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

New oblique views of Gruithuisen Domes

An oblique view of the northern portion of the Gruithuisen Gamma volcanic dome, from the northwest. From a new LROC Narrow Angle Camera (NAC) mosaic M1106087898LR, LRO orbit 15300, October 28, 2012; overall resolution 4.9 meters per pixel [NASA/GSFC/Arizona State University].

Sarah Braden
LROC News System

The last LROC Featured Image post on the Gruithuisen Domes featured some of the earliest Narrow Angle Camera (NAC) coverage of this amazing region.

Now LROC brings you an even more dramatic view of these volcanic domes from an oblique angle (viewing from East to West), from an altitude of 154 km (96 miles) above the lunar surface.

Located along the mare/highlands boundary, on the northeast border of Oceanus Procellarum (36.6°N, 319.9°E), the three Gruithuisen domes Gamma, Delta, and Northwest (NW) are primary examples of lunar silicic volcanism.

A thumbnail image of the 20376 x 6728 oblique NAC montage users can zoom into HERE. The crater Gruithuisen B is 9 km in diameter (north is to the right) [NASA/GSFC/Arizona State University].

Field of view seen at an oblique angle sketched out (arrows) on a photometric work-up of an LROC monochrome Wide Angle Camera (WAC) overview by Maurice Collins, originally presented as a Lunar Picture of the Day (LPOD), September 27, 2010 [NASA/GSFC/Arizona State University].

Silicic volcanism is relatively rare on the Moon. The Gruithuisen Domes pre-date the lunar mare in this region, so some portion of these domes has been covered by mare basalt, although there are also contacts with the older highlands material. Silicic volcanism might have been more widespread during the Moon's early history, however, any evidence for that may be buried beneath the maria. We know that the composition of the Gruithuisen Domes are different from that of the mare and the highlands from Earth-based telescopes, Lunar Prospector gamma-ray spectroscopy data, and Clementine multispectral data. The Gruithuisen Domes are characterized by relatively high reflectance and strong absorptions in the visible and ultraviolet. The Domes are also low in iron and titanium abundance compared to the lunar maria. New data from the Diviner instrument on the LRO spacecraft confirmed that the Gruithuisen Domes are silicic.

Colorized topography of the Gruithuisen Domes region derived from the 100 m/pixel LROC WAC DTM. Contour line interval is 220 meters [NASA/GSFC/Arizona State University].

Experience the full resolution oblique image HERE.

Related LROC Featured Images:

Gruithuisen Domes - Constellation Region of Interest
Morphology of lunar volcanic domes
LROC NAC DTM Viewer Gruithuisen Domes (ROI) 1 - 2 - 3 - 4 - 5
Hansteen alpha yields some of its secrets
Silicic volcanism on the Moon
Compton Belkovich - Constellation ROI
Hortensius Domes - Constellation ROI