Subsurface Mapping of Deserts and Polar Regions Using Radar Data on Earth and Mars

• Main Author: Xiong, Siting
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: UCL (University College London) 2019
• Subjects: Greenland; South Pole; Ice Sheet; South pole
• Online Access: https://discovery.ucl.ac.uk/id/eprint/10066203/1/Xiong_0_Thesis.pdf; https://discovery.ucl.ac.uk/id/eprint/10066203/

There are abundant resources buried underground that are difficult to be investigated remotely. This thesis is concerned with the development and utility of various novel processing methods for different radar instruments in the field of subsurface mapping on Earth and Mars. Firstly, advanced Synthetic Aperture Radar (SAR) imaging and Interferometric SAR (InSAR) techniques are applied to assess their potential for revealing subsurface features in the eastern Sahara Desert. The radar penetration depth at L-band (1.25 GHz) is estimated to be 1-2 m over paleochannels in the Sahara Desert, given an initial assumption that radar penetration occurs in the sand accumulation areas. The L-band frequency of previous and existing spaceborne SAR mission is shown to limit the penetration depth to a few metres below the surface. However, over the terrestrial ice-sheets, a radar instrument, the Multi-Coherent Radar Depth Sounder (MCoRDS) from the NASA Operation Ice Bridge (OIB) mission, can penetrate the ice sheet down to 3 km, revealing extensive englacial layers. An automated layer tracing method based on the Continuous Wavelet Transform (CWT) and Hough Transform (HT) is proposed to detect and digitise these englacial layers in Greenland. The results show that this proposed method can restore at least 72% of the isochrones when compared with previous results. Given the research interests of the department and inspired by the similarity of the layering phenomenon between the Earth and Martian polar regions, the layer tracing method is adjusted and applied to SHAllow RADar (SHARAD) radargrams from the Mars Reconnaissance Orbiter. This method is demonstrated on the SHARAD data in Promethei Lingula as this 6 is the only region with coherent subsurface echo returns near the south pole, resulting in the extraction of six distinct subsurface interfaces, which record past depositional and erosional history and may be associated with past climate change on Mars.