Identification of carbon dioxide in an exoplanet atmosphere

Carbon dioxide (CO2) is a key chemical species that is found in a wide range of planetary atmospheres. In the context of exoplanets, CO2 is an indicator of the metal enrichment (that is, elements heavier than helium, also called ‘metallicity’), and thus the formation processes of the primary atmospheres of hot gas giants. It is also one of the most promising species to detect in the secondary atmospheres of terrestrial exoplanets. Previous photometric measurements of transiting planets with the Spitzer Space Telescope have given hints of the presence of CO2, but have not yielded definitive detections owing to the lack of unambiguous spectroscopic identification. Here we present the detection of CO2 in the atmosphere of the gas giant exoplanet WASP-39b from transmission spectroscopy observations obtained with JWST as part of the Early Release Science programme. The data used in this study span 3.0–5.5 micrometres in wavelength and show a prominent CO2 absorption feature at 4.3 micrometres (26-sigma significance). The overall spectrum is well matched by one-dimensional, ten-times solar metallicity models that assume radiative–convective–thermochemical equilibrium and have moderate cloud opacity. These models predict that the atmosphere should have water, carbon monoxide and hydrogen sulfide in addition to CO2, but little methane. Furthermore, we also tentatively detect a small absorption feature near 4.0 micrometres that is not reproduced by these models

Major FA reduction in hippocampal commissure and corpus callosum of BTBR white matter.

<p>Voxelwise significant FA differences between BTBR (N = 9) versus B6 (N = 9, Z = 1.96, pc = .01). Representative T2-weighted anatomical images from a BTBR subject (top row) are shown for comparison. [CC: corpus callosum; DHc: dorsal hippocampal commissure; Fmi: Forceps minor of the corpus callosum].</p

Post-MRI blood gas levels.

<p>p_aCO₂ partial pressure of arterial CO₂ measured at the end of the fMRI scan. p_aCO₂ partial pressure of arterial CO₂ measured at the end of the fMRI scan. Arterial blood gas values are expressed in mmHg (mean ± SEM).</p

Reduced basal functional activity in the cortex of BTBR mice.

<p>Coronal view of the brain regions exhibiting increased (yellow-red) or reduced (blue) bCBV in BTBR (N = 10) versus B6 control subjects (N = 10, Z>3.1, pc = .01) [Acb: nucleus accumbens; Hyp: hypothalamus; Ins/Pir: insular/piriform cortex; mPFC: medial prefrontal cortex; Sp: septum; Ss: somatosensory cortex; Th; thalamus; Rs: retrosplenial cortex; VDb: ventral diagonal band].</p

Major white matter reorganisation in BTBR mice.

<p>Diffusion tensor tractography of white matter in a representative B6 (left) and BTBR (right) subject. Only white matter tracts originating from regions exhibiting statistically significant FA alterations are displayed [CC: corpus callosum; DHc: dorsal hippocampal commissure; Fmi: Forceps minor of the corpus callosum].</p

Widespread gray matter volume reductions in BTBR mice.

<p>Maps of the brain regions exhibiting altered grey matter volume in BTBR (N = 9) with respect to B6 controls (N = 9, Z>3.1, pc = .01). Blue indicates reduced, red/yellow indicates increased gray matter volume in BTBR mice vs B6 controls [Amy: amygdala; Cb: cerebellum; DHyp: dorsal hypothalamus; dPFC: dorsal prefrontal cortex; Ins: insular cortex; LTh: lateral thalamus; mPFC: medial prefrontal cortex; OB: olfactory bulbs; Rs: retrosplenial cortex; Vcxt: visual cortex].</p

Antero-posterior white matter reorganisation in BTBR mice.

<p>Diffusion tensor tractography of representative dorsal inter-hemispheric tracts in control (top) and BTBR (bottom) mice. Seed regions used for tractography are displayed in green/red [CC: corpus callosum; DHc: dorsal hippocampal commissure; Fmi: Forceps minor of the corpus callosum; Probst B.: Probst bundles].</p

BTBR exhibit widespread cortical thickness reductions.

<p>Average cortical thickness in B6 (left) and BTBR mice (center) and corresponding voxel-wise statistics (right, Z>2, pc = .01; blue indicates BTBRB6).</p