Astronomy and Astrophysics – Astrophysics
Scientific paper
Sep 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008dps....40.3605w&link_type=abstract
American Astronomical Society, DPS meeting #40, #36.05; Bulletin of the American Astronomical Society, Vol. 40, p.461
Astronomy and Astrophysics
Astrophysics
Scientific paper
Near-IR spectroscopy has indicated the presence of water ice and carbon dioxide ice on the surface of Titania. While H2O ice is clearly involatile, CO2 ice stability against sublimation over a seasonal cycle of Titania can be considered (Grundy et al., 2006). Recent analysis of the Sep. 8, 2001 stellar occultation by Titania has allowed to set surface pressure upper limits of 10-20 nbar for a CO2, CH4 or N2 atmosphere (Widemann et al., submitted to Icarus). At maximum temperature given by instantaneous equilibrium with solar input, a CO2 sublimation-induced atmosphere is still a factor of 3-6 lower than the upper limit provided by our analysis. Although the non-detection of an atmosphere of Titania is not surprising, our method demonstrates the power of stellar occultations to put upper limits down to pressure levels of ≈ 10 nbar, much more tenuous than on Pluto or Triton, by typical factors of 103.
This is promising in view of the detection of volatile ices on several KBOs. CH4 has been clearly detected on dwarf planets Eris, Makemake and Quaoar, while the presence of N2 on Eris is indirectly suggested. At a current distance of 43 AU, and with its large size which makes its ices marginally stable over the age of the Solar System (Schaller and Brown, 2007), Quaoar appears to be a favorable occultation target for an atmosphere. On a longer term, as pressure levels detected during refractive occultations are inversely proportional to distance, the upper limits obtained on Titania open promising perspectives to constrain atmospheres of large KBOs at a few nbar level.
Grundy, W.M., Young, L.A., Spencer, J.R., Johnson, R.E., Young, E.F. & Buie, M.W. 2006, Icarus 184, 543-555
Schaller, E.L. & Brown, M.E. 2007, Astrophys. J. 659, L61-L64
Lellouch Emmanuel
Sicardy Bruno
Widemann Thomas
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