Long slit spectropolarimetry of Jupiter and Saturn

Schmid, Hans Martin; Joos, F.; Buenzli, E.; Gisler, D.

doi:10.1016/j.icarus.2011.01.016

Cited by 26 publications

(32 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is similar to observations of Uranus and Neptune (Schmid et al 2006b) but for Titan the polarization is much stronger. On the other hand, similar polarization strength can be found in observations of Jupiter but there the limb polarization is essentially only present at the poles (e.g., Schmid et al 2011), indicating thick polar haze layers and non-polarizing reflection from the clouds along the equator.…”

Section: Detection Of the Limb Polarizationsupporting

confidence: 80%

HST observations of the limb polarization of Titan

Bazzon

Schmid

Buenzli

2014

A&A

Self Cite

View full text Add to dashboard Cite

Context. Titan is an excellent test case for detailed studies of the scattering polarization from thick hazy atmospheres. Accurate scattering and polarization parameters have been provided by the in situ measurements of the Cassini-Huygens landing probe. For Earth-bound observations Titan can only be observed at a backscattering situation, where the disk-integrated polarization is close to zero. However, with resolved imaging polarimetry a second order polarization signal along the entire limb of Titan can be measured. Aims. We present the first limb polarization measurements of Titan, which are compared as a test to our limb polarization models. Methods. Previously unpublished imaging polarimetry from the HST archive is presented, which resolves the disk of Titan. We determine flux-weighted averages of the limb polarization and radial limb polarization profiles, and investigate the degradation and cancelation effects in the polarization signal due to the limited spatial resolution of our observations. Taking this into account we derive corrected values for the limb polarization in Titan. The results are compared with limb polarization models, using atmosphere and haze scattering parameters from the literature. Results. In the wavelength bands between 250 nm and 2 μm a strong limb polarization of about 2−7% is detected with a position angle perpendicular to the limb. The fractional polarization is highest around 1 μm. As a first approximation, the polarization seems to be equally strong along the entire limb. The comparison of our data with model calculations and the literature shows that the detected polarization is compatible with expectations from previous polarimetric observations taken with Voyager 2, Pioneer 11, and the Huygens probe. Conclusions. Our results indicate that ground-based monitoring measurements of the limb-polarization of Titan could be useful for investigating local haze properties and the impact of short-term and seasonal variations of the hazy atmosphere of Titan. Planets with hazy atmospheres similar to Titan are particularly good candidates for detection with the polarimetric mode of the upcoming planet finder instrument at the VLT. Therefore, a good knowledge of the polarization properties of Titan is also important for the search and investigation of extra-solar planets.

show abstract

Section: Detection Of the Limb Polarizationsupporting

confidence: 80%

HST observations of the limb polarization of Titan

Bazzon

Schmid

Buenzli

2014

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…scat. the horizontal direction and then scattered again to the observer (Gehrels et al 1969;Schmid et al 2011). Grazing incidence to the atmosphere on the limb produces an excess of (ii) over (i), which results in vertical polarization.…”

Section: B Credibility Of the Resultsmentioning

confidence: 99%

Polarized Transmission Spectrum of Earth as Observed during a Lunar Eclipse

Takahashi¹,

Itoh²,

Hosoya³

et al. 2017

View full text Add to dashboard Cite

Polarization during a lunar eclipse is a forgotten mystery. Coyne & Pellicori (1970) reported the detection of significant polarization during the lunar eclipse on 1968 April 13. Multiple scattering during the first transmission through the Earth's atmosphere was suggested as a possible cause of the polarization, but no conclusive determination was made. No further investigations on polarization during a lunar eclipse are known. We revisit this mystery with an interest in possible application to extrasolar planets; if planetary transmitted light is indeed polarized, it may be possible to investigate an exoplanet atmosphere using "transit polarimetry." Here we report results of the first spectropolarimetry for the Moon during a lunar eclipse on 2015 April 4. We observed polarization degrees of 2-3 % at wavelengths of 500-600 nm; in addition, an enhanced feature was detected at the O 2 A band near 760 nm. The observed time variation and wavelength dependence are consistent with an explanation of polarization caused by double scattering during the first transmission through the Earth's atmosphere, accompanied by latitudinal atmospheric inhomogeneity. Transit polarimetry for exoplanets may be useful to detect O 2 gas and to probe the latitudinal atmospheric inhomogeneity, and it is thus worthy of serious consideration.

