Pluto may be a strange, faraway world, but scientists have learned it shares a familiar trait with Earth — a blue sky.
The first color images of a thin haze that surrounds Pluto show it to be reflecting a pale blue light, scientists working on NASA’s New Horizons mission said Thursday.
“Who would have expected a blue sky in the Kuiper Belt?” said the mission’s principal investigator, Alan Stern, referring to the region at the edge of the solar system that includes Pluto. “It’s gorgeous.”
Early observations from the mission showed a haze extending about 100 miles above Pluto’s surface, thicker than scientists expected because they believe the dwarf planet’s atmosphere has long been evaporating into space.
Scientists believe that particles within the haze are themselves gray or red, but they give off blue light to the human eye.
“A blue sky often results from scattering of sunlight by very small particles,” said Carly Howett, a researcher on the New Horizons science team. “On Earth, those particles are very tiny nitrogen molecules. On Pluto they appear to be larger — but still relatively small — soot-like particles we call tholins.”
Howett and Stern are scientists at the Southwest Research Institute in Boulder, Colo., which is leading the New Horizons mission alongside the Johns Hopkins Applied Physics Laboratory in Laurel.
The images of Pluto’s atmosphere, and of its surface and moons, were captured when the New Horizons spacecraft flew past the dwarf planet in July.
The data showed another similarity between Pluto and Earth, scientists said Thursday — the presence of water ice on Pluto’s surface.
They knew water ice was present on the dwarf planet, but across most of its surface, it lies beneath other types of ices. New data shows small areas where the water ice is exposed.
“Understanding why water appears exactly where it does, and not in other places, is a challenge that we are digging into,” said science team member Jason Cook, also of SwRI.
