- Published on Monday, 08 January 2018 08:00
In section 10: Planets and planetary systems
Dome C ultracarbonaceous Antarctic micrometeorites: Infrared and Raman fingerprints
Interplanetary dust particles travel across the solar system and represent the largest mass flux of extraterrestrial material falling on the Earth. Their small sizes (hundreds of microns or less) make their collection and analysis challenging. Dartois et al. analyze a small subset of these particles acquired from the Concordia/CSNSM micrometeorites collection performed in Antarctica, the so-called UltraCarbonaceous Antarctic MicroMeteorites (UCAMMs). These particles contain a large amount of nitrogen-rich organic matter not found elsewhere in extraterrestrial matter and probably originating from the outer solar system. The analyses show that both the C/Si and N/C abundance ratios in UCAMMs are the highest found in the solar system and are above the interstellar medium cosmic abundances. These finding are most important to understand the composition of outer solar system objects and the origin of primitive organics.
- Published on Friday, 05 January 2018 08:00
In section 6. Interstellar and circumstellar matter
Direct mapping of the temperature and velocity gradients in discs
The authors present a new, empirical method for locating the CO-isotopologue emitting surfaces from high spectral and spatial resolution ALMA observations of protoplanetary disks. They have applied this method to the disk surrounding IM Lupi, and present the first model-independent measurements of the radial and vertical gradients of temperature and velocity in a protoplanetary disk. The derived disk structure is consistent with that of an irradiated self-similar disk, in which the temperature increases and the velocity decreases towards the disk surface. The authors have also mapped the vertical CO snow line, which is located at approximately one gas scale-height at radii between 150 and 300 au, with a CO freeze-out temperature of 21 ± 2 K. In the outer disk (>300 au), the velocity rotation field becomes significantly sub-Keplerian, in agreement with the expected steeper pressure gradient. This should result in a very efficient inward migration of large dust grains, explaining the lack of millimeter continuum emission beyond 300 au.