Search Publications
The low electrical conductivity of Titan's lower atmosphere
Lorenz, Ralph D.
Titan's near-surface atmosphere, with a relatively high density and with weak ion production by cosmic rays or other sources, likely has a lower electrical conductivity than the Earth's, possibly <1 fS/m. Direct measurements by the Relaxation Probe on Huygens constrain it to be <0.5 pS/m, and extrapolation from higher altitudes suggests orde…
Schumann resonance on Titan: A critical Re-assessment
Lorenz, Ralph D.; Le Gall, Alice
Extremely Low Frequency (ELF) electric field signals recorded by the Huygens probe have previously been interpreted as indicating a Schumann Resonance (SR) in the ionosphere-ocean cavity. This interpretation required accommodation of a number of anomalous features with respect to the terrestrial SR, namely a lack of observed lightning discharges w…
The near-surface methane humidity on Titan
Lora, Juan M.; Ádámkovics, Máté
We retrieve vertical and meridional variations of methane mole fraction in Titan's lower troposphere by re-analyzing near-infrared ground-based observations from 17 July 2014 UT (Ádámkovics et al., 2016). We generate synthetic spectra using atmospheric methane profiles that do not contain supersaturation or discontinuities to fit the observations,…
Wind shear and turbulence on Titan: Huygens analysis
Lorenz, Ralph D.
Wind shear measured by Doppler tracking of the Huygens probe is evaluated, and found to be within the range anticipated by pre-flight assessments (namely less than two times the Brunt-Väisälä frequency). The strongest large-scale shear encountered was ∼5 m/s/km, a level associated with 'Light' turbulence in terrestrial aviation. Near-surface winds…
Eight-color maps of Titan's surface from spectroscopy with Huygens' DISR
Karkoschka, Erich; Schröder, Stefan E.
During the descent of the Huygens probe in Titan's atmosphere, the Descent Imager/Spectral Radiometer (DISR) acquired spectra of 3660 locations within 250 km of the landing site. Each spectrum consisted of 200 resolution elements between 480 and 960 nm wavelength. With the help of radiative transfer models, contributions from the atmosphere and su…
Titan's surface spectra at the Huygens landing site and Shangri-La
Le Mouélic, S.; Sotin, C.; D'Aversa, E. +6 more
Titan is an icy satellite of Saturn with a dense atmosphere and covered by a global photochemical organic haze. Ground based observations and the Huygens descent probe allowed to retrieve the main spectral signature of the water ice (Griffith, C.A. et al. [2003]. Science 300(5619), 628-630; Coustenis, A. et al. [2005]. Icarus 177, 89-105) at the s…
Titan's meridional wind profile and Huygens' orientation and swing inferred from the geometry of DISR imaging
Karkoschka, Erich
The altitude and zonal motion of the Huygens probe descending through Titan's atmosphere was determined early under the assumption of no meridional motion (Bird et al. [2005]. Nature 438, 800-802). By comparing images taken during the descent, Karkoschka et al. (Karkoschka et al. [2007]. Planet. Space Sci. 55, 1895-1935) determined the meridional …
The electrical properties of Titan's surface at the Huygens landing site measured with the PWA-HASI Mutual Impedance Probe. New approach and new findings
Lorenz, Ralph D.; Le Gall, Alice; Schwingenschuh, Konrad +9 more
Ten years after the successful landing of the Huygens Probe on the surface of Titan, we reassess the derivation of ground complex permittivity using the PWA-MIP/HASI measurements (Permittivity, Waves and Altimetry-Mutual Impedance Probe/Huygens Atmospheric Structure Instrument) at the frequencies 45, 90 and 360 Hz. For this purpose, we have develo…
The DISR imaging mosaic of Titan's surface and its dependence on emission angle
Karkoschka, Erich; Schröder, Stefan E.
The DISR (Descent Image/Spectral Radiometer) imagers took about 300 images during the descent of the Huygens probe in Titan's atmosphere. We combined them into a photometrically calibrated mosaic of Titan's surface within 100 km of the Huygens landing site with a resolution ranging from 1 km at 100 km distance from the landing site to 50 cm near t…
Observations of the surface of Titan by the Radar Altimeters on the Huygens Probe
Lorenz, R. D.; Plettemeier, D.; Witasse, O. +8 more
Results from the radar altimeters on board the Huygens probe are reported, noting the content of data archived on the NASA Planetary Data System and its ESA counterpart. These instruments provide unique high-resolution information on the topography and electrical properties of the Titan surface over a ∼15 km track across a boundary between a brigh…