Global Albedos of Pluto and Charon from LORRI New Horizons Observations

Global Albedos of Pluto and Charon from LORRI New Horizons Observations

Authors:

Burratti et al

Abstract:

The exploration of the Pluto-Charon system by the New Horizons spacecraft represent the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the Solar System's "Third Zone" within the context of a geologic world. Images of the entire illuminated surface of Pluto and Charon obtained by the Long Range Reconnaissance Imager (LORRI) camera provide a global map of Pluto that revealed surface albedo variegations larger than any other world except for Saturn's moon Iapetus. Normal reflectances on Pluto range from 0.08-1.0. Charon exhibits a much blander surface with normal reflectances ranging from 0.20-0.73. Pluto's albedo features are well-correlated with geologic features, although some exogenous low-albedo dust may be responsible for features seen to the west of the area informally named Tombaugh Regio. The albedo patterns of both Pluto and Charon are latitudinally organized, with the exception of Tombaugh Regio. The low-albedo areas of Pluto are darker than anything on Charon's surface. The phase curve of Pluto is similar to that of Triton, the large moon of Neptune, and a former KBO dwarf planet, while Charon's is similar to that of the Moon. Preliminary Bond albedos are 0.25 +/- 0.03 for Charon and 0.72 +/- 0.07 for Pluto. Maps of the Bond albedo for both Pluto and Charon are presented for the first time.

Algae Radically Reducing Glacier Albedo

The first ecological study of an entire glacier has found that microbes drastically reduce surface reflectivity and have a non-negligible impact on the amount of sunlight that is reflected into space.

The research, led by the University of Leeds and published today [12 June] in the journal FEMS Microbiology Ecology, will help improve climate change models that have previously neglected the role of microbes in darkening the Earth's surface.

Observing how life thrives at extreme cold temperatures also has important implications for the search for life on distant worlds, such as Jupiter's icy moon Europa.

Stefanie Lutz, a PhD student at the School of Earth and Environment at the University of Leeds, and lead author of the study, said: "Our three-week field trip revealed a 'microbial garden' of life forms flourishing in this cold environment, including snow algae, bacteria, fungi and even invertebrates.

"Skiers may have seen snow algae before, but not been able to identify it. They are visible to the naked eye as coloured snow – most often red – and are frequently referred to as 'watermelon snow'."

The study was carried out on the Mittivakkat Glacier in south east Greenland during the summer of 2012, which was the hottest summer and thus the fastest melting season recorded for 150 years.

"Our timing was serendipitous, as it meant we were able to see changes in microbial processes over an extremely fast melting season and observe a process from start to end across all habitats on a glacier surface. This is the most comprehensive study of microbial communities living on a glacier to date," said Lutz.

The research showed that, compared to pure snow and ice, the reflectivity of the glacier (known as the "albedo") can be reduced by up to 80% in places where coloured microbial populations are extremely dense, leading to the darkening of the glacier surface.

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