Taurus-Littrow (lunar valley)
Encyclopedia
Taurus–Littrow is a lunar
valley
located on the near side
at the coordinates . It served as the landing site for the American
Apollo 17
mission in December 1972, the last manned mission to the Moon to date.
The valley is located on the southeastern edge of Mare Serenitatis
along a ring of mountains formed between 3.8 and 3.9 billion years ago when a large object impacted the Moon, forming Mare Serenitatis and pushing rock outward and upward. Taurus–Littrow is located in the Taurus mountain range
and south of Littrow crater
, features after which the valley received its name. The valley's name, coined by the Apollo 17 crew, was eventually approved by the International Astronomical Union
in 1973.
Data collected on Apollo 17 show that the valley is composed primarily of feldspar
-rich breccia
in the large massif
s surrounding the valley and basalt
underlying the valley floor, covered by an unconsolidated layer of regolith
, or mixed materials, formed by various geologic events. Taurus–Littrow was selected as the Apollo 17 landing site after the other candidates were eliminated for various reasons. The landing site was chosen with the objectives of sampling highland material and young volcanic
material in the same location.
s began to upwell from the Moon's interior. As a result of these lavas, rock and soil samples from the area that were collected by Apollo 17 astronauts Eugene Cernan and Harrison Schmitt
gave insight to the natural history and geologic timeline of the Moon
.
Somewhere between 100 and 200 million years after the Serenitatis basin and Taurus–Littrow formed, the lavas that began to seep through the lunar crust
began to flood the low-lying areas. These lava flows were often accompanied by fire fountains that blanketed the surrounding area with tiny glass beads. These beads were sometimes colored orange, explaining the orange soil discovered by the Apollo 17 astronauts. Most of these beads, however, were darkly colored, resulting in the dark appearance of the Serenitatis basin from Earth.
The valley itself is elongated along an axis that points toward the center of Mare Serenitatis. Large massifs are located on either side of the valley, called the North and South massifs, respective to their geographic location in relation to each other. The height of these massifs give the valley a depth greater than that of the Grand Canyon
in the United States
. Along the South Massif lies Bear Mountain, named after a mountain of the same name near Harrison Schmitt's hometown of Silver City
, New Mexico
. The sculptured hills and East massif make up the east edge of the valley and to the west, a scarp
cuts across the valley floor and rises about two kilometres (1.2 miles) above it. The North and South massifs funnel into the main outlet of the valley into Mare Serenitatis, partially blocked by Family mountain.
Based on Apollo 17 observations, the valley floor is generally a gently rolling plane. Boulders of various sizes and other geologic deposits are scattered throughout the valley. At the ALSEP lunar experiment deployment area, located west of the immediate landing site, the boulders average about four meters in size and are higher in concentration than in other areas of the valley.
The Tycho
impact, which occurred between 15-20 and 70-95 million years ago, formed secondary crater
clusters in various locations of the Moon. Data from the examination of these clusters suggest that the central crater cluster in the valley formed as a result of said impact. Upon analysis of known secondary impact clusters resulting from the Tycho impact, it has been discovered that the majority of them have a downrange ejecta blanket
, or debris layer, with a distinctive 'birdsfoot' pattern. Apollo 17 observation data and comparison between the valley's central crater cluster and known Tycho secondary impacts shows many similarities between the two. The central crater cluster has a birdsfoot ejecta pattern that points in the direction of Tycho and the debris pattern of the light mantle points directly towards the South massif. The latter piece of evidence further supports the hypothesis that the light mantle formed as a result of an avalanche occurring on the aforementioned massif because of secondary Tycho impacts. Large-scale analysis suggests that the crater cluster may be part of a larger secondary cluster of Tycho, including craters on the North massif and other clusters as far north as Littrow crater. If indeed related, the smaller clusters form a large cluster that could be part of a nearby ray of Tycho.
, or reflectivity, is a direct result of the volcanic material and glass beads located there. The deeper craters on the valley floor act as 'natural drill holes' and allowed the astronauts to sample the subfloor basalt. These basalt samples are composed primarily of plagioclase
, but also contain amounts of clinopyroxene and other minerals.
