Images of Io

(click for high-res version)

Surface details captured with Keck adaptive optics in the K-band (upper left) show a comparable level of detail to visible light picture taken with the NASA Galileo orbiter (upper right).

The L-band image (lower left) is dominated by active volcanic hot spot emissions, such as Loki, located near the center of the disk. These spots can now be monitored from the ground.

An image of Io without adaptive optics (lower right) shows what the keck telescope would see without adaptive optics. Note that no hot spots are detected in this image.

Animation of Io orbiting Jupiter (MPEG, 4.5MB)

This movie shows Io, one of Jupiter's moons, orbiting around the immense planet with the great red spot.

The images of Io are from data collected with the NIRC2 infrared camera on the Keck Telescope. We used Keck adaptive optics images to render the views of Io but Jupiter and the stars in the background were rendered by an artist to put Io in perspective. Some of the movies include a grid that represents the plane of rotation of Io around Jupiter.

Io and Jupiter are illuminated by the Sun. When Io passes in the shadow of Jupiter, Io is eclipsed by Jupiter and becomes dark and this phenomenon is visible in the movie. When Io is in eclipse, the reflected light from the sun is minimized and only the thermal emission coming from the volcanic hot spots on Io's surface are detectable.

Each image of Io is based on composite maps of the Jovian moon observed at 3.5 microns with the Keck adaptive optics system and the NIRC2 infrared camera. Without adaptive optics it would not be possible for any ground-based telescope to see the surface details revealed in these images of Io. At Keck Observatory it is now possible for astronomers to study the volcanic activity of Io from the earth's surface; previously, high resolution data like this was only available from expensive spaced-based systems.

In the movie, the camera, and thus the perspective of the viewer, is tied to Io at a fixed distance from it. The camera follows Io and orbits around Jupiter but always points toward Io. This gives the impression that Jupiter is orbiting around Io, much like the Sun appears to orbit around the Earth from our perspective on the Earth's surface.

Io has no impact craters because it is continually being resurfaced by volcanic activity. Io is about 3,600 km (similar to the Moon) in diameter and completes one orbit around Jupiter every 1.8 days.

More detailed information can be found at Keck's Io Page

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