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The Question

(Submitted January 06, 1997)

I have an idea for space exploration. The idea in theory is simply to piggy back a satellite or probe to a comet with a travel time of 10 years or less. If there is such a comet. When the comet returns, download any and all information gathered. I haven't quite figured out how it would be attached.

I would like the e-mail address of someone I can correspond with on this. I need to know if this would work, or why it would not, in layman's terms, for I am not a scientist of any sort. Can you direct me to the right place?

The Answer

What an interesting idea! There are indeed short period comets. Comet Enke has a period of 3.3 years, and comet Wild-2 takes 6.15 years to make one complete trip around the Sun. In fact, there is a mission called STARDUST which is a collaboration of NASA/Jet Propulsion Laboratory, Lockheed Martin, and University of Washington, that will launch a low-mass probe to fly through the tail of comet Wild-2 and collect samples of that material. You should check out the web-page for this project, at They have a lot of detailed information about the project, both the scientific goals and the mechanics of the orbit, as well as a good amount of educational material related to the project.

As far as actually landing a probe on a comet, that may be pretty tricky. The nucleus of the comet can be tumbling around, due to the release of gases on the surface of the comet. This can make the attempted landing very difficult. In addition, once the probe was on the surface of the nucleus it could possibly be damaged by the outgassing. If this outgassing is not what you were planning to study, it could disturb the results of the experiments you were interested in. There is an ESA mission being planned that will land a probe on the surface of comet Wirtanen (see This mission is called ROSETTA.

It would be possible to place your probe into an orbit that is similar to the comet's orbit, either in front of it somewhat, or lagging behind the comet. By the time you've got the probe near the comet, you've already placed the probe in the comet's orbit and it will make its way round the inner solar system with the comet.

Comets are important to study because they are the oldest, most primitive bodies in our Solar System, and are thus the earliest record of the formation of the solar system. The material that comets are composed of is very rich in organic material; it is for this reason that comets are thought to possibly be involved in the origin of life on Earth. I encourage you to stay enthusiastic about comets, and new, never-been-done-before ideas about exploring them.

Here at Goddard's Exploration of the Univsrse Division, we have experience mainly with spacecraft that are launched into orbit around the Earth to observe stars and galaxies in the X-ray and gamma-ray regions of the spectrum. We don't have expertise at planning and designing comet encounter missions, so what I say below is mainly an educated guess. The folks at JPL who are working on the STARDUST mission will know much more, and I encourage you to talk to them about your idea.

So for further information, try sending your question to, or to the questions and comments section of the JPL main page at:

Padi Boyd,
for Imagine the Universe!

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