                          THEMIS: Image Detail

                                                                        
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                [14]                                                    
                                                                        
           Ulysses Patera                                               
          (Released 18 July                                             
                2002)                                                   
                                                                        
                [15]                                                    
                                                                        
           Image Context:                                               
                                                                        
         Context image                                                  
         credit: NASA/Mars                                              
         Orbiter Laser                                                  
         Altimeter (MOLA)                                               
         Team                                                           
                                                                        
           [ Find on map:                                               
           Javascript [16]                                              
              version ]                                                 
                                                                        
         [ Find on map: CGI                                             
           [17]  version ]                                              
                                                                        
         It is helpful to                                               
         look at the                                                    
         context for this                                               
         THEMIS image,                                                  
         which covers a                                                 
         large area over                                                
         the summit of                                                  
         Ulysses Patera.                                                
         Ulysses Patera is                                              
         one of the many                                                
         volcanoes that                                                 
         make up the giant                                              
         Tharsis volcanic                                               
         province, although                                             
         Ulysses itself is                                              
         fairly small in                                                
         comparison to the                                              
         other volcanoes in                                             
         this area. In the                                              
         context image,                                                 
         there are 3                                                    
         circular features                                              
         near the top of                                                
         the volcano. The                                               
         large, central                                                 
         feature is called                                              
         a "caldera", and                                               
         is the result of                                               
         volcanic activity                                              
         at Ulysses. The                                                
         other two circular                                             
         features are                                                   
         impact craters.                                                
         The THEMIS image                                               
         primarily spans                                                
         across the central                                             
         caldera, but also                                              
         covers a portion                                               
         of the                                                         
         northernmost                                                   
         impact crater. We                                              
         know that the                                                  
         large central                                                  
         caldera must have                                              
         formed earlier                                                 
         than the two                                                   
         craters, because                                               
         its circular form                                              
         has been cut by                                                
         the smaller crater                                             
         rims.                                                          
                                                                        
         In the THEMIS                                                  
         image, there are                                               
         stair-stepping                                                 
         plateaus in the                                                
         northern portion                                               
         of the image.                                                  
         These are part of                                              
         the rim of the                                                 
         northern crater,                                               
         and are caused by                                              
         collapse or                                                    
         subsidence after                                               
         the impact event.                                              
         Just to the south                                              
         of this crater,                                                
         "rayed" patterns                                               
         can be seen on                                                 
         part of the                                                    
         caldera floor. The                                             
         rayed pattern is                                               
         most likely due to                                             
         a landslide of                                                 
         material down the                                              
         crater rim slope.                                              
         Another                                                        
         possibility is                                                 
         that the impact                                                
         that formed the                                                
         northern crater                                                
         caused material to                                             
         be ejected                                                     
         radially, and then                                             
         parts of the                                                   
         ejecta have either                                             
         been buried or                                                 
         eroded away. Other                                             
         signs of mass                                                  
         movement events in                                             
         this image are                                                 
         dark streaks,                                                  
         caused by dust                                                 
         avalanches,                                                    
         visible in the                                                 
         caldera's northern                                             
         wall. In the                                                   
         central portion of                                             
         the image, there                                               
         are two                                                        
         lobe-shaped                                                    
         features-one                                                   
         overlaps the                                                   
         other-that appear                                              
         to have flowed                                                 
         westward. It is                                                
         likely that these                                              
         features are                                                   
         ejecta lobes,                                                  
         because they are                                               
         located adjacent                                               
         to the                                                         
         southeastern                                                   
         crater (see                                                    
         context image).                                                
         The fluidized                                                  
         appearance of                                                  
         these ejecta lobes                                             
         is probably due to                                             
         a significant                                                  
         amount of ice or                                               
         water being                                                    
         present in the                                                 
         soil at the time                                               
         of impact. We know                                             
         that the                                                       
         southeastern                                                   
         crater must have                                               
         formed after the                                               
         northern crater,                                               
         because the                                                    
         fluidized ejecta                                               
         lobe overlies the                                              
         rayed pattern. A                                               
         close-up look at                                               
         the fluidized                                                  
         ejecta lobes                                                   
         reveals a                                                      
         different surface                                              
         "texture" than the                                             
         surrounding                                                    
         caldera floor.                                                 
         This could be due                                              
         to compressional                                               
         features that                                                  
         formed during the                                              
         lobe emplacement,                                              
         or to contrasting                                              
         surface properties                                             
         that cause the                                                 
         flows to be eroded                                             
         differently than                                               
         the caldera floor.                                             
         In the lower                                                   
         portion of the                                                 
         image, there is a                                              
         cluster of small                                               
         circular features                                              
         in the                                                         
         southernmost part                                              
         of the central                                                 
         caldera. These                                                 
         features may be                                                
         layered material                                               
         that has since                                                 
         been eroded into                                               
         circular plateaus,                                             
         or they may be                                                 
         degraded volcanic                                              
         cones, which would                                             
         indicate a later                                               
         stage of                                                       
         smaller-scale                                                  
         volcanism within                                               
         the caldera.                                                   
         Volcanic cones are                                             
         common in many                                                 
         calderas on Earth,                                             
         and are formed                                                 
         after the initial                                              
         stage of volcanic                                              
         activity in that                                               
         caldera. Finally,                                              
         in the southern                                                
         wall of the                                                    
         caldera, there is                                              
         classic                                                        
         "spur-and-gully"                                               
         morphology. This                                               
         type of morphology                                             
         is often formed on                                             
         steepslopes, where                                             
         variations in wall                                             
         resistance cause                                               
         the surface to be                                              
         eroded more easily                                             
         in some areas.                                                 
                                                                        
