Henry G. Roe

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Until now, all the clouds imaged in Titan’s troposphere have been found at far southern latitudes (60 –90 south). The occurrence and location of these clouds is thought to be the result of convection driven by the maximum annual solar heating of Titan’s surface, which occurs at summer solstice (2002 October) in this south polar region. We report the first(More)
We have used the Hubble Space Telescope to directly measure the angular size of the large Kuiper Belt object 2003 UB313. By carefully calibrating the point-spread function of a nearby field star, we measure the size of 2003 UB313 to be mas, corresponding to a diameter of km or a size ∼5% larger than 34.3 1.4 2400 100 Pluto. The V-band geometric albedo of(More)
Using adaptive optics on the W.M. Keck II telescope we imaged Titan several times during 1999 to 2001 in narrowband near-infrared filters selected to probe Titan’s stratosphere and upper troposphere. We observed a bright feature around the south pole, possibly a collar of haze or clouds. Further, we find that solar phase angle explains most of the observed(More)
Observations of Titan's mid-latitude clouds from the W. M. Keck and Gemini Observatories show that they cluster near 350 degrees W longitude, 40 degrees S latitude. These clouds cannot be explained by a seasonal shift in global circulation and thus presumably reflect a mechanism on Titan such as geysering or cryovolcanism in this region. The rate of(More)
The spectrum of the bright Kuiper Belt object 2005 FY9 from 0.34 to 2.5 m is dominated by the red coloring of many outer solar system objects in the optical wavelength regime and by absorption due tomethane in the near-infrared. The solid methane absorption lines are significantly broader on 2005 FY9 than on any other solar system body, indicating long(More)
Images of Titan acquired over five nights in October 2004 using the adaptive optics system at the Keck Observatory show dramatic increases in tropospheric cloud activity at the south pole compared with all other images of Titan clouds to date. During this time, Titan’s south polar clouds brightened to more than 18 times their typical values. The Cassini Ta(More)
Nearly all adaptive optics images of Titan taken between December 2001 and November 2004 showed tropospheric clouds located within 30◦ of the south pole. We report here on a dissipation of Titan’s south polar clouds observed in twenty-nine Keck and Gemini images taken between December 2004 and April 2005. The near complete lack of south polar cloud activity(More)
Methane clouds, lakes and most fluvial features on Saturn's moon Titan have been observed in the moist high latitudes, while the tropics have been nearly devoid of convective clouds and have shown an abundance of wind-carved surface features like dunes. The presence of small-scale channels and dry riverbeds near the equator observed by the Huygens probe at(More)
With its substantial atmosphere of nitrogen, hydrocarbons and nitriles, Saturn's moon Titan is a unique planetary satellite. Photochemical processing of the gaseous constituents produces an extended haze that obscures the surface. Soon after the Voyager fly-bys in 1980 and 1981 photochemical models led to the conclusion that there should be enough liquid(More)
[1] We present spatially-resolved, low-resolution (l/Dl 1,500) spectroscopy of the leading hemisphere of Titan in the H-band (1.5–1.7 mm) using adaptive optics. Spatial variations of surface albedo are observed in images at 1.55– 1.57 mm, which are clearly distinct from stratospheric haze. There is a significant increase in albedo around the southern(More)