Comet Tails 1/2 performance?

[Kolano]

Today, I wanted to up the framerate to view earth optimumly. Later, when I started turning options back on, I noted a huge drop due to "Comet Tails".

With all options off except planets and earth aprox 1/3 of the viewpane, I get 60fps easily. Turning on comet tails imediately drops the framerate to 24fps, even if no comets are visible.

What's going on that is so impactful, particularly with no comets visible?