Earth and Space News: October 2011

Wednesday, October 26, 2011

Herschel Crater Vicinity Has Weaker Infrared Brightness Than Mimas Norm

Summary: The Herschel Crater vicinity has weaker infrared brightness than the Mimas norm, according to the Cassini-Huygens spacecraft’s Aug. 2, 2005, images.

The Herschel Crater vicinity has weaker infrared brightness than the Mimas norm, according to images obtained Aug. 2, 2005, by the Cassini-Huygens spacecraft’s Cassini orbiter.

The Cassini orbiter obtained multi-spectral views of Saturnian moon Mimas with its narrow-angle camera (NAC). One image was taken with a clear filter. Three color images were obtained with ultraviolet, green and infrared filters.

The Cassini Imaging Central Laboratory for Operations (CICLOPS), based at the Space Science Institute in Boulder, Colorado, serves as the imaging operations center for the Cassini-Huygens Mission to Saturn. CICLOPS initially processed the clear-filter image separately from the color images. The separate processing allowed for enhancement of bright and sharp contrasts in the clear-filter image’s visible features.

The imaging team created a color map by combining the three color images into a single black-and-white image. The color map allowed for mapping isolated regional color differences.

“This ‘color map’ was then superimposed over the clear-filter image . . .,” notes California Institute of Technology’s (Caltech) Susan M. Watanabe in her multimedia feature, “Mimas Showing False Colors -- 1,” published Aug. 5, 2005, on the National Aeronautics and Space Administration’s (NASA) Cassini-Huygens mission page.

The image produced by combining the color map with the brightness image allowed for associating color-differentiated Mimantean surface materials with geological features. “Shades of blue and violet in the image . . . are used to identify surface materials that are bluer in color and have a weaker infrared brightness than average Mimas materials, which are represented by green,” Watanabe explains.

Watanabe’s article includes the separately-processed clear-filter image and the composite image yielded by combining the color map with the processed clear-filter image. Mimas’ prominent feature, Herschel Crater, dominates both images.

The false color image reveals a broad surround of Herschel Crater by the unusual bluer surface materials. Yet, distribution of these materials in and around Herschel is not uniform. The greatest concentration of blueness occurs in the crater’s western environs.

“The origin of the color differences is not yet understood,” Watanabe observes. “It may represent ejecta material that was excavated from inside Mimas when the Herschel impact occurred. The bluer color of these materials may be caused by subtle differences in the surface composition or the sizes of grains making up the icy soil.”

The Cassini-Huygens spacecraft’s Imaging Science Subsystem (ISS) narrow-angle camera (NAC) obtained the four multi-spectral images on Aug. 2, 2005, from a distance of 228,000 kilometers (142,500 miles) from Mimas. The sun-Mimas-spacecraft (phase) angle measured 45 degrees.

At the time of the images, the Cassini-Huygens spacecraft’s position above Mimas was calculated at 25 degrees south latitude, 134 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 crater’s northernmost and southernmost latitudes reach to 18.14 degrees north and minus 21.5 degrees south, respectively. Its easternmost and westernmost longitudes extend to 90.91 degrees west and 131.1 degrees west, respectively.

Herschel Crater’s diameter, which spans 139 kilometers, approximates one-third of its parent body’s diameter. Mimas has a diameter of 394 kilometers, according to U.S. Astrogeology Science Center astrogeologist Raymond Milner Batson (July 8, 1931-May 5, 2013) in his 1984 NASA-published report, Voyage 1 and 2 Atlas of Six Saturnian Satellites.

The takeaways for the occurrence of infrared brightness in the Herschel Crater vicinity that is weaker than the Mimas norm are that a composite of four images obtained Aug. 2, 2005, by the Cassini-Huygens spacecraft’s narrow-angle camera (NAC) reveals color-differentiated surface materials on Saturnian moon Mimas; that the color variations are associated with geological features; that bluer materials, which have a weaker-than-average infrared brightness, surround Herschel Crater, with the greatest concentration occurring in the crater’s western environs; and that the color differences have a not-yet-understood origin.

