Jet Propulsion Laboratory California Institute of Technology Pasadena, California www.nasa.gov

Bear Fight Institute Multi-wavelength quantification of Io’s volcanic heat flow from Galileo NIMS data

Ashley Gerard Davies1 and Glenn J Veeder2

1 Jet Propulsion Laboratory- California Institute of Technology, Pasadena, CA, USA 2 Bear Fight Institute, Winthrop WA, USA

Io volcanoes ranked by thermal emission 90

60

) 30 °

0 Latitude ( Latitude -30

-60

-90 300 200 100 0

W. Longitude (°) Veeder et al. (2012) Icarus NASA Galileo mission – 1995-2003

NIMS

Visible Infrared Galileo Near Infrared Mapping Spectrometer

Range: 0.7 to 5.2 µm – up to 408 λ

Widely varying spatial, temporal and spectral resolutions

Over 1000 detections of thermal emission – Davies et al. 2011, 2012, 2014

The best data available of volcanic thermal emission from Io’s volcanoes PDART Goal:

Derive at-surface leaving spectral radiance as a function of wavelength - ForAt every surface hot leaving spot detectionspectral radiance in the as NIMS a function Io dataset of wavelength - Corrected for viewing-For every hot geometry spot detection in the NIMS Io dataset - Corrected for incident-Corrected sunlight for whereviewing geometry necessary -Corrected for incident sunlight where necessary Galileo Near Infrared Mapping Spectrometer

The best data available of volcanic thermal emission from Io’s volcanoes

- Constraint of silicate eruption temperature >1100 K at Zamama (Davies et al., 1997) - Measuring effusion rates at multiple volcanoes (Davies et al., 2001) - Mapping the temperature distribution of Loki Patera (Davies, 2003) - Identification of Pele as an active, overturning lava lake (Davies et al., 2001) - Extraction of possible ultramafic temperatures – Pillan (Davies et al., 2001) - Quantified thermal emission from 115 hot spots (Veeder et al., 2012, 2015) - Discovery of Stombolian-like explosion at Marduk Fluctus (Davies et al., 2018) title

Davies et al. 2019, LPSC abstract Davies et al. 2019, LPSC abstract Io from Earth: Keck AO data (4.7 µm) 90

60 Dazhbog P. Surt Thor Zal P.

) 30 Amirani ° Daedalus P. Loki P. Gish Bar P. 0 Janus P. Pillan Prometheus Tawhaki P.

Pele Tupan P. Latitude ( Latitude -30 Culann Ulgen P. Marduk F. Unnamed Masubi -60

-90 300 200 100 0 W. Longitude (°) Marchis et al. (2001) Icarus NIMS Io data: “Tubes” and “cubes”

Tube - radiance or reflectance formats

- unadulterated spectral radiance values

- 50% mirror swath overlap

- radiances added from adjacent pixels

- resulting spectrum is the best representation of spectral radiance NIMS Io data: “Tubes” and “cubes”

Cube - radiance or reflectance formats

- data resampled to remove 50% overlap

- better navigation applied

- hot spot radiances are mixed with surrounding pixels

- Cubes yield more precise locations of hot spots NIMS data 190 tubes processed into 181 cubes - all available from the NASA PDS

PDART work: grouped data into four classes - Night, subpixel - Night, extended sources - Day, subpixel - Day, extended sources NIMS data

Cube data: G1INNSPEC01, June 1996. See Davies and Ennis, 2011 Processing of NIMS tube data

Described in a long list of publications: Processing of NIMS tube data

Described in a long list of publications: Processing of NIMS tube data

Described in a long list of publications: Processing of NIMS tube data

Described in a long list of publications: Processing of NIMS tube data

Described in a long list of publications: Processing of NIMS tube data

Described in a long list of publications: Processing of NIMS tube data

Described in a long list of publications: Processing of NIMS tube data

Described in a long list of publications: Processing of NIMS tube data

Described in a long list of publications: Using cubes – Rathbun et al. 2018

“We reanalyzed Galileo NIMS observations (see next section) and determined the 3.5 μm brightness of 51 active volcanic features....”

“We used data from the Galileo NIMS to systematically determine the brightness for each active volcano in each image. To do this, we used the NIMS cubes (Lopes et al., 2001).” Using cubes – Rathbun et al. 2018

Comparison of new 3.5 µm radiances with values already published:

Rathbun et al. systematically underestimate thermal emission from Io’s most powerful volcanoes by up to five orders of magnitude. Using cubes – Rathbun et al. 2018 See Davies et al. (2012), GRL For all NIMS data – pre-processing

• Use NIMS tube data • Compare with cube data navigation to establish location (ongoing) • Read radiance data and navigation data into IDL arrays • CORE (FULL_DATA) • Nav backplanes (GEO_DATA) • Read wavelengths tables into IDL arrays • Read grating positions into IDL arrays (Pre orbit I24) • Incorporate NITED database into IDL structure (done for 1, 2 pending) • Clean arrays (each with a different flag) (done for 1,2) • NaN • -Inf • Negative numbers 1. Night, unresolved: processing workflow

• Use tube data • Get hot spot line and samples from database structure (2 adjacent samples in mirror sweep direction to account for the NIMS point spread function) • Add spectra to get total thermal emission spectrum • Adjust for viewing geometry (cosine correction) • A one-size-fits-all approach won’t work (cf. Rathbun et al. 2018).

The data need additional processing – we have examined each spectrum and classified them on the basis of anomalies found ( spreadsheet) Missing data, S2 (13)

Don’t use data <1 µm (5) Noise (14) Don’t use data <2 µm (6) Noise (14) This is fine as it is DAYTIME EXAMPLE

Patterning in data – jitter (8) or Booms (9) A work in progress: Results so far

- Processed and “scrubbed” all tubes - Some previously overlooked detections – Loki Patera, Pele, Zamama... - The discovery of the E4 Marduk Fluctus explosive event (thanks to Rebecca Davies, my high school summer intern) - Everything is preserved in IDL structures - Now incorporating temperature/area model fits

 Improved timelines of hot spot variability  Robust data for comparison with ground-based telescope data  Modelling of individual eruptions and episodes  More science nuggets to be mined from this dataset  Everything will be put on the PDS

An updated report will be delivered at AGU Prometheus – tube-fed lava flows See McEwen et al., 1998; Keszthelyi et al., 2001.

Landsat 7

Galileo I24 (Oct 1999) SSI image

Davies et al. (2006) Icarus, 184, 460-477. Prometheus – tube-fed lava flows

Main vent

Surface flows

Breakouts/skylights?

NIMS: 24INPROMTH91A 11 Oct 1999 Leone et al. (2009), Icarus, 187, 93-105. Average spatial resolution: 1.4 km/pixel Acknowledgements

NASA PDART Program, award 811073.02.37.01.99

PDS Node at New Mexico State University, Las Cruces, NM

This work was performed at JPL-Caltech and BFI under NASA contract. © Caltech 2019. Io volcanoes and heat flow

Davies et al. (2015) Icarus