Super-Earth and mini-Neptune laboratory haze analogues and their effects on exoplanetary atmospheric modeling

Thursday 5 July, 16:50

Using a custom PHAZER (Planetary HAZE Research) laboratory set-up, we experimentally simulated nine different metallicity (100x, 1000x, and 10000x solar) and temperature (300, 400 and 600 K) regimes of exoplanetary atmospheres. These conditions are a reasonable starting point for the atmospheric phase space of super-Earths and mini-Neptunes. These kinds of planets are the most common in our galaxy, yet without one in our own Solar System, laboratory data is necessary to provide many physical and chemical properties pertaining to possible aerosols in their atmospheres. These properties have implications for the radiative transfer from the top of the atmosphere to the surface, for the feasibility of observations from the Hubble Space Telescope (HST) and the upcoming James Webb Space Telescope (JWST), and for possible exoplanetary habitability. Photochemical haze analogues formed in all nine of our experiments. We analyzed these laboratory products with a suite of techniques, including atomic force microscopy, very high resolution mass spectrometry, and elemental combustion analysis. These particles were found to contain complex organics, with particle sizes in the Rayleigh scattering regime for remote sensing with JWST and HST. Additionally, the exoplanetary haze analogues were found to have very high carbon-to-nitrogen ratios and extremely low carbon-to-oxygen ratios compared to PHAZER’s standard Titan haze analogues. Using these laboratory data, we utilize a version of the CHIMERA (CaltecH Inverse ModEling and Retrieval Algorithms) modeling code to explore the effects these haze analogues have on the spectra of atmospheres of smaller, temperate exoplanets, including those of the recently discovered TRAPPIST-1 system.

Submitted by