View of icy Mimas beyond Saturn’s limb looks, from about 3 degrees above Saturn’s ringplane, toward the rings’ sunlit side; natural color view created from red, green and blue spectral-filter images acquired Sept. 4, 2007, by the Cassini-Huygens spacecraft’s narrow-angle camera (NAC) at approximate distances of 2.7 million kilometers (1.7 million miles) from Saturn and 2.8 million kilometers (1.8 million miles) from Mimas: courtesy NASA / JPL (Jet Propulsion Laboratory) / SSI (Space Science Institute), via NASA Cassini-Huygens mission pages

Acknowledgment

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

Image credits:

Clear-filter image (left), processed for surface feature brightness and sharpness, and composite image (right) of clear-filter’s brightness image and color map of three color images (ultraviolet, green, infrared) reveal color-differentiated variations in the composition or texture of surface materials on seventh-known Saturnian moon Mimas; blue materials = weaker infrared brightness, green materials = average Mimas surface materials; images processed from images obtained Aug. 2, 2005, by the Cassini-Huygens spacecraft’s narrow-angle camera (NAC), from a distance of 228,000 kilometers (142,500 miles); sun-Mimas-spacecraft (phase) angle at 45 degrees: NASA ID PIA06257; image addition date 2005-08-05; image credit NASA/JPL/Space Science Institute: May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA06257; 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/PIA06257; via NASA Cassini-Huygens mission pages @ https://www.nasa.gov/mission_pages/cassini/multimedia/pia06257.html

Batson, Raymond M. (Milner). Voyager 1 and 2 Atlas of Six Saturnian Satellites. NASA SP-464. Washington DC: National Aeronautics and Space Administration Scientific and Technical Information Branch, 1984.
Available via NASA NTRS (NASA Technical Reports Server) @ https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19840027171.pdf

Batson, Raymond M.; and Joel F. Russell, eds. Gazetteer of Planetary Nomenclature 1994. U.S. Geological Survey Bulletin 2129. Washington DC: United States Government Printing Office, 1995.
Available via USGS Publications Warehouse @ https://pubs.er.usgs.gov/publication/b2129

Herschel, William. “Account of the Discovery of a Sixth and Seventh Satellite of the Planet Saturn; With Remarks on the Construction of Its Ring, Its Atmosphere, Its Rotation on an Axis, and Its Spheroidical Figure. Read November 12, 1789.” Philosophical Transactions of the Royal Society of London, vol. LXXX, for the Year 1790, Part I: 1-20. London UK: Lockyer Davis and Peter Elmsly, Printers to The Royal Society, MDCCXC (1790).
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

Lavoie, Sue, site manager. “PIA06259: Mimas Showing False Colors #1.” NASA Jet Propulsion Laboratory Photojournal. Image addition date Aug. 5, 2005.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA06257

Lavoie, Sue, site manager. “PIA06259: Mimas Showing False Colors #2.” NASA Jet Propulsion Laboratory Photojournal. Image addition date Aug. 8, 2005.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA06259

Lavoie, Sue, site manager. “PIA10478: Mimas Adrift.” NASA Jet Propulsion Laboratory Photojournal. Image addition date Sept. 26, 2008.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA10478

Levy, David H. Skywatching. Revised and updated. San Francisco CA: Fog City Press, 1994.

Marriner, Derdriu. “Mimantean Crater Herschel Displays Subtle Colors in Close Flyby View.” Earth and Space News. Wednesday, Oct. 12, 2011.
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. “Mimantean Crater Herschel Reveals Dark Areas in Close Flyby View.” Earth and Space News. Wednesday, Oct. 19, 2011.
Available @ https://earth-and-space-news.blogspot.com/2011/10/mimantean-crater-herschel-reveals-dark.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.
Available @ https://earth-and-space-news.blogspot.com/2011/09/william-herschel-discovered-saturnian.html

Moore, Patrick, Sir. Philip’s Atlas of the Universe. Revised edition. London UK: Philip’s, 2005.

