The Temporal Brightening of Uranus' Northern Polar Hood From HST/WFC3 and HST/STIS Observations

Arjuna James; Patrick G. J. Irwin; Jack Dobinson; Michael H. Wong; Troy K Tsubota; Amy A. Simon; Leigh N. Fletcher; Michael T Roman; Nicholas A  Teanby; Daniel Toledo; Glenn S. Orton

doi:10.1029/2023JE007904

The Temporal Brightening of Uranus' Northern Polar Hood From HST/WFC3 and HST/STIS Observations

Arjuna James^*, Patrick G. J. Irwin, Jack Dobinson, Michael H. Wong, Troy K Tsubota, Amy A. Simon, Leigh N. Fletcher, Michael T Roman, Nicholas A Teanby, Daniel Toledo, Glenn S. Orton

^*Corresponding author for this work

Research output: Contribution to journal › Article (Academic Journal) › peer-review

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Abstract

Hubble Space Telescope Wide-Field Camera 3 (HST/WFC3) observations spanning 2015 to 2021 confirm a brightening of Uranus' north polar hood feature with time. The vertical aerosol model of Irwin et al. (2023, https://doi.org/10.1038/s41550-023-02047-0) (IRW23), consisting of a deep haze layer based at ∼5 bar, a 1–2 bar haze layer, and an extended haze rising up from the 1–2 bar layer, was applied to retrievals on HST Space Telescope Imaging Spectrograph (STIS) (HST/STIS) observations (Sromovsky et al., 2014, 2019, https://doi.org/10.1016/j.icarus.2014.05.016, https://doi.org/10.1016/j.icarus.2018.06.026) revealing a reduction in cloud-top CH4 volume mixing ratio (VMR) (i.e., above the deep ∼5 bar haze) by an average of 0.0019 ± 0.0003 between 40–80◦N (∼10% average reduction) from 2012 to 2015. A combination of latitudinal retrievals on the HST/WFC3 and HST/STIS data sets, again employing the IRW23 model, reveal a temporal thickening of the 1–2 bar haze layer to be the main cause of the polar hood brightening, finding an average increase in integrated opacity of 1.09 ± 0.08 (∼33% increase) at 0.8 µm north of ∼45°N, concurrent with a decrease in the imaginary refractive index spectrum of the 1–2 bar haze layer north of ∼40°N and longwards of ∼0.7 µm. Small contributions to the brightening were found from a thickening of the deep aerosol layer, with an average increase in integrated opacity of 0.6 ± 0.1 (58% increase) north of 45°N between 2012 and 2015, and from the aforementioned decrease in CH4 VMR. Our results are consistent with the slowing of a stratospheric meridional circulation, exhibiting subsidence at the poles.

Original language	English
Article number	e2023JE007904
Number of pages	29
Journal	Journal of Geophysical Research: Planets
Volume	128
Issue number	10
DOIs	https://doi.org/10.1029/2023JE007904
Publication status	Published - 3 Oct 2023

Bibliographical note

Funding Information:
We are grateful to the United Kingdom Science and Technology Facilities Council for funding this research. STFC Student ID: J74250F. This work used data acquired from the NASA/ESA HST Space Telescope, associated with OPAL program (PI: Simon, GO13937, with support provided to A. A. Simon, M. H. Wong, G. S. Orton, and T. K. Tsubota), and archived by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Some of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). L. N. Fletcher and M. T. Roman were supported by the European Research Council Consolidator Grant under the European Union's Horizon 2020 research and innovation program (723890). This work also used data acquired from the NASA/ESA HST Space Telescope, stored in the MAST archive by the Space Telescope Science Institute.

Funding Information:
We are grateful to the United Kingdom Science and Technology Facilities Council for funding this research. STFC Student ID: J74250F. This work used data acquired from the NASA/ESA HST Space Telescope, associated with OPAL program (PI: Simon, GO13937, with support provided to A. A. Simon, M. H. Wong, G. S. Orton, and T. K. Tsubota), and archived by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5‐26555. Some of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). L. N. Fletcher and M. T. Roman were supported by the European Research Council Consolidator Grant under the European Union's Horizon 2020 research and innovation program (723890). This work also used data acquired from the NASA/ESA HST Space Telescope, stored in the MAST archive by the Space Telescope Science Institute.

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© 2023. The Authors.

