In the center left of Pluto’s
vast heart-shaped feature – informally named “Tombaugh Regio” - lies a
vast, craterless plain that appears to be no more than 100 million years
old, and is possibly still being shaped by geologic processes. This
frozen region is north of Pluto’s icy mountains and has been informally
named Sputnik Planum (Sputnik Plain), after Earth’s first artificial
satellite. The surface appears to be divided into irregularly-shaped
segments that are ringed by narrow troughs. Features that appear to be
groups of mounds and fields of small pits are also visible. This image
was acquired by the Long Range Reconnaissance Imager (LORRI) on July 14
from a distance of 48,000 miles (77,000 kilometers). Features as small
as one-half mile (1 kilometer) across are visible. The blocky appearance
of some features is due to compression of the image.
Credit: NASA/JHUAPL/SWRI
"This terrain is not easy to explain," said Jeff Moore, leader of the
New Horizons Geology, Geophysics and Imaging Team (GGI) at NASA's Ames
Research Center in Moffett Field, California. "The discovery of vast,
craterless, very young plains on Pluto exceeds all pre-flyby
expectations."
This fascinating icy plains region -- resembling frozen mud cracks on
Earth -- has been informally named "Sputnik Planum" (Sputnik Plain)
after the Earth's first artificial satellite. It has a broken surface of
irregularly-shaped segments, roughly 12 miles (20 kilometers) across,
bordered by what appear to be shallow troughs. Some of these troughs
have darker material within them, while others are traced by clumps of
hills that appear to rise above the surrounding terrain. Elsewhere, the
surface appears to be etched by fields of small pits that may have
formed by a process called sublimation, in which ice turns directly from
solid to gas, just as dry ice does on Earth.
Scientists have two working theories as to how these segments were
formed. The irregular shapes may be the result of the contraction of
surface materials, similar to what happens when mud dries.
Alternatively, they may be a product of convection, similar to wax
rising in a lava lamp. On Pluto, convection would occur within a surface
layer of frozen carbon monoxide, methane and nitrogen, driven by the
scant warmth of Pluto's interior.
Pluto's icy plains also display dark streaks that are a few miles
long. These streaks appear to be aligned in the same direction and may
have been produced by winds blowing across the frozen surface.
The Tuesday "heart of the heart" image was taken when New Horizons
was 48,000 miles (77,000 kilometers) from Pluto, and shows features as
small as one-half mile (1 kilometer) across. Mission scientists will
learn more about these mysterious terrains from higher-resolution and
stereo images that New Horizons will pull from its digital recorders and
send back to Earth during the next year.
The New Horizons Atmospheres team observed Pluto's atmosphere as far
as 1,000 miles (1,600 kilometers) above the surface, demonstrating that
Pluto's nitrogen-rich atmosphere is quite extended. This is the first
observation of Pluto's atmosphere at altitudes higher than 170 miles
above the surface (270 kilometers).
The New Horizons Particles and Plasma team has discovered a region of
cold, dense ionized gas tens of thousands of miles beyond Pluto -- the
planet's atmosphere being stripped away by the solar wind and lost to
space.
"This is just a first tantalizing look at Pluto's plasma
environment," said New Horizons co-investigator Fran Bagenal, University
of Colorado, Boulder.
"With the flyby in the rearview mirror, a decade-long journey to
Pluto is over --but, the science payoff is only beginning," said Jim
Green, director of Planetary Science at NASA Headquarters in Washington.
"Data from New Horizons will continue to fuel discovery for years to
come."
Alan Stern, New Horizons principal investigator from the Southwest
Research Institute (SwRI), Boulder, Colorado, added, "We've only
scratched the surface of our Pluto exploration, but it already seems
clear to me that in the initial reconnaissance of the solar system, the
best was saved for last."
New Horizons is part of NASA's New Frontiers Program, managed by the
agency's Marshall Space Flight Center in Huntsville, Alabama. The Johns
Hopkins University Applied Physics Laboratory in Laurel, Maryland,
designed, built and operates the New Horizons spacecraft and manages the
mission for NASA's Science Mission Directorate. SwRI leads the mission,
science team, payload operations and encounter science planning.
Follow the New Horizons mission on Twitter and use the hashtag
#PlutoFlyby to join the conversation. Live updates are also available on
the mission Facebook page.
For more information on the New Horizons mission, including fact sheets, schedules, video and new images, visit:
http://www.nasa.gov/newhorizons
and
http://solarsystem.nasa.gov/planets/plutotoolkit.cfm
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