NASA’s Jet Propulsion Laboratory, Pasadena, California. “Space Images for NASA / JPL.” NASA Tech Briefs, vol. 34, no. 9 (September 2010): 46-47.
Available via NASA NTRS (NASA Technical Reports Server) @ https://ntrs.nasa.gov/search.jsp?R=20100033535
Available via NASA NTRS (NASA Technical Reports Server) @ https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100033566.pdf
Available via Tech Briefs @ https://www.techbriefs.com/component/content/article/tb/issue-archive/10999

U.S. Geological Survey. “Preliminary Pictorial Map of Mimas.” Atlas of the Saturnian Satellites. IMAP 1482. Prepared for the Voyager Imaging Team in cooperation with the Jet Propulsion Laboratory, California Institute of Technology and the National Aeronautics and Space Administration. Directed by R.M. (Raymond Milner) Batson / U.S. Geological Survey Branch of Astrogeologic Studies. Airbrush representation by Jay L. Inge. Data preparation and preliminary image processing by K.F. Mullins, Christopher Isbell, E.M. Lee, H.G. Morgan and B.A. Skiff. Reston VA: U.S. Geological Survey, 1982.
Available @ https://pubs.er.usgs.gov/publication/i1489
Available @ http://171.67.35.48/view/6829740

Watanabe, Susan, ed. “Mimas Showing False Colors -- 1.” NASA > Mission Pages > Cassini-Huygens Mission to Saturn > Multimedia. Aug. 5, 2005. Page last updated April 29, 2008.
Available @ https://www.nasa.gov/mission_pages/cassini/multimedia/pia06257.html

Watanabe, Susan, ed. “Up Close to Mimas.” NASA > Mission Pages > Cassini-Huygens Mission to Saturn > Multimedia. Aug. 5, 2005. Page last updated April 29, 2008.
Available @ https://www.nasa.gov/mission_pages/cassini/multimedia/pia06258.html

Whatmore, Rebecca, ed. “Bizarre Temperatures on Mimas.” NASA > Mission Pages > Cassini-Huygens Mission to Saturn > Multimedia. March 29, 2010.
Available @ https://www.nasa.gov/mission_pages/cassini/multimedia/pia12867.html

Whatmore, Rebecca, ed. “Color Near Herschel Crater.” NASA > Mission Pages > Cassini-Huygens Mission to Saturn > Multimedia. March 29, 2010. Page last updated May 12, 2010.
Available @ https://www.nasa.gov/mission_pages/cassini/multimedia/pia12572.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

Wednesday, October 19, 2011

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.

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

Levy, David H. Skywatching. Revised and updated. San Francisco CA: Fog City Press, 1994.

Moore, Patrick, Sir. Philip’s Atlas of the Universe. Revised edition. London UK: Philip’s, 2005.

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

Saturday, October 15, 2011

Five Tree Felling Plan Steps for Successful Removals and Worker Safety

Summary: Ralph Tompkins of ArborMaster Training, Inc., likes to be called Rip and to follow five tree felling plan steps for successful removals and worker safety.

Determining the direction of tree fall is the second in Ralph Tompkins' five-step felling plan for tree removal safety; direction indicated on OSHA diagram offers ample, clear pathway to ease removal: Occupational Safety & Health Administration (OSHA)/US Department of Labor, Public Domain, via OSHA

Five tree felling plan steps accommodate successful removals and worker safety, according to an article by Ralph Tompkins of ArborMaster Training, Inc., in Little Compton, Rhode Island, for Arborist News October 2011.

Working the Five-Step Felling Plan brings concerns that "Safety needs to remain the top priority" to the forefront with the first step identifying hazards and obstacles. The International Society of Arboriculture's Glossary of Arboricultural Terms considers "personal injury, property damage, or disruption of human activities" as results of hazardous conditions and situations. Arborists describe as obstacles houses and vehicles, people and personal property, trees and "whatever you can hurt or damage in the process of felling a tree."

Geometric principles of similar right triangles estimate tree height at positions where a stick's measurement from handhold to tip equals a tree's from cut to treetop.

Height estimates by hypsometers, rangefinders or sticks furnish information for establishing danger zones whose distance from tree base to circle perimeter equals 1.5 times tree height.

