When NASA's Deep Impact mission slammed into comet Tempel 1 in July 2005, The Planetary Society expected to make an immediate announcement about the winners of its "Great Comet Crater Contest" to guess the diameter of the crater created by the impact. However, one learns to expect the unexpected with space exploration; six months after the impactor kicked up an opaque cloud of comet debris, team scientists have learned a lot about Tempel 1 but can still only estimate the crater's size as being somewhere between 100 and 250 meters in diameter.
The Planetary Society has, therefore, selected at random three grand prize winners from the 1,865 contest entrants who submitted a guess within the estimated size range. The grand prize winners and their respective crater estimates are Wojciech Karcz, Tarnowskie Gory, Poland - 161 meters; Michael Ramo, Danielson, Connecticut - 153 meters; and Tim Thomas, Hayward, California - 141.4272 meters. Read additional information on the contest.
Contest rules stipulated that all entrants who guessed within 10 meters of the correct crater diameter would be entered into drawings for the grand prize, with three winners to be selected at random from that pool. Since the Deep Impact team announced a size range rather than a single figure, the number of entrants who fell within those parameters proved quite large.
"When we planned our experiment, we estimated how long it would take for the dust to fall back onto the comet, and multiplied that estimate by 4," said Lucy McFadden, Co-Investigator on Deep Impact. "We only had a limited time to observe because this was all happening at relative speeds of 22,000 miles per hour. To our surprise, the dust never cleared!"
Because the dust never cleared, the team used a combination of theoretical modeling and constraints provided by image processing to estimate the crater size to be between 100 and 250 meters in diameter.
More than 7,000 people from nearly 100 countries entered the contest, with the median guess of crater size being 90 meters. In addition to the three grand prize winners, the Society randomly selected 150 runners-up representing 24 nations: Australia, Austria, Belgium, Canada, China, Costa Rica, Czech Republic, Finland, France, Germany, India, Indonesia, Ireland, Mexico, Netherlands, Poland, Slovenia, South Africa, Spain, Sweden, Switzerland, the United Kingdom, USA, and Venezuela.
Each grand prize winner will receive a custom-made plaque from Ball Aerospace & Technologies Corp (BATC), who built the Deep Impact spacecraft. The plaque is made of the same kind of copper material that made up the heavy mass of the impactor, laser-engraved with the mission logo. The grand prize winners will also each receive a complimentary Planetary Society membership. The runner-up prizes will consist of a certificate and a Deep Impact spacecraft paper model provided by BATC.
"Since the impact on July 4, more than 7,000 contest entrants around the world have been waiting for the dust to settle so that the science team could estimate the size of the crater made by Deep Impact," said Emily Lakdawalla, Science and Technology Coordinator for The Planetary Society. "The very uncertainty of the final result has reminded all of us that no matter how many questions a space mission answers, it always raises more."
The Deep Impact mission was led by Principal Investigator Michael A'Hearn at the University of Maryland. BATC, in association with the University of Maryland and the Jet Propulsion Laboratory (JPL), developed and built the Deep Impact flyby spacecraft, impactor spacecraft, and science instruments, including three telescopes, two cameras and a spectrometer for analyzing the interior of the comet. Deep Impact is the eighth mission in NASA's Discovery Program, and the first mission to ever impact a comet nucleus in an effort to probe beneath its surface.