Might one utilize back lighting of Mars, as a control, for detecting and confirming it’s atmosphere? Then compare Mars’ 3-4 millibar atmosphere findings to that alleged for Pluto? What did other instruments show in regards to Pluto’s atmosphere?
The long range before photos of Pluto were translucent i.e. hazy. Was this due to optics and/or camera? Likewise might a haze to backshot photo of Pluto be due to such longer range effect of optics and/or camera?