Maybe not so mysterious - Just more space junk. A Blue Flame Indicates Complete Burning of Carbon Compounds. Also indicates possible fuel burn, as
Blue Flames Indicate Temperatures of 2,300 to 3,000 Degrees
Blue flames burn hotter than orange flames, with temperatures reaching up to 3,000 degrees Fahrenheit. Along with the complete burning of carbon, this is why gas-burning fires typically have a blue flame. They heat up more quickly and to higher temperatures than fires using other fuel sources, resulting in a blue flame. If a flame’s temperature drops to 2,200 degrees or below, however, it may turn to an orange or yellow color, especially if it uses a tangible fuel source like firewood.