Correlations between Cassini VIMS spectra and RADAR SAR images: Implications for Titan's surface composition and the character of the Huygens Probe Landing Site

Laurence A. Soderblom, Randolph L. Kirk, Jonathan I. Lunine, Jeffrey A. Anderson, Kevin H. Baines, Jason W. Barnes, Janet M. Barrett, Robert H. Brown, Bonnie J. Buratti, Roger N. Clark, Dale P. Cruikshank, Charles Elachi, Michael A. Janssen, Ralf Jaumann, Erich Karkoschka, Stéphane Le Mouélic, Rosaly M. Lopes, Ralph D. Lorenz, Thomas B. McCord, Philip D. NicholsonJani Radebaugh, Bashar Rizk, Christophe Sotin, Ellen R. Stofan, Tracie L. Sucharski, Martin G Tomasko, Stephen D. Wall

Research output: Contribution to journalArticle

106 Citations (Scopus)

Abstract

Titan's vast equatorial fields of RADAR-dark longitudinal dunes seen in Cassini RADAR synthetic aperture images correlate with one of two dark surface units discriminated as "brown" and "blue" in Visible and Infrared Mapping Spectrometer (VIMS) color composites of short-wavelength infrared spectral cubes (RGB as 2.0, 1.6, 1.3 μm). In such composites bluer materials exhibit higher reflectance at 1.3 μm and lower at 1.6 and 2.0 μm. The dark brown unit is highly correlated with the RADAR-dark dunes. The dark brown unit shows less evidence of water ice suggesting that the saltating grains of the dunes are largely composed of hydrocarbons and/or nitriles. In general, the bright units also show less evidence of absorption due to water ice and are inferred to consist of deposits of bright fine precipitating tholin aerosol dust. Some set of chemical/mechanical processes may be converting the bright fine-grained aerosol deposits into the dark saltating hydrocarbon and/or nitrile grains. Alternatively the dark dune materials may be derived from a different type of air aerosol photochemical product than are the bright materials. In our model, both the bright aerosol and dark hydrocarbon dune deposits mantle the VIMS dark blue water ice-rich substrate. We postulate that the bright mantles are effectively invisible (transparent) in RADAR synthetic aperture radar (SAR) images leading to lack of correlation in the RADAR images with optically bright mantling units. RADAR images mostly show only dark dunes and the water ice substrate that varies in roughness, fracturing, and porosity. If the rate of deposition of bright aerosol is 0.001-0.01 μm/yr, the surface would be coated (to optical instruments) in hundreds-to-thousands of years unless cleansing processes are active. The dark dunes must be mobile on this very short timescale to prevent the accumulation of bright coatings. Huygens landed in a region of the VIMS bright and dark blue materials and about 30 km south of the nearest occurrence of dunes visible in the RADAR SAR images. Fluvial/pluvial processes, every few centuries or millennia, must be cleansing the dark floors of the incised channels and scouring the dark plains at the Huygens landing site both imaged by Descent Imager/Spectral Radiometer (DISR).

Original languageEnglish (US)
Pages (from-to)2025-2036
Number of pages12
JournalPlanetary and Space Science
Volume55
Issue number13
DOIs
StatePublished - Nov 2007

Fingerprint

Huygens probe
landing sites
dunes
Titan
synthetic aperture radar
spectrometer
probe
spectrometers
aerosols
dune
ice
hydrocarbons
deposits
nitriles
aerosol
water
Earth mantle
synthetic apertures
hydrocarbon
composite materials

Keywords

  • Aerosols
  • Coatings
  • DISR
  • Dunes
  • Hydrocarbons
  • Mantles
  • Radar
  • SAR
  • Substrate
  • Tholin
  • Titan
  • Titriles
  • VIMS
  • Water ice

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Correlations between Cassini VIMS spectra and RADAR SAR images : Implications for Titan's surface composition and the character of the Huygens Probe Landing Site. / Soderblom, Laurence A.; Kirk, Randolph L.; Lunine, Jonathan I.; Anderson, Jeffrey A.; Baines, Kevin H.; Barnes, Jason W.; Barrett, Janet M.; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger N.; Cruikshank, Dale P.; Elachi, Charles; Janssen, Michael A.; Jaumann, Ralf; Karkoschka, Erich; Mouélic, Stéphane Le; Lopes, Rosaly M.; Lorenz, Ralph D.; McCord, Thomas B.; Nicholson, Philip D.; Radebaugh, Jani; Rizk, Bashar; Sotin, Christophe; Stofan, Ellen R.; Sucharski, Tracie L.; Tomasko, Martin G; Wall, Stephen D.

