Multi-Wavelength Quantification of Io's Volcanic Heat Flow from Galileo NIMS Data

We are processing all Io data obtained by Galileo's Near Infrared Mapping Spectrometer (NIMS) to derive at-surface leaving radiances for over 1000 detections of thermal emission from Io's active volcanoes. These spectra will allow robust quantification of thermal emission and effusion rate from over 115 volcanoes detected by NIMS. Products will be made available via NASA's Planetary Data System (PDS). Here, we report on progress in processing all suitable NIMS Io "tube" products, and report some previously overlooked detections. NIMS data contain the highest spatial and spectral resolution data of thermal emission from Io's active volcanoes [e.g., 1] but historically have been hard to access and process. Data access has been improved [2]. Now, by generating fully processed NIMS spectra, we will ensure wider planetary community access to an invaluable resource: an extensive set of Io's volcanic thermal emission spectra, which are also suitable for comparison with contemporaneous data obtained with ground-based telescopes [3]. NIMS was particularly well suited to observing thermal emission from ongoing or recent high-temperature (silicate) volcanic activity [1]. The NIMS wavelength range (0.7 to 5.2 µm) meant that it was sensitive to a wide range of surface temperatures (>1000 K to ~220 K) and lava surface exposure times (seconds to days). The PDS NIMS Io dataset contains 190 "tube" observations of spectral radiance, which were converted into 181 "cube" products. Particular care has to be taken in using NIMS data. Cube product intensities are resampled, which is often problematic for quantifying thermal emission. A recent analysis [4] relying exclusively on cubes underestimated 3.5 µm radiance from Io's most powerful hot spots (including Loki Patera, Amirani, Pillan and Pele) by up to five orders of magnitude [e.g., compare with 3, 5]. We use NIMS tube products, which contain robust radiance data [e.g., 3]. Acknowledgements: We thank the NASA PDART Program for support. This work was performed at JPL and BFI under NASA contract. References: [1] Davies, A. G. Volcanism on Io, CUP, 372 pages. 2007. [2] Cahill, J. et al., 3rd Plan. Data Workshop, abs.7071. 2017. [3] Davies, A. G. et al. GRL, 39, L01201. 2012. [4] Rathbun, J., Lopes, R. et al. Astro. J. 156, 5, 207. 2018. [5] Davies, A. G. et al. JGR, 106, E12, 33,079-33,104. 2001.