5 THE SHAPES OF UNMODIFIED SIMPLE IMPACT CRATERS HAVE BEEN PRECISELY DESCRIBED ON MANY PLANETARY BODIES. OVER TIME, IMPACT CRATERS ARE MODIFIED BY SURFACE PROCESSES SUCH AS VOLCANIC RESURFACING, SOIL CREEP, WIND EROSION AND BURIAL. AS A CRATER IS MODIFIED, IT EVOLVES THOUGH A CONTINUUM OF SHAPES ON THE WAY TO BECOMING TOTALLY ERASED. THIS SERIES OF INTERMEDIATE FORMS IS KNOWN AS THE "MODIFICATION SEQUENCE". WITH THE ADVENT OF VERY HIGH-RESOLUTION STEREO IMAGERY AND STEREO-DERIVED DEMS, WE ARE NOW POISED TO MEASURE THIS MODIFICATION SEQUENCE ON THE MARTIAN SURFACE WITH UNPRECEDENTED DETAIL. WE EXPECT THAT THIS SEQUENCE, AND THE ASSOCIATED SPECTRUM OF IMPACT CRATER SHAPES, ARE CHARACTERISTIC OF THE DOMINANT SURFACE PROCESSES (AEOLIAN EROSION AND BURIAL) AND SURFACE CONDITIONS (HIGH OR LOW SEDIMENT SUPPLY) AS WELL AS SURFACE MATERIALS (VOLCANIC PLAINS) THAT PREVAIL IN A PARTICULAR REGION. Other Administrative Action $0 6/15/19 Not listed THE SHAPES OF UNMODIFIED SIMPLE IMPACT CRATERS HAVE BEEN PRECISELY DESCRIBED ON MANY PLANETARY BODIES. OVER TIME IMPACT CRATERS ARE MODIFIED BY SURFACE PROCESSES SUCH AS VOLCANIC RESURFACING SOIL CREEP WIND EROSION AND BURIAL. AS A CRATER IS MODIFIED IT EVOLVES THOUGH A CONTINUUM OF SHAPES ON THE WAY TO BECOMING TOTALLY ERASED. THIS SERIES OF INTERMEDIATE FORMS IS KNOWN AS THE "MODIFICATION SEQUENCE". WITH THE ADVENT OF VERY HIGH-RESOLUTION STEREO IMAGERY AND STEREO-DERIVED DEMS WE ARE NOW POISED TO MEASURE THIS MODIFICATION SEQUENCE ON THE MARTIAN SURFACE WITH UNPRECEDENTED DETAIL. WE EXPECT THAT THIS SEQUENCE AND THE ASSOCIATED SPECTRUM OF IMPACT CRATER SHAPES ARE CHARACTERISTIC OF THE DOMINANT SURFACE PROCESSES (AEOLIAN EROSION AND BURIAL) AND SURFACE CONDITIONS (HIGH OR LOW SEDIMENT SUPPLY) AS WELL AS SURFACE MATERIALS (VOLCANIC PLAINS) THAT PREVAIL IN A PARTICULAR REGION. $0 6/15/19 4 THE SHAPES OF UNMODIFIED SIMPLE IMPACT CRATERS HAVE BEEN PRECISELY DESCRIBED ON MANY PLANETARY BODIES. OVER TIME, IMPACT CRATERS ARE MODIFIED BY SURFACE PROCESSES SUCH AS VOLCANIC RESURFACING, SOIL CREEP, WIND EROSION AND BURIAL. AS A CRATER IS MODIFIED, IT EVOLVES THOUGH A CONTINUUM OF SHAPES ON THE WAY TO BECOMING TOTALLY ERASED. THIS SERIES OF INTERMEDIATE FORMS IS KNOWN AS THE "MODIFICATION SEQUENCE". WITH THE ADVENT OF VERY HIGH-RESOLUTION STEREO IMAGERY AND STEREO-DERIVED DEMS, WE ARE NOW POISED TO MEASURE THIS MODIFICATION SEQUENCE ON THE MARTIAN SURFACE WITH UNPRECEDENTED DETAIL. WE EXPECT THAT THIS SEQUENCE, AND THE ASSOCIATED SPECTRUM OF IMPACT CRATER SHAPES, ARE CHARACTERISTIC OF THE DOMINANT SURFACE PROCESSES (AEOLIAN EROSION AND BURIAL) AND SURFACE CONDITIONS (HIGH OR LOW SEDIMENT SUPPLY) AS WELL AS SURFACE MATERIALS (VOLCANIC PLAINS) THAT PREVAIL IN A PARTICULAR REGION. Other Administrative Action $0 5/25/18 Not listed THE SHAPES OF UNMODIFIED SIMPLE IMPACT CRATERS HAVE BEEN PRECISELY DESCRIBED ON MANY PLANETARY BODIES. OVER TIME IMPACT CRATERS ARE MODIFIED BY SURFACE PROCESSES SUCH AS VOLCANIC RESURFACING SOIL CREEP WIND EROSION AND BURIAL. AS A CRATER IS MODIFIED IT EVOLVES THOUGH A CONTINUUM OF SHAPES ON THE WAY TO BECOMING TOTALLY ERASED. THIS SERIES OF INTERMEDIATE FORMS IS KNOWN AS THE "MODIFICATION SEQUENCE". WITH THE ADVENT OF VERY HIGH-RESOLUTION STEREO IMAGERY AND STEREO-DERIVED DEMS WE ARE NOW POISED TO MEASURE THIS MODIFICATION SEQUENCE ON THE MARTIAN SURFACE WITH UNPRECEDENTED DETAIL. WE EXPECT THAT THIS SEQUENCE AND THE ASSOCIATED SPECTRUM OF IMPACT CRATER SHAPES ARE CHARACTERISTIC OF THE DOMINANT SURFACE PROCESSES (AEOLIAN EROSION AND BURIAL) AND SURFACE CONDITIONS (HIGH OR LOW SEDIMENT SUPPLY) AS WELL AS SURFACE MATERIALS (VOLCANIC PLAINS) THAT PREVAIL IN A PARTICULAR REGION. $0 5/25/18 3 THE SHAPES OF UNMODIFIED SIMPLE IMPACT CRATERS HAVE BEEN PRECISELY DESCRIBED ON MANY PLANETARY BODIES. OVER TIME, IMPACT CRATERS ARE MODIFIED BY SURFACE PROCESSES SUCH AS VOLCANIC RESURFACING, SOIL CREEP, WIND EROSION AND BURIAL. AS A CRATER IS MODIFIED, IT EVOLVES THOUGH A CONTINUUM OF SHAPES ON THE WAY TO BECOMING TOTALLY ERASED. THIS SERIES OF INTERMEDIATE FORMS IS KNOWN AS THE "MODIFICATION SEQUENCE". WITH THE ADVENT OF VERY HIGH-RESOLUTION STEREO IMAGERY AND STEREO-DERIVED DEMS, WE ARE NOW POISED TO MEASURE THIS MODIFICATION SEQUENCE ON THE MARTIAN SURFACE WITH UNPRECEDENTED DETAIL. WE EXPECT THAT THIS SEQUENCE, AND THE ASSOCIATED SPECTRUM OF IMPACT CRATER SHAPES, ARE CHARACTERISTIC OF THE DOMINANT SURFACE PROCESSES (AEOLIAN EROSION AND BURIAL) AND SURFACE CONDITIONS (HIGH OR LOW SEDIMENT SUPPLY) AS WELL AS SURFACE MATERIALS (VOLCANIC PLAINS) THAT PREVAIL IN A PARTICULAR REGION. Funding Only Action $41.4k 11/8/17