Exoplanet secondary atmosphere loss and revival.

The next step on the path toward another Earth is to find atmospheres similar to those of Earth and Venus-high-molecular-weight (secondary) atmospheres-on rocky exoplanets. Many rocky exoplanets are born with thick (>10 kbar) H-dominated atmospheres but subsequently lose their H; this process has no known Solar System analog. We study the consequences of early loss of a thick H atmosphere for subsequent occurrence of a high-molecular-weight atmosphere using a simple model of atmosphere evolution (including atmosphere loss to space, magma ocean crystallization, and volcanic outgassing).

Multiplexed modulation of behavioral choice.

Stimuli in the environment, as well as internal states, influence behavioral choice. Of course, animals are often exposed to multiple external and internal factors simultaneously, which makes the ultimate determinants of behavior quite complex. We observed the behavioral responses of European leeches, Hirudo verbana, as we varied one external factor (surrounding water depth) with either another external factor (location of tactile stimulation along the body) or an internal factor (body distention following feeding).