Mars transit of Saturn in 9 BC

[selden]

While trying to find some pages describing mutual events of Saturn's moons, I came across a mention that Mars would have transited Saturn as seen from the Earth in January of 9 BC. ( See http://www.projectpluto.com/interest.htm )

So here's what it looks like in Celestia 1.2.5pre7, shortly after first contact.

(this is a link to a high resolution image.)

You'll need to use a recent pre-release of Celestia 1.2.5 to see this event. The planetary orbit calculations in 1.2.4 aren't accurate enough. Titan is a reddish dot in the lower right of the high resolution image. Presumably it'll be somewhere else when more accurate satellite orbits are implemented in the final release of 1.2.5.

My attempt to combine a sequence of images was foiled by the high magnification needed to see this from the Earth. The image was just too jittery, apparently due to single precision roundoff errors.

[Redfish]

This looks really weird 2 planets over each other. Are the sizes correct? It seems so totally wrong.

[selden]

Yup.
Weird.
But right.

Both Mars and Saturn are on the far side of the sun during this event, just about as far away as they can get from the Earth. Calculating the resulting angular diameters of the planets is left as an exercise for the reader

Here's another view of the event, showing the orbits and planet labels projected against Celestia's "Celestial Grid".
(this is a link to a high resolution image.)

Of course, you can use Celestia to explore the event yourself. Depending on where you locate your viewpoint at the Earth, the transit angles are slightly different. I picked the northeastern U.S.