The Global Color of Pluto from New Horizons

Abstract

The New Horizons flyby provided the first high-resolution color maps of Pluto. We present here, for the first time, an analysis of the color of the entire sunlit surface of Pluto and the first quantitative analysis of color and elevation on the encounter hemisphere. These maps show the color variation across the surface from the very red terrain in the equatorial region, to the more neutral colors of the volatile ices in Sputnik Planitia, the blue terrain of East Tombaugh Regio, and the yellow hue on Pluto’s North Pole. There are two distinct color mixing lines in the color–color diagrams derived from images of Pluto. Both mixing lines have an apparent starting point in common: the relatively neutral-color volatile-ice covered terrain. One line extends to the dark red terrain exemplified by Cthulhu Regio and the other extends to the yellow hue in the northern latitudes. There is a latitudinal dependence of the predominant color mixing line with the most red terrain located near the equator, less red distributed at mid-latitudes and more neutral terrain at the North Pole. This is consistent with the seasonal cycle controlling the distribution of colors on Pluto. Additionally, the red color is consistent with tholins. The yellow terrain (in the false color images) located at the northern latitudes occurs at higher elevations.

Cryovolcanic flooding in Viking Terra on Pluto

“…In this paper we have drawn comparisons between the Viking Terra features and Virgil Fossae from the earlier study by Cruikshank et al (2019a). Attention was initially drawn to Virgil Fossae by the nearly unique color both in the main trough and in the immediate surroundings, a color having only a few smaller exposures (e.g., Beatrice Fossae) on the hemisphere of Pluto imaged with high resolution by New Horizons (Olkin et al 2017). The varied and widespread coloration of Pluto's ices is attributed to refractory complex organic compounds (tholins) formed by photochemical reactions in the atmosphere and precipitated to the surface (Cheng et al 2017;Grundy et al 2018), and more directly by photolysis and radiolysis of CH 4 and N 2 in the surface ices (e.g., Cruikshank et al 2016).…”

Prebiotic Chemistry of Pluto

“…An especially prominent and interesting trough, Virgil Fossae, which is identified as a graben, has a nearly smooth floor that exhibits an exposure of H 2 O ice and a unique color (Fig. 4), first noted by A.H. Parker (personal communication) and Olkin et al (2017). The association of colored material with the fossae also occurs in a radiating graben cluster provisionally named Mwindo Fossae (Fig.…”

“…In the coldest regions at T = 35-40 K some radicals produced by photolysis of the native materials may be stable, depending on their rates of production and destruction by diffusion and reaction. Thus, the refractory tholin residue at room temperature in the Materese et al (2014,2015) studies appears to account for some of the colors Olkin et al, 2017;Grundy et al, 2018), although it does not necessarily represent the total molecular inventory on the planet.…”

Detection of ammonia on Pluto’s surface in a region of geologically recent tectonism

“…The red-colored region in and around the fossa is spatially coincident with a prominent exposure of H 2 O ice (as shown in Fig. 2B) that is seen in only a few other regions of Pluto’s surface ( 15 – 18 ). In the enlarged view of the western portion of the fossa from the Pluto base map (Fig.…”