Life in the Universe > Solar System

Missions to Comets

[Title: Missions to Comets]
[Image: Caption: suggest a nice artist's picture of a comet with a spacecraft passing (or the Rosetta lander on the surface of Wirtanen? I AM AFRAID THERE IS NOT YET ANY RELEVANT ARTIST IMAGE OF THE LANDER... THE ANCHORING SYSTEM IS STILL CHANGING, AND OF COURSE THAT WE DO NOT KNOW YET HOW THE SURFACE LOOKS)]
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Comets are believed to be very old objects that formed far out in the solar system. They contain ices and dust PARTICLES which, at least in those comets that have never come near to the Sun, must have remained unchanged since the formation of the solar system.
It is therefore of great interest to explore the comets, not only to learn more about the behaviour of the individual objects, but also to study the materials of which they consist in order to learn more about the processes that took place when our solar system was formed. Moreover, since the observations of Comet Halley in 1985-86, it is known that comets contain carbon-rich (organic) materials. Such studies have thus taken on a new dimension in connection with the search for the building blocks of life. It has even been suggested that comets may possibly carry (fossil) bacteria.
Although some of the cosmic dust particles that are picked up in the STRATOSPHERE by high-flying aircraft undoubtedly come from comets, the best way to study cometary material is obviously to send dedicated spacecraft to them in order to perform in-situ (on-the-spot) analysis.
Past missions
The first visit by a spacecraft to a comet took place on September 11, 1985, as NASA's International Cometary Explorer flew through the tail of Comet Giacobini-Zinner TO STUDY ITS INTERACTION WITH THE SOLAR WIND.
Soon thereafter, in early March 1986, an armada of no less than five spacecraft visited Comet Halley, the most famous of all comets. It has been observed by astronomers during more than 2000 years and moves around the Sun in an elliptical orbit with a period of about 75 years. The most detailed investigation, in particular of its "dirty snowball" nucleus, was carried out by ESA's Giotto spacecraft, WHICH FLEW BY IT FROM AN ALTITUDE OF ABOUT 600 KM.
Ambitious goals
One of the most ambitious future cometary missions is ESA's Rosetta that will be launched towards Comet Wirtanen in 2003, for a rendez-vous eight years later.
American missions to comets are also underway. The NASA Stardust spacecraft is now en route to Comet Wild 2. While flying through its coma in January 2004, it will capture a few micrograms of cometary dust and bring them back to Earth for detailed laboratory analysis two years later.
The NASA Deep Impact mission plans to create gigantic fireworks on the 4th of July 2005. It will impact about 350 kg of copper on the nucleus of comet Tempel 1 at high speed - this will make a big hole in the comet and will release a lot of freshly exposed cometary material. It is then the intention to perform a detailed analysis of the chemical composition of this material.
All these missions will provide fantastic wealth of new data within the next 15 years. They will give young astronomers, physicists and chemists a great chance to analyse very primitive cosmic material and, who knows, perhaps to find some of the missing links in our understanding of the formation of planet Earth. Most of all, however, it is hoped that they will also detect some of the building blocks of Life in the solar system. ] 6.3.1. The Giotto Mission to Comet Halley [Page no. 6.3.1] [Title: The Giotto Mission to Comet Halley] [Image: Caption: obviously the famous Giotto picture of the nucleus! maybe also the Padova painting?] [Text: Europe has a long tradition of cometary exploration: Giotto, the first mission to capture images of cometary nucleus was launched by ESA in 1985 and flew through the coma of Comet Halley in March 1986. Its name was a tribute to the first realistic painting of a comet, actually a fresco by the artist Giotto di Bondone made in 1301, and still visible on the wall of a chapel in Padova (Italy). The Giotto spacecraft confirmed the existence of an irregular and dark cometary nucleus and took unique images while it approached this object. On-board instruments discovered fluffy solid particles with organic compounds in the cometary coma. These observations signified a break-through in cometary science. Other spacecraft that visited Comet Halley in 1986 included the VEGA1 & VEGA2 missions (USSR) and Sakigake & Susei from Japan. Giotto flew on to encounter Comet Grigg-Skjellerup in July 1992, AND APPROACHED ITS NUCLEUS FROM AN ALTITUDE OF ABOUT 150 KM. ] 6.3.2. The Rosetta Mission to Comet Wirtanen [Page no. 6.3.2] [Title: The Rosetta Mission to Comet Wirtanen] [Image: Caption: suggest a picture of Rosetta and also of Wirtanen (ESO PR 27b/99)] An important mission to a comet will be launched by the European Space Agency (ESA) in early 2003. This mission, a cornerstone of the ESA programme, is called Rosetta. Just as the Rosetta Stone allowed Jean Francois Champollion to read the hieroglyphs of ancient Egypt, the Rosetta comet chaser will allow the scientists to read the origins of the solar system and, possibly, of Life in the solar system. The mission goal is a rendezvous with a comet named Wirtanen while it is still more than three times farther away from the Sun than planet Earth. This kind of space rendez-vous requires approaching the comet with a relative velocity almost equal to zero, and performing tricky flight manoeuvres. In-situ studies While it circles the comet, Rosetta will carry out prolonged and detailed studies of the nucleus and its environment. This takes place while the comet approaches the Sun and the surface of the nucleus is gradually heating up. At the same time, more cometary material is released - the astronomers say that it is getting more and more "active". In addition, a small module will land on the surface of the 1-km nucleus. It will deploy various miniaturised instruments to determine its physical and chemical properties. All the instruments are now being completed in European or American laboratories and will be integrated on-board the spacecraft or its lander. Asteroid fly-bys During its eight-year journey to the comet, Rosetta will also observe two asteroids during close fly-bys - they are named Otawara and Siwa .