Two Missions to Comets and You can have your Name tag Along

NASA currently has many exciting missions underway. Two of them, Stardust and Deep Impact involve voyages to comets, one with a sample return and the other with an impactor to collide with the comet.

Comets are leftover materials from when the planets formed more than 4.5 billion years ago. They contain many of the organic materials thought to be essential for the origin of life. An interesting new theory is that comets could have brought life to Earth when they collided with the planets in the early Solar System.

Stardust is the first of the two missions, already on its way to comet Wild-2, a comet that almost collided with Jupiter in 1974. This near collision caused its orbit to be deflected closer to the Sun: perfect for Stardust. The spacecraft was launched February 7, 1999 from Florida.

In January 2, 2004, Stardust will fly through the cloud of dust that surrounds the nucleus of the comet at 13,000 mph (21,000 kph,) over 6 times faster than a speeding bullet! But even at that speed, it will still take several hours to fly through the coma, the cloud of gas and dust coming off the comet's nucleus. The reason Stardust will fly in front of the comet is to avoid being hit by any debris coming off the comet itself.

Stardust will then collect samples from the comet, the first spacecraft to return extraterrestrial material from beyond the orbit of the Moon. Most particles from the comet are smaller than the diameter of a human hair. The particles will be captured using a material called aerogel, a special type of foamed glass, made so lightweight that it is barely visible and almost floats in air The sample capsule will be returned January 15, 2006 when the capsule lands in the Utah desert.

During the entire mission, Stardust will have flown a total or 5.2 billion kilometers (3.2 billion mile,) traveling at an average speed of 48,000 mph (78,000 kph.) Stardust will also collect several samples of interstellar dust for return and analysis.

The second mission to a comet, planned for launch December 30, 2004, is Deep Impact. This mission will not be returning samples however. Deep Impact will be making a spectacular football stadium sized crater, about a 100 feet deep into the comet Tempel.

There is actually two parts to Deep Impact, the flyby spacecraft and the impactor. Objectives of the mission are to observe how the crater forms, measuring the crater's depth and diameter, determining the composition of the crater interior and its ejecta and determine changes in natural outgassing produced by the impact.

The impactor is a battery-powered spacecraft that operates independently of the flyby spacecraft for just one day. It is called a "smart" impactor because, after its release, it takes over its own navigation and maneuvers into the path of the comet. A camera on the impactor captures and relays images of the comet's nucleus just seconds before collision. The impact is not forceful enough to make an appreciable change in the comet's orbital path around the Sun.

After release of the impactor, the flyby spacecraft maneuvers to a new path that, at closest approach passes 500 km (300 miles) from the comet. The flyby spacecraft observes and records data about the impact, the ejected material blasted from the crater, and the structure and composition of the crater's interior. After its shields protect it from the comet's dust tail passing overhead, the flyby spacecraft turns to look at the comet again.

There is one more very special thing about the Deep Impact mission: the public can really tag along on this one. Everyone is invited to submit their names, which will be included on a disc attached to the impactor spacecraft. To submit your name, go to http://deepimpact.jpl.nasa.gov/sendyourname/index.html.

You can make your own personalized certificate after you click the "Send My Name" button with your name entry.

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