Loki Spectra Update

Robert R. HowellUniversity of Wyoming

with help from Jani and Jason while on sabbatical at UA Fall 2005 and calibrated C10 images from Paul Geissler

Overview

• Loki-NIMS paper (Howell & Lopes) submitted to Icarus in February– Had hoped to have revisions done before meeting – not quite

– Probably will be submitted in next couple weeks

• 1997 Flow model correction for Pele rates ( ~May Icarus)

• Updates to volatile work: Concentrating on obtaining calibrated spectra in Loki region from Galileo SSI (and eventually Voyager – for UV)

– Update from spectra shown at Boulder workshop• Previous spectra all ratioed to reference region (white “island”)

• Paul Geissler provided calibrated images last summer

• I’ve learned how to produce those – and how to processes and register with ISIS to minimize “averaging” effects

– Have calibrated spectra of selected regions around Loki

– See spatial effects in “Band depth images” for 0.9 μm (pyroxene)

– See spatial effects in “BDR” for “feature” 0.757 μm

• Volatile work and spectra mentioned briefly in Loki-NIMS manuscript– Will move that to 2nd paper – submitted by end of summer

Flow model paper corrections

• 1997 Flow model correction for Pele rates: May(?) Icarus– As I mentioned to several people – some problem in basalt flow areal rates for Pele

– Theory not affected. Loki, Ulgen, Amaterasu checked and also OK

– Pele areal rates (m2/s) were too high as published by factor of ~12• Caused by wrong scale factor in IRIS FOV (or equivalently distance)

• Affects rates, but not time scales (which only depend on SHAPE of spectra)– So fast overturn times still apply – i.e. lava lake

• Corrected rates: (1000, 1600, 2800 m2/s) for (4, 1, ¼ day) time scales

• Product gives area of hot spot/flow: (also too high by 12)138 km2 (equivalent to 13 km diameter circle)

– Dark region in Fig. 2 of Radebaugh 2004) is 250 km2

• Just discovered yet another correction:– Minor part of paper is applying flow model to sulfur

• Clear that S flows don’t work – cool too quickly – rates too high

– Discovered I’d used an unrealistically large K for sulfur (3-10X)

– With better sulfur K flow rates even larger, time scales even shorter

– With new numbers sulfur works even more poorly than before

C10 Calibrated images (from Geissler) with ROI’s

Last year just ratioed to island ROI 0

Red “rim” regions ROI 5,6

Dark “patera” regions ROI 4, 7

Spectra of regions – with “dispersion”

Comparison with Geissler 1999: Loki

Comparison with Geissler 1999 : Island

Comparison with Geissler 1999: Dark regions

ROI 7: Dark at 0.4 μm mixed with S, not SO2

Comparison with Geissler 1999: Red Rims

Red rims match Geissler 1999 Red volcanic regions. (0.76 feature?)

Band depth map for 0.888 μm filter (pyroxene)

• Grey scale from 0.888 μm image

• Red = 0.888 μm absorption

• Blue = 0.888 μm emission

• Ignore rim effects for now

• Do see sublte variations in band strength– Weak in SE corner

– Stronger near inner and outer margins

• Present (weaker) in ROI 7 and “fissure”

Band depth map for 0.757 μm filter (unknown)

• Grey = 0.757 μm image– Red = absorption

– Blue = emission

• Artifacts from limited spectral resolution– 0.888 μm absorption

produces false adjacent channel emission

• Do see real “absorption” in 0.757 μm band around rim of patera

Spectra of groups of pixels: Rims

• 0.757 μm feature “real

Spectra of groups of pixels: Patera

• 0.757 μm feature “real

Voyage: Highest resolution, UV

Summary

• Subtle variations in spectra around Loki

• Rims look very similar to “red” regions– Short chain S

• 0.9 μm “pyroxene” absorption variable within patera

• 0.757 μm unknown absorption present in some “red” rim regions