Pluto: November 2012

Predicting the rate of escape and thermal structure of Pluto's upper atmosphere in preparation for the New Horizons Spacecraft encounter in 2015 is important for planning and interpreting the expected measurements.

Since the last Pluto volatile transport models were published (Hansen and Paige 1996), we have (i) new stellar occultation data from 2002 and 2006-2012 that have roughly twice the pressure as the discovery occultation of 1988, (ii) new information about the surface properties of Pluto, (iii) a spacecraft due to arrive at Pluto in 2015, and (iv) a new volatile transport model that is rapid enough to allow a large parameter-space search.

We present a 3D general circulation model of Pluto and Triton's atmospheres, which uses radiative-conductive-convective forcing. In both the Pluto and Triton models, an easterly (prograde) jet is present at the equator with a maximum magnitude of 10-12 m/s and 4 m/s, respectively.

On 28 November 2012 the Pluto-bound New Horizons spacecraft passed the halfway point between the orbits of Uranus and Neptune, zooming past another milepost on its historic trek to the planetary frontier.

Astronomers have used three telescopes at ESO's observatories in Chile to observe the dwarf planet Makemake as it drifted in front of a distant star and blocked its light. The new observations have allowed them to check for the first time whether Makemake is surrounded by an atmosphere.