The unconsolidated regolith layer on the valley floor has a thickness of about 14 metres (45.9 ft) and contains ejecta from many impacts, most notably Tycho. This enabled samples to be retrieved from this impact without having to visit the crater itself. The possibility that some craters in the valley could be secondary impacts of Tycho created further opportunities for sampling ejecta from that impact.
There are several geologic deposits on the valley floor originating from several different events in the geologic timeline of the Moon. One of these formations, the light mantle, is a deposit of lightly colored material in a series of projections extending about six kilometres (3.7 mi) from the south massif across the floor. Pre-mission analyses suggested that this deposit might be the result of an avalanche originating from the northern slope of the south massif. Post-mission analysis of samples of the material show that it is primarily composed of fine-grained material and scattered rock fragments that were presumably spread across the valley floor from the south massif at some point. Evidence from samples and visual observations taken during Apollo 17 show that the light mantle varies in thickness throughout the valley. Craters located farther away from the south massif penetrate through the light mantle to darker underlying material. Meanwhile, craters close to the south massif as wide as 75 metres (246.1 ft) do not appear to penetrate to darker material at all. The age of this formation is estimated to be about the same as the central crater cluster, or about 70-95 million years old.
Troctolite 76535
, a coarse-grained
troctolite
composed primarily of olivine
and plagioclase
was recovered in the valley as part of a rake sample. The sample has been called the most interesting to be returned from the Moon. This sample has been the subject of thermochronological
calculations in order to determine whether the Moon ever generated a core dynamo
or formed a metallic core
.
Rocks sampled in the immediate vicinity of the Lunar Module
are mostly vesicular
coarse-grained subfloor basalt, with some appearance of fine-grained basalt as well. Much of the valley floor, as displayed in observations of the immediate landing area, is predominately regolith and fragments varying in sizes excavated by several impacts in the Moon's history.
crater, Tsiolkovskiy
crater on the far side
, among others. All but Taurus–Littrow were eventually eliminated for scientific and/or operational reasons. A landing at Tycho was thought to be too dangerous because of the rough terrain found there, a landing on the far side in Tsiolkovskiy would add the expense of communications satellites necessary to maintain contact between the crew and ground control during surface operations, and a landing in Copernicus was regarded as low priority.
Taurus–Littrow was eventually selected with the objectives of sampling ancient highland material and young volcanic material in the same landing site. The Taurus–Littrow site offered both of these in the form of highland material in the Tycho ejecta sampled and the prospect that some of the craters in the area could be volcanic vents.
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
valley
Valley
In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...
located on the near side
Near side of the Moon
The near side of the Moon is the lunar hemisphere that is permanently turned towards the Earth, whereas the opposite side is the far side of the Moon. Only one side of the Moon is visible from Earth because the Moon rotates about its spin axis at the same rate that the Moon orbits the Earth, a...
at the coordinates . It served as the landing site for the American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
Apollo 17
Apollo 17
Apollo 17 was the eleventh and final manned mission in the American Apollo space program. Launched at 12:33 a.m. EST on December 7, 1972, with a three-member crew consisting of Commander Eugene Cernan, Command Module Pilot Ronald Evans, and Lunar Module Pilot Harrison Schmitt, Apollo 17 remains the...
mission in December 1972, the last manned mission to the Moon to date.
The valley is located on the southeastern edge of Mare Serenitatis
Mare Serenitatis
Mare Serenitatis is a lunar mare that sits just to the east of Mare Imbrium on the Moon.It is located within the Serenitatis basin, which is of the Nectarian epoch. The material surrounding the mare is of the Lower Imbrian epoch, while the mare material is of the Upper Imbrian epoch...
along a ring of mountains formed between 3.8 and 3.9 billion years ago when a large object impacted the Moon, forming Mare Serenitatis and pushing rock outward and upward. Taurus–Littrow is located in the Taurus mountain range
Montes Taurus
Montes Taurus is a rugged, jumbled mountainous region on the Moon. These peaks are located on a highland region to the east of the Mare Serenitatis, in the northeastern quadrant of the Moon's near side. The selenographic coordinates of this range are 28.4° N, 41.1° E, and they have a diameter of...
and south of Littrow crater
Littrow (crater)
Littrow is a lunar crater that is located in the northeastern part of the Moon's near side, on the east edge of Mare Serenitatis. Some distance to the northeast is the prominent crater Römer, while to the south is Vitruvius....