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Planetary Science at Bristol
Elliott, T. (Principal Investigator)
1/04/18 → 28/02/22
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James, A., Irwin, P. G. J., Dobinson, J., Wong, M. H., Tsubota, T. K., Simon, A. A., Fletcher, L. N., Roman, M. T., Teanby, N. A., Toledo, D., & Orton, G. S. (2023). The Temporal Brightening of Uranus' Northern Polar Hood From HST/WFC3 and HST/STIS Observations. Journal of Geophysical Research: Planets, 128(10), Article e2023JE007904. https://doi.org/10.1029/2023JE007904

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title = "The Temporal Brightening of Uranus' Northern Polar Hood From HST/WFC3 and HST/STIS Observations",

abstract = "Hubble Space Telescope Wide-Field Camera 3 (HST/WFC3) observations spanning 2015 to 2021 confirm a brightening of Uranus' north polar hood feature with time. The vertical aerosol model of Irwin et al. (2023, https://doi.org/10.1038/s41550-023-02047-0) (IRW23), consisting of a deep haze layer based at ∼5 bar, a 1–2 bar haze layer, and an extended haze rising up from the 1–2 bar layer, was applied to retrievals on HST Space Telescope Imaging Spectrograph (STIS) (HST/STIS) observations (Sromovsky et al., 2014, 2019, https://doi.org/10.1016/j.icarus.2014.05.016, https://doi.org/10.1016/j.icarus.2018.06.026) revealing a reduction in cloud-top CH4 volume mixing ratio (VMR) (i.e., above the deep ∼5 bar haze) by an average of 0.0019 ± 0.0003 between 40–80◦N (∼10% average reduction) from 2012 to 2015. A combination of latitudinal retrievals on the HST/WFC3 and HST/STIS data sets, again employing the IRW23 model, reveal a temporal thickening of the 1–2 bar haze layer to be the main cause of the polar hood brightening, finding an average increase in integrated opacity of 1.09 ± 0.08 (∼33% increase) at 0.8 µm north of ∼45°N, concurrent with a decrease in the imaginary refractive index spectrum of the 1–2 bar haze layer north of ∼40°N and longwards of ∼0.7 µm. Small contributions to the brightening were found from a thickening of the deep aerosol layer, with an average increase in integrated opacity of 0.6 ± 0.1 (58% increase) north of 45°N between 2012 and 2015, and from the aforementioned decrease in CH4 VMR. Our results are consistent with the slowing of a stratospheric meridional circulation, exhibiting subsidence at the poles.",

author = "Arjuna James and Irwin, {Patrick G. J.} and Jack Dobinson and Wong, {Michael H.} and Tsubota, {Troy K} and Simon, {Amy A.} and Fletcher, {Leigh N.} and Roman, {Michael T} and Teanby, {Nicholas A} and Daniel Toledo and Orton, {Glenn S.}",

note = "Funding Information: We are grateful to the United Kingdom Science and Technology Facilities Council for funding this research. STFC Student ID: J74250F. This work used data acquired from the NASA/ESA HST Space Telescope, associated with OPAL program (PI: Simon, GO13937, with support provided to A. A. Simon, M. H. Wong, G. S. Orton, and T. K. Tsubota), and archived by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Some of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). L. N. Fletcher and M. T. Roman were supported by the European Research Council Consolidator Grant under the European Union's Horizon 2020 research and innovation program (723890). This work also used data acquired from the NASA/ESA HST Space Telescope, stored in the MAST archive by the Space Telescope Science Institute. Funding Information: We are grateful to the United Kingdom Science and Technology Facilities Council for funding this research. STFC Student ID: J74250F. This work used data acquired from the NASA/ESA HST Space Telescope, associated with OPAL program (PI: Simon, GO13937, with support provided to A. A. Simon, M. H. Wong, G. S. Orton, and T. K. Tsubota), and archived by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5‐26555. Some of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). L. N. Fletcher and M. T. Roman were supported by the European Research Council Consolidator Grant under the European Union's Horizon 2020 research and innovation program (723890). This work also used data acquired from the NASA/ESA HST Space Telescope, stored in the MAST archive by the Space Telescope Science Institute. Publisher Copyright: {\textcopyright} 2023. The Authors.",

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doi = "10.1029/2023JE007904",

language = "English",

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T1 - The Temporal Brightening of Uranus' Northern Polar Hood From HST/WFC3 and HST/STIS Observations

AU - James, Arjuna

AU - Irwin, Patrick G. J.

AU - Dobinson, Jack

AU - Wong, Michael H.

AU - Tsubota, Troy K

AU - Simon, Amy A.

AU - Fletcher, Leigh N.

AU - Roman, Michael T

AU - Teanby, Nicholas A

AU - Toledo, Daniel

AU - Orton, Glenn S.

