Rosetta prototype flies on Stardust
7 February 1999Congratulations from the Rosetta team on the successful launch of Stardust!What do the Giotto, Vega, Stardust, Contour and Rosetta comet missionsall have in common? The answer is they all carry European-builtinstruments designed to study what comet dust is made of.
The latest in this long line of dust analysers is flying on board NASA's Stardust spacecraft which lifted off from Florida on 7 February. The instrument, known as CIDA (Comet and Interstellar Dust Analyser) is a prototype of an instrument which will eventually fly on ESA's Rosetta spacecraft. Principal Investigator for both instruments is Dr. Jochen Kissel of the Max-Planck-Institut f|r Extraterrestrische Physik (MPE) in Garching, Germany.
Both the COSIMA (Cometary Secondary Ion Mass Analyzer) instrument on Rosetta and CIDA (on Stardust) are known as time-of-flight mass spectrometers. Their purpose is to intercept comet dust and perform real-time analysis of their composition as the particles hit the instrument.
When a high speed dust particle hits the target on CIDA, ions (atoms or molecules with an electrical charge) are naturally produced. On Rosetta the impact velocity of the dust will be so small that the experiment will not work unless the particles are bombarded with ions from an ion source.
In both cases, the ions from the dust are extracted by an electrostatic field. The analyser then measures the time each ion takes to reach the detector. Heavier ions take longer to travel through the instrument than lighter ones, so their masses can be calculated from their flight times.
CIDA was made in Germany by von Hoerner & Sulger, GmbH under contract to the German Space Agency. The CIDA software was developed by the Finnish Meteorological Institute.
Stardust will flyby comet Wild 2 on 2 January 2004. It will gather cometary and interstellar dust samples, which will be returned to Earth two years later for analysis.
CIDA will also fly on NASA's Contour mission to Comets Encke, SW3 and d'Arrest. Contour will launch in July 2002.
The COSIMA experiment on Rosetta will study the chemical composition of dust emitted by Comet Wirtanen.
Detailed information will be returned on:
- The elemental, molecular and isotopic composition of cometary dust particles.
- The chemical states of the particles.
- The organic (carbon-based) and inorganic phase of the dust particles.
Results from the ESA's Giotto mission (PIA instrument) and Russia's Vega missions (PUMA) to Halley's Comet revealed the presence of so-called CHON particles, which were predominantly made of carbon, hydrogen, oxygen and nitrogen. Other comet particles are similar in composition to an ancient, almost unaltered type of meteorite known as a carbonaceous chondrite. Scientists would like to know more about these particles because they may have contributed to the beginning of life on Earth - and, perhaps, other planets.
COSIMA will also allow scientists to learn more about the origin and evolution of comets. Previous studies indicate that comets were born about 5 billion years ago in the cold, outer reaches of a giant nebula (dust cloud) which enveloped the Sun. They grew from ices which condensed onto interstellar dust particles.
There are thought to be millions of comets in the dark outer reaches of the Solar System, far beyond Pluto. We only see them when they head towards the Sun and produce tails as they start to vapourise.