What's going on with Venus?

Lots of findings and groovy images from the Venus Express team. In particular this strange vortex discovered at the South Pole (imaged in infrared), which has an unexpected elongated morphology.

I wasn't aware that Venus has no intrinsic magnetic field, unlike Earth, to shelter it from the solar wind. Apparently the reason for this is not well understood since presumably Venus has a similar metal composition to the Earth and may also have a molten core. A quick internet search suggests that the prevailing theories posit Venus's slow rotation and/or lack of plate tectonics as possible causes.