The root of anomalously specular reflections from solid surfaces on Saturn's moon Titan
Abstract
Saturn's moon Titan has a methane cycle with clouds, rain, rivers, lakes, and seas; it is the only world known to presently have a volatile cycle akin to Earth's tropospheric water cycle. Anomalously specular radar reflections (ASRR) from Titan's tropical region were observed with the Arecibo Observatory (AO) and Green Bank Telescope (GBT) and interpreted as evidence for liquid surfaces. The Cassini spacecraft discovered lakes/seas on Titan, however, it did not observe lakes/seas at the AO/GBT anomalously specular locations. A satisfactory explanation for the ASRR has been elusive for more than a decade. Here we show that the ASRR originate from one terrain unit, likely paleolakes/paleoseas. Titan observations provide ground-truth in the search for oceans on exoearths and an important lesson is that identifying liquid surfaces by specular reflections requires a stringent definition of specular; we propose a definition for this purpose.
Additional Information
This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received 17 May 2019. Accepted 20 April 2020. Published 16 June 2020. We are sincerely grateful to the entire Cassini, Arecibo Observatory, and Green Bank Telescope teams for enabling this research. J.D.H. gratefully acknowledges the Natural Sciences and Engineering Research Council of Canada, Post Graduate Scholarship Program and NASA Postdoctoral Program for financial support. J.D.H. thanks Bonnie Buratti for professional mentorship. Part 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. R.D.L. acknowledges the support of NASA Grant 80NSSC18K1389. Author Contributions: J.D.H. led the analysis and writing of the article. A.G.H., D.B.C., and J.I.L. worked closely with J.D.H. on all aspects of the analysis and writing. G.J.B., S.M.M., and R.D.K. assisted with the AO/GBT, VIMS, and stereo topography analyses respectively. All authors contributed to the data acquisition and discussions. Data availability. The complete AO/GBT dataset is thoroughly described and presented in Black et al.2. The updated AO/GBT subradar locations are provided in Supplementary Data 1. The complete Cassini RADAR dataset, including all images, altimetry observations, and stereo topography is available from the NASA Planetary Data System (PDS) at: https://pds-imaging.jpl.nasa.gov/volumes/radar.html. Titan Trek is a NASA web-based portal with a browsing tool that allows for easy viewing and layering of Cassini RADAR images as well as other Cassini data of Titan; it is available at https://trek.nasa.gov/titan/. The authors declare no competing interests. Nature Communications thanks Carrie Anderson and the other anonymous reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.Attached Files
Published - s41467-020-16663-1.pdf
Supplemental Material - 41467_2020_16663_MOESM1_ESM.pdf
Supplemental Material - 41467_2020_16663_MOESM2_ESM.docx
Supplemental Material - 41467_2020_16663_MOESM3_ESM.xlsx
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Additional details
- PMCID
- PMC7298017
- Eprint ID
- 104026
- Resolver ID
- CaltechAUTHORS:20200624-162147295
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- NASA Postdoctoral Program
- NASA/JPL/Caltech
- 80NSSC18K1389
- NASA
- Created
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2020-06-25Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences