Previously thought to be a trace gas released as ice vaporizes, cyanogen in jets suggests it is shaken loose from complex organic dust particles from Halley’s nucleus. The pinwheel effect results from rotation of the nucleus.
“Most comets look the same each night,” added Larson. “Few have this much dust. That’s what makes Halley so exciting.” Six weeks later and half a world away at the Space Research Institute, I met Larson again at apartments in prague. He was consulting with scientists overseeing the imminent Halley encounters by Soviet and European spacecraft. One goal of those flybys was to take the first pictures of a comet nucleus. “We did not appreciate the jets,” explained a worried Roald Sagdeev, director of the two Soviet Vega probes that would fly within 8,000 to 9,000 kilometers of Halley on March 6 and 9. The VEGA cameras were designed to focus on the brightest object they detected. Designers had presumed that would be the nucleus. But the Soviets had lately realized that a strong jet might be brighter; it could shunt the cameras away from the nucleus. Now a simulator was letting the Soviets program the VEGA computers to recognize and reject jets.
Even if the cameras failed, other instruments would analyze molecules spewing off the comet, thereby helping determine precisely what Halley is made of. Dust counters would measure impacts by tiny particles expected to bombard the VEGAs.
The spacecraft would also analyze plasmas—diffuse soups of ions and other electrically charged particles. Waves of plasma blow off the sun at speeds of about 500 kilometers a second, creating the so-called solar wind. The comet was also making its own plasmas, largely as solar radiation broke up molecules streaming off its nucleus. When they meet, these intensely energized plasmas can reach temperatures of a million degrees or higher—even though a single atom-scale particle may occupy a baseball-size volume of space.
“Ninety-nine percent of the matter in the universe is in plasma form,” said Sagdeev. “The comet creates a unique event: dust, charged particles, magnetic fields, and the solar wind all reacting with one another. Understanding these complex interactions could help us explain other processes, such as how galaxies form and how our solar nebula behaved in its early days.” http://www.bbc.co.uk/news/science-environment-22912623
The Vega mission posed the Soviets’ strongest challenge yet to American dominance in planetary exploration, particularly since the United States had decided it could not afford a mission to the comet. “A repartition of duties in space,” Sagdeev termed it.
Vega also represented a great personal risk to the energetic Sagdeev. He had strong-armed the complex mission through the Soviet bureaucracy with surprising swiftness. He had invited a host of Western scientists to participate in the project. And now he opened his institute to U. S. journalists, granting us freedom to prowl the halls. No Soviet mission had courted such national embarrassment should it fail.