Dark ray crater material on Ganymede - a 1 to 5-µm perspective

Details Dark ray crater material on Ganymede - a 1 to 5-µm perspective Dark ray crater material on Ganymede - a 1 to 5-µm perspective

Apr 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eaeja.....7806h&link_type=abstract

EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #7806

Other

Scientific paper

Dark ray craters on Ganymede are believed to result at least partially from impactor contamination because they occur on many terrain types of many ages [1,2]. Of the many dark ray craters on Ganymede, Kittu, Antum, Tammuz, Mir, and Melkart impact craters were all observed by the Near Infrared Mapping Spectrometer (NIMS) at a spatial resolution better than 10 km/pixel. Of these five dark ray craters, Kittu crater possesses a visible color spectrum distinctly flatter than other dark ray craters, more similar to C-type asteroid material rather than redder D-type material [2]. We investigate the near infrared characteristics of the dark ejecta from Kittu and the other four craters for spectral evidence of impactor contamination. Using waterice albedo or bidirectional reflectance models, we first subtract the effect of water ice from the dark ejecta. We then can compare the residual spectrum to mixtures of Ganymede, Callisto, and other nonice materials. Our initial work for the dark ejecta of Kittu shows that the 1 to 5-μm spectrum of this Kittu dark material is very similar to a 50/50 linear mixture of the hydrated Ganymede nonice material [3] and the less-hydrated Callisto non-ice material [4,5]. Other work shows that the spectrum of Callisto nonice material between 1 and 4 microns is similar to CM chondritic material. We therefore infer, along with previous workers, a possible compositional similarity between C-type asteroids and Callisto non-ice material and conclude, consistent with [2], that the Kittu impactor was spectrally similar to a C-type asteroid. Other areas on Ganymede, not related to dark ray craters, do not show any evidence of impactor contamination in the infrared and are spectrally very similar to mixtures of only water ice and the Ganymede nonice endmember [5]. The dark ejecta of Kittu is depleted in CO_2 relative to the surrounding terrain that is unaffected by the impact. Depletion of CO_2 in dark ejecta is common on Ganymede, and CO_2-rich impact craters are rare (unlike for Callisto) [6]. We postulate that the depletion of CO_2 in dark ejecta relative to surrounding terrain is consistent with impact contamination in all cases, and due to the mixing of CO_2-depleted impactor material with Ganymede surface material. References: [1] Conca et al., LPSC XII, 172--174, 1981. [2] Schenk, P. and W.B. McKinnon, Icarus, 89, 318--346, 1991. [3] McCord et al., Science, 292, 1523--1525, 2001. [4] McCord et al., J. Geophys. Res., 103, 8603--8626, 1998. [5] Hibbitts et al., Bull. Amer. Astron. Soc., 34, #23.01, 2002. [6] Hibbitts et al., J. Geophys. Res., in press, 2003.

Affiliated with

Also associated with

No associations

Rating

Dark ray crater material on Ganymede - a 1 to 5-µm perspective does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Dark ray crater material on Ganymede - a 1 to 5-µm perspective, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dark ray crater material on Ganymede - a 1 to 5-µm perspective will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-843944