J/AJ/156/207 Brightness of active Ionian volcanoes (Rathbun+, 2018)
The global distribution of active Ionian volcanoes and implications for tidal
heating models.
Rathbun J.A., Lopes R.M.C., Spencer J.R.
<Astron. J., 156, 207 (2018)>
=2018AJ....156..207R 2018AJ....156..207R (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Spectroscopy ; Planets
Keywords: planets and satellites: fundamental parameters -
planets and satellites: surfaces - techniques: imaging spectroscopy
Abstract:
Tidal heating is the major source of heat in the outer solar system.
Because of its strong tidal interaction with Jupiter and the other
Galilean satellites, Io is incredibly volcanically active. We use the
directly measured volcanic activity level of Io's volcanoes as a proxy
for surface heat flow and compare it to tidal heating model predictions.
Volcanic activity is a better proxy for heat flow than simply the
locations of volcanic constructs. We determine the volcanic activity
level using three data sets: the Galileo Photopolarimeter Radiometer
(PPR), Galileo Near-Infrared Mapping Spectrometer (NIMS), and New
Horizons LEISA. We also present a systematic reanalysis of the Galileo
NIMS observations to determine the 3.5 µm brightness of 51 active
volcanoes. We find that potential differences in volcanic style between
high and low latitudes make high-latitude observations unreliable for
distinguishing between tidal heating models. Observations of Io's polar
areas, such as those by Juno, are necessary to unambiguously understand
Io's heat flow. However, all three of the data sets examined show a
relative dearth of volcanic brightness near 180 W (anti-Jovian point)
and the equator, and the only data set with good observations of the
sub-Jovian point (LEISA) also shows a lack of volcanic brightness in that
region. These observations are more consistent with the mantle-heating
model than the asthenospheric-heating model. Furthermore, all three of
the data sets are consistent with fourfold symmetry in longitude and peak
heat flow at mid-latitudes, which best matches with the combined heating
case of Tackley et al. (2001Icar..149...79T 2001Icar..149...79T).
Description:
The Galileo Near-Infrared Mapping Spectrometer (NIMS) instrument
(Carlson et al. 1992SSRv...60..457C 1992SSRv...60..457C) obtained spectral image cubes with
as many as 408 and as few as 12 spectral channels between 0.7 and 5.2 µm
(Lopes et al. 2004Icar..169..140L 2004Icar..169..140L). For data obtained at night or in
eclipse, simply fitting one or more blackbody curves to the data yields
quantitative information about the volcano's activity. For daytime data,
only the longer wavelengths are fitted, to minimize the inexact subtraction
of reflected sunlight. We reanalyzed Galileo NIMS observations and
determined the 3.5 µm brightness of 51 active volcanic features. All
of the 51 features were observed multiple times, so an average value
is used in our analysis.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 65 287 Brightness of hotspots measured in NIMS
observations by the systematic process described
--------------------------------------------------------------------------------
See also:
J/A+A/427/371 : Galilean satellites ephemerides (Lainey+, 2004)
J/other/SoSyR/49.383 : Galilean satellites + Jupiter positions
(Narizhnaya, 2015)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "date" Date Date of the observation
12- 24 A13 --- ID Observation identifier
26- 30 F5.1 deg Lat [-52.3/41.8] Latitude
32- 36 F5.1 deg Long [33.4/308.8] Longitude
38- 47 A10 --- Name Volcano identifier
49- 56 E8.2 W/um Flux [159000/1.06e+13] The 3.5 micron flux density
58- 65 E8.2 W/um e_Flux [6.62e+07/8.89e+13]? Uncertainty in Flux
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 28-Mar-2019