Apollo 15 Imaged Full Length and Cobra Head of Vallis Schröteri

Summary: Fourth lunar-landing mission Apollo 15 imaged the full length and cobra head of Vallis Schröteri in the near side’s northwestern quadrant.

Oblique view shows Vallis Schröteri (center right) winding toward dark-floored Herodotus Crater (upper right) and away from bright-floored Aristarchus Crater (upper left); photograph by automatically operated Fairchild Mapping (Metric) Camera, SIM (Scientific Instrument Module) Bay, Apollo 15 Service Module; July 31-Aug. 2, 1971); NASA ID S71-44666: Generally not subject to copyright in the United States, via NASA Image and Video Library

Fourth lunar-landing mission Apollo 15 imaged the full length and cobra head of Vallis Schröteri (Schroter’s Valley), a sinuous rille (German: “groove”) on the Aristarchus Plateau in the near side’s northwestern quadrant.

Apollo 15 launched Monday, July 26, 1971, as the ninth crewed mission in the Apollo spaceflight program. The mission made 74 lunar orbits before returning to Earth for a North Pacific Ocean splashdown Saturday, Aug. 7, 1971. Command Module Pilot Alfred “Al” Merrill Worden (born Feb. 7, 1932) and the automatically operated Fairchild Mapping (Metric) Camera in the Service Module’s SIM (Scientific Instrument Module) Bay are credited with photographing Vallis Schröteri while Commander David Randolph Scott (born June 6, 1932) and Lunar Module Pilot James “Jim” Benson Irwin (March 17, 1930-Aug. 8, 1991) explored the lunar surface Friday, July 30, to Monday, Aug. 2.

Vallis Schröteri winds across the Aristarchus Plateau, an elevated rocky rise in the northwestern Oceanus Procellarum (Ocean of Storms). Mare Imbrium (Sea of Showers) lies to the plateau’s northeast.

Vallis Schröteri classifies as a sinuous rille, one of the three types of channels that cleave the lunar surface. Sinuous rilles, which have an ancient riverbed-like appearance, are thought to be the remains of collapsed, ancient lava tubes. Vallis Schröteri ranks as the moon’s largest sinuous rille.

Vallis Schröteri is centered at 26.16 degrees north latitude, minus 51.58 degrees west longitude. The sinuous rille’s northernmost and southernmost latitudes extend to 26.32 degrees north and 24.16 degrees north, respectively. The rille marks easternmost and westernmost longitudes at minus 49.28 degrees west and minus 53.63 degrees west, respectively. Vallis Schröteri’s diameter spans 185.32 kilometers.

Vallis Schröteri begins in the Aristarchus Plateau’s southeastern part and ends on the northwestern part’s western edge. The lava channel broadens at its head into a distinctive shape known as the Cobra Head and narrows, snakelike, toward its toe.

Vallis Schröteri’s head hovers to the north of Aristarchus Plateau’s prominent craters, Aristarchus and Herodotus. The Cobra Head lies northwest of Aristarchus and north-northeast of Herodotus.

Aristarchus Crater is centered at 23.73 degrees north latitude, minus 47.49 degrees west longitude. The bright crater registers northernmost and southernmost latitudes at 24.39 degrees north and 23.07 degrees north, respectively. Aristarchus obtains easternmost and westernmost longitudes of minus 46.77 degrees east and minus 48.21 degrees east, respectively. Its diameter measures 39.99 kilometers.

The Cobra Head, which more closely approaches Herodotus than Aristarchus, appears to be flicking its tongue toward Herodotus. British selenographer Thomas Gwyn Elger (Oct. 27, 1836-Jan. 9, 1897) traced the beginning of Vallis Schröteri’s to within Herodotus. “On the N. there is a gap through which the well-known Serpentine cleft passes on to the floor” (page 84), Elger noted in describing Herodotus in his tour of the lunar near side, The Moon: A Full Description and Map of its Principal Physical Features, published in 1895.

Elger elaborated after detailing the rille’s traversal of Aristarchus Plateau: “. . . N. of Aristarchus . . . it swerves slightly towards the S., becoming wider and wider, up to a place a few miles N. of Herodotus, where it expands into a broad valley; and then, somewhat suddenly contracting in width, and becoming less coarse, enters the ring-plain through a gap in the N. wall, as before mentioned” (page 85).

