SETI bioastro: Fw: Jupiter Hot Spot Makes Trouble For Theory

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Date: Wed Feb 27 2002 - 13:08:17 PST

----- Original Message -----
Sent: Wednesday, February 27, 2002 2:43 PM
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Subject: Jupiter Hot Spot Makes Trouble For Theory

Dolores Beasley
Headquarters, Washington Feb. 27, 2002
(Phone: 202/358-1753)

Steve Roy
Marshall Space Flight Center, Huntsville, Ala.
(Phone: 256/544-6535)

Megan Watzke
Chandra X-ray Observatory Center, Cambridge, Mass.
(Phone: 617/496-7998)

RELEASE: 02-34


     A pulsating hot spot of X-rays has been discovered in the
polar regions of Jupiter's upper atmosphere by NASA's Chandra
X-ray Observatory. Previous theories cannot explain either the
pulsations or the location of the hot spot, prompting
scientists to search for a new process to produce Jupiter's X-

"The location of the X-ray hot spot effectively retires the
existing explanation for Jupiter's
X-ray emission, leaving us very unsure of its origin," said
Randy Gladstone of the Southwest Research Institute in San
Antonio and lead author of a paper on the results in the Feb.
28, 2002, issue of the journal Nature. "The source of ions
that produce the X-rays must be a lot farther away from
Jupiter than previously believed."

Chandra observed Jupiter for 10 hours on Dec. 18, 2000, when
NASA's Cassini spacecraft was flying by Jupiter on its way to
Saturn. The X-ray observations revealed that most of the
auroral X-rays come from a pulsating hot spot that appears at
a fixed location near the north magnetic pole of Jupiter.

Bright infrared and ultraviolet emissions have also been
detected from this region in the past. The X-rays were
observed to pulsate with a period of 45 minutes, similar to
the period of high-latitude radio pulsations detected by
NASA's Galileo and Cassini spacecraft.

An aurora of X-ray light near Jupiter's polar regions had been
detected by previous satellites. However, scientists were
unable to determine the exact location of the X-rays. The
accepted theory holds that the X-rays are produced by
energetic oxygen and sulfur ions that became excited as they
ran into hydrogen and helium in Jupiter's atmosphere. Oxygen
and sulfur ions (originally from Jupiter's moon Io) are
energized while circulating around Jupiter's enormous
magnetosphere. And some -- the purported X-ray producers --
get dumped into Jupiter's atmosphere when they return to the
region of Io's orbit.

Chandra's ability to accurately determine the location of the
X-rays proved this model incorrect, as ions from regions of
Jupiter's magnetic field near Io cannot reach the high Jovian
latitudes where most of the X-rays were observed.

This result has its own problems. At the large distances
required for the source of the ions --at least 30 times the
radius of Jupiter -- spacecraft measurements have shown that
there are not nearly enough energetic oxygen and sulfur ions
to account for the observed X-ray emission.

One possibility is that heavy ions among the particles flowing
out from the Sun as the solar wind are captured in the outer
regions of Jupiter's magnetic field, then accelerated and
directed toward its magnetic pole. Once captured, the ions
would bounce back and forth in the magnetic field from pole to
pole in an oscillating motion that might explain the

The High Resolution Camera used for the Chandra observations
was built by the Smithsonian Astrophysical Observatory in
Cambridge, Mass. NASA's Marshall Space Flight Center in
Huntsville, Ala., manages the Chandra program, and TRW, Inc.,
Redondo Beach, Calif., is the prime contractor. The
Smithsonian's Chandra X-ray Center controls science and flight
operations from Cambridge, Mass.

Images and additional information about this result are
available at:


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