The second of the five tree felling plan steps gives the direction that a tree may fall because of a backward, forward or sideward lean weight. A plumb line dropped down from the center spot in a tree's canopy hits the ground in such a way as to specify direction of fall. A tree's bad side identifies the backward, forward or sideward-leaning direction of fall whereas the good side indicates the location where all cutting operations must finish.

Sawyers generally judge backward-leaning and straight-standing trees as easily felled by gravity once pull lines and wedges lift them over center and sideward-leaning trees as dangerous.

The third of the five tree felling plan steps keeps clear of personnel, excepting the sawyer, the "escape route away from the base of the tree."

The best escape route leads the sawyer over a "path of egress" on the tree's good side, "opposite the direction of fall at a 45-degree angle." It minimizes "unplanned event" occurrences within the "15-foot (4.5 m) radius of the tree base" where 80 to 90 percent of tree felling accidents take place. It needs to be straightforward since side-leaning, weak-fibered eucalyptus, tree of heaven and white pine cannot hold hinges like strong-fibered hickory, ponderosa pine and white oak.

The fourth step offers three notches, with open-face notches of 70 to 90 degrees providing, through hinges working longer, greater control than conventional or Humboldt notches.

Sawyers prefer hinge lengths at 80 percent, and hinge thickness at 7 to 10 percent, of a tree's diameter, excepting dry, fibrous, frozen or large-sized trees.

Chain saw-made bore cuts, cuts into tree rears and stepped back cuts away from notch apexes qualify as fifth in the five tree felling plan steps. Back-leaning, open-face-notched and straight-standing trees require back cuts whereas open-face notches in tight-spaced trees respond as well as conventional or Humboldt notches to stepped back cuts. Bore cuts saw nicely into forward-leaning trees unless chain saw bar top-, not bottom-, effected cuts provoke "barber chair" splits vertically upward and kickbacks into sawyers.

Margins for error in urban environments turn out to be "very small" so planning procedures must consider alternative methods when felling trees turns unprofitable and unsafe.

felling direction, danger area and safe retreat paths: Occupational Safety & Health Administration (OSHA)/US Department of Labor, Public Domain, via OSHA

Acknowledgment

My special thanks to:
talented artists and photographers/concerned organizations who make their fine images available on the internet;
University of Illinois at Urbana-Champaign for superior on-campus and on-line resources.

Image credits:

Determining the direction of tree fall is the second in Ralph Tompkins' five-step felling plan for tree removal safety: Occupational Safety & Health Administration (OSHA)/US Department of Labor, Public Domain, via OSHA @ https://www.osha.gov/SLTC/etools/logging/manual/felling/felling_direction.html

felling direction, danger area and safe retreat paths: Occupational Safety & Health Administration (OSHA)/US Department of Labor, Public Domain, via OSHA @ https://www.osha.gov/SLTC/etools/logging/manual/felling/retreat_path.html

For further information:

International Society of Arboriculture. 2005. Glossary of Arboricultural Terms. Champaign IL: International Society of Arboriculture.

Marriner, Derdriu. 13 August 2011. “Natives and Non-Natives as Successfully Urbanized Plant Species.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/08/natives-and-non-natives-as-successfully.html

Marriner, Derdriu. 11 June 2011. “Tree Ring Patterns for Ecosystem Ages, Dates, Health and Stress.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/06/tree-ring-patterns-for-ecosystem-ages.html

Marriner, Derdriu. 9 April 2011. “Benignly Ugly Tree Disorders: Oak Galls, Powdery Mildew, Sooty Mold, Tar Spot.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/04/benignly-ugly-tree-disorders-oak-galls.html

Marriner, Derdriu. 12 February 2011. “Tree Load Can Turn Tree Health Into Tree Failure or Tree Fatigue.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/02/tree-load-can-turn-tree-health-into.html

Marriner, Derdriu. 11 December 2010. “Tree Electrical Safety Knowledge, Precautions, Risks and Standards.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2010/12/tree-electrical-safety-knowledge.html

Tompkins, Ralph. October 2011. "Working the Five-Step Felling Plan." Arborist News 20(5): 12-16.

