COMET HaleBopp put on the best cometary display in centuries during its recent visit, but another comet is likely to become much more famous in the near future. European scientists are planning a rendezvous with Comet Wirtanen and hope to land a bundle of experiments on its surface.
The Rosetta satellite mission to Wirtanen will provide us with a wealth of new information about comets and will also give us a glimpse back in time. Comets are thought to be cosmic leftovers, chunks of the raw material from which the planets and the sun itself were made.
The mission is also important from an Irish point of view. A research team at St Patrick's College, Maynooth, led by Prof Susan McKenna Lawlor, is deeply involved in the project, working on key components of the lander which will reach Wirtanen's surface.
The Rosetta mission is named after the Rosetta Stone, the archeological find which provided a translation key that unlocked the secrets of the Egyptian hieroglyphs.
Scientists hope that the Rosetta satellite will open up a new understanding of comets, one of the most puzzling of astral bodies.
"Comets can give us a clue as to how the solar system began," explained Rosetta project scientist Dr Gerhard Schwehm. Kept safe in the frozen reaches beyond the solar system, they represent pristine samples of the material from which the planets were built.
The mission itself is ambitious by any standards. "It pushes the technology to its limits because it is a fairly long mission and because the rendezvous will happen so far away from the sun, explained Dr Schwehm.
The satellite will be solar powered but will have to operate at distances of up to 465 million miles from, the sun. So special highly sensitive solar panels have been designed for Rosetta.
Operating beyond the orbit of Mars, sometimes when on the far side of the sun, communications will be difficult.
It will have a high degree of robotic self reliance and be capable of hibernating for years at a time without attention. It will also need special insulation band "central heating" to keep it from freezing in the emptiness of space.
Liftoff is planned for 2003, and it will take eight years to reach Comet Wirtanen. Flight controllers will use the gravity of Mars and the Earth like a sling shot to impel Rosetta into position, looping Mars once and the Earth twice.
On the way it will visit two asteroids, giving us a closer view of these chunks of space rock.
Rosetta will first encounter the comet in 2011 and go into orbit in April 2012, flying between six and 30 miles above its surface. For 18 months it will send back pictures and data as the comet begins to melt from approaching the sun.
The most demanding part of the flight will come when the satellite releases a lander which will anchor itself to the comet.
It will sample the surface and then drill down a metre to analyse what lies just beneath. It will also be able to hop about to sample other parts of the comet.
Prof McKenna Lawlor is a member of the steering committee for the lander and her group's contribution is central to the success of this part of the flight. Maynooth's COSAC experiment, carried on the lander, will study the chemistry of Wirtanen, sampling both gases and ice samples which will be melted in onboard ovens.
Her campus company, Space Technology Ireland Ltd, established in 1986, is separately responsible for providing some of the equipment that will allow Rosetta to communicate with the lander. This device will store, transmit and decode orders sent by Rosetta and data returned by the lander.
The lander will be recording when Wirtanen loops the sun, watching as it brews up its coma and tail. This will give scientists a clear "inside view of the comet nucleus.
Rosetta will relay data from Wirtanen for about 18 months. By 2014 it will become just another piece of space junk.
But scientists will he analysing the data for decades to come.
