Giant icy mountains in Plutos southern hemisphere tower more than 3,500 metres high in the first high-resolution images that New Horizons sent back. The peaks sheer height signals that they are made of water ice, the only material that could buttress such huge ridges at Plutos frigid temperatures of less than −223 °C, just 50 °C above absolute zero. Bright rims near the tops of the peaks named after Nepalese explorer Tenzing Norgay could represent a fresh coat of frozen nitrogen or other types of ice.
Nearly every feature coming into view is shaped by ice in some fashion. Planetary scientists already knew from ground-based observations that Pluto had nitrogen, methane and carbon monoxide ice on its surface. The images are now beginning to reveal just where those frosts lie, and how they behave.
A bright, heart-shaped feature, informally dubbed Tombaugh Regio after Pluto discoverer Clyde Tombaugh, displays a concentration of carbon monoxide ice.