Tadpole and Lava Tube (NAC DTM)

An irregularly shaped depression, resembling a tadpole, first and largest in a sinuous chain of pits. A 14.4 km field of view from LROC Narrow Angle Camera-derived Digital Terrain Model (NAC-DTM) of the tadpole-shaped start of the informally named "Gruithuisen K Sinuous Rille chain" complex in north central Oceanus Procellarum. Color shaded-relief depicts elevation derived from photo-interferometry based on four LROC Narrow Angle Camera observations and resulting in an array of highly granular practical data, packaged into LROC NAC DTM PITVENT; higher elevations are red and white, lower elevations are blue and purple [NASA/GSFC/Arizona State University].

J. Stopar

LROC News System

Today's feature is an irregularly shaped, steep-walled mare depression that looks a bit like a tadpole; it is about 8 km long and located at the northwest end of a 60-km long, sinuous chain of pits (35.284°N, 315.901°E) northwest of Gruithuisen crater.

The pit chain was one of the first and most spectacular candidates proposed for an intact lunar lava tube (i.e., one with uncollapsed segments).

This depression may be the source vent for the lava flows that host the pit chain (see image below).

The unnamed first among many candidate features surveyed for hints of underground voids, lava tubes, etc., west of Gruithuisen K crater in north central Oceanus Procellarum. LROC WAC mosaic swept up over three sequential orbits July 12, 2011; 77.2° incidence, resolution 57.9 meters from 42.5 km [NASA/GSFC/Arizona State University].

Volcanic vents tend to be sub-circular or elongate, like today's feature, which is roughly 600 meters deep and has steep inner walls (~35° slopes). Similarly sized and shaped features include examples near Sulpicius Gallus crater and the Orientale basin. Dark, low-albedo, materials surrounding the Sulpicius Gallus and Orientale features suggest formation through explosive pyroclastic eruptions; however, further exploration is still needed to confirm this interpretation.

Collapse pits, with sharp and nearly vertical walls, like the one in the Marius Hills (shown in a previous post) suggest fairly recent collapse of ancient lava tubes. The chain of pits near Gruithuisen, however, has more subdued topography, and likely formed earlier in the history of the Moon (perhaps more than 1 or 2 billion years ago).

An early mission Commissioning LROC NAC observation, covering a cross-section of the sinuous depression chain. LROC NAC M102443238LR, LRO orbit 272, July 17, 2009; incidence angle 77.85° at 1.54 meters resolution, from 155.56 km over 35.47°N, 316.56°E [NASA/GSFC/Arizona State University].

Intact lava tubes have long been thought to be important to future exploration. Many have speculated that uncollapsed portions of lava tubes could be used to shield explorers from harmful radiation, as well as provide a relatively warm and stable environment that is buffered from the large temperature variations at the surface.

Many hope that uncollapsed lava tubes will be located near volcanic materials that can be used in construction or energy-generation processes. However, we still have not explored inside any lava tubes on another planet, though many engineers and scientists are currently working to enable such activities. In the meantime, LROC images combined with other data sets, can be used to search for additional lava tube candidates.

Explore today's tadpole-shaped vent in more detail: LROC NAC M1103837710.

Continue Reading about this fascinating lava tube candidate and the sinuous pit chain, or explore the Sulpicius Gallus vent and Orientale Basin vent in more detail.

Even more to explore:

Collapsing Tube

Pit craters in NAC DTM topography

Pyroclastics and an unnamed Procellarum vent
Source vent for Rima Prinz I
Craters on the Schrödinger pyroclastic cone
Morphology and distribution of volcanic vents in the Orientale basin from Chandrayaan-1
Unassuming volcanic vent north of Aristarchus Plateau
New pyroclastic structures identified using LROC data
A dark cascade at Sulpicius Gallus
Hyginus and pyroclastics
Layer of pyroclastics in Sinus Aestuum
Lavoisier Pyroclastics
Pyroclastic Excavation
Pyroclastic Trails
Pyroclastic Vent at Orientale DTM

Pit craters in NAC DTM topography

The crisp morphology of the central Mare Fecunditatis pit (white arrow) stands out in elevation data and suggests a relatively young age. This pit is about 200-m in length and 45 m deep. Image width is 5 km; north is up. Color shaded-relief created from NAC DTM FecundPit; higher elevations shown in red and lower elevations in blue and purple [NASA/GSFC/Arizona State University].

