Probing for Evidence of Plumes on Europa With HST/Stis

Sparks, W. B.; Hand, K. P.; McGrath, M. A.; Bergeron, E.; Cracraft, M.; Deustua, Susana E.

doi:10.3847/0004-637x/829/2/121

Cited by 222 publications

(221 citation statements)

References 30 publications

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“…Attempts to confirm the presence of plumes through the observation of plume aurora have not been successful (Roth et al 2014a(Roth et al , 2015 and earlier searches with Galileo did not reveal signs of geophysical activity (Phillips et al 2000). Recently, HST images of Europa in transit of Jupiter, taken with an FUV filter by Sparks et al (2016), revealed absorption features at the limb on three occasions in 2014 January, March and April. If the absorption is due to water vapor, the plume features require line-of-sight H 2 O column densities in the range of (0.7-3.3)×10 17 cm −2 .…”

Section: Introductionmentioning

confidence: 99%

DETECTION OF A HYDROGEN CORONA IN HST Lyα IMAGES OF EUROPA IN TRANSIT OF JUPITER

Roth

Retherford

Ivchenko

et al. 2017

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We report far-ultraviolet observations of Europa in transit of Jupiter obtained with the Space Telescope Imaging Spectrograph of the Hubble Space Telescope on six occasions between 2014 December and 2015 March. Absorption of Jupiter's bright hydrogen Lyα dayglow is detected in a region several moon radii above the limb in all observations. The observed extended absorption provides the first detection of an atomic hydrogen corona around Europa. Molecular constituents in Europa's global sputtered atmosphere are shown to be optically thin to Lyα. The observations are consistent with a radially escaping H corona with maximum densities at the surface in the range of (1.5-2.2)×10 3 cm −3 , confirming the abundances predicted by Monte Carlo simulations. In addition, we search for anomalies around the limb of Europa from absorption by localized high H 2 O abundances from active plumes. No significant local absorption features are detected. We find that an H 2 O plume with line-of-sight column density in the order of 10 16 cm −2 , as inferred by Roth et al. would not be detectable based on the statistical fluctuations of the transit measurements, and hence is not excluded or further constrained. The presence of plumes with line-of-sight column densities of >2×10 17 cm −2 can be excluded at a 3-σ level during five of our six observations.

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Section: Introductionmentioning

confidence: 99%

DETECTION OF A HYDROGEN CORONA IN HST Lyα IMAGES OF EUROPA IN TRANSIT OF JUPITER

Roth

Retherford

Ivchenko

et al. 2017

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“…If such activity continued today, then direct study of the oceanic composition may be possible, but the question of modern geologic activity remains. Recent observations using the Hubble Space Telescope (HST) have hinted at the possibility of active water vapor plumes at Europa (Roth et al 2014a(Roth et al , 2014bSparks et al 2016Sparks et al , 2017. However, the detections have been sporadic and tenuous, making confirming the existence of plumes difficult.…”

Section: Introductionmentioning

confidence: 99%

“…We simulate an area 156 km in radius (corresponding to our ALMA resolution in this region) centered on 276°W and 16°. 8 S, which is coincident with the Galileo thermal anomaly in the potential plume source region (Sparks et al 2016(Sparks et al , 2017. We model the case of an endogenic thermal anomaly by raising the geothermal heat flux beneath the lowest layer of our simulation (five diurnal skin depths ≈0.75 m at our best-fit parameters).…”

Section: Fits To Alma and Galileo Ppr Observationsmentioning

confidence: 99%

“…Therefore, high-resolution thermal data may present another, perhaps more robust, way of identifying active regions in the case of Europa. Sparks et al (2016Sparks et al ( , 2017 detected potential off-limb absorption near the crater Pwyll in HST images of Europa as it transited Jupiter. This location is coincident with a nighttime thermal excess in brightness temperatures measured by the Galileo Photopolarimeter Radiometer (PPR; Spencer et al 1999;Moore et al 2009).…”

Section: Introductionmentioning

confidence: 99%

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ALMA Thermal Observations of a Proposed Plume Source Region on Europa

Trumbo

Brown

Butler

2017

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We present a daytime thermal image of Europa taken with the Atacama Large Millimeter Array. The imaged region includes the area northwest of Pwyll Crater, which is associated with a nighttime thermal excess seen by the Galileo Photopolarimeter Radiometer and with two potential plume detections. We develop a global thermal model of Europa and simulate both the daytime and nighttime thermal emission to determine if the nighttime thermal anomaly is caused by excess endogenic heat flow, as might be expected from a plume source region. We find that the nighttime and daytime brightness temperatures near Pwyll Crater cannot be matched by including excess heat flow at that location. Rather, we can successfully model both measurements by increasing the local thermal inertia of the surface.

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“…The heavy energetic ions, which have their own precipitation patterns, remove ice in the very top layer (see below) and also preferentially eliminate smaller grains (e.g., Cassidy et al, 2013 ). In addition, the possible presence of endogenic activity, such as a plume on Europa ( Roth et al, 2014;Sparks et al, 2016 ), may create local discrepancies in the spatial distribution of grain sizes and therefore correlations with geomorphological units ( Ligier et al, 2016 ).…”

Section: Bombardment Patternsmentioning

confidence: 99%

Magnetospheric considerations for solar system ice state

Paranicas¹,

Hibbitts²,

Kollmann³

et al. 2018

Icarus

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a b s t r a c tThe current lattice configuration of the water ice on the surfaces of the inner satellites of Jupiter and Saturn is likely shaped by many factors. But laboratory experiments have found that energetic proton irradiation can cause a transition in the structure of pure water ice from crystalline to amorphous. It is not known to what extent this process is competitive with other processes in solar system contexts. For example, surface regions that are rich in water ice may be too warm for this effect to be important, even if the energetic proton bombardment rate is very high. In this paper, we make predictions, based on particle flux levels and other considerations, about where in the magnetospheres of Jupiter and Saturn the ∼MeV proton irradiation mechanism should be most relevant. Our results support the conclusions of Hansen and McCord (2004), who related relative level of radiation on the three outer Galilean satellites to the amorphous ice content within the top 1 mm of surface. We argue here that if magnetospheric effects are considered more carefully, the correlation is even more compelling. Crystalline ice is by far the dominant ice state detected on the inner Saturnian satellites and, as we show here, the flux of bombarding energetic protons onto these bodies is much smaller than at the inner Jovian satellites. Therefore, the ice on the Saturnian satellites also corroborates the correlation.

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Probing for Evidence of Plumes on Europa With HST/Stis

Cited by 222 publications

References 30 publications

DETECTION OF A HYDROGEN CORONA IN HST Lyα IMAGES OF EUROPA IN TRANSIT OF JUPITER

DETECTION OF A HYDROGEN CORONA IN HST Lyα IMAGES OF EUROPA IN TRANSIT OF JUPITER

ALMA Thermal Observations of a Proposed Plume Source Region on Europa

Magnetospheric considerations for solar system ice state

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