Stratospheric aerosols on Jupiter from Cassini observations

Abstract

We retrieved global distributions and optical properties of stratospheric aerosols on Jupiter from ground-based NIR spectra and multiple-phase-angle images from Cassini Imaging Science Subsystem (ISS). A high-latitude haze layer is located at ∼10–20mbar, higher than in the middle and low latitudes (∼50mbar). Compact sub-micron particles are mainly located in the low latitudes between 40°S and 25°N with the particle radius between 0.2 and 0.5μm. The rest of the stratosphere is covered by the particles known as fractal aggregates. In the nominal case with the imaginary part of the UV refractive index 0.02, the fractal aggregates are composed of about a thousand 10-nm-size monomers. The column density of the aerosols at pressure less than 100mbar ranges from ∼107cm−2 at low latitudes to ∼109cm−2 at high latitudes. The mass loading of aerosols in the stratosphere is ∼10−6gcm−2 at low latitudes to ∼10−4gcm−2 in the high latitudes. Multiple solutions due to the uncertainty of the imaginary part of the refractive index are discussed. The stratospheric haze optical depths increase from ∼0.03 at low latitudes to about a few at high latitudes in the UV wavelength (∼0.26μm), and from ∼0.03 at low latitudes to ∼0.1 at high latitudes in the NIR wavelength (∼0.9μm).