Graphene in Titan
- 1Physical Research Laboratory, Ahmedabad, India
- 2Center for Nanoscience, Indian Institute of Science, Bangalore, India
- 3Academia Sinica, Institute of Astronomy and Astrophysics, Taiwan
- 4National Synchrotron Radiation Research Center, Hsinchu, Taiwan
- 5University of Rennes-1, CNRS, IPR (Institute de Physique de Rennes), Rennes, France
- 6Indian Centre for Space Physics, Kolkata, India
- 7Department of Medical Research, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan.
- 8Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai, India
- 9International Space University, Strasbourg, France
- 10School of Physical Sciences, University of Kent, Canterbury, UK
Benzene (C6H6) ice has been observed in the Titan’s stratosphere [1], and benzonitrile (C6H5CN) is a possible constituent in the benzene and nitrogen-rich environment of Titan’s atmosphere [2]. The energetic processing of such aromatic molecules can synthesize large and complex aromatic molecules such as the Polycyclic Aromatic Hydrocarbons (PAHs). To-date a number of laboratory experiments have reported the formation of complex organics from the energetic processing of aromatic molecules [3-6]. In particular, Scanning Electron Microscopy (SEM) micrographs of the residues resulting from irradiated benzene ices are found to contain geometrically shaped particles [6]. Therefore, by employing electron microscopes, we can understand the physical nature of the dust leftover from the aromatic molecule irradiation.
In the present investigation, we subjected benzonitrile ice made at 4 K to vacuum ultraviolet (9 eV) radiation at two beamlines, BL03 and BL21A2 of Taiwan Light Source at NSRRC, Taiwan. After irradiation, the ice was warmed to room temperature, which left a brownish residue on the Potassium Bromide (KBr) substrate. The VUV spectrum of the residue is observed to have characteristic aromatic signatures. The residue is then transferred to a quantifoil grid for High-Resolution Transmission Electron Microscope (HR- TEM) imaging. HR-TEM micrographs revealed the presence of graphene in the residue. This result suggests that N-graphene could be present in benzene and nitrogen-rich icy clouds of Titan. The high masses observed by the Cassini plasma spectrometer in Titan’s atmosphere could then be attributed to the presence of N-graphene along with the more common tholins [7].
References
[1] Vinatier S. et al. (2018) Icarus, 310, 89.
[2] Loison J. C. et al. (2019) Icarus 329, 55.
[3] Strazzulla G. et al. (1991) A&A, 241, 310.
[4] Callahan M. P. et al. (2013) Icarus, 226, 1201.
[5] James R. et al. (2019) RSC Adv. 9 (10), 5453.
[6] Rahul K. K. et al. (2020) Spectrochim. Acta A, 231, 117797.
[7] Rahul K. K. et al. (2020) arXiv:2008.10011.
How to cite: Kushwaha, R. K., Mallya, A., Sahu, D., Meka, J. K., Chou, S.-L., Wu, Y.-J., Gupta, D., Das, A., Lo, J.-I., Cheng, B.-M., Rajasekhar, B. N., Bhardwaj, A., Hill, H., Padmanabhan, J., Mason, N. J., and Sivaraman, B.: Graphene in Titan, European Planetary Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-480, https://doi.org/10.5194/epsc2021-480, 2021.
