Weekly Colloquium at the SETI Institute

While the prevalence of stellar multiplicity has been known for many decades, it is now becoming increasingly clear that planetary systems are also frequent around Main Sequence stars. This raises the natural question of the connection between stellar multiplicity and planet formation, a topic that was mostly ignored until the last few years. Does the presence of a stellar companion alter, prevent or promote the formation of planets? In which way? Characterizing observational trends as a function of the stellar companion's mass and orbital properties can help identify the most important physical effects induced by the companion, if any. In this talk, I will review some key results from a number of recent surveys based on the Spitzer, Kepler and Herschel space observatories, as well as ground-based facilities. Building on these surveys, I will draw a global picture of our current understanding of the subject and will propose that, while planetary systems exist in a very diverse range of multiple stellar systems, they may not all form through the same process.

On April 22, 2012, a 1/4 Hiroshima bomb detonation was heard in a wide area around Lake Tahoe. A small few meter sized asteroid crashed in our atmosphere, broke in fragments, pieces of which were seen falling down over the Colama/Lotus region by Doppler weather radar. This is right above Sutter's Mill, where the first gold was discovered by James Marshall on January 24, 1848. This led to the California Gold Rush that shaped our state as it is today. The recent fall of the meteorites has created a second rush in the area, not unlike the gold rush days of lore, now many are trying to recover the precious space rocks. Those turn out to be of a primitive carbonaceous chondrite type, the very meteorites that scientists love to study to learn about prebiotic compounds for the origin of life. SETI Instittue meteor astronomer Dr. Peter Jenniskens, who runs a night-time video surveillance network in that area to map meteor showers and who found the second recovered meteorite from this fall, will talk about the efforts made by NASA Ames Research Center and the SETI Institute to coordinate the recovery and learn as much as possible about the asteroid that shook people's imagination.

It is clear that the chondritic meteorites - those having essentially solar composition - carry unique information about the origin and early history of the solar system and the materials from which the planets formed. Yet it is a highly complex record that centuries of work and highly sophisticated modern techniques have not been able to decipher. Even the most fundamental issues, the origin of the chondrite classes and the origin of the chondrules that distinguish the meteorites from other materials, are still disputed.

Dr. Sears will argue that recent data from spacecraft on the nature of asteroid surfaces, advances in determining the chronology meteorites and their components, experiments flown on NASA's microgravity facility (the vomit comet), and the lunar samples returned from the Fra Mauro region of the Moon, make it clear that chondrules are impact melt spherules and the classes are caused by metal-silicate fractionation on asteroidal surfaces. In other words, the chondritic meteorites owe their major properties to asteroidal processes and that we must see through these to understand the information they carry about the early solar system and beyond. 

Seismic waves have been for long time the only messenger reporting on the
conditions deep inside the Earth. While global seismology provides amazing
details about the structure of our planet, it is only sensitive to the mechanical
properties of rocks and not to their chemical composition. In the last few years
KamLAND and Borexino have started measuring anti-neutrinos produced by
Uranium and Thorium inside the Earth.

Such "Geoneutrinos" double the number of tools available to study the Earth's
interior, enabling a sort of global chemical analysis of the planet, albeit for two
elements only.

Dr. Gratta will discuss the results of these new measurements and put them in
the context of the Earth Sciences.