         [Source: ASU                                                   
         THEMIS Science                                                 
         Team]                                                          
                                                                        
         Note: this THEMIS                                              
         visual image has                                               
         not been                                                       
         radiometrically                                                
         nor geometrically                                              
         calibrated for                                                 
         this preliminary                                               
         release. An                                                    
         empirical                                                      
         correction has                                                 
         been performed to                                              
         remove                                                         
         instrumental                                                   
         effects. A linear                                              
         shift has been                                                 
         applied in the                                                 
         cross-track and                                                
         down-track                                                     
         direction to                                                   
         approximate                                                    
         spacecraft and                                                 
         planetary motion.                                              
         Fully calibrated                                               
         and geometrically                                              
         projected images                                               
         will be released                                               
         through the                                                    
         Planetary Data                                                 
         System in                                                      
         accordance with                                                
         Project policies                                               
         at a later time.                                               
                                                                        
         NASA's Jet                                                     
         Propulsion                                                     
         Laboratory manages                                             
         the 2001 Mars                                                  
         Odyssey mission                                                
         for NASA's Office                                              
         of Space Science,                                              
         Washington, D.C.                                               
         The Thermal                                                    
         Emission Imaging                                               
         System (THEMIS)                                                
         was developed by                                               
         Arizona State                                                  
         University, Tempe,                                             
         in collaboration                                               
         with Raytheon                                                  
         Santa Barbara                                                  
         Remote Sensing.                                                
         The THEMIS                                                     
         investigation is                                               
         led by Dr. Philip                                              
         Christensen at                                                 
         Arizona State                                                  
         University.                                                    
         Lockheed Martin                                                
         Astronautics,                                                  
         Denver, is the                                                 
         prime contractor                                               
         for the Odyssey                                                
         project, and                                                   
         developed and                                                  
         built the orbiter.                                             
         Mission operations                                             
         are conducted                                                  
         jointly from                                                   
         Lockheed Martin                                                
         and from JPL, a                                                
         division of the                                                
         California                                                     
         Institute of                                                   
         Technology in                                                  
         Pasadena.                                                      
                                                                        
         Image Credit:                                                  
         NASA/JPL/Arizona                                               
         State University                                               
                                                                        
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         Image (TIF) [21]  ]                                            
                                                                        
                   Parameter   Value             Parameter   Value      
                                                                        
                    Latitude   3                Instrument   VIS        
                                                                        
                   Longitude   121.6W           Resolution   19         
                               (238.4E)                (m)              
                                                                        
         Image Size (pixels)   3043x1239        Image Size   57.8x23.5  
                                                      (km)              
                                                                        
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  [2] http://themis.asu.edu/goals.html
  [3] http://themis.asu.edu/mission.html
  [4] http://themis.asu.edu/themis_pics.html
  [5] http://themis.asu.edu/themis_team.html
  [6] http://tes.asu.edu/neweducation.html
  [7] http://mars.jpl.nasa.gov/odyssey/
  [8] http://tes.asu.edu/
  [9] http://tes.asu.edu/
  [10] http://tes.asu.edu/MINITES/
  [11] http://tes.asu.edu/MINITES/
  [12] http://www.asu.edu/
  [13] http://www.nasa.gov/
  [14] latest.html
  [15] fullimages/20020718a.jpg
  [16]
/mars-bin/
mars_js_frames.pl?CENT_LAT=2.958163073&CENT_LON=121.
6320697&RESCALE=64&TNAIL_LINK=20020718a
  [17]
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6320697&RESCALE=64&TNAIL_LINK=20020718a
  [18] /fullimages/20020718a.gif
  [19] /fullimages/20020718a.jpg
  [20] /fullimages/20020718a.png
  [21] /fullimages/20020718a.tif
  [22] http://validator.w3.org/check/referer
