Tiger stripes (Enceladus)

Lore & Background

First observed on May 20, 2005, by the Cassini spacecraft's ISS camera, the tiger stripes were seen obliquely during an early flyby. Higher resolution observations on July 14, 2005, revealed them to be low ridges with a central fracture. The Composite Infrared Spectrometer (CIRS) showed elevated surface temperatures, indicating present-day cryovolcanism centered on the stripes. The name 'tiger stripes' is unofficial, based on their distinctive albedo. In November 2006, they were assigned the official names Alexandria Sulcus, Cairo Sulcus, Baghdad Sulcus, and Damascus Sulcus; Baghdad and Damascus sulci are the most active, while Alexandria Sulcus is the least active. The stripes are tectonic fractures, likely fissures in the lithosphere, with hook-shaped bends on the anti-Saturnian hemisphere and bifurcating tips on the sub-Saturnian hemisphere. Virtually no impact craters are found on or near them, suggesting a very young surface age.

Reader's Guide

The tiger stripes are significant as the locus of Enceladus's cryovolcanic activity, confirmed by Cassini's July 14, 2005 flyby. The CIRS instrument measured color temperatures of 113–157 kelvins, far warmer than the expected 68 kelvins, and data from ISS, INMS, CDA, and CIRS showed a plume of water vapor, ice, methane, carbon dioxide, and nitrogen emanating from jets within the stripes. This plume is the source of material for Saturn's E Ring, as confirmed by Cassini's first two close flybys in 2005. The stripes' composition includes coarse-grained crystalline water ice, trapped carbon dioxide ice, and simple organics not found elsewhere on Enceladus. The crystalline ice provides an age constraint of a few decades to a thousand years for surface exposure. The stripes' geologic setting and lack of craters indicate a young surface, with age estimates of 4–100 million years or 0.5–1 million years depending on cratering flux assumptions. The discovery of over 100 geysers and the plume's material suggests a near-surface body of liquid water, though an alternative hypothesis proposes clathrate hydrates as the source.

Did You Know?

• Baghdad and Damascus sulci are the most active tiger stripes, while Alexandria Sulcus is the least active.
• The tiger stripes have an average length of 130 kilometers, width of 2 kilometers, and depth of 500 meters.
• The plume from the tiger stripes is the source of material for Saturn's E Ring.