Inktomi (crater)
Youngest major surface feature on Saturn's moon Rhea.
Inktomi, also called the Splat, is a bright, rayed impact crater on Saturn’s moon Rhea. It measures 47.2 kilometers across and sits in the southern hemisphere at 14.1°S, 112.1°W. Named after the Lakota spider-god Iktomi, it is likely the youngest large feature on Rhea, with an estimated age between 8 and 280 million years.
Geologically, Inktomi is a complex crater about 3.6 kilometers deep on average, though parts of its floor vary by up to 0.5 kilometers. Its central peak is roughly 14 kilometers wide and rises 1.25 kilometers above the floor, but instead of a single conical mountain, it consists of a tangle of ridges and smaller peaks. The crater’s rayed ejecta suggests the impact came from the west at an angle, blasting clean water ice from beneath the surface and creating a patch much lighter than its surroundings. Data from Cassini’s VIMS instrument confirms the ice is pure, without impurities. Images show a continuous ejecta blanket with very few small craters, pointing to a recent impact. A 3D anaglyph from Cassini VIMS reveals a hilly floor and a low, prominent central peak complex. Outside the bright rays, regular secondary craters appear, while clusters of tiny craters on the eastern floor and adjacent ejecta were likely formed by steep-angle debris from the Inktomi strike.
Quick Facts
- Diameter
- 47.2 km
- Depth
- ~3.6 km (mean depth)
- Eponym
- Iktomi
- Location
- Rhea
- Age
- 8 to 280 million years
Facts from the source article.
Lore & Background
Inktomi is a complex crater with a central peak, roughly 47 kilometers in diameter and averaging about 3.6 kilometers deep, though some sections vary by up to 0.5 kilometers. Its central peak structure is not a typical conical mountain but a complex system of converging ridges and subsidiary mountain peaks, about 14 kilometers wide and rising 1.25 kilometers above the crater floor.
The rayed ejecta pattern indicates an oblique impact from the west, which ejected pure water ice from beneath Rhea's surface, creating a region contrastingly lighter than the surrounding areas. Analysis of Cassini's VIMS data revealed clean water ice without impurities at the crater and in its ejecta. A 3-dimensional anaglyph constructed from Cassini VIMS images shows a hilly crater floor with a prominent but topographically low central peak complex.
Reassessment of images from orbit confirms a continuous ejecta blanket almost devoid of small craters, indicative of a geologically recent impact. While regular radial secondaries occur outside the continuous ejecta blanket associated with the bright rays, clusters of numerous small craters were identified in the eastern part of the crater floor and in the adjacent continuous ejecta, likely created by material ejected from the Inktomi impact at a steep angle.
Reader's Guide
Inktomi's significance lies in its status as the youngest major surface feature on Rhea, with an age estimate spanning 8 to 280 million years. The crater's rayed ejecta pattern and continuous ejecta blanket almost devoid of small craters confirm its recent formation. The impact excavated pure water ice from beneath Rhea's surface, and Cassini's VIMS data showed this ice to be clean and without impurities, providing insight into the moon's subsurface composition. The oblique impact from the west and the complex central peak structure—a system of converging ridges rather than a simple conical peak—offer clues about impact dynamics on icy bodies. The presence of small craters in the eastern crater floor and adjacent ejecta, likely from steep-angle ejected material, further informs models of secondary cratering. Inktomi's youth and well-preserved features make it a key site for understanding recent geological processes on Rhea.
Did You Know?
- Inktomi is informally nicknamed the Splat.
- The crater is named for the Lakota spider-god Iktomi.
- Its central peak is a complex system of converging ridges and subsidiary peaks, not a typical conical mountain.
More in Moons of Saturn, Part 2 1-24
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