Press Release

Last Chance to Make a Guess on Celestial Fireworks: The Great Comet Crater Contest

By SpaceRef Editor
June 29, 2005
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Last Chance to Make a Guess on Celestial Fireworks: The Great Comet Crater Contest

On July 3, 2005, at 10:52 PM (PT) NASA’s Deep Impact spacecraft will slam an impactor into Comet Tempel 1.  The Planetary Society invites people worldwide to guess how big a crater the resultant hole will be. The “Great Comet Crater Contest” can be found at

If you propel a chunk of metal into a comet at extremely high speed, will it sink like a stone in snow or blast a sizeable crater out of the surface? Are comets as solid as rocks or as fluffy as snowballs?  Scientists will, hopefully, soon have the answer.  When Comet Tempel 1 is hit, the Deep Impact flyby spacecraft will watch the birth of a new crater with its cameras and other instruments.  By studying the size and shape of the hole, and the composition and motion of the comet debris that flies away from the impact, scientists hope to learn how comets are put together.

“Over 5,000 people from 84 countries have already entered our contest to guess the diameter of the crater,” said Emily Lakdawalla, The Planetary Society’s Science and Technology Coordinator,  “and we will be accepting entries right up until impact.”

The Planetary Society will also celebrate Deep Impact’s arrival at Comet Tempel 1 with a public event called “Comet Bash” in Glendora, California.  Comet Bash attendees will witness live images on a giant screen and watch updates from mission control; learn about comets, the threat of Near Earth Objects, and the Deep Impact mission; and enjoy a program that includes Bill Nye the Science Guy and Apollo astronaut Rusty Schweickart.   For more information, visit

Scientists themselves can only guess how big of a crater Deep Impact will make on Tempel 1 because they are not certain what the composition or structure of the comet is.  They do know that Comet Tempel 1 is irregularly shaped and its size is estimated to be 14.4 by 4.4 by 4.4 kilometers (8.9 by 2.7 by 2.7 miles) across.  The density of the comet is estimated to be less than that of water, meaning it is probably quite porous.

Comet Tempel 1 will collide with the copper impactor, which weighs 370 kilograms (816 pounds), with a velocity of 10.2 kilometers per second (22,800 miles per hour).  Based on experiments and theoretical models incorporating the best guesses for Tempel 1’s properties, scientists predict that the impact crater will be on the order of 100 meters across.   In other words, the actual size of the crater is likely to be closer to 100 meters than it is to be 10 meters or 1000 meters, but that still leaves a lot of wiggle room for guessing its size.

That’s where the contest comes into play.  Anyone may enter the Great Comet Crater Contest by logging on to The Planetary Society’s website at Deep Impact mission facts and figures will help entrants come up with their best educated guess for the diameter of the crater that Deep Impact will create on the surface of Comet Tempel 1.  Only ONE contest entry per person is allowed.

Guesses must be made in meters, but the website does include a conversion chart for Americans who are more comfortable thinking in feet and inches.  Contest participants may enter online at the website; entries will be accepted until the moment of impact.  Three grand prizes will be awarded for the best guess of the crater’s diameter. All entrants who guess within 10 meters of the correct crater diameter will be entered into drawings for the grand prize. Runner-Up prizes will be awarded to up to 150 additional correct entrants.

Each grand prize will be a custom-made plaque from Ball Aerospace, who built the Deep Impact Spacecraft.  The plaque will be made of the same kind of copper material that makes 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 Ball Aerospace.

“For years the Deep Impact science team has been debating about the size of the crater that will form because that will teach us so much about the interior of the comet,” said Lucy McFadden, Deep Impact co-investigator, University of Maryland.  “We are pleased that The Planetary Society is offering this contest so that the public can anticipate the experiment’s outcome with us.”

The Deep Impact mission is led by Principal Investigator Michael A’Hearn at the University of Maryland.  Ball Aerospace & Technologies Corp., 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 attempt impact with a comet nucleus in an effort to probe beneath its surface.


For more information, contact Susan Lendroth at phone: (626) 793-5100 ext. 237, e-mail:


Now celebrating its 25th anniversary, The Planetary Society has inspired millions of people to explore other worlds and seek other life. Today, its international membership makes the non governmental Planetary Society the largest space interest group in the world.  Carl Sagan, Bruce Murray and Louis Friedman founded The Planetary Society in 1980.


SpaceRef staff editor.