Alien invasion in Solar System
The Solar System has been invaded by aliens. But there is little need for panic, as the interlopers are 36 tiny grains of stardust passing through from interstellar space. Nasas Cassini spacecraft, which has been orbiting Saturn since 2004, has detected a faint, but distinct signature of dust which has come from beyond our own star system.
The orbiter, which is studying the ice giant, has been collecting and sampling dust grains using its on-board analyser. The vast majority were ejected in jets which spray from the surface of Saturns geologically active moon Enceladus. But among the myriad microscopic grains collected by Cassini, a special few - just 36 grains - stood out from the crowd. Scientists have concluded that these specks of material came from interstellar space - the space between the stars.
The grains look distinct from Solar System dust because they are travelling at high speed and follow a completely different trajectory. It is not the first time that alien dust has been spotted in the Solar System. In the 1990s, the ESA/NASA Ulysses mission made the first in-situ observations of this material, which were later confirmed by NASAs Galileo spacecraft.
From that discovery, we always hoped we would be able to detect these interstellar interlopers at Saturn with Cassini, said Dr Nicolas Altobelli, Cassini project scientist at the European Space Agency and lead author of the study. We knew that if we looked in the right direction, we should find them.
However, unlike Ulysses and Galileo, Cassini was able to analyse the composition of the dust for the first time, showing it to be made of a very specific mixture of minerals, not ice. The dust grains were speeding through the Saturn system at over 45,000 mph, fast enough to avoid being trapped inside the solar system by the gravity of the sun and its planets.
The grains all had a surprisingly similar chemical make-up, containing major rock-forming elements like magnesium, silicon, iron and calcium in average cosmic proportions.
Cosmic dust is produced when stars die, but with the vast range of types of stars in the universe, we naturally expected to encounter a huge range of dust types over the long period of our study, said Dr Frank Postberg of the University of Heidelberg, a co-author of the paper and co-investigator of Cassinis dust analyser.
The authors speculate that dust in a star-forming region could have been destroyed, then recondensed multiple times as shock waves from dying stars passed through.
Were thrilled Cassini could make this detection, given that our instrument was designed primarily to measure dust from within the Saturn system, as well as all the other demands on the spacecraft, said Marcia Burton, a Cassini fields and particles scientist at NASAs Jet Propulsion Laboratory in Pasadena, California, and a co-author of the paper. The Cassini-Huygens mission is a cooperative project of NASA, ESA and the Italian Space Agency.
The long duration of the Cassini mission has enabled us to use it like a micrometeorite observatory, providing us privileged access to the contribution of dust from outside our solar system that could not have been obtained in any other way, added Dr Altobelli.
Source: The Telegraph