J. Stopar

LROC News System

Eight mare pits have been discovered so far on the Moon, five of which preserve void spaces (sublunarean voids) beneath overhanging mare layers. The pit featured above, located in central Mare Fecunditatis (0.917°S, 48.66°E), however, does not have an obvious void space. The pit is almost 200 m wide and about 45 m deep.

The central Mare Fecunditatis pit has a concave shape, with gentler slopes (outer funnel) near the upper mare surface, and a steeper-walled inner pit (see image below). Variations in wall slopes are consistent with a fine-grained, particulate layer (regolith) overlying more coherent mare layers. The steep inner pit suggests collapse into a small void space. The debris in the pit floor consists of both regolith and mare blocks from the upper layers.

Pit crater (0.92°S, 48.66°E) near Messier B, now generally designated the Central Fecunditatis pit crater to distinguish it for a more recently discovered skylight in southwest Fecunditatis. LRO's longevity has enabled repeated narrow angle photography of selected areas on the Moon, allowing for the team at Arizona State University to build up very high-resolution, NAC-based digital terrain models. 540 meter field of view from LROC NAC observation M1105602888R, LRO orbit 15232, October 23, 2012; 35.18° incidence angle, resolution 93 cm from 108.28 km over 0.92°S, 49°E [NASA/GSFC/Arizona State University]

Left: color shaded-relief of NAC-derived elevation data. Reds are higher elevations, purple lower elevations. Right: elevation profile of a north-to-south cross-section through the pit. The inner pit has steep walls, while slopes near the mare surface (outer funnel) are more gentle [NASA/GSFC/Arizona State University].

The lack of raised rim or ejecta around the pit, indicates that it most likely formed through collapse, rather than as an impact event. While this pit is not located near any obvious tectonic features or volcanic constructs, the collapse may have occurred into part of an old lava tube. The crispness of the pit morphology, suggests that the collapse occurred relatively recently (geologically speaking, at least), perhaps much less than 1 billion years ago. Pits are among some of the youngest landforms on the Moon, and are similar in age to many fresh craters (such as Tycho, Copernicus, or Aristarchus).

More recently identified pit crater in southwest Mare Fecunditatis (6.752°S, 42.76°E), discovered during Wagner and Robinson survey. A 325 meter-wide field of view from LROC NAC M167926438R, LRO orbit 9881, August 14, 2011; 42.25° incidence angle, resolution 56 cm from 26.73 km over 6.71°S, 42.72°E [NASA/GSFC/Arizona State University].

Read More About Lunar Pits:  Lunar pits were recently featured in the news and the focus of a scientific publication ("Distribution, formation mechanisms, and significance of lunar pits," Robert V. Wagner and Mark S. Robinson, Icarus, July 2014; pg. 52-60).

The pits are of particular interest to lunar scientists because they could offer access to subsurface materials, making them important targets for further research and exploration.

Explore the pit in the full-resolution LROC NAC observation HERE.

More Pits:

On the Moon, as on Earth, location is everything
Pit crater in Fecunditatis
Copernicus Collapse Pit
Twin mare pit craters in the Lake of Death
Impact melt collapse pit
Failed skylights of Copernicus
New view of the Sinas pit crater in Mare Tranquillitatis
Sublunarean void
New views of lunar pits
How Common are Mare Pit Craters?

Melt pit on the floor of Louville D 

Natural Bridge on the Moon
Depths of Mare Ingenii 

Banded Slump in Berzelius W

A complex interplay of slumping and slides in the northwest wall of Berzelius W result in banding patterns; downslope is toward the bottom right in this 230 meter-wide field of view from LROC NAC observation M174921824R, LRO orbit 10912, November 3, 2011; 53.59° incidence angle, resolution 40 cm from 23.87 km over 38.06°N, 53.02°E [NASA/GSFC/Arizona State University].

