Accretionary Wedge #49: Out of This World »« Mystery Flora: Lilies of a Day

New at Rosetta Stones: Volcanic Snow on Io

Right, well, you knew someone had to do it. One of us had to do up Io. I mean, how can you have an Accretionary Wedge dealing with geology in space without Io?

And I thought, really, that it would be a bit of a lark, you know. Just, “Oh, look! Volcanoes in space. Everybody knows about Io, but here’s some lovely pictures and a few facts and have a nice day.” Almost boring, really, considering everybody babbles about Io’s volcanism, and sniggers things like, “Looks like a pizza, dunnit?”

But as I researched a bit, and then a bit more, squee after squee happened, culminating in the discovery that the USGS – yes, that’s right, the United States Geological Survey – has done up a geologic map of the thing. Nerdgasm? Oh, honey. All I can say is, it’s a good thing our office building was built to withstand subduction zone quakes. Wowza.

Voyager 1 acquired this image of Io on 4 March 1979 at 5:30 p.m. (PST) about 11 hours before closest approach to the Jupiter moon. The distance to Io was about 490,000 km (304,000 miles). An enormous volcanic eruption can be seen silhouetted against dark space over Io’s bright limb. The brightness of the plume has been increased by the computer as it is normally extremely faint, whereas the relative color of the plume (greenish white) has been preserved. Image courtesy NASA Planetary Photojournal.

So go check it out, but don’t forget to submit your own entry for our 49th Accretionary Wedge. Get out there. Explore the universe. Bring a rock hammer – you’re likely to need it.

Only do it fast, because your entries are due by midnight Pacific time tonight, and stragglers won’t be picked up until the next rocket blasts off next week.

This five-frame sequence of New Horizons images captures the giant plume from Io’s Tvashtar volcano. Snapped by the probe’s Long Range Reconnaissance Imager (LORRI) as the spacecraft flew past Jupiter in 2007, this first-ever movie of an Io plume clearly shows motion in the cloud of volcanic debris, which extends 330 km (200 miles) above the moon’s surface. Only the upper part of the plume is visible from this vantage point. The plume’s source is 130 km (80 miles) below the edge of Io’s disk, on the far side of the moon. Image courtesy NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

Comments

  1. says

    Yay Flagstaff! (I’m certain the map was done at the USGS campus there). I interned there two summers, starting as a computer operator (loading decks of cards into the PDP-11s for 5-hour image processing runs), and later even doing a bit of coding on the Pioneer Venus data. Having seen the unprocessed Voyager images, compared to the final results, it’s amazing what they were able to do with 32 kB of RAM. I assume that “more with less” attitude still exists there, although all the people I knew are now retired.

  2. lpetrich says

    I remember a documentary that featured Linda Morabito’s recollections of how she discovered Io’s volcanic activity during Voyager 1’s flyby of Jupiter. She was doing optical-navigation work, looking for stars in deliberately overexposed pictures of Jupiter’s big moons and finding their picture-relative positions. All this data then gets fed into some complicated software that uses it as input to improve the software’s estimate of the spacecraft’s orbit.

    One day she saw an odd shape at Io’s edge. Was it another one of Jupiter’s moons? Though Jupiter has a lot of them, there wasn’t any that was big enough and in the right place for that. Was it some camera artifact? There was no known camera artifact that looked like that. Was it a cloud? Io does not have a detectable atmosphere. Was it a volcanic eruption?

    Some planetologists had recently proposed that Io had had lots of recent volcanic activity from being heated by Jupiter’s tides. Because of orbit resonances, close to 8:4:2:1, Jupiter’s other big moons make its orbit have a forced eccentricity, meaning that it gets continually kneaded by Jupiter’s gravity.

    When they saw Voyager 1’s pictures of Io, they tried to date its surface by counting impact craters. There were hardly any, meaning that Io is either recently eroded, recently resurfaced, or both, as the the Earth is. There were also some structures that looked like volcanoes. But active ones? They weren’t willing to claim that.

    When the Voyager imaging team returned from the weekend of LM’s discovery, they found that this shape was at one of the putative volcanic features, and looking through some of the spacecraft’s other pictures and enhancing them, they found evidence for some others.

    DAYS OF AIR AND SPACE CALENDAR, Volcanism on Io (discovery) – Wikipedia, etc.

    I confess that I like accounts of discoveries.