Hell, Half a Billion Miles Away

There are many candidates for least-hospitable place in the solar system, but Jupiter’s moon Io is high on the list.  It is a violent, volcanic world, about 2,200 miles in diameter, orbiting so close to Jupiter’s cloud tops that it’s constantly being pulled and stressed by Jupiter’s powerful gravity. The result, as you see in this image from the New Horizons spacecraft, is giant, frequent volcanic eruptions.  In this picture, shot on Feb. 28 and just posted by the New Horizons team, you see a plume from a volcano called Tvashtar, spewing 180 miles out into space.  You’re looking mostly at the night side of Io, illuminated by sunlight reflected by the Jovian clouds.  New Horizons raced by last week, using Jupiter’s gravity to gain speed on the way to Pluto and the Kuiper Belt.  (If you look carefully at about the nine o’clock point on Io’s limb, you’ll see a second, smaller plume, coming from a volcano called Prometheus.  That one is about 40 miles high.) Io is like no other known place in the solar system.  Scientists expected that like most small bodies with little or no atmosphere, Io would be pitted with craters.  Instead, passing spacecraft have shown calderas.  The volcanic activity is enough that much of the surface has been formed from lava, covering over most impact craters. New Horizons still has many images to send, and some will be combined to make color pictures, but you can find more raw imagery from it of the Jovian system HERE.  A mysterious, remote place.  Reminds you there’s no place like home.