In: Planetary and Space Science, Vol. 55, No. 13, 11.2007, p. 2025-2036.

Research output: Contribution to journalArticle

Soderblom, LA, Kirk, RL, Lunine, JI, Anderson, JA, Baines, KH, Barnes, JW, Barrett, JM, Brown, RH, Buratti, BJ, Clark, RN, Cruikshank, DP, Elachi, C, Janssen, MA, Jaumann, R, Karkoschka, E, Mouélic, SL, Lopes, RM, Lorenz, RD, McCord, TB, Nicholson, PD, Radebaugh, J, Rizk, B, Sotin, C, Stofan, ER, Sucharski, TL, Tomasko, MG & Wall, SD 2007, 'Correlations between Cassini VIMS spectra and RADAR SAR images: Implications for Titan's surface composition and the character of the Huygens Probe Landing Site', Planetary and Space Science, vol. 55, no. 13, pp. 2025-2036. https://doi.org/10.1016/j.pss.2007.04.014
Soderblom, Laurence A. ; Kirk, Randolph L. ; Lunine, Jonathan I. ; Anderson, Jeffrey A. ; Baines, Kevin H. ; Barnes, Jason W. ; Barrett, Janet M. ; Brown, Robert H. ; Buratti, Bonnie J. ; Clark, Roger N. ; Cruikshank, Dale P. ; Elachi, Charles ; Janssen, Michael A. ; Jaumann, Ralf ; Karkoschka, Erich ; Mouélic, Stéphane Le ; Lopes, Rosaly M. ; Lorenz, Ralph D. ; McCord, Thomas B. ; Nicholson, Philip D. ; Radebaugh, Jani ; Rizk, Bashar ; Sotin, Christophe ; Stofan, Ellen R. ; Sucharski, Tracie L. ; Tomasko, Martin G ; Wall, Stephen D. / Correlations between Cassini VIMS spectra and RADAR SAR images : Implications for Titan's surface composition and the character of the Huygens Probe Landing Site. In: Planetary and Space Science. 2007 ; Vol. 55, No. 13. pp. 2025-2036.
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T1 - Correlations between Cassini VIMS spectra and RADAR SAR images

T2 - Implications for Titan's surface composition and the character of the Huygens Probe Landing Site

AU - Soderblom, Laurence A.

AU - Kirk, Randolph L.

AU - Lunine, Jonathan I.

AU - Anderson, Jeffrey A.

AU - Baines, Kevin H.

AU - Barnes, Jason W.

AU - Barrett, Janet M.

AU - Brown, Robert H.

AU - Buratti, Bonnie J.

AU - Clark, Roger N.

AU - Cruikshank, Dale P.

AU - Elachi, Charles

AU - Janssen, Michael A.

AU - Jaumann, Ralf

AU - Karkoschka, Erich

AU - Mouélic, Stéphane Le

AU - Lopes, Rosaly M.

AU - Lorenz, Ralph D.

AU - McCord, Thomas B.

AU - Nicholson, Philip D.

AU - Radebaugh, Jani

AU - Rizk, Bashar

AU - Sotin, Christophe

AU - Stofan, Ellen R.

AU - Sucharski, Tracie L.

AU - Tomasko, Martin G

AU - Wall, Stephen D.

