The reflectance spectrum of Titan's surface at the Huygens landing site determined by the descent imager/spectral radiometer |
| |
| Authors: | SE Schröder HU Keller |
| |
| Institution: | Max-Planck-Institut für Sonnensystemforschung, Max-Planck-Strasse 2, 37191 Katlenburg-Lindau, Germany |
| |
| Abstract: | The descent imager/spectral radiometer aboard the Huygens probe successfully acquired images and spectra of the surface of Titan. To counter the effects of haze and atmospheric methane absorption it carried a surface science lamp to illuminate the surface just before landing. We reconstruct the reflectance spectrum of the landing site in the 500-1500 nm range from downward looking visual and infrared spectrometers data that show evidence of lamp light. Our reconstruction is a followup to the analysis by Tomasko et al. 2005. Rain, winds and haze during the Huygens probe's descent to Titan's surface. Nature 438, 765-778], who scaled their result to the ratio of the up- and down flux measured just before landing. Instead, we use the lamp flux from the calibration experiment, and find a significantly higher overall reflectance. We attribute this to a phase angle dependance, possibly representing the opposition surge commonly encountered on solar system bodies. The reconstruction in the visible wavelength range is greatly improved. Here, the reflectance spectrum features a red slope, consistent with the presence of organic material. We confirm the blue slope in the near-IR, featureless apart from a single shallow absorption feature at 1500 nm. We agree with Tomasko et al. that the evidence for water ice is inconclusive. By modeling of absorption bands we find a methane mixing ratio of 4.5±0.5% just above the surface. There is no evidence for the presence of liquid methane, but the data do not rule out a wet soil at a depth of several centimeters. |
| |
| Keywords: | 95 55 Pe 95 75 Fg 96 12 Kc 96 30 Nd |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
