**Utterly Alien**

by Dr. Tony Phillips

There\'s a planet in our solar system so cold that in winter its
nitrogen atmosphere freezes and falls to the ground.  The empty sky
becomes perfectly clear, jet-black even at noontime.  You can see
thousands of stars. Not one twinkles.\
\
The brightest star in the sky is the Sun, so distant and tiny you could
eclipse it with the head of a pin.  There\'s a moon, too, so *big* you
couldn\'t blot it out with your entire hand. Together, moonlight and
sunshine cast a twilight glow across the icy landscape revealing . . .
what? twisted spires, craggy mountains, frozen volcanoes?\
\
No one knows, because no one has ever been to Pluto.\
\
\"Pluto is an alien world,\" says Alan Stern of the Southwest Research
Institute in Colorado.  \"It\'s the only planet never visited or
photographed by NASA space probes.\"\
\
That\'s about to change.  A robot-ship called New Horizons is scheduled
to blast off for Pluto in January 2006.  It\'s a long journey: More than
6 billion kilometers (about 3.7 billion miles). New Horizons won\'t
arrive until 2015.\
\
\"I hope we get there before the atmosphere collapses,\" says Stern, the
mission\'s principal investigator.  Winter is coming, and while it\'s
warm enough now for Pluto\'s air to float, it won\'t be for long.
Imagine seeing a planet\'s atmosphere collapse. New Horizons might!\
\
\"This is a flyby mission,\" notes Stern.  "Slowing the spacecraft down
to *orbit* Pluto would burn more fuel than we can carry.\" New Horizons
will glide past the planet furiously snapping pictures. \"Our best
images will resolve features the size of a house,\" Stern says.\
\
The cameras will also target Pluto\'s moon, Charon. Charon is more than
half the size of Pluto, and the two circle one another only 19,200
kilometers (12,000 miles) apart.  (For comparison, the Moon is 382,400
kilometers \[239,000 miles\] from Earth.) No wonder some astronomers
call the pair a \"double planet.\"\
\
Researchers believe that Pluto and Charon were created billions of years
ago by some terrific impact, which split a bigger planet into two
smaller ones.  This idea is supported by the fact that Pluto and Charon
spin on their sides like sibling worlds knocked askew. \
\
Yet there are some curious differences:  Pluto is bright; Charon is
darker.  Pluto is covered with frozen nitrogen; Charon by frozen water. 
Pluto has an atmosphere; Charon might not. \"These are things we plan to
investigate,\" says Stern.\
\
Two worlds. So alike, yet so different. So utterly alien.  Stay tuned
for New Horizons.

Find out more about the New Horizons mission at
[pluto.jhuapl.edu/](http://pluto.jhuapl.edu/). Kids can learn amazing
facts about Pluto at spaceplace.nasa.gov/en/kids/pluto.

This article was provided by the Jet Propulsion Laboratory, California
Institute of Technology, under a contract with the National Aeronautics
and Space Administration.

![](media/image1.jpeg){width="4.001388888888889in"
height="2.498611111111111in"}

*New Horizons spacecraft will get a gravity assist from Jupiter on its
long journey to Pluto-Charon. Credit: Southwest Research Institute (Dan
Durda)/Johns Hopkins University Applied Physics Laboratory (Ken
Moscati).*

Note to editors: This image can be downloaded at
[http://spaceplace.nasa.gov/astro_clubs/NH_jupiter.jpg](http://spaceplace.nasa.gov/astro_clubs/new_horizons.jpg)
.