Lavoisier pyroclastics

Irregular "peanut-shaped" depression, perhaps a former fire-fountain vent, at the head of a floor fracture skirting the western floor of Lavoisier crater, on the west-northwest frontier of Oceanus Procellarum. Low reflectance material, thought to be pyroclastics, appears to have flowed and pooled, eastward and throughout the ancient crater floor. 15 km-wide field of view from a mosaic of LROC NAC observations M105055584L & R, from early in the LRO mission, spacecraft orbit 637, August 16, 2009; resolution 1.6 meters per pixel, incidence angle 57.3° from 162.45 km above 38.32°N, 231.59°E  [NASA/GSFC/Arizona State University].

Raquel Nuno
LROC News System

Lavoisier crater has many geologic forms that give insight into its history. On the floor are concentric craters, which exhibit an inner and outer rim; these strange craters are thought to have formed as a subsurface discontinuity, such as a strong rock layer below loose regolith, which interfered with the passage of the impact shock wave.

Fractures, which are caused by uplift of brittle material, are also abundant and point to subsurface magmatic intrusions or viscous relaxation as possible formation mechanisms.

The peanut-shaped irregular formation, just within the west wall of Lavoisier crater (71 km, 38.17°N, 278.75°E), in an image of the entire crater. Pyroclastic deposits encircle the crater floor, visible as areas of slightly darker appearance in this LROC WAC mosaic stacked from seven sequential monochrome (643 nm) observations by LROC Wide Angle Camera captured after local sunrise November 23, 2010; average resolution 65 meters from 49.5 km [NASA/GSFC/Arizona State University].

Today's Featured Image, found on the western edge of the floor of Lavoisier crater, shows low reflectance material that appears to have flowed from the head of one of these fractures. These flow fronts have been identified by lunar scientists as being the remnants of pyroclastic deposits. The irregular depression is not just another fracture, but a source vent for the eruption that created these deposits!

Context for the context. The west by northwest extremes of Oceanus Procellarum hosts several deposit remnants of fire-fountain pyroclastic volcanism. On the edge of the vast plains to the east and farside highlands to the west, dykes of volcanic faulting offer clues to the long-sought definitive origin for the Procellarum basin that, like Mare Tranquillitatis, does not seem to have formed from a single basin-forming impact. Breakthrough data was collected by the sensitive GRAIL A and B probes. Image stacked from from seven sequential orbital monochrome (643 nm) observations by LRO LROC Wide Angle Cameras of the region, soon after local sunrise, November 23, 2010; average resolution 65 meters, from 49.5 km [NASA/GSFC/Arizona State University].

The eruption (or eruptions) that threw these pyroclastic deposits out onto the surface are thought to be an energetic style of volcanic eruption called fire fountains. Eruptions like this are more chaotic due to the presence of volatile elements in the magma. Since magma source regions are hundreds of kilometers below the surface, pyroclastics are of interest to scientists because they provide information about the deep interior at the time of eruption. Understanding the distribution and composition of these deposits provide a path to deciphering the evolution of the interior conditions of the Moon through time. The Lavoisier pyroclastics and many other similar deposits are key sites for future robotic and human exploration.

Investigate the mantling of pyroclastics over the crater floor up close with the full resolution NAC mosaic, HERE.

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Lavoisier Crater
Pyroclastic Excavation
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Pyroclastics and Vent
Hyginus Crater and Pyroclastics