original: the color has been speculated to be due to organic compounds on its surface .
simplifications: the color has been speculated to be due to organic compounds on its surface . the color has been thought to be due to organic compounds on its surface . the color seems to be because of organic compounds on its surface . the color is speculated to be due to organic compounds on the surface . the color has been speculated to be due to organic compounds on its surface the color has been thought to be due to organic compounds on its surface . the color has been speculated due to organic compounds on its surface . the color has been speculated to be due to organic compounds on its surface .