Where does Titan Sand Come From: Insight from Mechanical Properties of Titan Sand Candidates

TL;DR

This study investigates the mechanical properties of Titan sand candidates, revealing that organic tholin is too soft and brittle for long-distance transport, suggesting local origin near Titan's equatorial dunes.

Contribution

It provides the first mechanical property measurements of Titan sand analogs, linking material properties to sand mobility and origin.

Findings

Tholin has significantly lower elastic modulus and hardness than silicate sand.

Tholin's fracture toughness indicates high brittleness.

Results suggest Titan sand is likely sourced locally near the dunes.

Abstract

Extensive equatorial linear dunes exist on Titan, but the origin of the sand, which appears to be organic, is unknown. We used nanoindentation to study the mechanical properties of a few Titan sand candidates, several natural sands on Earth, and common materials used in the Titan Wind Tunnel, to understand the mobility of Titan sand. We measured the elastic modulus (E), hardness (H), and fracture toughness (Kc) of these materials. Tholin's elastic modulus (10.4+/-0.5 GPa) and hardness (0.53+/-0.03 GPa) are both an order of magnitude smaller than silicate sand, and is also smaller than the mechanically weak white gypsum sand. With a magnitude smaller fracture toughness (Kc=0.036+/-0.007 MPa-m^(1/2)), tholin is also much more brittle than silicate sand. This indicates that Titan sand should be derived close to the equatorial regions where the current dunes are located, because tholin is too soft and brittle to be transported for long distances.