Starship Asterisk*

[img3="Of the millions of dust grains Cassini has sampled at Saturn, a few dozen appear to have come from beyond our solar system. Scientists believe these special grains have interstellar origins because they moved much faster and in different directions compared to dusty material native to Saturn. Credit: NASA/JPL-Caltech"]http://www.jpl.nasa.gov/images/cassini/ ... 414-16.jpg[/img3][hr][/hr]

NASA's Cassini spacecraft has detected the faint but distinct signature of dust coming from beyond our solar system. The research, led by a team of Cassini scientists primarily from Europe, is published this week in the journal Science.

Cassini has been in orbit around Saturn since 2004, studying the giant planet, its rings and its moons. The spacecraft has also sampled millions of ice-rich dust grains with its cosmic dust analyzer instrument. The vast majority of the sampled grains originate from active jets that spray from the surface of Saturn's geologically active moon Enceladus.

But among the myriad microscopic grains collected by Cassini, a special few -- just 36 grains -- stand out from the crowd. Scientists conclude these specks of material came from interstellar space -- the space between the stars.

Alien dust in the solar system is not unanticipated. In the 1990s, the ESA/NASA Ulysses mission made the first in-situ observations of this material, which were later confirmed by NASA's Galileo spacecraft. The dust was traced back to the local interstellar cloud: a nearly empty bubble of gas and dust that our solar system is traveling through with a distinct direction and speed. ...

• Science 352(6283):312 (15 Apr 2016) DOI: 10.1126/science.aac6397

neufer wrote:Why can't we build a wall to keep out interstellar dust (and make Alpha Centauri pay for it)