J. Stopar

LROC News System

Berzelius W (7.17 km; 38.137°N, 53.103°E), on the northeast limb of the Moon (as seen from the Earth), exhibits abundant evidence for mass wasting.

Materials of varying albedo create intricate patterns on the walls of the crater, including the banding patterns featured in the opening image. 

This particular portion of the wall includes a block of slumped material, as indicated by the characteristic arcuate faults near the crater's rim crest (see image below). The slumped material is overprinted by finger-like flows of finer particles that moved as slides of dry debris.

Arrow indicates the arcuate faults at the head of the slumped material in the wall of Berzelius W. This slumping may have triggered the associated narrower and finger-like landslides of lower albedo (darker) boulders and debris; 600 meter field of view [NASA/GSFC/Arizona State University].

When did these mass-wasting events occur? Did they occur during the impact event, shortly after while the landscape was still ringing from the shock of impact, or millennia later? The lack of high albedo (bright) ejecta around the crater and the subdued appearance of the rim crest indicate that this crater did not form particularly recently; perhaps it is between 1 and 2 billion years old. 

Berzelius W (7.17 km; 38.137°N, 53.103°E) in 35.7 km-wide field of view from LROC WAC monochrome (604 nm) mosaic of M161965061C and M161971828C, LRO orbit 9003 and 9004, June 6, 2011; 73.5° incidence at 61.5 meters resolution from 44.9 km [NASA/GSFC/Arizona State University].

The crisp edges of the debris flows and arcuate scarps in the walls, however, suggest that they are much younger than the crater. So, while this landslide probably did not form yesterday, it is likely significantly younger than the crater itself, probably less than half its age. However, without more data, it is impossible to know precisely when these events occurred. Repeated imaging over many decades may provide more insight into how crater walls age with time. Alternatively, samples returned from crater walls may provide a method to age-date mass-wasting events. 

Try to find at least three other examples of mass-wasting features in the western half of this crater below. Pan and zoom to find examples of landslides, talus deposits, and boulder tracks:

Full 850 meter-wide field of view from remarkably high resolution LROC NAC observation M174921824R [NASA/GSFC/Arizona State University].

View full-window HERE.

Related Features:

Slumping Rim of Darwin C

Rim Slumping

Top of the Landslide

Melt on a Rim

Relative Timing of Geologic Events in Mare Frigoris

Eroding Crater Walls

Slope Resurfacing

Granular Flow

Ballistic boulder at Hecataeus N

A house-sized boulder left a clear impression, immediately beyond the east rim of a young 1.6-km crater (rim crest to the left), all in a full-sized reproduction, 988 meter-wide field of view from LROC NAC observation M182995612R, LRO orbit 12068, February 4, 2012; 48.59° incidence, resolution 85 cm from 83.56 km over 20.98°S, 80.74°E [NASA/GSFC/Arizona State University].

J. Stopar

LROC News System

The boulder above (21.085°S, 80.777°E) in the opening image is likely debris ejected during the violent excavation of the 1.6-km diameter crater immediately to the west (left).

The boulder was deposited ballistically; the distance it travelled and its time of flight are related to its ejection angle and velocity.

For the boulder, was this flight a "small step" or a "giant leap?"

Looking at the image above, we can deduce that the boulder was deposited with enough force to make a noticeable impression in the ground. However, a more forceful landing would have highly fragmented the boulder.

More examples of surface impressions formed by ballistic boulders from the fresh impact near Hecataeus N. Spotty trails mark where boulders rolled into a pre-existing crater (small yellow arrows). Another larger, boulder (25 meters in diameter, large white arrow) was thrown out of the crater to the southwest and carved a furrow in the ejecta blanket, coming to rest when it intersected a pre-existing crater rim (topographic high) [NASA/GSFC/Arizona State University].

The boulder is located about 500 meters east of the crater rim crest, which is only about a third of the crater diameter. Thus, this boulder did not travel very far or very fast.

Explore the entire crater and its ejecta below:

Fresh impact on the west flank of Hecataeus N 4.3 km field of view from LROC NAC mosaic M182995612LR, LRO orbit 12068, February 4, 2012; 48.59° incidence, resolution 85 cm from 83.56 km over 20.98°S, 80.74°E [NASA/GSFC/Arizona State University].

