New Horizons Observes Jupiter's Volcanic Moon
3/14/2007 ,


Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute


NASA recently published a stunning view of Jupiter's volcanic moon Io, acquired by the Pluto-bound New Horizons spacecraft, during its recent rendezvous with Jupiter. The image shows a gigantic volcanic plume ejected during the ongoing eruption of the Ionian volcano Tvashtar.


The plume is over 300 km high. It is illuminated by direct sunlight, and sunlight reflected off Jupiter.


The day-side of Io is overexposed in this relatively long exposure to bring out the faint details in the plume's complex structure.


The image was obtained applying the Long Range Reconnaissance Imager (LORRI) device aboard New Horizons, 19 hours after arrival at Jupiter on 28 February 2007. The spacecraft was 2.3 million km from Io.


The sunlit plume faintly illuminates the surface below it. "New Horizons and Io continue to astonish us with these unprecedented views of the solar system's most geologically active body," said John Spencer, deputy leader of the New Horizons Jupiter Encounter Science Team, and an Io expert from Southwest Research Institute.


Like our Moon, Io keeps one side turned to its parent planet. As this image shows the far side of Io that faces away from Jupiter, the giant planet only illuminates a slender crescent of Io's night-side, highlighting the edge of the disk at lower right. Another plume, believed to be emanating from the volcano Masubi, is illuminated by Jupiter just above this lower right edge.


A faint plume, barely visible at the 2 o'clock position, could be the first plume observed from the volcano Zal Patera.  


As in other New Horizons images of Io, mountains reflect light from the setting Sun just beyond the terminator (the line between the day and night sides). The most prominent, visible as a bright vertical line, is the edge of a plateau about 4.5 km high, similar in height to the Colorado Rockies.


Image processing has been applied to reduce high contrast in the original data.


Io is the innermost of the Galilean moons. It is the fourth largest moon in the Solar System. With a diameter of 3,630 km, Io is somewhat larger than our Moon (3,476 km across). It also orbits its parent planet at a similar distance of about 400,000 km.


Due to Jupiter's strong gravity, which is 250% greater than that of Earth, Io orbits Jupiter in only 1.7 days. (Jupiter is approximately 320 times more massive than Earth.)


Further reading

A Midnight Plume

New Horizons Mission Homepage



Aymen Mohamed Ibrahem