Cassini Finds Interstellar Dust Around Saturn

Tuesday, 19 April 2016 - 5:36PM
NASA
ESA
Solar System
Tuesday, 19 April 2016 - 5:36PM
Cassini Finds Interstellar Dust Around Saturn
Saturn has a little piece of the universe that lies outside our solar system, as Cassini recently detected that there are traces of interstellar dust surrounding the winged planet. 

Cassini has been orbiting Saturn since 2004, and in the last dozen years has sampled many millions of dust grains in the planet's atmosphere. Now, NASA reports that a miniscule portion of that dust--36 grains, to be exact--comes from interstellar space. 

Scientists have been hoping to make this discovery ever since interstellar material was observed by the 1990s ESA/NASA Ulysses mission. The dust was found to have originated from an interstellar dust cloud--a denser-than-average region of the interstellar medium through which our galaxy is moving at a predetermined speed and direction. 

Opening quote
"From that discovery, we always hoped we would be able to detect these interstellar interlopers at Saturn with Cassini. We knew that if we looked in the right direction, we should find them," study lead author Nicolas Altobelli, Cassini project scientist at the European Space Agency, said in a statement. "Indeed, on average, we have captured a few of these dust grains per year, traveling at high speed and on a specific path quite different from that of the usual icy grains we collect around Saturn."
Closing quote

The grains were moving at extremely high speeds: over 45,000 mph, which allowed them to avoid becoming mired in our solar system by the gravity of the sun and planets to reach Saturn's orbit. By analyzing these grains with Cassini's cosmic dust analyzer instrument, the researchers found that while dust from within our solar system was mostly made of ice, these unique grains surrounding Saturn were composed of rock-forming elements such as magnesium, silicon, iron and calcium in average cosmic proportions, while sulfur and carbon were found to be less concentrated than in the cosmos in general. But most curious of all, the chemical composition was fairly uniform, which the researchers wouldn't expect to find.

Opening quote
"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 co-author Frank Postberg of the University of Heidelberg.
Closing quote

Although we don't know exactly why this uniformity, or "processing" within the interstellar medium, would take place, but they speculate that it's the result of originating from a star-forming region of the universe. As the shock waves from dying stars pass through the interstellar medium, the dust could be destroyed and then recondense in a specific way, leading to dust grains of very similar composition.
Science
Space
NASA
ESA
Solar System

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