View full-window HERE.

The house-sized boulder (yellow arrow), which left its impression just beyond the east rim of the unnamed young 1.6-km crater that, in turn, sits on the west flank of Hecataeus N, shown in the context of a 7.86 km-wide field of view from LROC NAC mosaic M182995612LR, LRO orbit 12068, February 4, 2012; 48.59° incidence, resolution 85 cm from 83.56 km over 20.98°S, 80.74°E [NASA/GSFC/Arizona State University].

The fresh crater (center) on the southwest slope of Hecataeus N (10.82 km; 20.91°S, 80.944°E) excavates the deepest material originally turned up by "N" while both, in turn, sampled the very ancient Hecataeus interior (southwestern half of this 40-km wide field of view) and, even further, material turned out by Humboldt, to the south (see below), a powerful impact that significantly filled in and covered over the floor of Hecataeus. This is an example of something planners look when making good landing site choices, ones likely to efficiently utilize precious resources. LROC WAC observation M177109146C (604 nm), LRO orbit 11236, November 28, 2011; 68.1° incidence, resolution 58.91 meters from 43.76 km [NASA/GSFC/Arizona State University].

A general schematic map of geological types, representing the relative stratigraphy of the lunar surface affected by Hecataeus and Humboldt, in the south equatorial latitudes of the far eastern hemisphere, where the farside highlands begin, The fresh crater on the west flank of Hecataeus N is marked by an arrow.

The grooves carved by boulders ejected at relatively low velocities are in many ways similar to the spotty tracks etched by boulders sliding, rolling, and bouncing down steep slopes. Also, boulder tracks (like these) often resemble the astronauts' footprints on the lunar surface, since both have relatively recently disturbed the soil in narrow paths. 

In honor of the 45th anniversary of the Apollo 11 lunar landing (July 20, 1969), revisit some of our previous posts about large boulders visited by astronauts:

Pinpoint Landing on the Ocean of Storms (Apollo 12)

Trail of Discovery at Fra Mauro (Apollo 14) 

Retracing the Steps of Apollo 15

Astronaut's Eye View of Apollo 16 Site

Station 6 - Apollo 17 

Finally, revisit some of the best LROC images of the Apollo 11 landing site and see if you can find any large boulders. You should find very few large boulders, as the mission planners sought a low-risk site for the first Moon landing:

High Noon at Tranquility Base 

Apollo 11: Second look 

A Stark Beauty All Its Own 

"Houston, Tranquility base here." 

Flip Book - Apollo 11 

Soaring over the Apennines

This is another LROC NAC mosaic viewers may really want to see using the "see all sizes" download option that accompany slideshow images in Flickr. An oblique view, looking west over the Apennine Mountains toward Hadley Rille (above -north is to the right).  The morning shadows are much as they were July 30, 1971, when Dave Scott and Jim Irwin flew on their backs over range at bottom, flipped forward and landed on the broad plain between those hills and Rima Hadley. Hadley Base, their landing site, and the descent stage of the Apollo 15 lunar module Falcon is right where they left it, just within the resolution of full scale reproductions of this image. 

Notable features in a thumbnail of LROC NAC oblique mosaic M1123519889LR, LRO orbit 17751, May 18, 2013; spacecraft and cameras slew 55.22° from orbital nadir, 76.87° incidence angle, average resolution 2.87 meters from 130.27 km over 26.11°N, 11.75°E [NASA/GSFC/Arizona State University].

J. Stopar

LROC News System

Apollo mission planners selected an adventurous landing site for Apollo 15 (26.132219°N, 3.633861°E), on a relatively small patch of lava plains (mare). 

This site is nestled between the towering Apennine mountains to the east, attaining heights of 3-5 km, and the 200 meter deep, v-shaped valley of Hadley Rille to the west.

The experience gained from the successful landings of the preceding Apollo missions afforded mission controllers confidence that a landing descending through a mountain range was possible, though it required a steeper descent angle (25° rather than 14°).

