXXV, Part II: 347-409. London UK: Peter Elmsly, Printer to The Royal Society, 1795.
Available via Biodiversity Heritage Library @ https://biodiversitylibrary.org/page/51831451

International Astronomical Union. “Herschel .” USGS Astrogeology Science Center > Gazetteer of Planetary Nomenclature. Last updated Aug. 14, 2008.
Available @ https://planetarynames.wr.usgs.gov/Feature/2478

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Available @ https://earth-and-space-news.blogspot.com/2011/10/mimantean-crater-herschel-displays.html

Marriner, Derdriu. “Mimantean Crater Herschel Honors Mimas Discoverer William Herschel.” Earth and Space News. Wednesday, Sept. 7, 2011.
Available @ https://earth-and-space-news.blogspot.com/2011/09/mimantean-crater-herschel-honors-mimas.html

Marriner, Derdriu. “Mimantean Crater Herschel Partially Overlies Oeta Chasma.” Earth and Space News. Wednesday, Oct. 5, 2011.
Available @ https://earth-and-space-news.blogspot.com/2011/09/mimantean-crater-herschel-partially.html

Marriner, Derdriu. “William Herschel Discovered Mimas With Newly Built 40-Foot Telescope.” Earth and Space News. Wednesday, Sep. 21, 2019.
Available @ https://earth-and-space-news.blogspot.com/2011/09/william-herschel-discovered-mimas-with.html

Marriner, Derdriu. “William Herschel Discovered Saturnian Moon Mimas Sept. 17, 1789.” Earth and Space News. Wednesday, Sept. 14, 2011.
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Available @ https://pubs.er.usgs.gov/publication/i1489
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Whatmore, Rebecca, ed. “Examining Herschel Crater.” NASA > Mission Pages > Cassini-Huygens Mission to Saturn > Multimedia. March 29, 2010.
Available @ https://www.nasa.gov/mission_pages/cassini/multimedia/pia12568.html

Whatmore, Rebecca, ed. “Streaked Craters in False-Color.” NASA > Mission Pages > Cassini-Huygens Mission to Saturn > Multimedia. March 29, 2010. Available @ https://www.nasa.gov/mission_pages/cassini/multimedia/pia12571.html

Whatmore, Rebecca, ed. “Streaks and Markings on Mimas.” NASA > Mission Pages > Cassini-Huygens Mission to Saturn > Multimedia. March 29, 2010.
Available @ https://www.nasa.gov/mission_pages/cassini/multimedia/pia12571.html