Gertrude (crater)

Gertrude is the largest crater on Titania, a moon of Uranus. This impact basin features a peak ring and measures between 326 and 400 kilometers in diameter, which is roughly one-fifth to one-quarter of Titania’s own size.

The crater was first spotted by the Voyager 2 spacecraft as it flew past the Uranian system in January 1986. Its name comes from Gertrude, the mother of Prince Hamlet in Shakespeare’s Hamlet, following the convention of naming Titania’s features after female Shakespearean characters. The International Astronomical Union officially adopted the name in 1988.

The crater is surprisingly shallow. In 1989, planetary scientist P. M. Schenk estimated its depth at only 1 to 3 kilometers. Its rim rises about 2 kilometers above the crater floor, and at the center sits a large dome roughly 150 kilometers wide and 2 to 3 kilometers high—formed when the surface uplifted right after the impact. For a crater this size, both the rim and dome are low, suggesting the terrain has relaxed over time.

The dome itself has few smaller craters on it, indicating it was reshaped later. Linear ridges cut across Gertrude and the nearby Messina Chasmata. Surrounding the crater are plains that are less heavily cratered than most of Titania’s surface, likely the remains of Gertrude’s ancient ejecta blanket.

Based on depth-to-diameter ratios of smaller Titania craters, Gertrude’s original depth may have been around 6 to 6.5 kilometers. Its current shallowness implies a period of relaxation, during which the crust slowly crept and smoothed out extreme topography. The central dome is a telltale sign of this process, and the crater’s floor resembles that of Tirawa, a large relaxed crater on Saturn’s moon Rhea.