NASA's Cassini orbiterhas become the first spacecraft to determine the composition of dustparticles originating outside of our solar system. The discoverygrants a rare insight regarding the processes that may be occurringin the interstellar medium.
Cassini's longevity hasallowed the spacecraft to undertake a wide variety of roles sincearriving in the Saturnian system in 2004. The probe has characterizedthe ringed gas giant and her moons, as well as using its Cosmic DustAnalyzer (CDA) instrument to examine particles ejected from vast geysers in the southern hemisphere of Enceladus.
Now, among themultitude of particles harvested from Enceladus, theCassini science team have detected 36 particles that originated frombeyond our solar system. Had the particles not been intercepted bythe CDA, the velocity of the micrometeorites, which were thought tobe moving in excess of 45,000 mph (72,000 km/h), would likely havepassed straight through our solar system.
Upon analysis, itbecame apparent that the particles bore a striking resemblance to oneanother. Furthermore, the CDA determined that the samples containedan abundance of known rock forming elements such as magnesium andiron, yet exhibited a deficiency of minerals such as sulphur andcarbon compared to the cosmic norm.
The uniformity of theparticles surprised the Cassini team. Micrometeorites of the typerecently detected by the spacecraft are thought to be created anddistributed through the death throws of innumerable stars. The sheervariety of progenitor stars were expected to create dust particleswith widely contrasting compositions. Yet, this trend is not apparentin the particles captured by Cassini.
The uniformity could beexplained were it to be proved that there is some process at work ininterstellar space that is processing the particles after they arecreated. The Cassini team has put forward the theory that, as thenewly-created particles travel, subsequent supernovae send shockwavesthrough the interstellar medium, destroying and reconstructing thedust grains multiple times. This would have the effect of mixing thematerials into the particles we see today.
Our knowledge of theprocesses that take place in the interstellar medium is stillrelatively juvenile. To date, humanity has succeeded in sending onlyone spacecraft beyond the heliosphere – the name given to the borderof our Sun's influence, and the beginning of the realm beyond.
Voyager one, which hasbeen charting interstellar space since its entry (depending on who you asked) in August 2012, will soon be joined by itstwin, Voyager 2. Together, they serve as our most distant emissaries,working to shed light on mankind's new frontier, and in so doinggather data to support theories such as those posed by the Cassiniscience team.
Source: NASA