, features after which the valley received its name. The valley's name, coined by the Apollo 17 crew, was eventually approved by the International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
in 1973.
Data collected on Apollo 17 show that the valley is composed primarily of feldspar
Feldspar
Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....
-rich breccia
Breccia
Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....
in the large massif
Massif
In geology, a massif is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole...
s surrounding the valley and basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
underlying the valley floor, covered by an unconsolidated layer of regolith
Regolith
Regolith is a layer of loose, heterogeneous material covering solid rock. It includes dust, soil, broken rock, and other related materials and is present on Earth, the Moon, some asteroids, and other terrestrial planets and moons.-Etymology:...
, or mixed materials, formed by various geologic events. Taurus–Littrow was selected as the Apollo 17 landing site after the other candidates were eliminated for various reasons. The landing site was chosen with the objectives of sampling highland material and young volcanic
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
material in the same location.
Formation and geography
Several million years after the formation of Mare Serenitatis, lavaLava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
s began to upwell from the Moon's interior. As a result of these lavas, rock and soil samples from the area that were collected by Apollo 17 astronauts Eugene Cernan and Harrison Schmitt
Harrison Schmitt
Harrison Hagan "Jack" Schmitt is an American geologist, a retired NASA astronaut, university professor, and a former U.S. senator from New Mexico....
gave insight to the natural history and geologic timeline of the Moon
Lunar geologic timescale
The lunar geological timescale divides the history of Earth's Moon into five generally recognized periods: the Copernican, Eratosthenian, Imbrian , Nectarian, and Pre-Nectarian...
.
Somewhere between 100 and 200 million years after the Serenitatis basin and Taurus–Littrow formed, the lavas that began to seep through the lunar crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
began to flood the low-lying areas. These lava flows were often accompanied by fire fountains that blanketed the surrounding area with tiny glass beads. These beads were sometimes colored orange, explaining the orange soil discovered by the Apollo 17 astronauts. Most of these beads, however, were darkly colored, resulting in the dark appearance of the Serenitatis basin from Earth.
The valley itself is elongated along an axis that points toward the center of Mare Serenitatis. Large massifs are located on either side of the valley, called the North and South massifs, respective to their geographic location in relation to each other. The height of these massifs give the valley a depth greater than that of the Grand Canyon
Grand Canyon
The Grand Canyon is a steep-sided canyon carved by the Colorado River in the United States in the state of Arizona. It is largely contained within the Grand Canyon National Park, the 15th national park in the United States...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. Along the South Massif lies Bear Mountain, named after a mountain of the same name near Harrison Schmitt's hometown of Silver City
Silver City, New Mexico
Silver City is a town in Grant County, New Mexico, in the United States. As of the 2000 census, the town population was 10,545. It is the county seat of Grant County. The city is the home of Western New Mexico University.-History:...
, New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
. The sculptured hills and East massif make up the east edge of the valley and to the west, a scarp
Fault scarp
A fault scarp is the topographic expression of faulting attributed to the displacement of the land surface by movement along faults. They are exhibited either by differential movement and subsequent erosion along an old inactive geologic fault , or by a movement on a recent active fault...
cuts across the valley floor and rises about two kilometres (1.2 miles) above it. The North and South massifs funnel into the main outlet of the valley into Mare Serenitatis, partially blocked by Family mountain.
Based on Apollo 17 observations, the valley floor is generally a gently rolling plane. Boulders of various sizes and other geologic deposits are scattered throughout the valley. At the ALSEP lunar experiment deployment area, located west of the immediate landing site, the boulders average about four meters in size and are higher in concentration than in other areas of the valley.
The Tycho
Tycho (crater)
Tycho is a prominent lunar impact crater located in the southern lunar highlands, named after the Danish astronomer Tycho Brahe . To the south is the crater Street; to the east is Pictet, and to the north-northeast is Sasserides. The surface around Tycho is replete with craters of various sizes,...
impact, which occurred between 15-20 and 70-95 million years ago, formed secondary crater
Secondary crater
Secondary craters are impact craters formed by the ejecta that was thrown out of a larger crater. They sometimes form radial crater chains.-External links:*...
clusters in various locations of the Moon. Data from the examination of these clusters suggest that the central crater cluster in the valley formed as a result of said impact. Upon analysis of known secondary impact clusters resulting from the Tycho impact, it has been discovered that the majority of them have a downrange ejecta blanket
Ejecta blanket
An ejecta blanket is a generally symmetrical apron of ejecta that surrounds crater; it is layered thickly at the crater’s rim and thin to discontinuous at the blanket’s outer edge....
