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Summary of Proposal MTH1275

TitleDetermining the size of the Zhamanshin Impact Event via SAR
Investigator Garvin, James - NASA, Sciences and Exploration Directorate (SED)
Team Member
President Frawley, James - Herring Bay Geophysics, geophysics
SummaryThe Zhamanshin impact structure (ZIS) was formed approximately 870,000 years ago in low-lying volcaniclastic sediments north of the Aral sea in an explosion of uncertain magnitude. It is possible the impacting body delivered a kinetic energy of impact over 20,000 megatons (TNT equivalent), making the ZIS formation event the largest in the past 3 million years of Earth history. However, careful analysis of the spatial extent of the impact deposits and putative rim of the impact event has been hampered by limited access and the lack of suitable remote sensing data. The primary objective of this effort is refined determination of the size of the ZIS feature on the basis of surface textures that will be identified by means of analysis of TSX SAR data. Using Spotlight mode data, a new determination of the initial crater rim and extent of preserved ejecta deposits will be completed, and compared with field data compiled during the 1989 Soviet Academy of Sciences expedition to the crater by the PI (J. Garvin). Specific methods to be used for the analysis will include co-registration of TSX SAR with the 30m G-DEM data (controlled by ICESat-1 ground control points), comparative analysis of 1-3 m scale TSX SAR backscatter variations in the context of 30m topography, slopes, and slope curvature, and detailed comparison with newly available optical remote sensing from Landsat 7 and EO-1. The data required include: (1) One set of TSX Spotlight mode images covering a swath of 30 km over a 30 km frame length (azimuth) at < 2m resolution (1 look); (2) an interferometry-derived DEM of the crater region from TSX (with Tandem-X?) at 12 m horizontal posting (x,y), with effective vertical precision of < 7m [covering a 40 km x 40 km field of view centered on the center: 48 degrees 24'N, 60 degrees 58'E]. Using these data in combination with existing field data (including a 1989 gravimetric map) and other remote sensing data (Landsat 7 ETM+, EO-1 ALI and Hyperion, ASTER G-DEM, and SRTM 90m DEM, plus ICESat-1 ground-tracks, and SIR-C quad-polarimetric data at 25m resolution), the preserved rim and limits of preserved ejecta will be derived, from which one or more models of the total kinetic energy (KE) of the impact will be estimated. Deliverables will include at least one peer-reviewed research paper in a suitable journal, a report to the DLR, and special Level 3 data analysis products that merge TSX data with the other data mentioned. Ultimately, the scientific value of the proposed research will have a bearing on the recognition of new impact craters on Earth, and on the understanding of subdued impact landforms on Mars. Funding for the research will come from NASA's Goddard Space Flight Center and NASA Headquarters.

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