12:00 PM - 12:15 PM
[PPS06-06] Investigation of the exposures of impact melt rocks inside the Nectaris basin for future missions
Keywords:Moon, Impact basin, Impact melt rock, the Nectaris basin
Lunar crater records provide us with key information on the impact history in the solar system. Especially, age determinations of impact basins (impact structures 300 km in diameter) are important for understanding the bombardment history before 3.8 billion years ago. While relative ages of most of large impact basins are determined based on the stratigraphic relationship, crater densities, and its topographic degradation states, the absolute ages are poorly constrained yet. For age determinations of impact basins, sampling impact melt rocks of basins and isotopic analyses of rocks are required.
In this study, to identify the candidate sites for sampling impact melt of impact basin in future sample return missions, we used multi-band image data and Digital Terrain Models (DTMs) acquired by Multiband Imager (MI) and Terrain Camera (TC) onboard SELENE (Kaguya), and high-resolution images (0.5 to 2.0 m per pixel scale) obtained by Narrow Angle Camera onboard Lunar Reconnaissance Orbiter (LRO). We focus on the Nectaris basin, which is regarded as one of the most important basins to determine whether the late heavy bombardment occurred and the magnitude if it has occurred. Although the Nectaris impact melts are expected to be cumulated inside the inner ring of the basin (Cintala and Grieve 1998, Vaughan et al. 2013), most of the inner floor is covered by mare basalts, which have erupted after the basin formation. Therefore, we investigated large craters inside the Nectaris inner ring. We found that rims of three large craters (Fracastorius, Bohnenberger, and Beaumont) have low FeO content (<2 wt%), much lower than that of surrounding mare basalts, suggesting that the large craters were formed before mare basalt eruptions and the crater rim materials might be originated from the Nectaris impact melt sheet.
Here we will report fresh outcrops identified as candidate exposures of the Nectaris impact melt rocks and its composition. Furthermore, we will discuss the potential for differentiation of impact melt sheet. We also discuss observation scenario in future missions based on the topography and boulder density.
In this study, to identify the candidate sites for sampling impact melt of impact basin in future sample return missions, we used multi-band image data and Digital Terrain Models (DTMs) acquired by Multiband Imager (MI) and Terrain Camera (TC) onboard SELENE (Kaguya), and high-resolution images (0.5 to 2.0 m per pixel scale) obtained by Narrow Angle Camera onboard Lunar Reconnaissance Orbiter (LRO). We focus on the Nectaris basin, which is regarded as one of the most important basins to determine whether the late heavy bombardment occurred and the magnitude if it has occurred. Although the Nectaris impact melts are expected to be cumulated inside the inner ring of the basin (Cintala and Grieve 1998, Vaughan et al. 2013), most of the inner floor is covered by mare basalts, which have erupted after the basin formation. Therefore, we investigated large craters inside the Nectaris inner ring. We found that rims of three large craters (Fracastorius, Bohnenberger, and Beaumont) have low FeO content (<2 wt%), much lower than that of surrounding mare basalts, suggesting that the large craters were formed before mare basalt eruptions and the crater rim materials might be originated from the Nectaris impact melt sheet.
Here we will report fresh outcrops identified as candidate exposures of the Nectaris impact melt rocks and its composition. Furthermore, we will discuss the potential for differentiation of impact melt sheet. We also discuss observation scenario in future missions based on the topography and boulder density.