The landing site of Apollo 15 (direct center), on Hadley Rille Delta between the Apennine mountain range on the southeast periphery of Mare Imbrium and Rima Hadley, winding through the distinctly darker mare material of Palus Putredinis. LROC WAC GLD100 elevation overlain atop LROC 100 meter global mosaic. The peaks of the Apennine Mountains rise more than 5 km over the interior of the Imbrium basin [NASA/GSFC/Arizona State University].

A captioned video of the descent of Apollo 15 conveys the excitement of astronauts David Scott and James Irwin as they set down near Hadley Rille. The Hadley Rille landing site also presented an opportunity to test the capabilities of the new lunar roving vehicle (LRV).

"Down on the plain at Hadley." Newly realigned video (3:37) of the landing of Apollo 15, July 30, 1971. [LunarModule5].

The Apennine Mountain Range formed during the Imbrium basin-forming event, and it was hoped these mountains contained materials from very early in the Moon's history (which they did!). As astronauts Irwin and Scott descended over the Apennines, they reported a floating sensation that resulted from glimpsing mountain peaks passing by the windows of the Lunar Module (LM). The descent was a complete success, and the LM set down near the planned site! Although, the astronauts were a little surprised to land with one foot-pad in a small crater, placing the vehicle on a slant.

Cmdr. Dave Scott captured this view of the Apollo 15 lunar module Falcon where it came to rest tilting toward the Apennine mountains beyond, while Jim Irwin checked out the first of the three Apollo "J mission" lunar rovers. See full-size mosaic of two color images from the panorama (AS15-86-11600 and 11601) HERE [NASA/JSC/ALSJ].

Three EVAs (or traverses) were planned for Apollo 15 using the LRV, two of which allowed sampling part of the Apennine Mountain Range to the south and southeast and required long (multi-kilometer) traverses.

Thumbnail of a mosaic of black and white images from Science Station 6, during the second EVA of the Apollo 15 expedition, on the slopes of the "Apennine Front." In the full-size panorama, HERE, the lunar module Falcon is visible, several kilometers away, between Hadley rille on the far left and Mt. Hadley, dominating the center of this mosaic [AS15-85-11481-11492, NASA/JSC/ALSJ].

Astronauts Scott and Irwin were accomplished field geologists; listen HERE as Commander Scott recently reflected on his Apollo 15 experience, including the importance of field-geology training.

The tiny arrow marks the location of the LM, just barely within the resolution of the LROC NAC mosaic (at full-scale), while LRO orbited over a spot 130 km away. Of course, the landing zone has been documented with remarkable detail from LRO, from better vantages [NASA/GSFC/Arizona State University].

Related Posts:

Man's first wheels on the Moon at 41 years

Retracing the Steps of Apollo 15: Constellation Region of Interest

Apollo 15 Lunar Laser Ranging Retroreflector - A Fundamental Point on the Moon

Layers near Apollo 15 Landing Site

Hadley Rille and the Mountains of the Moon

Kaguya captures Hadley Rille and Apollo 15

The original interplanetary mountaineers

Traverse plots of Apollo 15 EVA 1 & 2 (August 1 and 2, respectively), the routes astronauts Dave Scott and Jim Irwin drove south to the lower slope of Mons Hadley Delta (from the "Elbow" bend in Rima Hadley, southward, toward the left). Elevations above that of the landing site (LM). For scale, the dogleg distance the astronauts travelled from the LM to Elbow crater along the edge of Hadley Rille over EVA 1 is roughly 4.5 km. Oblique LROC NAC mosaic M1123519889RL, LRO orbit 17751, May 18, 2013; spacecraft and camera slew 55.21° from orbital nadir, 76.87° angle of incidence, resolution 2.87 meters from 130.27 km over 26.11°N, 11.15°E  [NASA/GSFC/Arizona State University].

J. Stopar

LROC News System

The lofty Apennine Mountain Range has two prominent peaks near the Apollo 15 landing site: Mons) Hadley (relative height 4 km) to the northeast and Mons Hadley Delta (3.5 km) toward the south.

Between these two peaks lies the "Swann Range," named for Apollo 15 Geology Team Leader Gordon Swann.