, or debris layer, with a distinctive 'birdsfoot' pattern. Apollo 17 observation data and comparison between the valley's central crater cluster and known Tycho secondary impacts shows many similarities between the two. The central crater cluster has a birdsfoot ejecta pattern that points in the direction of Tycho and the debris pattern of the light mantle points directly towards the South massif. The latter piece of evidence further supports the hypothesis that the light mantle formed as a result of an avalanche occurring on the aforementioned massif because of secondary Tycho impacts. Large-scale analysis suggests that the crater cluster may be part of a larger secondary cluster of Tycho, including craters on the North massif and other clusters as far north as Littrow crater. If indeed related, the smaller clusters form a large cluster that could be part of a nearby ray of Tycho.
Composition
Evidence from the Apollo 17 mission shows that the massifs surrounding the valley are composed primarily of feldspar-rich breccia and that basalt underlies the valley floor, a result of the lava flows during the valley's history. Seismic studies suggest that the basalt below the valley floor is about 1400 metres (4593.2 feet) thick. Above the layer of subfloor basalt lies a deposit of unconsolidated material of various compositions ranging from volcanic material to impact-formed regolith. The valley floor's unusually low albedoAlbedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
, or reflectivity, is a direct result of the volcanic material and glass beads located there. The deeper craters on the valley floor act as 'natural drill holes' and allowed the astronauts to sample the subfloor basalt. These basalt samples are composed primarily of plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
, but also contain amounts of clinopyroxene and other minerals.
The unconsolidated regolith layer on the valley floor has a thickness of about 14 metres (45.9 ft) and contains ejecta from many impacts, most notably Tycho. This enabled samples to be retrieved from this impact without having to visit the crater itself. The possibility that some craters in the valley could be secondary impacts of Tycho created further opportunities for sampling ejecta from that impact.
There are several geologic deposits on the valley floor originating from several different events in the geologic timeline of the Moon. One of these formations, the light mantle, is a deposit of lightly colored material in a series of projections extending about six kilometres (3.7 mi) from the south massif across the floor. Pre-mission analyses suggested that this deposit might be the result of an avalanche originating from the northern slope of the south massif. Post-mission analysis of samples of the material show that it is primarily composed of fine-grained material and scattered rock fragments that were presumably spread across the valley floor from the south massif at some point. Evidence from samples and visual observations taken during Apollo 17 show that the light mantle varies in thickness throughout the valley. Craters located farther away from the south massif penetrate through the light mantle to darker underlying material. Meanwhile, craters close to the south massif as wide as 75 metres (246.1 ft) do not appear to penetrate to darker material at all. The age of this formation is estimated to be about the same as the central crater cluster, or about 70-95 million years old.
Troctolite 76535
Troctolite 76535
Troctolite 76535 is a lunar sample discovered and collected on the Apollo 17 mission in 1972 in the Taurus-Littrow valley. It has a mass of about 156 grams and is about 5 centimeters across at its widest point.-Description:...
, a coarse-grained
Granularity
Granularity is the extent to which a system is broken down into small parts, either the system itself or its description or observation. It is the "extent to which a larger entity is subdivided...
troctolite
Troctolite
Troctolite is a mafic intrusive rock type. It consists essentially of major but variable amounts of olivine and calcic plagioclase along with variable minor pyroxene. It is an olivine-rich, pyroxene-depleted relative of gabbro. However, unlike gabbro, no troctolite corresponds in composition to a...
composed primarily of olivine
Olivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....
and plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
was recovered in the valley as part of a rake sample. The sample has been called the most interesting to be returned from the Moon. This sample has been the subject of thermochronological
Thermochronology
Thermochronology is the study of the thermal evolution of a region of a planet. Thermochronologists use radiometric dating along with the closure temperatures that represent the temperature of the mineral being studied at the time given by the date recorded, to understand the thermal history of a...
calculations in order to determine whether the Moon ever generated a core dynamo
Dynamo theory
In geophysics, dynamo theory proposes a mechanism by which a celestial body such as the Earth or a star generates a magnetic field. The theory describes the process through which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field over astronomical time...
or formed a metallic core
Planetary core
The planetary core consists of the innermost layer of a planet.The core may be composed of solid and liquid layers, while the cores of Mars and Venus are thought to be completely solid as they lack an internally generated magnetic field. In our solar system, core size can range from about 20% to...
