Genomewide Expression Analysis in Zebrafish mind bomb Alleles with Pancreas Defects of Different Severity Identifies Putative Notch Responsive Genes

10.1371/journal.pone.0001479PLoS ONE3

Infrared limb sounding of Titan with the Cassini Composite InfraRed Spectrometer: effects of the mid-IR detector spatial responses.

The composite infrared spectrometer (CIRS) instrument on board the Cassini Saturn orbiter employs two 1x10 HgCdTe detector arrays for mid-infrared remote sensing of Titan's and Saturn's atmospheres. In this paper we show that the real detector spatial response functions, as measured in ground testing before launch, differ significantly from idealized "boxcar" responses. We further show that neglecting this true spatial response function when modeling CIRS spectra can have a significant effect on interpretation of the data, especially in limb-sounding mode, which is frequently used for Titan science. This result has implications not just for CIRS data analysis but for other similar instrumental applications

Seasonal Disappearance of Far-Infrared Haze in Titan's Stratosphere

A far-infrared emission band attributed to volatile or refractory haze in Titan's stratosphere has been decreasing in intensity since Cassini's arrival in 2004. The 220 cm(sup -1) feature, first seen by the Voyager Infrared Interferometer Spectrometer, has only been found in Titan's winter polar region. The emission peaks at about 140 km altitude near the winter stratospheric temperature minimum. Observations recorded over the period 2004-2012 by the Composite Infrared Spectrometer on Cassini show a decrease in the intensity of this feature by about a factor of four. Possible seasonal causes of this decline are an increase in photolytic destruction of source chemicals at high altitude, a lessening of condensation as solar heating increased, or a weakening of downwelling of vapors. As of early 2012, the 220 cm(sup -1) haze has not yet been detected in the south. The haze composition is unknown, but its decrease is similar to that of HC3N gas in Titan's polar stratosphere, pointing to a nitrile origin

SEASONAL DISAPPEARANCE OF FAR-INFRARED HAZE IN TITAN'S STRATOSPHERE

A far-infrared emission band attributed to volatile or refractory haze in Titan's stratosphere has been decreasing in intensity since Cassini's arrival in 2004. The 220cm-1 feature, first seen by the Voyager Infrared Interferometer Spectrometer, has only been found in Titan's winter polar region. The emission peaks at about 140km altitude near the winter stratospheric temperature minimum. Observations recorded over the period 2004-2012 by the Composite Infrared Spectrometer on Cassini show a decrease in the intensity of this feature by about a factor of four. Possible seasonal causes of this decline are an increase in photolytic destruction of source chemicals at high altitude, a lessening of condensation as solar heating increased, or a weakening of downwelling of vapors. As of early 2012, the 220cm-1 haze has not yet been detected in the south. The haze composition is unknown, but its decrease is similar to that of HC3N gas in Titan's polar stratosphere, pointing to a nitrile origin. © 2012. The American Astronomical Society. All rights reserved

Meridional variations of C2H2 and C2H6 in Jupiter's atmosphere from Cassini CIRS infrared spectra

