Volcanic Processes in the Gassendi Region of the Moon. Issue 9 (18th September 2020)

• Record Type: Journal Article
• Authors: Giguere, Thomas A.; Hawke, B. Ray; Gillis‐Davis, Jeffrey J.; Lemelin, Myriam; Boyce, Joseph M.; Trang, David; Lawrence, Samuel J.; Stopar, Julie D.; Campbell, Bruce A.; Gaddis, Lisa R.; Blewett, David T.; Gustafson, J. Olaf; Peterson, Chris A.; Runyon, Cassandra R.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 9(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-18
• Subjects: Moon -- volcanism -- surface materials and properties -- interiors -- remote sensing; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1029/2019JE006034
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: The lunar floor‐fractured crater Gassendi and surrounding area were examined with high‐resolution Lunar Reconnaissance Orbiter imagery and other remote sensing data to characterize and understand the volcanic processes in the southwestern region of the Moon. This study was selected because the Gassendi region exhibits a variety of volcanic features (e.g., cryptomaria deposits, pyroclastic deposits, maria, and lava lakes) and team participants have studied this region for 30 years (Hawke et al., 1991, https://doi.org/10.1029/92GL02921 ). This study confirms the existence of a previously identified cryptomare deposit and identifies an additional cryptomare deposit west of Gassendi crater and a pyroclastic northeast of Gassendi. Spectral and geochemical anomalies associated with dark‐haloed impact craters reveal cryptomaria deposits in the western Gassendi crater floor and previously unmapped mare basalt within northeastern Gassendi. We identified three separate lava lakes on the northeast, northwest, and southwest floor of Gassendi crater based on morphology analogous to terrestrial lava lakes, geochemical signatures, and digital terrain data. Crater count (model) age data suggest that the lava lakes were active at ~3.6 Ga (300 Ma after floor emplacement). Criteria used to identify lava lakes in Gassendi were applied globally to locate candidate lava lakes within floor‐fractured craters. With the identification of lava lake morphology, both in Gassendi crater and in other floor‐fractured craters, the current ascent and eruption models should be revised to allow for at least short‐term connection between magma supply at depth and surface lava lakes. Hence, this integration of multiple perspectives afforded by recent remote data sets reveals new views about lunar volcanic processes. Plain Language Summary: The lunar impact crater Gassendi (110‐km diameter) and surrounding area was examined with the most recent spacecraft images to understand the volcanic processes. The Gassendi area once hosted various types of volcanism similar to Earth. These eruptions are ancient, nearly four billion year old, and include both visible and buried lava flows, fire‐fountain deposits, and lakes of lava. There are two buried lava flows to the west of Gassendi crater that have different compositions and reside at different depths. Northeast of Gassendi we discovered a fire‐fountain deposit. We identified three separate lava lakes on the northeast, northwest, and southwest floor of Gassendi crater based on morphology analogous to terrestrial lava lakes, geochemical signatures of high‐iron, low‐silica lava rock, and 3‐D terrain data. Crater count (model) age data suggests the lava lakes were active 300 million years after floor emplacement. The lava lakes were supplied with magma through fractures in the floor of Gassendi. A preliminary search was conducted for lava lakes within floor‐fractured craters around the Moon and lava lake morphology was identified in six other craters, which may require a revision of the current eruption models for floor‐fractured craters. Key Points: Three lava lakes were identified on the northeast, northwest, and southwest floor of lunar floor‐fractured crater Gassendi (110‐km diameter) Two Nectarian‐aged cryptomare deposits west of Gassendi crater were emplaced from different sources or evolved between eruptions A previously unmapped pyroclastic deposit and source vent was identified in the highlands northeast of Gassendi crater