APEX this week: Titan seen by VLT-ESPRESSO

Our Astrobiology and Planetary Exploration (APEX) seminar series this Friday 20th February at 13:00 GMT features the following talk:

• Rafael Rianço Silva (Lisbon / UCL / KCL) - Titan seen by VLT-ESPRESSO: The first search for minor chemical compounds with Ultra-High-Resolution Visible spectra on Titan’s atmosphere

An abstract for Rafael’s talk can be found below.

Please note that APEX continues at Fridays at lunchtimes this term from 1-2 pm GMT, in Birkbeck room MAL 612, 6th floor of the Birkbeck main Malet Street building, and online (unless specified ‘online only’ below).

A hybrid (in-person and online) format will continue this term but, of course, we warmly encourage in-person attendance to support our visiting speakers.

Details of the forthcoming APEX programme can be found at the link below. The latest information will be advertised in advance of each meeting.  If you are not on our regular mailing lists and are interested in attending these seminars, please contact joanna.fabbri AT ucl.ac.uk.

Abstract

The atmosphere of Titan is a unique natural laboratory for the study of atmospheric evolution and photochemistry akin to that of the primitive Earth, with a wide array of complex molecules discovered through infrared and sub-mm spectroscopy. A recent work by our team has shed light on Titan’s poorly explored visible High-Resolution Spectrum,  identifying tens of previously unknown methane visible high-resolution features and obtaining the first tentative detection of C3 on Titan through its 405 nm “comet”-band.

Taking this study one step further, we observed Titan with VLT-ESPRESSO at its Ultra High-Resolution (R = 190 000) in December 2024 - the observations of Titan with the highest spectral resolution conducted so far. This unprecedented spectral resolution at high signal-to-noise ratio coupled with our original Doppler-based line detection method allowed us to retrieve an updated empirical, low Temperature ultra-high resolution linelist of methane, from 400 nm to 780 nm, with thousands of new CH4 lines, for which no similar theoretical linelists are yet available. Interestingly, these newly detected individual absorption lines explain previous low-resolution visible methane absorption bands. Beyond methane, these observations associated to an updated C3 linelist enabled us to confirm the detection of C3 on Titan’s atmosphere, as predicted by photochemical models. 

This study of Titan’s atmosphere with ultra-high-resolution visible spectroscopy presents a unique opportunity to observe a planetary target with a CH4-rich atmosphere, from which CH4 optical proprieties can be studied. It also showcases the use of a close planetary target to test new methods for chemical retrieval of minor atmospheric compounds, in preparation for upcoming studies of cold terrestrial exoplanet atmospheres.

Links 

• Rafael Rianço Silva’s LinkedIn profile
• APEX programme for this term
• Recordings of previous APEX talks

APEX Seminars

The Astrobiology and Planetary Exploration (APEX) seminar series takes place this term on Friday lunchtimes, from 1-2pm, in Birkbeck room MAL 612, on the 6th floor of the Birkbeck main Malet Street building, and online.  As in previous years, we will operate a hybrid (online and in-person) model for both speakers and attendees. Details of the forthcoming APEX programme can be found via the link below.

• Link to further information about our APEX seminars

Some of our past APEX talks can also be viewed online.