Wednesday, October 12, 2011

Mimantean Crater Herschel Displays Subtle Colors in Close Flyby View

Summary: Mimantean crater Herschel displays subtle colors in a close flyby view obtained Feb. 13, 2010, by Cassini Orbiter’s narrow angle camera.

Mimantean crater Herschel displays subtle colors in a close flyby view obtained during the Cassini-Huygens spacecraft’s closest-ever flyby Feb. 13, 2010.

An image described by Rebecca Whatmore for the National Aeronautics and Space Administration (NASA) website’s March 29, 2010, multimedia feature, “Color Near Herschel Crater,” reveals subtle colors in the terrain in and around Herschel Crater on Saturnian moon Mimas. The image captures the northern part of the natural satellite’s leading, or forward-facing, hemisphere, which leads in the direction of Mimas’ orbit around its primary.

“The natural color of Mimas visible to the human eye may be a uniform gray or yellow color, but this mosaic has been contrast-enhanced and shows differences at other wavelengths of light,” stated Whatmore. Subtle blues color Herschel Crater and its environs. The older, densely cratered terrain beyond Herschel Crater’s environs exhibits a greenish cast.

“The origin of the color differences is not yet understood, but may be caused by subtle differences in the surface composition between the two terrains,” Whatmore noted. Color variations between the terrain in Herschel Crater’s vicinity and distant terrain also are consistent with false color images obtained Aug. 2, 2005, by Cassini orbiter’s narrow-angle camera.

The Cassini-Huygens spacecraft launched Wednesday, Oct. 15, 1997, at 08:43:00 Universal Coordinated Time (4:43 a.m. Eastern Daylight Time), from Cape Canaveral Air Force Station (CCAFS) Space Launch Complex 40 (SLC-40) as the fourth space probe visitor to Saturn and the first Saturn orbiter. The Cassini-Huygens spacecraft comprises two elements. The Cassini orbiter carries 12 instruments. The Huygens probe is equipped with six instruments.

The spacecraft successfully executed Saturn orbital insertion (SOI) Thursday, July 1, 2004, at 02:48 UTC (Wednesday, June 30, at 10:48 p.m. EDT). On Saturday, Feb. 13, 2010, the spacecraft made its closest-ever flyby of Mimas, approaching within approximately 9,500 kilometers (5,900 miles) of the Saturnian moon.

During the Feb. 13 close flyby, the Cassini orbiter’s narrow-angle camera obtained ultraviolet, green and infrared images of Herschel Crater and its environs. The images were captured at an approximate distance of 16,000 kilometers (10,000 miles) from Mimas.

Based at the Space Science Institute in Boulder, Colorado, the Cassini imaging team reprojected the images, using orthographic projection, into a single mosaic in order to exaggerate the terrain’s color variations. The color image was then combined with a high-resolution, black-and-white image, taken in visible light with Cassini orbiter’s wide-angle camera. The resulting false-color view of Herschel Crater benefits from the high-resolution information provided by the visible light’s clear-filter images and the color information revealed by the ultraviolet, green and infrared filter images.

The Cassini-Huygens mission, commonly known as Cassini, is designed as a collaborative project involving NASA, the European Space Agency (ESA; Agence spatiale européenne) and the Italian Space Agency (ASI; Agenzia Spaziale Italiana). NASA’s Jet Propulsion Laboratory (JPL) in California designed, developed and assembled the Cassini orbiter and its two onboard cameras, a narrow-angle camera (NAC) and a wide-angle camera (WAC). The Jet Propulsion Laboratory manages the Saturn-focused mission on behalf of NASA’s Science Mission Directorate (SMD) in Washington.

The Cassini orbiter’s name honors Italian (naturalized French astronomer and engineer Giovanni Domenico Cassini (June 8, 1625-Sept. 14, 1712). Cassini’s astronomical contributions include discovering four Saturnian moons and Saturn’s Cassini Division. Cassini discovered his first Saturnian moon, Iapetus in Oct. 25, 1671. He discovered Rhea on Dec. 23, 1672. His discovery of Tethys occurred on March 21, 1684. Cassini made his discovery of Dione on March 21, 1684. He discovered the Cassini Division, a region between Saturn’s A ring and B ring, in 1675 via a refracting telescope at the Paris Observatory.

