Can Clay Mimic the High Reflectivity of Briny Water Below the Martian SPLD?
Article
Cosciotti, Barbara, Mattei, Elisabetta, Brin, Alessandro, Lauro, Sebastian Emanuel, Stillman, David E., Cunje, Alister, Hickson, Dylan, Caprarelli, Graziella and Pettinelli, Elena. 2023. "Can Clay Mimic the High Reflectivity of Briny Water Below the Martian SPLD?" Journal of Geophysical Research: Planets. 128 (3). https://doi.org/10.1029/2022JE007513
| Article Title | Can Clay Mimic the High Reflectivity of Briny Water Below the Martian SPLD? |
|---|---|
| ERA Journal ID | 210883 |
| Article Category | Article |
| Authors | Cosciotti, Barbara, Mattei, Elisabetta, Brin, Alessandro, Lauro, Sebastian Emanuel, Stillman, David E., Cunje, Alister, Hickson, Dylan, Caprarelli, Graziella and Pettinelli, Elena |
| Journal Title | Journal of Geophysical Research: Planets |
| Journal Citation | 128 (3) |
| Article Number | e2022JE007513 |
| Number of Pages | 12 |
| Year | 2023 |
| Publisher | John Wiley & Sons |
| Place of Publication | United States |
| ISSN | 2169-9097 |
| 2169-9100 | |
| Digital Object Identifier (DOI) | https://doi.org/10.1029/2022JE007513 |
| Web Address (URL) | https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JE007513 |
| Abstract | It has recently been suggested that clay minerals, which are widespread on the Martian surface, could be the possible source of the basal bright reflections detected by MARSIS at Ultimi Scopuli, instead of briny water. This hypothesis is based on dielectric measurements on a wet Ca-Montorillonite (STx-1b) sample conducted at 230 K, which reported permittivity values (apparent permittivity of 39 at 4 MHz) compatible with the median value of 33 retrieved by MARSIS 4 MHz data inversion in the high reflectivity area. These experimental results are, however, incompatible with well-established dielectric theory and with laboratory measurements on clays, at MARSIS frequency and Martian temperatures, reported in the literature. Here, we replicate the experiment using a setup to precisely control the rate of cooling/warming and the temperature inside and outside the clay sample. We found that the rate of cooling, the position of the temperature sensor and, consequently, the thermal equilibrium between the sample and the sensor play a fundamental role in the reliability of the measurements. Our results indicate that even for a large water content in the clay sample, at 230 K and 4 MHz, the apparent permittivity is only 8.4, dropping to 4.1 at 200 K, ruling out clays as a possible source of the bright reflections detected by MARSIS at the base of the SPLD. |
| Keywords | clay materials; Briny Water; SPLD |
| ANZSRC Field of Research 2020 | 370507. Planetary geology |
| Public Notes | Files associated with this item cannot be displayed due to copyright restrictions. |
| Byline Affiliations | Third University of Rome, Italy |
| Southwest Research Institute, United States | |
| University of Illinois Chicago, United States | |
| Colorado School of Mines, United States | |
| Institute for Advanced Engineering and Space Sciences | |
| Centre for Astrophysics |
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