Hydrocarbons such as acetylene (C2H2) and ethane (C2H6) are important tracers in Jupiter's atmosphere, constraining our models of the chemical and dynamical processes. However, our knowledge of the vertical and meridional variations of their abundances has remained sparse. During the flyby of the Cassini spacecraft in December 2000, the Composite Infrared Spectrometer (CIRS) instrument was used to map the spatial variation of emissions from 10 to 1400 cm-1 (1000-7 μm). In this paper we analyze a zonally averaged set of CIRS spectra taken at the highest (0.48 cm-1) resolution, firstly to infer atmospheric temperatures in the stratosphere at 0.5-20 mbar via the ν4 band of CH4, and in the troposphere at 150-400 mbar, via the H2 absorption at 600-800 cm-1. Stratospheric temperatures at 5 mbar are generally warmer in the north than the south by 7-8 K, while tropospheric temperatures show no such asymmetry. Both latitudinal temperature profiles however do show a pattern of maxima and minima which are largely anti-correlated between the two levels. We then use the derived temperature profiles to infer the vertical abundances of C2H2 and C2H6 by modeling tropospheric absorption (∼200 mbar) and stratospheric emission (∼5 mbar) in the C2H2ν5 and C2H6ν9 bands, and also emission of the acetylene (ν4 + ν5) - ν4 hotband (∼0.1 mbar). Acetylene shows a distinct north-south asymmetry in the stratosphere, with 5 mbar abundances greatest close to 20° N and decreasing from there towards both poles by a factor of ∼4. At 200 mbar in contrast, acetylene is nearly flat at a level of ∼ 3 × 10-9. Additionally, the abundance gradient of C2H2 between 10 and 0.1 mbar is derived, based on interpolated temperatures at 0.1 mbar, and is found to be positive and uniform with latitude to within errors. Ethane at both 5 and 200 mbar shows increasing VMR towards polar regions of ∼1.75 towards 70° N and ∼2.0 towards 70° S. An explanation for the meridional trends is proposed in terms of a combination of photochemistry and dynamics. Poleward, the decreasing UV flux is predicted to decrease the abundances of C2H2 and C2H6 by factors of 2.7 and 3.5, respectively, at latitude 70°. However, the lifetime of C2H6 in the stratosphere (3 × 1010   s at 5 mbar) is much longer than the dynamical timescale for meridional mixing inferred from Comet SL-9 debris (5 - 50 × 108   s), and therefore the rising abundance towards high latitudes likely indicates that meridional mixing dominates over photochemical effects. For C2H2, the opposite occurs, with the relatively short photochemical lifetime (3 × 107   s), compared to meridional mixing times, ensuring that the expected photochemical trends are visible. © 2006 Elsevier Inc. All rights reserved

FIRST OBSERVATION IN THE SOUTH OF TITAN'S FAR-INFRARED 220 cm(-1) CLOUD

An emission feature at 220 cm-1 which has been attributed to a cloud of condensed material in Titan's winter stratosphere has been seen for the first time in the south. This feature had previously been found only at high northern latitudes during northern winter and spring. The material emitting at 220 cm-1, as yet unidentified, may be volatiles associated with nitrile gases that accumulate in the absence of ultraviolet sunlight. Not detected as recently as 2012 February, the 220 cm-1 feature clearly appeared at the south pole in Cassini spectra recorded on 2012 July 24, indicating a rapid onset of the emission. This is the first indication of the winter buildup of condensation in the southern stratosphere that has been expected as the south pole moves deeper into shadow. In the north the 220 cm-1 feature continued to decrease in intensity with a half-life of 3 years. © 2012. The American Astronomical Society. All rights reserved

Infrared observations of saturn and Titan from Cassini

The Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft has been orbiting Saturn for 2-1/2 years. CIRS is a Fourier transform spectrometer that measures atmospheric thermal structure and dynamics, and atmospheric composition, of Saturn and Titan. CIRS also maps the temperatures and dynamical processes of the rings and icy moons. © 2007 Optical Society of America

TITAN'S SURFACE BRIGHTNESS TEMPERATURES

Radiance from the surface of Titan can be detected from space through a spectral window of low opacity in the thermal infrared at 19 μm (530 cm -1). By combining Composite Infrared Spectrometer observations from Cassini's first four years, we have mapped the latitude distribution of zonally averaged surface brightness temperatures. The measurements are corrected for atmospheric opacity as derived from the dependence of radiance on the emission angle. At equatorial latitudes near the Huygens landing site, the surface brightness temperature is found to be 93.7 0.6 K, in excellent agreement with the in situ measurement. Temperature decreases toward the poles, reaching 90.5 0.8 K at 87°N and 91.7 0.7 K at 88°S. The meridional distribution of temperature has a maximum near 10°S, consistent with Titan's late northern winter. © 2009 The American Astronomical Society. All rights reserved