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March
9, 2007: Andy Cheng has seen it all. The scientist
from Johns Hopkins' Applied Physics Lab has worked on the
Galileo mission to Jupiter, the Cassini mission to Saturn,
the NEAR mission to asteroid 433 Eros and many others during
his decades-long career. Alien vistas are old hat to him.
But
even he was amazed when he laid eyes on this photo of Io's
Tvashtar volcano, taken Feb. 28th by the New Horizons spacecraft:
Above:
A volcanic eruption on Io photographed by New Horizons on
Feb. 28, 2007. [More]
Omigod!
I can't believe it. "That was my first reaction,"
says Cheng. "The LORRI image of the Tvashtar plume is
the best and most detailed plume image that any of us -- including
longtime Jupiter experts -- have ever seen."
LORRI
is an 8-inch telescope onboard New Horizons, NASA's Pluto-bound
spacecraft. "The telescope was designed to take high-resolution
pictures of Pluto and its moons when New Horizons reaches
the outer solar system in 2015," explains Cheng, the
principal investigator for LORRI, which is short for Long
Range Reconnaissance Imager.
Last
week New Horizons flew past Jupiter for a quick velocity boost,
and "this gave us an opportunity to take some pictures,"
he says. Cheng and colleagues trained the telescope on Jupiter's
moons Io, Europa, Callisto and Ganymede and on Jupiter itself.
Many of the pictures are stunning: gallery.
"Future
LORRI images of Pluto and Charon will have even more detail
and higher resolution, because New Horizons will bring us
at least a thousand times closer than we came to Io,"
notes Cheng. Of course, no one has any idea what LORRI will
see, because Pluto has never been visited by a space probe.
"That's why we're going."
Catching
a volcano blowing its top on Io isn't really a big surprise,
notes Cheng. "Io is in a constant state of eruption."
To
understand why, he suggests, dig a paperclip out of your desk
drawer. Flex the clip rapidly back and forth many times, and
touch the flexure. Careful! It's hot. The combination of flexing
+ internal friction heats the clip to surprisingly high temperatures.
 The
same thing happens to Io. Gravitational forces exerted on
Io by Jupiter and the other large moons raise tidal bulges
in Io's solid crust 30 meters high. This flexing action, like
the flexing of a paperclip, makes Io's interior molten hot
and, as a result, the moon has hundreds of active volcanoes.
Right:
An exaggerated rendition of Io's terrible tides. [more]
"We
were actually hoping to catch a different volcano—Prometheus,"
says Cheng. Prometheus is an old and reliable volcano on Io
which has been photographed many times before by Voyager and
Galileo. It appears in the New Horizons photo, too; "It's
the little mushroom-shaped plume at 9 o'clock," he points
out.
Tvashtar's
plume dwarfed grand old Prometheus, rising 180 miles (290
km) above Io's surface. (For comparison, volcanoes on Earth
spew their gas and dust just a few miles high.) "The
patchy and filamentous structure seen in the Tvashtar plume
suggests to me that condensation from gas to solid particulates
is occurring," he says. In other words, the gas could
be crystallizing in the cold space above Io to form a kind
of sulfurous snow.
Volcanoes
spewing snow? It is an alien world.
On
to Pluto!
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New Horizons is the first mission
in NASA's New Frontiers Program of medium-class spacecraft
exploration projects. The Discovery and New Frontiers Program
Office at NASA's Marshall Space Flight Center manages the
New Frontiers Program for NASA Headquarters. The JHU Applied
Physics Laboratory manages the New Horizons mission for NASA's
Science Mission Directorate.
Author: Dr.
Tony Phillips | Production Editor:
Dr. Tony Phillips | Credit: Science@NASA
| More
Information |
| New
Horizons -- mission home page
Grand
Theft Pluto -- (Science@NASA) New Horizons flew
past Jupiter on Feb. 28th and stole some velocity for
its trip to Pluto
Jupiter
Flyby Photo Gallery
New
Horizons Animations
Credits:
New Horizons is the first mission in NASA's New Frontiers
Program of medium-class spacecraft exploration projects.
The Discovery and New Frontiers Program Office at NASA's
Marshall Space Flight Center manages the New Frontiers
Program for NASA Headquarters. The JHU Applied Physics
Laboratory manages the New Horizons mission for NASA's
Science Mission Directorate. The mission team also includes
NASA's Goddard Space Flight Center, Greenbelt, Md.;
NASA's Jet Propulsion Laboratory, Pasadena, Calif.;
the U.S. Department of Energy, Washington; Southwest
Research Institute, Boulder, Colo.; and several corporations
and university partners.
NASA's
Future: The
Vision for Space Exploration |
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