Planetary geologists have strongly suspected that Venus was active in some way since the various US and Russian missions in the 80's/90's. There's a ton of cle

Planetary geologists have strongly suspected that Venus was active in some way since the various US and Russian missions in the 80's/90's. There's a ton of clear volcanic features on Venus. Past missions have seen hints (variable SO2 levels) that volcanism might be active today, as well. However, active volcanoes don't require Earth-like plate tectonics. The current thought (unchanged since the late 80's early 90's) is that most of Venus's surface is about the same age and dates to ~300-500 million years ago. That's very young compared to the rest of the solar system other than Earth. It appears to have undergone a more-or-less complete resurfacing at around that time. In addition to volcanoes, there are a number of topographic features consistent with relatively recent deformation (basically, lots of big cracks and some compressional wrinkles). However, there are no clear plate boundaries as Earth has. The current thought is that Venus's deformation and volcanism is directly driven by mantle convection. Earth's plate tectonics is actually mostly subduction driven. There's a lot of horizontal motion of plates on Earth. On Venus, there's not a huge amount of horizontal motion on the surface (there's clearly no subduction on Venus). The thought is that there's no athenosphere (very weak, thin layer in the mantle with 1%-5% melt) on Venus to allow large horizontal motions. Interestingly, Venus might be a decent analouge to what pre-plate-tectonic Earth was like. (That part is just my speculation, and I'm not a planetary geologist, so take it with a grain of salt.) Proper plate tectonics probably didn't begin on Earth until around 2 billion years ago (the details are still hotly debated). Prior to this time, subduction doesn't seem to be occuring, and there's not much evidence for large horizontal motion. At any rate, this is just another piece of evidence that Venus's volcanism is still at least somewhat active today, as opposed to all dating to ~300Ma. Incidentally, I just realized that there's a GSA Today article from last year that (briefly) summarizes Venus's geology. GSA Today articles are meant to be very easily readable and only semi-technical (i.e. assumes only general geologic knowledge). It's well worth a read, if you're intested: http://geology.gsapubs.org/content/42/1/95.full http://geology.gsapubs.org/content/42/1/95.full