show abstract

“…We use CCA-particles rather than PCA-particles in the model atmospheres because they can yield the high polarization values that have been observed at the poles of Jupiter (see e.g. Schmid et al 2011). Because PCA-particles are more compact, light is on average scattered more within each particle, which decreases the degree of polarization of the scattered light.…”

Section: Polar Haze Particlesmentioning

confidence: 99%

“…For the horizontal inhomogeneities, we use banded structures similar to the belts and zones that circle Jupiter and Saturn, cyclonic spots such as the long lived Great Red Spot on Jupiter and the Great Dark Spot that Voyager-2 observed on Neptune, and polar hazes such as those covering the north and south poles of Jupiter and Saturn. In particular the latter hazes are known to strongly polarize the incident sunlight, as observed at small phase angles from Earth (Schmid et al 2011), and at intermediate phase angles from spacecraft observations (see e.g. West et al 1983;Smith & Tomasko 1984).…”

Section: Introductionmentioning

confidence: 98%

Flux and polarization signals of spatially inhomogeneous gaseous exoplanets

Karalidi

Stam

Guirado

2013

A&A

View full text Add to dashboard Cite

Aims. We present numerically calculated, disk-integrated, spectropolarimetric signals of starlight that is reflected by vertically and horizontally inhomogeneous gaseous exoplanets. We include various spatial features that are present on Solar System's gaseous planets: belts and zones, cyclonic spots, and polar hazes, to test whether such features leave traces in the disk-integrated fux and polarization signals. Methods. Broadband flux and polarization signals of starlight that is reflected by gaseous exoplanets are calculated using an efficient, adding-doubling radiative transfer code, that fully includes single and multiple scattering and polarization. The planetary model atmospheres are vertically inhomogeneous and can be horizontally inhomogeneous, and contain gas molecules and/or cloud and/or aerosol particles.Results. The broadband flux and polarization signals are sensitive to cloud top pressures, although in the presence of local pressure differences, such as in belts and clouds, the flux and polarization phase functions have similar shapes as those of horizontally homogeneous planets. Fitting flux phase functions of a planet with belts and zones using a horizontally homogeneous planet could theoretically yield cloud top pressures that differ by a few hundred mbar from those derived from fitting polarization phase functions. In practice, however, observational errors and uncertainties in cloud properties would make such a fit unreliable. A cyclonic spot like Jupiter's Great Red Spot, covering a few percent of the disk, located in equatorial regions, and rotating in and out of the observer's view yields a temporal variation of a few percent in the broadband flux and a few percent in the degree of polarization. Polar hazes leave strong traces in the polarization of reflected starlight in spatially resolved observations, especially seen at phase angles near 90 • . Integrated across the planetary disk, polar hazes that cover only part of the planetary disk, change the broadband degree of polarization of the reflected light by a few percent. Such hazes have only small effects on locally reflected broadband fluxes and negligible effects on disk-integrated broadband fluxes. Conclusions. Deriving the presence of belts and zones in the atmospheres of gaseous exoplanets from broadband flux and polarization observations will be extremely difficult. Cyclonic spots could leave temporal changes in the broadband flux and polarization signals of a few percent. Polar hazes that cover a fraction of the planetary disk, and that are composed of small, Rayleigh scattering particles, change the broadband degree of polarization by at most a few percent.

show abstract

Long slit spectropolarimetry of Jupiter and Saturn

Cited by 26 publications

References 38 publications

HST observations of the limb polarization of Titan

HST observations of the limb polarization of Titan

Polarized Transmission Spectrum of Earth as Observed during a Lunar Eclipse

Flux and polarization signals of spatially inhomogeneous gaseous exoplanets

Contact Info

Product

Resources

About