SETI Institute Weekly Colloquium - Upcoming Speakers
Saturn's ring system is an astrophysical disk that is neither light-years away nor billions of years in the past. We can visit this disk at close range and observe a number of phenomena that also operate in disks of other kinds. As a result, we see small-scale processes that shape ring texture, connect those processes to the bodies and structures that cause them, and watch closely as the disk changes with time.
We will discuss recent Cassini observations that elucidate disk processes including 1) "self-gravity wakes" and "spiral density waves," both of which were originally proposed for galaxies but are observed with exquisite precision in Saturn's rings, 2) "propeller" features caused by 100-meter to km-sized moonlets embedded in the disk; these are the first objects ever to have their orbits tracked while embedded in a disk, rather than orbiting in free space, and hold the potential of deepening our understanding of planetary migration, and 3) irregular edge shapes in the gaps opened up by larger moons (10 km and more), which may hold clues to angular momentum transport.
Stardust was the first spacecraft ever to bring back to Earth extraterrestrial materials from beyond the Moon. It was two missions in one spacecraft. Stardust returned the first samples from a known primitive solar system body, the Jupiter-family comet Wild 2. Stardust also carried a separate collector that was exposed the interstellar dust stream for 200 days before the encounter with the comet. These tiny rocks — a trillion would fit into a teaspoon — were identified in the returned collector by a small army of more than 30,000 citizen scientists, through a project called Stardust@home. Dr. Westphal will present results of laboratory analyses of samples from both collectors, including laboratory analyses of seven particles that are likely the first individual rocks from the local interstellar medium ever identified.