It was a quiet day at work today so I poked through the list of papers to be
presented at the upcoming DPS meeting in Madison Wisconsin, Oct. 10-13
and I picked up a few interesting items.
i) It appears that large Jupiter sized gas giant planets are formed by direct
condensation from the planetary disk.
The other major competing theory is that the gas giant's first accrete
from planetisimals. Then, when the core planet reaches several earth masses,
it starts accumulating gas from the surrounding nebular. There is evidence
for both theories.
It's calculated that the direct condensation mechanism occurs much more
rapidly than the planetisimal formation mechanism.
Spectrographic observations of TMC-1, the young binary system that is
ejecting a Jup size planet, indicate the system is too young to have formed a
jupiter sized planet by the planetisimal accreation mechanism.
ii) David Grinspoon is giving a talk and paper on the (postulated)
climatalogical history of Venus.
If Venus wasn't volcanically active, belching out water and sulfur
compounds, it wouldn't have a cloud deck. The aforementioned compounds react with surface rocks in a geologically short time and remove themselves from the atm. This changes the greenhouse effect quite radically.
Variation in Venus's greenhouse effect in turn effect the surface temp.,
which in turn effects the plasticity of the crust, which effects the amount of
volcanism. Over geological times there is a feed back loop between the
climate and the geologic state of Venus.
Venus may have been several very different planets in times' past, being
both hotter and cooler than it is now.
iii) The presence of earth sized extra-solar planets may be detected through
the perturbations they bring about in the density of their systems zodiacal
dust clouds. These dust clouds may be observed by the next generation of IR