- Original Caption Released with Image:
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This unusual image shows Io glowing in the darkness of Jupiter's shadow.
It is a combination of eight images taken by the New Horizons Long Range
Reconnaissance Imager (LORRI) between 14:25 and 14:55 Universal Time on
February 27, 2007, about 15 hours before the spacecraft's closest approach
to Jupiter. North is at the top of the image.
Io's surface is invisible in the darkness, but the image reveals glowing
hot lava, auroral displays in Io's tenuous atmosphere and volcanic plumes
across the moon. The three bright points of light on the right side of Io
are incandescent lava at active volcanoes - Pele and Reiden (south of the
equator), and a previously unknown volcano near 22 degrees north, 233
degrees west near the edge of the disk at the 2 o'clock position.
An auroral glow, produced as intense radiation from Jupiter's
magnetosphere bombards Io's atmosphere, outlines the edge of the moon's
disk. The glow is patchy because the atmosphere itself is patchy, being
denser over active volcanoes. In addition to the near-surface glow, there
is a remarkable auroral glow suspended 330 kilometers (200 miles) above
the edge of the disk at the 2 o'clock position; perhaps this glowing gas
was ejected from the new volcano below it. Another glowing gas plume,
above a fainter point of light, is visible just inside Io's disk near the
6 o'clock position; this plume is above another new volcanic eruption
discovered by New Horizons.
On the left side of the disk, near Io's equator, a cluster of faint dots
of light is centered near the point on Io that always faces Jupiter. This
is the region where electrical currents connect Io to Jupiter's
magnetosphere. It is likely that electrical connections to individual
volcanoes are causing the glows seen here, though the details are
mysterious.
Total exposure time for this image was 16 seconds. The range to Io was
2.8 million kilometers (1.7 million miles), and the image is centered at
Io coordinates 7 degrees south, 306 degrees west. The image has been
heavily processed to remove scattered light from Jupiter, but some
artifacts remain, such as dark patches in the background.
- Image Credit:
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NASA/Johns Hopkins University Applied Physics Laboratory/Southwest
Research Institute
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