N1 - Funding Information: We are grateful to the United Kingdom Science and Technology Facilities Council for funding this research. STFC Student ID: J74250F. This work used data acquired from the NASA/ESA HST Space Telescope, associated with OPAL program (PI: Simon, GO13937, with support provided to A. A. Simon, M. H. Wong, G. S. Orton, and T. K. Tsubota), and archived by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Some of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). L. N. Fletcher and M. T. Roman were supported by the European Research Council Consolidator Grant under the European Union's Horizon 2020 research and innovation program (723890). This work also used data acquired from the NASA/ESA HST Space Telescope, stored in the MAST archive by the Space Telescope Science Institute. Funding Information: We are grateful to the United Kingdom Science and Technology Facilities Council for funding this research. STFC Student ID: J74250F. This work used data acquired from the NASA/ESA HST Space Telescope, associated with OPAL program (PI: Simon, GO13937, with support provided to A. A. Simon, M. H. Wong, G. S. Orton, and T. K. Tsubota), and archived by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5‐26555. Some of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). L. N. Fletcher and M. T. Roman were supported by the European Research Council Consolidator Grant under the European Union's Horizon 2020 research and innovation program (723890). This work also used data acquired from the NASA/ESA HST Space Telescope, stored in the MAST archive by the Space Telescope Science Institute. Publisher Copyright: © 2023. The Authors.

PY - 2023/10/3

Y1 - 2023/10/3

N2 - Hubble Space Telescope Wide-Field Camera 3 (HST/WFC3) observations spanning 2015 to 2021 confirm a brightening of Uranus' north polar hood feature with time. The vertical aerosol model of Irwin et al. (2023, https://doi.org/10.1038/s41550-023-02047-0) (IRW23), consisting of a deep haze layer based at ∼5 bar, a 1–2 bar haze layer, and an extended haze rising up from the 1–2 bar layer, was applied to retrievals on HST Space Telescope Imaging Spectrograph (STIS) (HST/STIS) observations (Sromovsky et al., 2014, 2019, https://doi.org/10.1016/j.icarus.2014.05.016, https://doi.org/10.1016/j.icarus.2018.06.026) revealing a reduction in cloud-top CH4 volume mixing ratio (VMR) (i.e., above the deep ∼5 bar haze) by an average of 0.0019 ± 0.0003 between 40–80◦N (∼10% average reduction) from 2012 to 2015. A combination of latitudinal retrievals on the HST/WFC3 and HST/STIS data sets, again employing the IRW23 model, reveal a temporal thickening of the 1–2 bar haze layer to be the main cause of the polar hood brightening, finding an average increase in integrated opacity of 1.09 ± 0.08 (∼33% increase) at 0.8 µm north of ∼45°N, concurrent with a decrease in the imaginary refractive index spectrum of the 1–2 bar haze layer north of ∼40°N and longwards of ∼0.7 µm. Small contributions to the brightening were found from a thickening of the deep aerosol layer, with an average increase in integrated opacity of 0.6 ± 0.1 (58% increase) north of 45°N between 2012 and 2015, and from the aforementioned decrease in CH4 VMR. Our results are consistent with the slowing of a stratospheric meridional circulation, exhibiting subsidence at the poles.

AB - Hubble Space Telescope Wide-Field Camera 3 (HST/WFC3) observations spanning 2015 to 2021 confirm a brightening of Uranus' north polar hood feature with time. The vertical aerosol model of Irwin et al. (2023, https://doi.org/10.1038/s41550-023-02047-0) (IRW23), consisting of a deep haze layer based at ∼5 bar, a 1–2 bar haze layer, and an extended haze rising up from the 1–2 bar layer, was applied to retrievals on HST Space Telescope Imaging Spectrograph (STIS) (HST/STIS) observations (Sromovsky et al., 2014, 2019, https://doi.org/10.1016/j.icarus.2014.05.016, https://doi.org/10.1016/j.icarus.2018.06.026) revealing a reduction in cloud-top CH4 volume mixing ratio (VMR) (i.e., above the deep ∼5 bar haze) by an average of 0.0019 ± 0.0003 between 40–80◦N (∼10% average reduction) from 2012 to 2015. A combination of latitudinal retrievals on the HST/WFC3 and HST/STIS data sets, again employing the IRW23 model, reveal a temporal thickening of the 1–2 bar haze layer to be the main cause of the polar hood brightening, finding an average increase in integrated opacity of 1.09 ± 0.08 (∼33% increase) at 0.8 µm north of ∼45°N, concurrent with a decrease in the imaginary refractive index spectrum of the 1–2 bar haze layer north of ∼40°N and longwards of ∼0.7 µm. Small contributions to the brightening were found from a thickening of the deep aerosol layer, with an average increase in integrated opacity of 0.6 ± 0.1 (58% increase) north of 45°N between 2012 and 2015, and from the aforementioned decrease in CH4 VMR. Our results are consistent with the slowing of a stratospheric meridional circulation, exhibiting subsidence at the poles.

U2 - 10.1029/2023JE007904

DO - 10.1029/2023JE007904

M3 - Article (Academic Journal)

SN - 2169-9097

VL - 128

JO - Journal of Geophysical Research: Planets

JF - Journal of Geophysical Research: Planets

IS - 10

M1 - e2023JE007904

ER -

The Temporal Brightening of Uranus' Northern Polar Hood From HST/WFC3 and HST/STIS Observations

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