The Apennine Mountain Range contains some of the largest peaks on the Moon Mons Hadley rivals the prominences of notable terrestrial mountains like Mt. Rainier and Mt. Fuji, and Mt. Erebus in Antarctica when measured from base to summit.

Elevation profile of Mons Hadley Delta, measured from the Apollo 15 landing site (left) through the peak (right); data from the LROC WAC-derived GLD100 Digital Terrain Model (DTM), with relative heights of notable terrestrial mountains shown for scale. Mons Hadley Delta is not the largest peak in the Apennines, and Scott and Irwin scaled only a small portion of the mountain's contact zone with the Hadley Delta plain [NASA/GSFC/Arizona State University].

The first Apollo 15 EVA took astronauts David Scott and James Irving southward along the edge of Hadley Rille and to the base of Mt. Hadley Delta near St. George crater. This traverse took them to a height of just over 65 meters above the landing site on the mare plain. At this height, much of the surface material of the mountain comprises debris that, over eons, slid down the upper slopes through mass-wasting. Materials collected in this area primarily consist of regolith, as there are very few surface boulders.

Mons Hadley Delta (high-resolution mosaics HERE); Mosaic of Dave Scott's Station 9 panorama (AS15-82-11084-88), from northeastern wall of the "Station 9 crater," a relatively fresh 15 meter-wide feature characterized by soft clod-like blocks of pressure-pressed regolith formed at small impact. Station 9 crater is about 240 meters immediately northeast of Rima Hadley; Apollo 15 (EVA 3), August 2, 1971 [Dave Scott/NASA/JSC/ALSJ].

The second EVA took the astronauts southeast to "South Cluster" and Spur craters. At Spur crater, a very old crystalline rock fragment was collected, containing evidence of geologic processes more than 4 billion years old and representing a piece of the original anorthositic crust of the Moon. They also discovered an unusual green material composed of volcanic glass.

This traverse ascended about 95 meters in elevation, up the base of Mons Hadley Delta. At times, the slope was steep enough (~ 18°) that the rover had difficulty getting traction, and the mountain peak loomed so high overhead, that the astronauts could not lean back far enough to get it in the frame of their cameras.

Apparent outcrops (arrows) may represent a high-lava mark approximately 85 meter up the south slope of Mons Hadley. AS15 magazine 84. View a more dramatic mosaic from this panorama HERE [NASA/JSC/Apollo 15 Lunar Surface Journal/Arizona State University].

During this traverse, the astronauts commented that they thought they could detect a high-mark where lava might once have filled the basin at the base of nearby Mt. Hadley around a height of 85 meters above the current mare plain.

LROC projection with traverse courses of Apollo 15 expedition to Hadley Delta, July 30-August 2, 1971 [NASA/GSFC/Arizona State University].

From Science Station 6. It definitely worthwhile to see a larger, high-resolution mosaic of this, reported to be Dave Scott's favorite photograph from the expedition (HERE). Through a 500-mm lens, from Science Station 6 up on the Apennine Front, the lunar module Falcon and ALSEP components are seen from 4.7 km, backdropped by the North Complex crater group and flank of Mons Hadley, on the plain's opposite bank [NASA/JSC].

Apollo 15, Science Station 6, Spur Crater, on the Apennine Front, August 1, 1971. Dave Scott employs his 500 mm lens and black and white magazine 84 to capture the image immediately above, the Apollo 15 lunar module Falcon and North Complex crater group in context of the high mountains surrounding the Hadley Delta landing site. Still clipped from live video transmission relayed from remote-operated color TV camera on the lunar rover [NASA/JSC/ALSJ].

After capturing his black and white 500 mm panorama, Cmdr. Scott returned employed color magazine 86 and a less awkward smaller focal length. The reproduction here is too small to see the lunar module, but a much cleaner full resolution version is available HERE. Though it is not as detailed, and coherent backscatter is more problematic than the black and white at 500 mm, the full-resolution color image more closely matches the unaided human eye.  AS15-86-11618 [NASA/JSC/ALSJ].

While the Apollo 15 astronauts scarcely climbed the lower slopes of a lunar mountain, they made many important discoveries. What challenges, findings, and fun (like slope skiing) might future explorers experience on the powdery mountains of the Moon?

