       exit: ->
         @el.find('button[name="to-select"]').removeClass 'hidden'
         @el.find('.what-kind').hide()
+        @removePriorAsteroids()
 
     asteroidTool:
       enter: ->

    y_avg = Math.round(y_sum/@numFrames)
    rad_x = Math.abs( (Math.max.apply null, [xs...]) - (Math.min.apply null, [xs...]) ) * 4
    rad_y = Math.abs( (Math.max.apply null, [ys...]) - (Math.min.apply null, [ys...]) )* 4
    
    for surface in [@markingSurfaceList...]
      svgElement = surface.addShape 'ellipse', class: "prior-asteroid", opacity: 0.75, cx: x_avg, cy: y_avg, rx: rad_x, ry: rad_y, fill: "none", stroke: "rgb(20,200,20)", 'stroke-width': 4


  stopLoading: ->
    @el.removeClass 'loading'

  removePriorAsteroids: ->
    console.log "removing prior asteroids"
    for priorAsteroid in [@el.find('.prior-asteroid')...]
      priorAsteroid.remove() 

  showExistingAsteroids: ->
    return if @TRAINING_SUBJECT is null
    xs = []
    ys = []
    x_sum = null
    y_sum = null
    for priorAsteroid, i in [@TRAINING_SUBJECT.metadata.asteroids...]
      xs[i] = priorAsteroid.x
      ys[i] = priorAsteroid.y
