Mar 9 1999
From The Space Library
At a briefing at NASA Headquarters, scientists explained how sigmoids--fiery S-shapes on the Sun's surface-would help them "predict when potentially dangerous and disruptive blasts of electrically charged gas will come hurtling toward Earth." These solar explosions, or coronal mass ejections (CMEs), have the power to disable power grids, damage satellites, and scramble communications networks. Previously, scientists could detect solar explosions once they had occurred, providing two or three days for Earth to prepare for potential problems, but they were unable to predict the CMEs. With the Japanese Yohkoh spacecraft's discovery of sigmoids, scientists would be able to issue a warning five or six days in advance of a solar explosion. Sarah E. Gibson of Cambridge University in England described the sigmoids as slinky-like structures, related to the Sun's underlying magnetic field. Alphonse Sterling of the Institute of Space and Astronautical Science of Japan likened the structures to "loaded guns," with a high probability of discharging. Scientists explained further that "not every CME is presaged by a sigmoid, but most sigmoids signal very large CMEs." The Yohkoh images showed that the sigmoid's S-shape is the precursor to a CME, confirmed by the appearance of an arch shape following the blast.
Joseph G. Beerer of NASA's Jet Propulsion Laboratory stated that all of the instruments aboard Mars Global Surveyor were operating, and that the craft had begun mapping Mars, approximately one year later than originally planned. NASA had launched the craft in November 1996, and Surveyor had entered orbit around Mars in September 1997. NASA had delayed the mapping portion of the mission when scientists detected a structural problem with one of the craft's solar panels. To avoid placing excessive stress on the panel, the flight team had opted to proceed cautiously in aerobraking. Aerobraking, a pioneering operation, was necessary to position the spacecraft for its Mars mapping mission.
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