In their contribution to The Geological Society of America Special Paper 477, published in 2011, planetary volcanologists William Brent Garry and Jacob Elvin Bleacher considered possible origins of the fan-shaped feature uniquely positioned on Herodotus crater’s north inner wall and extending to the floor. Barry and Bleacher suggested an association with the Cobra Head’s formation or with wall degradation.

Herodotus Crater’s dark, lava-flooded floor contrasts with the crater’s bright neighbor, Aristarchus. Herodotus is centered at 23.25 degrees north latitude, minus 49.84 degrees west longitude. The thin-rimmed crater’s northernmost and southernmost latitudes touch 23.85 degrees north and 22.66 degrees north, respectively. Easternmost and westernmost longitudes reach minus 49.19 degrees west and minus 50.48 degrees west, respectively. Herodotus Crater has a diameter of 35.87 kilometers.

The IAU approved Vallis Schröteri as the crater’s official name in 1961, during the organization’s XIIth (12th) General Assembly, held Tuesday, Aug. 15, to Thursday, Aug. 24, in Berkeley, California. The name honors German astronomer Johann Hieronymus Schröter (Aug. 30, 1745-Aug. 29, 1816). The lunar and planetary astronomer’s accomplishments included an early study on lunar topography, Selenotopographische Fragmente zur genauern kenntniss der Mondfläche (Selenotopographical Fragments Intended to Promote a More Accurate Knowledge of the Moon’s Surface), published in 1791.

In their 1977 article, “The Aristarchus-Harbinger Region of the Moon,” planetary geologist Stanley Harris Zisk and six co-authors credit Christiaan Huygens (April 14, 1629-July 8, 1695) with the first recording and sketch of the most conspicuous lunar rille, made in 1686 (page 73). Retired physicist Jim Mosher noted in The Moon-Wiki that the Dutch astronomer-mathematician may have recorded Vallis Schröteri “as early as May 1686.”

Craters Aristarchus and Herodotus received official name approval in 1935, during the IAU’s Vth (5th) General Assembly, held Wednesday, July 10, to Wednesday, July 17, in Paris, France. Aristarchus honors Aristarchus of Samos (ca. 310-ca. 230 BCE). The ancient Greek astronomer-mathematician is credited with the first known heliocentric model of the solar system. Herodotus Crater’s namesake is Herodotus of Halikarnassus (ca. 484-408 BCE). The ancient Greek historian is known as The Father of History, a title conferred on him in the first century BCE by assassinated Roman statesman Marcus Tullius Cicero (Jan. 3, 106-Dec. 7, 43 BCE).

The takeaways for Apollo 15’s images of the full length and Cobra Head of Vallis Schröteri are that the lava channel ranks as the moon’s largest sinuous rille (German: “groove”) and that the Cobra Head begins near or in dark-floored Herodotus Crater.

Oblique view, photographed by Apollo 15 Command Module Pilot Al Worden, captures Vallis Schröteri’s Cobra Head (upper center) with dark-floored Herodotus Crater (center left) and bright-floored Aristarchus (lower center); NASA ID AS15-88-12002: Generally not subject to copyright in the United States, via NASA Image and Video Library

Acknowledgment

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

Image credits:

Oblique view shows Vallis Schröteri (center right) winding toward dark-floored Herodotus Crater (upper right) and away from bright-floored Aristarchus Crater (upper left); photograph by automatically operated Fairchild Mapping (Metric) Camera, SIM (Scientific Instrument Module) Bay, Apollo 15 Service Module; July 31-Aug. 2, 1971); NASA ID S71-44666: 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-S71-44666; NASA, Public Domain, via Internet Archive @ https://archive.org/details/S71-44666

Oblique view, photographed by Apollo 15 Command Module Pilot Al Worden, captures Vallis Schröteri’s Cobra Head (upper center) with dark-floored Herodotus Crater (center left) and bright-floored Aristarchus (lower center); NASA ID AS15-88-12002: 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-as15-88-12002

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