Md. mission adds to data on Jupiter

New Horizons spacecraft takes look at planet, moons on way to Pluto

In Focus -- Science

October 10, 2007|By Frank D. Roylance | Frank D. Roylance,SUN REPORTER

Like Columbus cruising the Canary Islands en route to the New World, the Maryland-run New Horizons spacecraft got a close look at Jupiter last February on its way to a 2015 first date with the dwarf planet Pluto.

Data from the flyby, to be reported in this week's edition of the journal Science, provide new glimpses of the bizarre Jovian system - including eruptions on the volcanic moon Io that hurl a ton of sulfur dioxide into space every second, and huge belches of electrically charged particles that break from Jupiter's grip like blobs in a lava lamp.

"Knowledge of the Jovian system is important for understanding the origin and formation of our planetary system. As the largest and most massive planet, Jupiter played a critical role in that process," said Norbert Krupp, of the Max-Planck Institute in Germany, in a "perspective" article on the mission in Science.

New Horizons' scientists reported on their discoveries yesterday in Orlando, Fla., at a meeting of the American Astronomical Society's Division for Planetary Sciences.

NASA's $700 million New Horizons mission - the first ever to Pluto - was designed at the Johns Hopkins University Applied Physics Laboratory near Laurel. It's managed from a control center on the APL campus.

New Horizons was the eighth spacecraft to visit Jupiter since 1973. It was launched from Cape Canaveral in January 2006 - the fastest spacecraft ever rocketed from Earth.

In February, more than 500 million miles from Earth, the craft entered the Jovian system at 44,200 mph. It passed within 1.4 million miles of the huge planet, flying through the turbulent "magnetosphere," where charged particles blown out from the sun are swept up by Jupiter's magnetic field.

Jupiter's magnetosphere is the largest in the solar system - 200 times as wide as Jupiter itself. It extends hundreds of millions of miles beyond Jupiter, away from the sun, like a giant windsock.

New Horizons flew about 110 million miles down the "magnetotail," scientists said, the first such traverse in history.

Along the way, its instruments were buffeted by blobs of electrically charged plasma, called "plasmoids," ripped from Jupiter's magnetosphere and swept down the magnetotail like shreds of a flag whipped by hurricane winds.

Scientists led by David J. McComas of the Southwest Research Institute in San Antonio and Ralph L. McNutt at APL discovered that the blobs carry signatures hinting at their origins.

Some were composed mostly of hydrogen ions, evidently torn from the upper reaches of Jupiter's atmosphere. Others carried sulfur and oxygen ions blown into space by Io's volcanoes, pulled away by the solar wind and flushed down the magnetotail.

The plasmoids varied in strength, speed and periodicity. At some regions of the magnetotail, the plasmoids seemed to pass by New Horizons in pulses that occurred every three or four days. Elsewhere, they had 10-hour periods that seemed to correspond with the 10-hour rotation of Jupiter.

Understanding Jupiter's magnetosphere will help scientists understand Earth's, too.

"This shield protects us and all terrestrial life from the harsh interplanetary environment," Krupp said.

New Horizons' instruments also recorded a huge volcanic eruption on Io. The odd volcanic "plume" rose 217 miles above the mouth of the Tvashtar volcano and fell across a region 680 miles wide. But it didn't behave like a volcano on Earth, according to a paper co-authored by John R. Spencer of the Southwest Research Institute.

Rather than rising, spreading out and falling in a ballistic trajectory like artillery shot from a volcanic cone, material in the plume seemed to emerge as gas, condense into solid particles of basalt high in the plume, then slide down the plume's "shock front" to the surface.

In other studies, scientists reported fields of rippled clouds that zip around Jupiter's equator; bright clouds of ammonia ice that briefly form where gas wells up from deep in the atmosphere; auroras where charged particles were falling onto the planet's atmosphere; and loose clumps of dust where they had looked for tiny moons.

They also mapped the surface composition of Europa. The Jovian moon might have a liquid ocean beneath its surface ice. Scientists are trying to analyze the chemistry of "non-ice" material on the surface for clues to the biological potential of the water below.

But the mapping suggests the non-ice material didn't come from below. Instead, it appears to be sulfur from Io, deposited on Europa's surface.

In all, the team made more than 700 observations at Jupiter - 10 times what they originally planned for Pluto. "We badly stressed out our operations team, but they came out smelling like a rose," said Hal Weaver, APL's New Horizons project scientist.

Flush with success, they're asking the operations team to nearly triple the Pluto observations. They also intend to start planning now, instead of in 2012, Weaver said, "while we have those lessons learned fresh in our minds."

NASA's New Horizons Mission

Flight plan: Launched Jan. 19, 2006, conducted Jupiter flyby February and March 2007. Will study Pluto and its moons during a July 2015 flyby, then explore icy Kuiper Belt objects until 2020.

Statistics: Current speed, 46,000 mph. Distance from Earth: 755 million miles. Distance from Pluto: 2.2 billion miles. Current one-way radio transmission time: 45 minutes. Mission cost: $700 million.

Operations near Jupiter: Included photographing eruption of Tvashtar volcano on Jovian moon Io; mapping surface of Europa; searching for new moons in Jupiter's faint rings; exploring electromagnetic environment in Jupiter's magnetotail.

Mission management: Johns Hopkins University's Applied Physics Laboratory.

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