Titan's Surface, Revealed by HST Imaging

Smith, Peter H.; Lemmon, M. T.; Lorenz, Ralph D.; Sromovsky, L. A.; Caldwell, John; Allison, M.

doi:10.1006/icar.1996.0023

Cited by 229 publications

(149 citation statements)

References 20 publications

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“…Space Telescope (Smith et al, 1996), and groundbased speckle imaging (Gibbard et al, 1999). These observations indicate a number of dark areas whose surface re¯ectivity has been determined to be close to zeroÐ entirely consistent with deposits of liquid hydrocarbons (principally methane and ethane) on the surface, and dif®cult to account for by anything else.…”

Section: Introduction and Previous Workmentioning

confidence: 82%

Analytic investigation of climate stability on Titan: sensitivity to volatile inventory

Lorenz

McKay

Lunine

1999

Planetary and Space Science

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We develop a semiempirical grey radiative model to quantify Titan's surface temperature as a function of pressure and composition of a nitrogen-methane-hydrogen atmosphere, solar¯ux and atmospheric haze. We then use this model, together with non-ideal gas-liquid equilibrium theory to investigate the behavior of the coupled surface-atmosphere system on Titan. We ®nd that a volatile-rich Titan is unstable with respect to a runaway greenhouseÐsmall increases in solar luminosity from the present value can lead to massive increases in surface temperature. If methane has been photolyzed throughout Titan's history, then this runaway can only be avoided if the photolytic ethane is removed from the surface-atmosphere system. #

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Section: Introduction and Previous Workmentioning

confidence: 82%

Analytic investigation of climate stability on Titan: sensitivity to volatile inventory

Lorenz

McKay

Lunine

1999

Planetary and Space Science

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“…Recently, ground-based observations have shown that Titan has a light curve due to surface albedo features that are visible in methane continuum regions from 0.93 to 2.03 µm (Lemmon et al 1993(Lemmon et al , 1995Griffith 1993;Coustenis et al 1995). Observations with the Hubble Space Telescope have been used to map the surface features responsible for the light curve in many of the methane windows (Smith et al 1996, Meier et al 2000, and ground-based adaptive optics (Combes et al 1997) and speckle (Gibbard et al 1999) images have shown surface features at the longer wavelengths. Visibility of the surface indicates a two-way transmission of the light, which we can use to measure the methane abundance.…”

Section: Introductionmentioning

confidence: 99%

Methane Abundance on Titan, Measured by the Space Telescope Imaging Spectrograph

Lemmon

Smith

Lorenz

2002

Icarus

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Although methane is the dominant absorber in Titan's reflection spectrum, the amount of methane in the atmosphere has only been determined to an order of magnitude. We analyzed spectra from the Space Telescope Imaging Spectrograph, looking at both a bright surface region (700-km radius) and a dark surface region. The difference between the spectra of the two regions is attributed to light that has scattered off the surface, and therefore made a roundtrip through all of Titan's methane. Considering only absorption, the shape of the difference spectrum provides an upper limit on methane abundance of 3.5 km-am. Modeling the multiple scattering in the atmosphere further constrains the methane abundance to 2.63 ± 0.17 km-am. In the absence of supersaturation and with a simplified methane vertical profile, this corresponds to a surface methane-mole fraction near 3.8% and a relative humidity of 0.32. With supersaturation near the tropopause, the surface methane mole fraction could be as low as 3%. c 2002 Elsevier Science (USA)

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“…After selection (but before launch), Griffith et al [43] realized that Cassini's VIMS and ISS would also be able to see the surface. This prediction was confirmed by spatially-resolved near-infrared observations of Titan's surface from both HST [134] and ground-based adaptive optics [31]. Cassini has been a phenominal success (see [24] for a review of Cassini discoveries at Titan to date).…”

Section: Historymentioning

confidence: 80%

“…They are interrupted only by the large bright region Xanadu. First seen from HST observations [134], Xanadu's unique spectrum shows that it is not composed of pure water ice [7] as had initially been assumed [134]. RADAR observations …”

Section: Cassini-huygens Discoveriesmentioning

confidence: 92%

AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance

et al. 2011

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We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVI-ATR). With independent delivery and direct-to-Earth communications, AVI-ATR could contribute to Titan science either alone or as part of a sustained Titan Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan's global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven instruments-2 near-IR cameras, 1 near-IR spectrometer, a RADAR altimeter, an atmospheric structure suite, a haze sensor, and a raindrop detector-AVIATR could accomplish a significant subset of the scientific objectives of the aerial element of flagship studies. The AVIATR spacecraft stack is composed of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan's atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earthyear nominal mission. We propose a novel 'gravity battery' climb-then-glide strategy to store energy for optimal use during telecommunications sessions. We would optimize our science by using the flexibility of the airplane platform, generating context data and stereo pairs by flying and banking the AV instead

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Titan's Surface, Revealed by HST Imaging

Cited by 229 publications

References 20 publications

Analytic investigation of climate stability on Titan: sensitivity to volatile inventory

Analytic investigation of climate stability on Titan: sensitivity to volatile inventory

Methane Abundance on Titan, Measured by the Space Telescope Imaging Spectrograph

AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance

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