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Abstract
In October and November 2014, spectra covering the 1.436 to 1.863-μm wavelength range from the SINFONI Integral Field Unit Spectrometer on the Very Large Telescope showed the presence of a vast bright north polar cap on Uranus, extending northward from about 40°N and at all longitudes observed. The feature, first detected in August 2014 from Keck telescope images, has a morphology very similar to the southern polar cap that was seen to fade before the 2007 equinox. At strong methane-absorbing wavelengths (for which only the high troposphere or stratosphere is sampled) the feature is not visible, indicating that it is not a stratospheric phenomenon. We show that the observed northern bright polar cap results mainly from a decrease in the tropospheric methane mixing ratio, rather than from a possible latitudinal variation of the optical properties or abundance of aerosol, implying an increase in polar downwelling near the tropopause level.
Original language | English |
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Pages (from-to) | 5329-5335 |
Number of pages | 7 |
Journal | Geophysical Research Letters |
Volume | 45 |
Issue number | 11 |
Early online date | 14 Jun 2018 |
DOIs | |
Publication status | Published - 16 Jun 2018 |
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