English: Boundary between dark and light terrain on
Ganymede. The photo is
PIA02577 at the JPL Planetary Photojournal. It was taken by the
Galileo spacecraft.
Original NASA caption:
The ancient, dark terrain of
Nicholson Regio (left) shows many large
impact craters, and zones of
fractures oriented generally parallel to the boundary between the dark and bright regions of
Jupiter's moon
Ganymede. In contrast, the bright terrain of
Harpagia Sulcus (right) is less cratered and relatively smooth.
The nature of the boundary between ancient, dark terrain and younger, bright terrain, the two principal terrain types on Ganymede, was explored by NASA's
Galileo spacecraft on
May 20,
2000. Subtle parallel ridges and grooves show that Harpagia Sulcus's land has been smoothed out over the years by tectonic processes.
North is to the top of the picture. The
Sun illuminates the surface from the left. The image, centered at ?14 degrees latitude and 319 degrees longitude, covers an area approximately 213 by 97 kilometers (132 by 60 miles.) The resolution is 121 meters (about 250 feet) per picture element. The images were taken on May 20, 2000, at a range of 11,800 kilometers (about 7,300 miles).