The Huygens probe honors Christiaan Huygens (April 14, 1629-July 8, 1695). The Dutch astronomer, inventor, mathematician and physicist’s astronomical contributions include discovery of Titan, Saturn’s largest moon, and studying Saturn’s rings. Huygens made his discovery of Saturn’s Titanic moon on March 25, 1655.

The takeaways for Mimantean crater Herschel’s subtle color displays are that the Cassini-Huygens spacecraft’s Cassini orbiter obtained ultraviolet, green and infrared filtered images of the crater’s neighborhood during a closest-ever flyby on Feb. 13, 2010; that a false color view released by NASA on March 29 shows bluish colors for Herschel Crater and its environs; that terrain distanced from the large impact crater reveals a greenish cast; and that the terrain-dependent color variations are hypothesized as reflecting “subtle differences in the surface composition between the two terrains.”

Acknowledgment

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

Image credits:

Herschel Crater dominates the right lower half of false color view of northern part of Mimantean moon’s leading hemisphere; mosaic combines ultraviolet, green and infrared filter images with black-and-white, high resolution clear-filter image obtained Feb. 13, 2010, by Cassini orbiter during closest-ever flyby; NASA ID PIA12572; 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/PIA12572; 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/PIA12572; via NASA Cassini-Huygens mission pages @ https://www.nasa.gov/mission_pages/cassini/multimedia/pia12572.html

Artist’s concept of Saturn Orbital Insertion (SOI) maneuver shows that the Cassini-Huygens spacecraft has just crossed the ring plane, just after the beginning of firing by the spacecraft’s main engine (center) in order to reduce velocity with respect to Saturn; NASA ID PIA03883; image addition date 2002-12-11; image credit NASA/JPL: May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA03883; 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-PIA03883

For further information:

Lavoie, Sue, site manager. “PIA03883: Artists’s Conception of Cassini Saturn Orbit Insertion.” NASA Jet Propulsion Laboratory Photojournal. Image addition date Dec. 11, 2002.
Available @ https://photojournal.jpl.nasa.gov/catalog/pia03883

Levy, David H. Skywatching. Revised and updated. San Francisco CA: Fog City Press, 1994.

Moore, Patrick, Sir. Philip’s Atlas of the Universe. Revised edition. London UK: Philip’s, 2005.

Wednesday, October 5, 2011

Mimantean Crater Herschel Partially Overlies Oeta Chasma

Summary: Mimantean crater Herschel partially overlies Oeta Chasma with the crater’s north-northwest rim and hosts a set of lineaments across its interior.

Mimantean crater Herschel partially overlies Oeta Chasma, a chasm angling at the crater’s north-northwest rim, while a set of lineaments cross Herschel’s interior.

Herschel Crater lies on the leading hemisphere, the hemisphere facing the direction of motion, of its parent body, Saturnian moon Mimas. “The most prominent single feature on Mimas is Herschel, an unrelaxed complex crater 130 kilometers in diameter,” stated University of Arizona Lunar and Planetary Laboratory astrogeologist Steven K. Croft in his report, “Mimas: Tectonic Structure and Geologic History,” published by NASA in June 1991 (page 95).

The International Astronomical Union’s (IAU) Gazetteer of Planetary Nomenclature centers Herschel Crater at minus 1.38 degrees south latitude, 111.76 degrees west longitude. The large impact crater obtains north and south latitudinal extremes of 18.14 degrees north and minus 21.5 degrees south, respectively. It registers its eastern and western longitudinal extents at 90.91 degrees west and 131.1 degrees west, respectively. Herschel Crater’s diameter measures 139 kilometers.

Steven K. Croft’s June 1991 report considered two geologic features coincident with Herschel Crater. He examined a set of lineaments across the crater’s surface and a chasm partially superimposed by Herschel.

