From Newsgroup: sci.space.news


http://pluto.jhuapl.edu/Multimedia/Science-Photos/image.php?page=1&gallery_id=2&image_id=408

Pluto's Mysterious, Floating Hills

Release Date: February 4, 2016

The nitrogen ice glaciers on Pluto appear to carry an intriguing cargo: numerous, isolated hills that may be fragments of water ice from Pluto's surrounding uplands. These hills individually measure one to several
miles or kilometers across, according to images and data from NASA's New Horizons mission.

The hills, which are in the vast ice plain informally named Sputnik
Planum within Pluto's "heart," are likely miniature versions of the
larger, jumbled mountains on Sputnik Planum's western border. They are
yet another example of Pluto's fascinating and abundant geological
activity.

Because water ice is less dense than nitrogen-dominated ice, scientists
believe these water ice hills are floating in a sea of frozen nitrogen
and move over time like icebergs in Earth's Arctic Ocean. The hills are
likely fragments of the rugged uplands that have broken away and are
being carried by the nitrogen glaciers into Sputnik Planum. "Chains" of
the drifting hills are formed along the flow paths of the glaciers. When
the hills enter the cellular terrain of central Sputnik Planum, they
become subject to the convective motions of the nitrogen ice, and are
pushed to the edges of the cells, where the hills cluster in groups
reaching up to 12 miles (20 kilometers) across.

At the northern end of the image, the feature informally named
Challenger Colles - honoring the crew of the lost space shuttle
Challenger - appears to be an especially large accumulation of these
hills, measuring 37 by 22 miles (60 by 35 kilometers). This feature is
located near the boundary with the uplands, away from the cellular
terrain, and may represent a location where hills have been "beached"
due to the nitrogen ice being especially shallow.

The image shows the inset in context next to a larger view that covers
most of Pluto's encounter hemisphere. The inset was obtained by New
Horizons' Multispectral Visible Imaging Camera (MVIC) instrument. North
is up; illumination is from the top-left of the image. The image
resolution is about 1050 feet (320 meters) per pixel. The image measures
a little over 300 miles (almost 500 kilometers) long and about 210 miles
(340 kilometers) wide. It was obtained at a range of approximately 9,950
miles (16,000 kilometers) from Pluto, about 12 minutes before New
Horizons' closest approach to Pluto on July 14, 2015.

Credit: NASA/Johns Hopkins University Applied Physics
Laboratory/Southwest Research Institute

SEEN-BY: 154/30 2320/100 0 1 227/0