PY - 2007/11

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N2 - Titan's vast equatorial fields of RADAR-dark longitudinal dunes seen in Cassini RADAR synthetic aperture images correlate with one of two dark surface units discriminated as "brown" and "blue" in Visible and Infrared Mapping Spectrometer (VIMS) color composites of short-wavelength infrared spectral cubes (RGB as 2.0, 1.6, 1.3 μm). In such composites bluer materials exhibit higher reflectance at 1.3 μm and lower at 1.6 and 2.0 μm. The dark brown unit is highly correlated with the RADAR-dark dunes. The dark brown unit shows less evidence of water ice suggesting that the saltating grains of the dunes are largely composed of hydrocarbons and/or nitriles. In general, the bright units also show less evidence of absorption due to water ice and are inferred to consist of deposits of bright fine precipitating tholin aerosol dust. Some set of chemical/mechanical processes may be converting the bright fine-grained aerosol deposits into the dark saltating hydrocarbon and/or nitrile grains. Alternatively the dark dune materials may be derived from a different type of air aerosol photochemical product than are the bright materials. In our model, both the bright aerosol and dark hydrocarbon dune deposits mantle the VIMS dark blue water ice-rich substrate. We postulate that the bright mantles are effectively invisible (transparent) in RADAR synthetic aperture radar (SAR) images leading to lack of correlation in the RADAR images with optically bright mantling units. RADAR images mostly show only dark dunes and the water ice substrate that varies in roughness, fracturing, and porosity. If the rate of deposition of bright aerosol is 0.001-0.01 μm/yr, the surface would be coated (to optical instruments) in hundreds-to-thousands of years unless cleansing processes are active. The dark dunes must be mobile on this very short timescale to prevent the accumulation of bright coatings. Huygens landed in a region of the VIMS bright and dark blue materials and about 30 km south of the nearest occurrence of dunes visible in the RADAR SAR images. Fluvial/pluvial processes, every few centuries or millennia, must be cleansing the dark floors of the incised channels and scouring the dark plains at the Huygens landing site both imaged by Descent Imager/Spectral Radiometer (DISR).

AB - Titan's vast equatorial fields of RADAR-dark longitudinal dunes seen in Cassini RADAR synthetic aperture images correlate with one of two dark surface units discriminated as "brown" and "blue" in Visible and Infrared Mapping Spectrometer (VIMS) color composites of short-wavelength infrared spectral cubes (RGB as 2.0, 1.6, 1.3 μm). In such composites bluer materials exhibit higher reflectance at 1.3 μm and lower at 1.6 and 2.0 μm. The dark brown unit is highly correlated with the RADAR-dark dunes. The dark brown unit shows less evidence of water ice suggesting that the saltating grains of the dunes are largely composed of hydrocarbons and/or nitriles. In general, the bright units also show less evidence of absorption due to water ice and are inferred to consist of deposits of bright fine precipitating tholin aerosol dust. Some set of chemical/mechanical processes may be converting the bright fine-grained aerosol deposits into the dark saltating hydrocarbon and/or nitrile grains. Alternatively the dark dune materials may be derived from a different type of air aerosol photochemical product than are the bright materials. In our model, both the bright aerosol and dark hydrocarbon dune deposits mantle the VIMS dark blue water ice-rich substrate. We postulate that the bright mantles are effectively invisible (transparent) in RADAR synthetic aperture radar (SAR) images leading to lack of correlation in the RADAR images with optically bright mantling units. RADAR images mostly show only dark dunes and the water ice substrate that varies in roughness, fracturing, and porosity. If the rate of deposition of bright aerosol is 0.001-0.01 μm/yr, the surface would be coated (to optical instruments) in hundreds-to-thousands of years unless cleansing processes are active. The dark dunes must be mobile on this very short timescale to prevent the accumulation of bright coatings. Huygens landed in a region of the VIMS bright and dark blue materials and about 30 km south of the nearest occurrence of dunes visible in the RADAR SAR images. Fluvial/pluvial processes, every few centuries or millennia, must be cleansing the dark floors of the incised channels and scouring the dark plains at the Huygens landing site both imaged by Descent Imager/Spectral Radiometer (DISR).

KW - Aerosols

KW - Coatings

KW - DISR

KW - Dunes

KW - Hydrocarbons

KW - Mantles

KW - Radar

KW - SAR

KW - Substrate

KW - Tholin

KW - Titan

KW - Titriles

KW - VIMS

KW - Water ice

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