Croft defined lineaments as a class comprising “. . . a large number of long, narrow features. Lineament widths range from near the limit of resolution (1-2 km on the best images) to about 4 km. Lineament segments range in length from a few tens to several hundreds of kilometers” (page 95). He found that most lineaments “. . . are members of curvilinear sets of parallel structures with fairly constant spacings and distinct orientations.”

For convenience, Croft referred to Herschel’s set of unnamed lineaments as Herschel-Galahad. The name indicated the nearby feature, Galahad Crater.

Lying to the southwest of Herschel, Galahad is centered at minus 45.32 degrees south latitude, 145.31 degrees west longitude. It marks northernmost and southernmost latitudes at minus 40.42 degrees south and minus 50.42 degrees south, respectively. Its easternmost and westernmost longitudes occur at 138.63 degrees west and 152.63 degrees west, respectively. Galahad Crater has a diameter of 34 kilometers.

The set of Herschel-Galahad lineaments is centered at 30 degrees south latitude, 130 degrees west longitude, according to Croft’s determination. He placed their spacing at 15 to 30 kilometers and their direction at a northeast-to-southwest trend.

The second feature considered with respect to Herschel Crater is Oeta Chasma. The IAU’s Gazetteer of Planetary Nomenclature defines a chasma (plural: chasmata) as a “deep, elongated, steep-sided depression.”

“. . . Oeta Chasma is directly superposed by Herschel,” (page 96) noted University of Arizona Lunar and Planetary Laboratory astrogeologist Steven K. Croft in his report, “Mimas: Tectonic Structure and Geologic History,” published by NASA in June 1991. Herschel’s north-northwestern rim overlies southeastern portions of the elongated, northeast-to-southwest-oriented chasm.

Oeta Chasma is centered at 19 degrees north latitude and 122.7 degrees west longitude. The degraded chasm registers its northernmost and southernmost latitudes at 35 degrees north and 8 degrees north, respectively. It obtains easternmost and westernmost longitudes at 111.4 degrees west and 132 degrees west, respectively. Oeta Chasma’s diameter spans 110 kilometers.

Croft’s study of Herschel Crater in the context of its parent body’s tectonic structure and geologic history proposed a sequence for the crater, its lineaments and Oeta Chasma. The formation of Oeta Chasma occurred before the impact that punched Herschel Crater into the Mimantean surface. “The degraded chasmata formed first, followed by the Herschel impact, and then the lineaments . . .” (page 96). The set of Herschel-Galahad lineaments “. . . crosses Herschel, indicating structural activity after Herschel’s formation.”

The takeaway for Mimantean crater Herschel’s partial overlying of Oeta Chasma and for the presence of a set of lineaments across the crater’s floor is that the sequence of events for Herschel Crater, its chasm and its curvilinear set probably occurred firstly with Oeta Chasma’s formation, secondly with Herschel Crater’s impact and then, thirdly, with the Herschel-Galahad lineaments’ crosscut of Herschel Crater.

Geologic sketch map of Mimas shows Herschel Crater (left center), with Oeta Chasma angled at the crater’s north-northwest rim, Herschel-Galahad set’s curvilinear crosscut of Herschel’s surface and Galahad Crater (lower left); S.K. Croft, Mimas: Tectonic Structure and Geologic History (1991), page 97: Public Domain, via NASA NTRS (NASA Technical Reports Server)

Acknowledgment

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

Image credits:

“Mimas drifts along in its orbit against the azure backdrop of Saturn’s northern latitudes in this true color view”: Cassini Orbiter spacecraft narrow angle camera image, obtained Jan. 18, 2005, at an approximate distance of 1.4 million kilometers (870,000 miles) from Saturn; NASA ID PIA06176; image addition date 2005-02-08; 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/PIA06176; 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/PIA06176

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Available @ https://planetarynames.wr.usgs.gov/DescriptorTerms

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Lavoie, Sue, site manager. “PIA06176: Mimas Blues.” NASA Jet Propulsion Laboratory Photojournal. Image addition date Feb. 8, 2005.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA06176

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Available via NASA NTRS (NASA Technical Reports Server) @ https://ntrs.nasa.gov/search.jsp?R=19920001510

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