Explore the first two of the Apollo 15 traverses in more detail below by panning and zooming. The numbers indicate relative elevations of the paths travelled by the astronauts.

Related Posts:
Soaring Over Mighty Mt. Hadley
Apollo 15 departs Hadley Rille Delta
Water found in the Apollo 15 Genesis Rock
Follow the Tracks (Apollo 15)
Hadley Rille and the Mountains of the Moon
Retracing the Steps of Apollo 15 Constellation Region of Interest
Apollo 15 Laser Ranging Retroreflector: a Fundamental Point on the Moon
LROC's First Look at the Apollo Landing Sites
'Man's first wheels on the Moon' at 41 years
Bowditch Lava Terraces
Lunar Kipuka
Remnants of the Imbrium Impact
Hadley-Apennine: the Apollo 15 Landing Site
The Mighty Apennine Mountain Range
Layers near Apollo 15 Landing Site
LROC Explores Apollo 15 (YouTube video)
Kaguya captures Rima Hadley

The complex case at Lassell K

An early morning view looking east-to-west from an altitude of 86 km across the southern portion of the Lassell Massif, an irregularly shaped series of hills and steep-walled depressions. North is to the right in this LROC NAC oblique mosaic M1108311369LR, LRO orbit 15611, November 23, 2012; 71.73° incidence angle, spacecraft and camera slew 56.64° from orbital nadir, resolution above 2 meters from 85.65 km over 14.63°S, 355.69°E [NASA/GSFC/Arizona State University].

J. Stopar

LROC News System

The Lassell Massif is a complex area of rugged terrain located in northeastern Mare Nubium (14.7°S, 351.0°E). This undulating terrain of hills and steep-walled depressions is 45 km across from north to south and 25 km across from east to west.

The southern portion of the massif comprises several prominent elongate depressions (like Lassell K and Lassell G, seen below) that are clustered together.

The Lassell Massif in Mare Nubium; north is to the right. Prominent features of the Lassell Massif region include Lassell C, K, and G [NASA/GSFC/Arizona State University].

The clustering and irregular shape of these negative-relief features is reminiscent of volcanic calderas on Earth and other terrestrial planets, including Mars. Calderas generally form through collapse as magma retreats from the vent area. Overlapping collapse features suggest multiple episodes of magma advance and retreat over time. Lassell K and G may be part of a volcanic caldera!

Lassell K and G could, however, instead represent a series of clustered impact craters, which are relatively common on the Moon.

Remote sensing data displayed in eight diverse views of the 1000 meter-high profile of Lassell massif, collected by four spacecraft (all of them post-Apollo) presented in an overlapping 40.2 km-wide field of view, visible throughout both day and night. The largest crater at center-left is Lassell C (8.74 km; 14.67°S, 350.64°E) [Clementine, LRO, Chandrayaan-1 and Chang'e-2].

Lassell K (left) and portion of Lassell G (right). The upper walls of these steep-walled depressions have dark, low-reflectance, boulders and downslope streamers (arrows), where a thin layer of dark material, possibly pyroclastic, has eroded out of the wall [NASA/GSFC/Arizona State University].

Looking closely at this region, we see other features that are typical of volcanic eruptions including: dark mantling layers interpreted as possible pyroclastics, a subdued or mantled terrain, and even a possible volcanic cone.

Taken together, these features suggest a complex volcanic history for this region. If the Lassell Massif is constructed from a series of volcanic extrusions, it may represent an unusual type of silicic volcanism on the Moon (perhaps similar in composition to rhyolite).

Read more about the Lassell massif and its unusual style of volcanism in a study presented by members of the Lunar Reconnaissance Orbiter Camera team and colleagues to the 44th Lunar and Planetary Science Conference (2013): "The Lassell Massif, Evidence for Complex Volcanism on the Moon," #2504.

The full oblique image (below) along with other images and compositional data sets may reveal more clues to the timing and nature of volcanism in the Lassell region. However, returning rock samples to Earth and exploring the slopes of this structure from the surface may be the only way to confirm its origins.

