NASA Postpones Pluto Mission Launch

Brian Handwerk
for National Geographic News

Updated January 17, 2006

NASA officials postponed until tomorrow the planned launch of the New Horizons spacecraft, which was set to blast off today on a nine-year, three-billion-mile (five-billion-kilometer) journey to Pluto.

The most distant official planet in the solar system has never hosted a scientific mission.

"This is the capstone of the initial reconnaissance of the planets, the first mission to the last planet," said Alan Stern, the mission's principal investigator.

"The United States is going to go down in history for the initial reconnaissance of the planets," said Stern, who is based at the Southwest Research Institute's Department of Space Studies in Boulder, Colorado.

Long Ride Ahead

The 1,050-pound (476-kilogram) New Horizons spacecraft will be the fastest in history.

The probe was set to lift off this afternoon from Cape Canaveral, Florida, aboard an Atlas V launch vehicle. But windy conditions delayed the launch, which is rescheduled for 1:16 p.m. ET tomorrow.

Barring mishap, New Horizons should reach the distance of lunar orbit only nine hours after lift off tomorrow.

It will reach and pass Jupiter in just 13 months but won't reach Pluto until 2015 at the earliest.

Tomorrow's launch window will allow the craft to reach and pass Jupiter in early 2007, using the giant planet's gravity as a slingshot to speed its journey to Pluto, cutting five years of travel time.

Stern believes the biggest postlaunch hurdle will be maintaining the spacecraft in an energy-saving hibernation mode—a first for a NASA planet-reconnaissance mission. Hibernation begins, in tentative stages, after the 2007 Jupiter flyby.

"There will be a learning curve," Stein said. "It's revolutionary. But we'll have to ease into that learning curve and do it right, or we could lose the mission."

Ice Dwarf

Pluto is an ice dwarf that differs fundamentally from more familiar planet types, such as rocky planets (Mercury, Venus, Earth, and Mars) and gas giants (Jupiter, Saturn, Uranus, and Neptune).

Some scientists question whether Pluto should be considered a planet at all.

Surface temperatures on Pluto are estimated to hover around –387° F (–233° C).

"We discovered in the 1990s, much to our surprise, that the solar system is littered with these little icy planets," Stern said. "They are the most populous category, and we haven't been to a single one. It's as if we explored only the extreme northern climates on Earth and never visited the more typical climes."

"In fact, we think that these icy planets are very common across the entire galaxy."

The 700-million-U.S.-dollar mission will also study Pluto's primary moon, Charon, and the Kuiper Belt.

A huge swath of icy, rocky bodies in the outermost solar system, the Kuiper belt is believed to contain more than a hundred thousand miniature worlds. They orbit in the frigid realm beyond Neptune.

The materials found in the belt are thought to be leftovers from planet formation and may reveal secrets of the origins of our solar system.

Pluto and other Kuiper belt objects appear to contain large amounts of organic compounds, such as frozen methane and water ice.

Scientists theorize that Kuiper belt objects may have delivered these materials to Earth billions of years ago, providing the raw ingredients for life.

Early "Earth"?

The New Horizons design is ultraefficient. If successful, the spacecraft will conduct its Pluto and Charon observations using less power than two hundred-watt lightbulbs.

During a five-month study the piano-size probe will map and measure Pluto's geology and landform origins, as well as its surface compositions and temperatures. The probe will also study the planet's atmosphere and two smaller moons that were discovered last year.

The craft will also deliver dramatic high-resolution images and will analyze space-dust particles.

Pluto's primary moon, Charon, is about half Pluto's size. The pair constitute a "double planet" locked in dual orbit that is unique in our solar system but likely more common elsewhere in space.

Astronomers hope to learn more about how the double planet system formed. Many believe that Pluto collided with some celestial body eons ago and that the resulting debris eventually condensed to form Charon.

A similar scenario may have spawned our own Earth-moon system.

Pluto's atmosphere is also believed to be leaking rapidly into space.

The process, called hydrodynamic escape, may have caused the rapid depletion of hydrogen from Earth's early atmosphere—making our planet suitable for life.

"I think that a thousand years from now the U.S. will be known for space exploration in much the same way that Spain is known for its exploration of the Americas in the 1500s," Stern said.

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