Comet dust

By studying grains of comet dust, scientists hope to increase their understanding of the Solar System. 

COMET DUST

These scientists are studying dust—but not just ordinary dust particles. 
These ones come from a comet. In 2004, the Stardust probe went to within 200 km of the comet Wild-2 and dived in amongst its hair. 
The spaceship then deployed an ingenious system of collectors to trap the comet dust escaping from the core. 

Janet Borg – Astrophysicist IAS/Soleil Synchrotron - SMIS line 
The Americans call it a huge tennis racquet with a 40 cm diameter, consisting of 130 identical collectors in a material called the aerogel, which is like a kind of glass fume. 
It is a very, very low-density material with the special property of slowing down the particles that hit it, but without destroying them. 

That is why intact comet dust could be brought back to Earth in 2006. After careful extraction from the aerogel, this precious harvest was sent to laboratories all over the world. 
Janet Borg's team is delighted to have received 4 new grains measuring less than 15 microns in diameter, i.e. 1/10th the thickness of a hair. To study them, the scientists have chosen infrared spectrometry. 


Janet Borg – Astrophysicist IAS/Soleil Synchrotron - SMIS line 
Infrared radiation is non-destructive, since it has a high wavelength. 
It is low-energy, and so when it passes through the particle, it does not change the structure of the particle. 


Infrared radiation also makes each molecule vibrate in a unique way. 
This tells the scientists the mineralogical composition of the dust particles, and whether any organic matter or water is present. 
Why use infrared radiation produced by such a big machine as the Soleil Synchrotron? 


Janet Borg 
The advantages of Synchrotron radiation come mainly from its strong brightness; it is extremely intense over a width of just a few microns (2 to 4 microns). 

Whilst classic infrared radiation would give the overall composition of these dust particles, Synchrotron radiation will let us create a real cartography of the sample. 
Scientists can then find out if the particles are homogeneous or an agglomeration of little grains. Like all studies carried out on comet dust, this will improve our understanding of comet formation, providing insight into the formation of the Solar System. 


Janet Borg 
The Solar System was formed 4.6 thousand million years ago, and started with the cloud that collapsed which created the Sun, and then when the Sun was there, all the rest gradually collected and made 7 or 8 planets, and then there was residue repelled by a vortex, by winds pushing it out, and that is what the comets are. 
For us, comets are witnesses to the origins of the Solar System.