We present mid-infrared spectra and images from the GEMINI-N ( + Michelle ) observations of fragments SW3- [ B ] and SW3- [ C ] of the ecliptic ( Jupiter Family ) comet 73P/Schwassmann-Wachmann 3 pre-perihelion .
We observed fragment B soon after an outburst event ( between 2006 April 16 – 26 UT ) and detected crystalline silicates .
The mineralogy of both fragments was dominated by amorphous carbon and amorphous pyroxene .
The grain size distribution ( assuming a Hanner modified power-law ) for fragment SW3- [ B ] has a peak grain radius of a _ { p } \sim 0.5 µm , and for fragment SW3- [ C ] , a _ { p } \sim 0.3 µm ; both values larger than the peak grain radius of the size distribution for the dust ejected from ecliptic comet 9P/Tempel 1 during the Deep Impact event ( a _ { p } = 0.2 µm ) .
The silicate-to-carbon ratio and the silicate crystalline mass fraction for the submicron to micron-size portion of the grain size distribution on the nucleus of fragment SW3- [ B ] was 1.341 ^ { +0.250 } _ { -0.253 } and 0.335 ^ { +0.089 } _ { -0.112 } , respectively , while on the nucleus of fragment SW3- [ C ] was 0.671 ^ { +0.076 } _ { -0.076 } and 0.257 ^ { +0.039 } _ { -0.043 } , respectively .
The similarity in mineralogy and grain properties between the two fragments implies that 73P/Schwassmann-Wachmann 3 is homogeneous in composition .
The slight differences in grain size distribution and silicate-to-carbon ratio between the two fragments likely arises because SW3- [ B ] was actively fragmenting throughout its passage while the activity in SW3- [ C ] was primarily driven by jets .
The lack of diverse mineralogy in the fragments SW3- [ B ] and SW3- [ C ] of 73P/Schwassmann-Wachmann 3 along with the relatively larger peak in the coma grain size distribution suggests the parent body of this comet may have formed in a region of the solar nebula with different environmental properties than the natal sites where comet C/1995 O1 ( Hale-Bopp ) and 9P/Tempel 1 nuclei aggregated .