Europlanet Science Congress 2020
Virtual meeting
21 September – 9 October 2020
Europlanet Science Congress 2020
Virtual meeting
21 September – 9 October 2020
EPSC Abstracts
Vol.14, EPSC2020-960, 2020
https://doi.org/10.5194/epsc2020-960
Europlanet Science Congress 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Carbon-grain sublimation: a new top-down component to protostellar chemistry

Merel van 't Hoff1, Edwin Bergin1, Jes Jorgensen2, and Geoffrey Blake3
Merel van 't Hoff et al.
  • 1University of Michigan, Astronomy, United States of America (mervth@umich.edu)
  • 2University of Copenhagen, Denmark
  • 3California Institute of Technology, United States of America

One of the main goals in the fields of exoplanets and planet formation is to determine the composition of terrestrial, potentially habitable, planets and to link this to the composition of protoplanetary disks. A longstanding puzzle in this regard is the Earth's severe carbon deficit; Earth is 2-4 orders of magnitude depleted in carbon compared to interstellar grains and comets. The solution to this conundrum is that carbon must have been returned to the gas phase in the inner protosolar nebula, such that it could not get accreted onto the forming bodies. A process that could be responsible is the sublimation of carbon grains at the so-called soot line (~300 K) early in the planet-formation process. I will argue that the most likely signatures of this process are an excess of hydrocarbons and nitriles inside the soot line around protostars, and a higher excitation temperature for these molecules compared to oxygen-bearing complex organics that desorb around the water snowline (~100 K). Moreover, I will show that such characteristics have indeed been reported in the literature, for example, in Orion KL, although not uniformly, potentially due to differences in observational settings or related to the episodic nature of protostellar accretion. If this process is active, this would mean that there is an heretofore unrecognized component to the carbon chemistry during the protostellar phase that is acting from the top down - starting from the destruction of larger species - instead of from the bottom up from atoms. In the presence of such a top-down component, the origin of organic molecules needs to be re-explored. 

How to cite: van 't Hoff, M., Bergin, E., Jorgensen, J., and Blake, G.: Carbon-grain sublimation: a new top-down component to protostellar chemistry, Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-960, https://doi.org/10.5194/epsc2020-960, 2020