The Tvashtar plume on Io, seen by the Hubble Space Telescope (HST) and by
New Horizons.
(A): The image in which the plume was discovered, taken by HST in
ultraviolet light on Feb. 14, 2007, at a wavelength of 260 nm. The red
diamond indicates location of the Tvashtar hot spot seen later by New
Horizons. (B): An HST image of Io and the Tvashtar plume seen against
Jupiter; sulfur gas in the plume absorbs ultraviolet light, making the
plume look reddish in this color composite. The composite is composed of
images taken at 260 nm (blue), 330 nm (green), and 410 nm (red). Other
images in this montage are in visible light from the Long-Range
Reconnaissance Imager (LORRI). The scale bar is 200 kilometers long and
the yellow star indicates the projected location of the hot spot at the
Tvashtar plume source. The dashed line is the terminator, the line
dividing day from night on Io. (C): The highest-resolution view of the
full plume, at a resolution of 12.4 kilometers (7.7 miles) per pixel and a
solar phase angle of 102 degrees, showing the complex filamentary
structure of the plume. The images are sharpened by un-sharp masking; the
dark line at the edge of the disk is an artifact of this sharpening. (D):
An image at 145-degree phase angle at 22.4 kilometers (13.8 miles) per
pixel, showing the time variability of the details of the plume structure
and its persistent bright top. (F-J): Sequence of frames at 2-minute
intervals showing dynamics in the upper part of the plume (the source is
on the far side of Io). Colored diamonds track individual features whose
speeds, projected on the plane of the sky, are shown in (E).
This image appears in the Oct. 12, 2007, issue of Science magazine, in a
paper by John Spencer, et al.