page_title: Tholin
section_title: Rhea
hierarchical_section_title: Tholin / Occurrence / Moons / Rhea
caption_attribution_description: English: Scientists from NASA’s New Horizons mission used state-of-the-art computer simulations to show that the surface of Pluto’s informally named Sputnik Planum is covered with churning ice "cells" that are geologically young and turning over due to a process called convection. The scene above, which is about 250 miles (400 kilometers) across, uses data from the New Horizons Ralph/Multispectral Visible Imaging Camera (MVIC), gathered July 14, 2015.
context_page_description: Tholins are a wide variety of organic compounds formed by solar ultraviolet or cosmic rays irradiation of simple carbon-containing compounds such as carbon dioxide, methane or ethane, often in combination with nitrogen or water. Tholins are disordered polymer-like materials made of repeating chains of linked subunits and complex combinations of functional groups. Tholins do not form naturally on modern-day Earth, but they are found in great abundance on the surfaces of icy bodies in the outer Solar System, and as reddish aerosols in the atmosphere of outer Solar System planets and moons.
  In the presence of water, tholins can be raw materials for prebiotic chemistry, i.e. the non-living chemistry that forms the basic chemicals which form life. Their existence has implications for the origins of life on Earth, and possibly on other planets. As particles in an atmosphere, tholins scatter light, and can affect habitability.
context_section_description: The extensive dark areas on the trailing hemisphere of Saturn's moon Rhea are thought to be deposited tholins.
caption: Close-up view of Sputnik Planitia on Pluto as viewed by the New Horizons spacecraft, showing nitrogen ice glaciers and reddish-colored tholins.
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