View assorted sizes of an unlabeled sample of a mosaic from the LROC observation above, HERE.

View oblique in full-window, HERE.

Related LROC Featured Images:

New Views of the Gruithuisen Domes

Lassell D Ejecta

The Fourth Mairan Dome

Farside Highlands Volcanism

Up From the Depths

Aristarchus Spectacular

A splendid oblique view of Larmor Q

LROC NAC view of the south wall and rim of splendiferous Larmor Q crater, looking obliquely east-to-west; LROC NAC oblique mosaic M174081337LR, LRO orbit 10788, October 24, 2011; 44.93° incidence angle, resolution roughly 2.3 meters, spacecraft and camera suite slewed 67° from orbital nadir, 59.44 km over 28.84°N, 211.72°E [NASA/GSFC/Arizona State University].

J. Stopar

LROC News System

Larmor Q (28.674°N, 176.32°E) is sub-circular crater, whose  23 km diameter is measured north to south and 19 km measured east to west.

But Larmor Q is not just another stunning crater; it is also scientifically interesting.  Oblique images, like the one below, provide a unique vantage point that can help with geologic interpretation.

Oblique view (reduced for web-browsing) of Larmor Q crater, looking east-to-west. The crater is wider in the north-south direction than in the east-west direction. Click for larger image [NASA/GSFC/Arizona State University].

One of the most obvious features of Larmor Q is the large accumulation of slumped wall materials inside the crater. This crater is a transitional morphology between smaller simple craters like this one, HERE, and larger, complex craters like Tycho or Copernicus.

The crater Giordano Bruno (21 km in diameter) is another example of a transitional crater. Wall slumping in transitional craters affects the final crater shape. When the northern wall of Larmor Q failed, the northern rim crest of the crater moved outward, contributing to the larger crater diameter in the north-south direction.

Prominent features of Larmor Q include slumped wall material and impact melt deposits; located at 176.313°E, 28.634°N [NASA/GSFC/Arizona State University].

This oblique image of Larmor Q is also useful for studying the distribution of impact melt, which, in turn, can tell us how impact melt is generated and interacts with the forming crater. In Larmor Q, most of the impact melt rock is located inside the crater opposite the largest slumped materials.

View of impact melt deposits inside Larmor Q. The melt has splashed up the southern wall (left) and ponded in the floor of the crater (center of image)[NASA/GSFC/Arizona State University].

Flows of impact melt on the rim of Larmor Q crater now solidified into lobate deposits [NASA/GSFC/Arizona State University].

There are also several relatively small deposits (flows) of impact melt rock on the crater rim. Because the largest concentration of impact melt occurs opposite the largest slumped materials, we infer that the melt “splashed” up on the southern wall primarily as a result of the slumped material impinging on the crater floor.

LROC Wide Angle Camera (WAC) image of the 18.3 km diameter crater Larmor Q. Slumping of the crater walls has not yet covered all the impact melt on its floor. LROC WAC monochrome (604 nm) observation M136389155C, LRO orbit 5233, August 14, 2010; 54.83° angle of incidence, resolution 82 meters from 58.4 km [NASA/GSFC/Arizona State University].

NASA ILIADS application simulated orbital view (not too dissimilar to the oblique perspective of the LROC Featured Image released May 13, 2014) shows the region of the lunar farside highland terrain between Larmor Q (23 x 19 km; 28.674°N, 176.32°E, bottom center) and Mare Moscoviense (275 km; 27.28°N, 148.1°E), perhaps the most immediately eye-catching feature of the Moon's opposing hemisphere, 750 km away and 1000 meters higher in average elevation above global mean. LROC WAC 100 meter global mosaic imagery applied to LRO LOLA laser altimeter-based digital elevation model [NASA/MSFC].

The full resolution oblique view of Larmor Q crater contains more fascinating clues of the impact cratering process, HERE.

Related LROC Featured Images:

Dense Fractures on the Floor of Larmor Q

The View Inside of a Tilted Crater

Very Oblique View of Giordano Bruno

Ryder Spectacular!

Sunset Over Giordano Bruno

Necho's Jumbled Floor

View from the Other Side