Sunday, March 8, 2009

Voyager 1 Southern Hemisphere Mosaic

It only took a year but I finally finished the huge, southern hemisphere mosaic of Io using images acquired by Voyager 1 in March 1979.

This mosaic uses 33 images acquired by the narrow-angle camera on-board Voyager 1 shortly before the spacecraft's encounter with the volcanic moon. Click on the image at right to embiggen, but click here if you want to see the full resolution version (warning: 5 MB PNG file). This mosaic is in an orthographic map projection with a pixel scale of 730 m/pixel. The central latitude and longitude of the mosaic is 18.23 South, 317.64 West, though the images in this mosaic generally cover only the southern hemisphere. For details on what features are covered by this mosaic, check out the labeled version I have created.

This mosaic reveals a number of volcanic features: patera, flow fields, tholi, plumes (though I still need to finish the version that highlights them, the Masubi and Pele plumes are visible in some of the limb images used to make this mosaic), in various shapes and sizes. Paterae in the south polar region tend to be larger than those nearer to the equator, suggestive of differences in lithospheric properties and magma source regions in Io's mantle.

I will talke a bit more about this mosaic later today, and talk a little about the discovery of volcanism on Io that took place 30 years ago today. But for now, I need sleep.


  1. Really nice work !! I did not realize that these old Voyager 1 pictures were so sharp. I just regret that Loki does not appear in the mosaic. Wasn't it possible to reproject a Voyager 1 loki picture and to add it north of Purgine patera ?
    Congratulations for this great site !

  2. I am trying to stick using the Voyager imaging teams different mosaic designs when deciding which images to use for these mosaics. That's why Loki is missing in the Southern Hemisphere mosaic; it wasn't covered in that mosaic design. It WAS covered in the lower resolution, 4-color northern hemisphere mosaic, but that one has a lot more missing images and smeared images, so it will take me a bit longer to figure out how to parse that one down.