Cassini Scientist on Cosmic Dust Analyzer
Right now we are excited that we collected many mass spectra of fresh dust emerging from Enceladus. Mass spectra provide information about the composition of the particles. We obtained about 1,500 spectra during the flyby.
We just started the data reduction process which may take some time. Like many of you, we are all eager to know what this data are telling us; however our data require careful analysis and interpretation.
Our mass spectrometer is not like instruments you find in university labs. In space we cannot just catch the particle and prepare it carefully for examination– the particles hit the detector with a speed of about 18 kilometers per second (40,000 miles per hour). Instead, we analyze the composition of the plasma created by the striking particles. The plasma constituents are separated in a strong electric field and accelerated toward a multiplier at the instrument centre. From the ions’ time of flight we get the ion masses and finally the composition of the particle–in theory. In reality things are much more difficult because within the plasma, the ionized atoms and molecules react with each other and form new compounds. Thus, to interpret an impact ionization mass spectrum correctly we have to understand the chemistry going on in the impact plasma. In other words, things aren’t always clear cut: a Carbon Monoxide (CO) reading does not necessarily imply that the grain really contains CO.
We are working hard in Heidelberg and as soon as we are certain of our results, we will share it with all of you. This could take several weeks. So we wait patiently for the news to unfold on this tiny moon.
–Sascha from Heidelberg, Germany