In Situ Measurements of the Size and Density of Titan Aerosol Analogues

TL;DR

This study provides in situ measurements of the size, number density, and density of Titan aerosol analogues (tholins), revealing that many existing models overestimate particle densities.

Contribution

It presents new experimental data on Titan aerosol analogues' physical properties across various methane concentrations and energy sources, improving model accuracy.

Findings

Measured particle densities are lower than those used in many Titan models.

Particle size and number density vary with methane concentration and energy source.

Results suggest revisions to current Titan atmospheric and surface process models.

Abstract

The organic haze produced from complex CH4/N2 chemistry in the atmosphere of Titan plays an important role in processes that occur in the atmosphere and on its surface. The haze particles act as condensation nuclei and are therefore involved in Titan's methane hydrological cycle. They also may behave like sediment on Titan's surface and participate in both fluvial and aeolian processes. Models that seek to understand these processes require information about the physical properties of the particles including their size and density. Although measurements obtained by Cassini-Huygens have placed constraints on the size of the haze particles, their densities remain unknown. We have conducted a series of Titan atmosphere simulation experiments and measured the size, number density, and particle density of Titan aerosol analogues, or tholins, for CH4 concentrations from 0.01% to 10% using two different energy sources, spark discharge and UV. We find that the densities currently in use by many Titan models are higher than the measured densities of our tholins.