GEOL 2810 Planetary Science Seminar

"The Crater to Basin Transition on the Moon and Mercury"

M 3:00-5:20 • Spring, 2015 • Lincoln Field 105

 

Course Notes

 

Class 1, 1/26/15: David and Ross summarized the broad outline of the course. For those of you who would like some more background on impact cratering in general and on the Moon, it is worth reviewing Stoffler New Views of the Moon, Chapter 5.

Class 9, 4/13/15: There were some questions regarding oblique impact events, including possible elongation perpendicular to the impactor trajectory. For reference, laboratory experiments by Gault and Wedekind (1978) show that at obliques angles ~10 degrees, the crater can be more elongated perpendicular to the trajectory. This is additionally referenced by Schultz and Lutz-Garihan (1982), although they were more concerned about highly oblique (<5 degrees) impacts on Mars, which are elongated parallel to the impact trajectory. See also Wichman and Schultz (1994) for an anlysis of Crisium basin on the Moon and Andrews-Hanna and Zuber (2010) for a discussion of the effect of planetary curvature on forming elliptical craters for the largest impact events (e.g., SPA).

Magnetic Anomalies: Recent work by Shea et al. (2012) suggests that the lunar core dynamo and thus magnetic dipole were longer lived than previously thought, lasting until at least ~3.7 Ga. The Wieczorek et al. (2012) paper suggests that the magnetic anomalies on the Moon, concentrated along the N/NW portions of SPA may be due to magnetic carriers from the SPA-forming impactor locking in the signature of the early lunar magnetic field. As an alternative to this hypothesis, Purucker et al. (2012) suggest that the magnetic carriers may be large dikes concentrated in the N/NW portion of SPA and in the general region where there is also a concentration of surface mare. It will be interesting to compare the predictions of this hypothesis with the recent GRAIL results from Andrews-Hanna et al. (2014) during Class 11.

Class 10, 4/20/15: There were some questions about how iSALE computes changes in strength, damage etc., during the impact process. The iSALE manual discusses the equations used and their various constants. See section 4 specifically. For more information take a look at Collins et al. (2004) which looks at damage and deformation in impact modeling. The lunar near/farside dichotomy was also discussed in class. The Japanese Kaguya team give their intepretations on the dichotomy here. Two papers discussing basin structure and evolution based on Kaguya findings are Namiki et al. (2009) and Ishihara et al. (2009). Take a look at these and compare them to the GRAIL work as well as the Mohit and Phillips (2006) paper that was discussed in class.