The heartbeat of the volcano: The discovery of episodic activity at Prometheus on Io

Davies, A. G.; Wilson, Lionel; Matson, D. L.; Leone, Giovanni; Keszthelyi, L.

doi:10.1016/j.icarus.2006.05.012

Cited by 29 publications

(36 citation statements)

References 60 publications

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“…Ignoring heliocentric distance effects discussed below, the stability seen in the recent IR data may be easiest to understand if the atmosphere seen at 19 µm is primarily supported by frost sublimation, because of the long-term stability of albedo patterns on Io (Geissler et al 1999b). Because Prometheus-type plumes have typical lifetimes of several years Soderblom 1983, Keszthelyi et al 2001), the observed stability may also be consistent with volcanic support, though there is considerable variability in thermal infrared emission even from long-lived plume sources like Prometheus (Davies 2003), with likely corresponding variability in gas output. Unfortunately we have only sporadic data on the longitudinal distribution of volcanic or plume activity during the period of these observations.…”

Section: Time Variations?mentioning

confidence: 86%

Mid-infrared detection of large longitudinal asymmetries in Io's SO atmosphere

Spencer¹,

Lellouch²,

Richter³

et al. 2005

Icarus

103

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We have observed about 16 absorption lines of the ν 2 SO 2 vibrational band on Io, in disk-integrated 19 µm spectra taken with the TEXES high spectral resolution mid-infrared spectrograph at the NASA Infrared Telescope Facility in November 2001, December 2002, and January 2004 These are the first ground-based infrared observations of Io's sunlit atmosphere, and provide a new window on the atmosphere that allows better longitudinal and temporal monitoring than previous techniques. Dramatic variations in band strength with longitude are seen that are stable over at least a 2 year period. The depth of the strongest feature, a blend of lines centered at 530.42 cm -1 , varies from about 7% near longitude 180 to about 1% near longitude 315 W, as measured at a spectral resolution of 57,000. Interpretation of the spectra requires modeling of surface temperatures and atmospheric density across Io's disk, and the variation in non-LTE ν 2 vibrational temperature with altitude, and depends on the assumed atmospheric and surface temperature structure. About half of Io's 19µm radiation comes from the sun-heated surface, and half from volcanic hot spots with temperatures primarily between 150 and 200 K, which occupy about 8% of the surface. The observations are thus weighted towards the atmosphere over these lowtemperature hot spots. If we assume that the atmosphere over the hot spots is representative of the atmosphere elsewhere, and that the atmospheric density is a function of latitude, the most plausible interpretation of the data is that the equatorial atmospheric column density varies from about 1.5 x 10 17 cm -2 near longitude 180 W to about 1.5 x 10 16 cm -2 near longitude 300 W, roughly consistent with HST UV spectroscopy and Lyman-α imaging. The inferred atmospheric kinetic temperature is less than about 150 K, at least on the anti-Jupiter hemisphere where the bands are strongest, somewhat colder than inferred from HST UV spectroscopy and millimeter-wavelength spectroscopy. This longitudinal variability in atmospheric density correlates with the longitudinal variability in the abundance of optically thick, near-UV bright SO 2 frost. However it is not clear whether the correlation results from volcanic control (regions of large frost abundance result from greater condensation of atmospheric gases supported by more vigorous volcanic activity in these regions) or sublimation control (regions of large frost abundance produce a more extensive atmosphere due to more extensive sublimation). Comparison of data taken in 2001, 2002, and 2004 shows that with the possible exception of longitudes near 180 W between 2001 and 2002, Io's atmospheric density does not appear to decrease as Io recedes from the sun, as would be expected if the atmosphere were supported by the sublimation of surface frost, suggesting that the atmosphere is dominantly supported by direct volcanic supply rather than by frost sublimation. However, other evidence such as the smooth variation in atmospheric abundance with latitude, and atmospheric ch...

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Section: Time Variations?mentioning

confidence: 86%

Mid-infrared detection of large longitudinal asymmetries in Io's SO atmosphere

Spencer¹,

Lellouch²,

Richter³

et al. 2005

Icarus

103

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“…To avoid this confusion, and to avoid naming a class after what appears to be a unique feature on Io (Loki) we use the term "Patera" volcanism to describe activity within patera, both flows and lava lakes. We note that a patera eruption becomes a Promethean eruption when the patera overflows (at Prometheus, for example, Davies, 2003b). Pelean activity corresponds to vigorous resurfacing of a patera by the rapid replacement of the crust of a lava lake (seen at Pele), with sustained thermal emission at short infrared wavelengths.…”

Section: Introductionmentioning

confidence: 93%

Keck AO survey of Io global volcanic activity between 2 and 5 μm

Marchis

Mignant

Chaffee

et al. 2005

Icarus

Self Cite

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“…This is plausible if Io's crust is pervasively layered as widely suspected (e.g., McEwen et al, 2004) and if the magma is close to neutrally buoyant with respect to the crust (consistent with patera observations; Davies et al, 2006). The effect on temperatures in the crust of magma intrusions was modeled by Stevenson and McNamara (1988), who were focused on how much conductive heat flow might be missing from ground-based IR estimates of Io's heat flow.…”

Section: Crustal Parametersmentioning

confidence: 80%

“…This may not be the case generally, in that magma may be injected laterally along sills at shallow levels and not reach the surface (Stevenson and McNamara, 1988;Leone and Wilson, 2001;Davies et al, 2006). This is plausible if Io's crust is pervasively layered as widely suspected (e.g., McEwen et al, 2004) and if the magma is close to neutrally buoyant with respect to the crust (consistent with patera observations; Davies et al, 2006).…”

Section: Crustal Parametersmentioning

confidence: 84%