US:A little bit of stardust falls to earth this weekend, all going well. A satellite returns from deep space tomorrow carrying a precious cargo, dust captured from a comet.
The Stardust satellite is scheduled to make a fiery re-entry through the atmosphere and then gently plop to earth by parachute at 10.12am Irish time. It will have completed an epic journey, having looped the sun three times and covered about 4.66 billion km on its way back from a visit to comet Wild-2.
The spacecraft performed its final manoeuvre early yesterday morning to put it on course for a landing in the Utah desert. It got to within 150 miles of the comet's nucleus and will have spent almost seven years in space by the time it returns.
The US Nasa (National Aeronautics and Space Administration) mission was launched from Cape Canaveral, Florida, on February 7th, 1999. Its main goal was a close encounter with Wild-2 to collect dust samples from the comet.
The dust will tell researchers much about what comets are made of and whether they carry the kinds of carbon-based substances needed to build life.
Along the way to Wild-2, however, the 56.8kg (125lb) satellite also picked up samples of the interstellar dust reaching our solar system from deep space. The particles are worth more than gold dust to the scientists who will study them.
These materials are believed to consist of leftovers from the formation of our sun and solar system. These pre-solar grains could provide clues about the evolution of the sun and planets.
Stardust used a specially designed dust mop to collect its samples. Similar to a large tennis racket, the mop carried a substance called aerogel to both capture and securely hold the minute interstellar dust and the comet grains for the journey home.
Nasa will hope for a softer landing for Stardust than the Genesis sample return mission. The satellite crash-landed in the desert on September 8th, 2004, when its parachute failed to open, although scientists were able to rescue some of its solar wind particles.
The parachute had better work, as Stardust will be setting a re-entry speed record for a manmade object, hitting the atmosphere at 46,440km/h (28,860mph). This will break the record held since May 1969 by the returning Apollo 10 command module.