The Deep Impact Mission

A Prediction of What They May Find

NASA is sending a spacecraft to rendezvous with comet Tempel 1 near the orbit of Mars. On July 4, 2005 the spacecraft will launch a probe to impact the comet and then will make spectroscopic observations of the fireball that will be created at the time of impact. By analyzing the spectrum of the fireball, they hope to gather information about the comet's chemical composition. Dr. Paul LaViolette expects that there is a high probability that they may detect volatile acids such as hydrogen fluoride, hydrogen, chloride, and hydrogen bromide. If such acids are detected, this will help support his contention that the highly acidic layer found in 15,800 year old Antarctic ice, called the "Main Event," may be of extraterrestrial origin. The Main Event contains unusually high levels of hydrogen fluoride and hydrogen chloride that form a series of regularly spaced peaks. In a paper he published in April 2005 in Planetary and Space Science, he demonstrated that these acid peaks recur with a period approximating that of the sunspot cycle. He concluded that this could occur if these halogens were of extraterrestrial origin, possibly dust and gas from a nebular cloud that then surrounded the solar system, and whose rate of entry into the inner solar system would have depended on the phase of the solar cycle. He proposed that this nebular cloud had been generated from cometary debris in the solar system vicinity that had become vaporized by an elevated flux of cosmic ray radiation occurring at that time. It is known that comets contain much larger quantities of volatile materials than do meteorites since the latter lose most of their volatiles during their hot passage through the Earth's atmosphere.

Another element that should be kept a look out for is tin. In 1983 he published the results of his Ph.D. research of Greenland ice dating from the last ice age and found that certain samples containing high levels of tin were associated with high levels of iridium and tin, both of which are cosmic dust indicators. Later analysis also showed that this tin sample had an anomalous isotope ratio, an indication of its extraterrestrial origin. Also later researchers reported discovering tin as a component in interstellar dust particles. LaViolette predicted that future spacecraft-comet rendezvous missions may discover the presence of tin in comets.

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