.
Rocks sampled in the immediate vicinity of the Lunar Module
Apollo Lunar Module
The Apollo Lunar Module was the lander portion of the Apollo spacecraft built for the US Apollo program by Grumman to carry a crew of two from lunar orbit to the surface and back...
are mostly vesicular
Vesicular texture
Vesicular texture is a volcanic rock texture characterised by a rock being pitted with many cavities at its surface and inside. The texture is often found in extrusive aphanitic, or glassy, igneous rock...
coarse-grained subfloor basalt, with some appearance of fine-grained basalt as well. Much of the valley floor, as displayed in observations of the immediate landing area, is predominately regolith and fragments varying in sizes excavated by several impacts in the Moon's history.
| Mineral | Microscopic volume % | Megascopic volume % |
|---|---|---|
| Plagioclase | 22-45 | 20-50 |
| Clinopyroxine | 31-51 | 30-70 |
| Olivine | 0-7 | 0-10 |
| Ilmenite Ilmenite Ilmenite is a weakly magnetic titanium-iron oxide mineral which is iron-black or steel-gray. It is a crystalline iron titanium oxide . It crystallizes in the trigonal system, and it has the same crystal structure as corundum and hematite.... /opaques |
13-26 | 5-25 |
| Cristobalite Cristobalite The mineral cristobalite is a high-temperature polymorph of silica, meaning that it has the same chemical formula, SiO2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the quartz group which also include coesite, tridymite and stishovite... |
0-6 | - |
| Spinel Spinel Spinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4. Balas ruby is an old name for a rose-tinted variety.-Spinel group:... |
Trace | - |
| Glass Glass Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives... |
Trace | - |
Landing site selection
As Apollo 17 was the final lunar mission of the Apollo program, several different scientific objectives were identified in order to maximize the scientific productivity of the mission. Landing sites considered for previous missions, but were rejected were reconsidered. Taurus–Littrow was one of several potential landing sites considered for Apollo 17 along with Tycho crater, CopernicusCopernicus (lunar crater)
Copernicus is a prominent lunar impact crater named after the astronomer Nicolaus Copernicus, located in eastern Oceanus Procellarum. It is estimated to be about 800 million years old, and typifies craters that formed during the Copernican period in that it has a prominent ray system.-...
crater, Tsiolkovskiy
Tsiolkovskiy (crater)
Tsiolkovskiy is a large lunar impact crater that is located on the far side of the Moon. It lies in the southern hemisphere, to the west of the crater Gagarin, and northwest of Milne. Just to the south is Waterman, with Neujmin to the south-southwest. This feature was discovered on photographs sent...
crater on the far side
Far side of the Moon
The far side of the Moon is the lunar hemisphere that is permanently turned away, and is not visible from the surface of the Earth. The far hemisphere was first photographed by the Soviet Luna 3 probe in 1959, and was first directly observed by human eyes when the Apollo 8 mission orbited the Moon...
, among others. All but Taurus–Littrow were eventually eliminated for scientific and/or operational reasons. A landing at Tycho was thought to be too dangerous because of the rough terrain found there, a landing on the far side in Tsiolkovskiy would add the expense of communications satellites necessary to maintain contact between the crew and ground control during surface operations, and a landing in Copernicus was regarded as low priority.
Taurus–Littrow was eventually selected with the objectives of sampling ancient highland material and young volcanic material in the same landing site. The Taurus–Littrow site offered both of these in the form of highland material in the Tycho ejecta sampled and the prospect that some of the craters in the area could be volcanic vents.
External links
- Apollo 17 Preliminary Science Report
- Geological Survey Professional Paper 1080 — Apollo 17 Professional Paper
- LAC 43 — Lambert Conformal Projection map
- Apollo Image Atlas — Images of Taurus–Littrow
- 43D1S2(25) Apollo 17 Traverses — Apollo 17 traverse map
- Apollo 17 Sample Catalog — Catalog of samples from Taurus–Littrow