Rev 51 Enceladus Zeta Orionis Occultation Analysis Status 9 January 2008

Enceladus Plume Occultation In Rev 51 zeta Orionis was occulted by Enceladus’ plume This is the perfect geometry to get a horizontal cut through the plume and detect density variations in the gas jets

Enigmatic Enceladus High density dust jets Are there corresponding high density gas streams?

Outline FUV analysis HSP data Jets / probability Location of jets Comparison to models

FUV analysis Occ is easy to detect Star drifted from pixel 13 to pixel 12 over the course of the observation

FUV analysis Plume occults zeta Orionis in time records 89 and 90 Signal falls into spatial rows 11 to 15, summed for these spectra Integration time = 5 sec

Water column density: FUV, Ian’s analysis Two occulted time records combined Column density derived from short wavelength region of spectrum and from long wavelength region gives different but similar values

Water column density: FUV, Candy’s analysis Time record 89 Mota 2005 cross-sections Best fit column density = 1.5 x cm -2 Time record 90 Mota 2005 cross-sections Best fit column density = 1.65 x cm -2 Column density almost identical to 2005

HSP Data: Bonnie’s analysis Statistical analysis applied to find features that are probably real Assumes signal is Poisson distribution Six different bin sizes employed Possible real features: 1 (b) m = (c) m = (d) m = (e) m = 0.026

HSP Data, summed to 200 msec b. Cairo (V) Start time: T16:59: Closest point to limb: 17:07:20.8 Deepest absorption: 17:07:21.0 e. Damascus III d. Baghdad (VI) Closest point c. Cairo (VIII) or Baghdad (I) a. Ingress f. Egress

Hot Spot Locations (Spitale & Porco, 2007) End Start Start to end a) Ingress b) Cairo V c) Cairo VIII or Baghdad I Closest to limb d) Baghdad VI e) Damascus III f) Egress S/c viewed from this side a b c d e f

Hot Spot Locations (Spitale & Porco, 2007) End Start Start to end Cairo V Cairo VIII or Baghdad I Baghdad VI extension? Closest to limb Baghdad VI no absorption Damascus III

Precise geometry polar plot Asterisks show possible absorptions in UVIS data Circles show clusters of dust jets visible in images

FUV - HSP Comparison Work in Progress Times of two FUV integrations Since these are averages over 5 sec the peak density at plume center could be x higher

Ray height from ingress to egress Trajectory kernels from _052T37_alleph.bsp Reconstruction, not quite final

Optical Depth vs. Rayheight Best fit: z -2.3

Optical Depth vs. Time

Monte Carlo model results - Predicted Plume Shape Work in Progress Occultation Track across plume model

Summary of Results Column density in 2005 ~ = 2007 ~ = 1.6 x cm -2 Peak density may be higher HSP data shows features which may be real Possible to correlate to dust jets mapped in images Change in opacity is minimal however - gas streams do not appear to be as collimated as dust jets Plume density structure still best characterized as ~z -2.3 where z is rayheight Consistent with simple Tian et al model

Future Plans LPSC EGU GRL Paper