Study Findings: Atmospheric Carbon Depletion as a Tracer of Water Oceans and Biomass on Temperate Terrestrial Exoplanets

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Credit: NASA/JPL-Caltech

Nature Astronomy abstract of the study findings:

The conventional observables to identify a habitable or inhabited environment in exoplanets, such as an ocean glint or abundant atmospheric O2, will be challenging to detect with present or upcoming observatories. Here we suggest a new signature. A low carbon abundance in the atmosphere of a temperate rock`y planet, relative to other planets of the same system, traces the presence of a substantial amount of liquid water, plate tectonics and/or biomass. Here we show that JWST can already perform such a search in some selected systems such as TRAPPIST-1 via the CO2 band at 4.3 μm, which falls in a spectral sweet spot where the overall noise budget and the effect of cloud and/or hazes are optimal. We propose a three-step strategy for transiting exoplanets: detection of an atmosphere around temperate terrestrial planets in about 10 transits for the most favourable systems; assessment of atmospheric carbon depletion in about 40 transits; and measurements of O3 abundance to disentangle between a water- versus biomass-supported carbon depletion in about 100 transits. The concept of carbon depletion as a signature for habitability is also applicable for next-generation direct-imaging telescopes.

Citation: Triaud, A.H.M.J., de Wit, J., Klein, F. et al. Atmospheric carbon depletion as a tracer of water oceans and biomass on temperate terrestrial exoplanets. Nat Astron (2023).
https://doi.org/10.1038/s41550-023-02157-9

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Study Findings: A Resonant Sextuplet of Sub-Neptunes Transiting the Bright Star HD 110067

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Image (Credit): Neptune as captured by the James Webb Space Telescope’s near-infrared camera. (NASA, ESA, CSA, and STScI)

Nature abstract of the study findings:

Planets with radii between that of the Earth and Neptune (hereafter referred to as ‘sub-Neptunes’) are found in close-in orbits around more than half of all Sun-like stars. However, their composition, formation and evolution remain poorly understood. The study of multiplanetary systems offers an opportunity to investigate the outcomes of planet formation and evolution while controlling for initial conditions and environment. Those in resonance (with their orbital periods related by a ratio of small integers) are particularly valuable because they imply a system architecture practically unchanged since its birth. Here we present the observations of six transiting planets around the bright nearby star HD 110067. We find that the planets follow a chain of resonant orbits. A dynamical study of the innermost planet triplet allowed the prediction and later confirmation of the orbits of the rest of the planets in the system. The six planets are found to be sub-Neptunes with radii ranging from 1.94R⊕ to 2.85R⊕. Three of the planets have measured masses, yielding low bulk densities that suggest the presence of large hydrogen-dominated atmospheres.

Citation: Luque, R., Osborn, H.P., Leleu, A. et al. A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067. Nature 623, 932–937 (2023).
https://doi.org/10.1038/s41586-023-06692-3

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Study Findings: A Planetary Collision Afterglow and Transit of the Resultant Debris Cloud

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Image (Credit): Artist’s rendering of two colliding planets. (NASA)

Nature abstract of the study findings:

Planets grow in rotating disks of dust and gas around forming stars, some of which can subsequently collide in giant impacts after the gas component is removed from the disk. Monitoring programmes with the warm Spitzer mission have recorded substantial and rapid changes in mid-infrared output for several stars, interpreted as variations in the surface area of warm, dusty material ejected by planetary-scale collisions and heated by the central star: for example, NGC 2354–ID8, HD 166191 and V488 Persei. Here we report combined observations of the young (about 300 million years old), solar-like star ASASSN-21qj: an infrared brightening consistent with a blackbody temperature of 1,000 Kelvin and a luminosity that is 4 percent that of the star lasting for about 1,000 days, partially overlapping in time with a complex and deep, wavelength-dependent optical eclipse that lasted for about 500 days. The optical eclipse started 2.5 years after the infrared brightening, implying an orbital period of at least that duration. These observations are consistent with a collision between two exoplanets of several to tens of Earth masses at 2–16 astronomical units from the central star. Such an impact produces a hot, highly extended post-impact remnant with sufficient luminosity to explain the infrared observations. Transit of the impact debris, sheared by orbital motion into a long cloud, causes the subsequent complex eclipse of the host star.

Citation: Kenworthy, M., Lock, S., Kennedy, G. et al. A planetary collision afterglow and transit of the resultant debris cloud. Nature 622, 251–254 (2023).
https://doi.org/10.1038/s41586-023-06573-9

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Study Findings: Constraining Cosmological Parameters Using the Cluster Mass–Richness Relation

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If you don’t understand the research title, you are not alone. The abstract is even worse:

The cluster mass–richness relation (MRR) is an observationally efficient and potentially powerful cosmological tool for constraining the matter density Ωm and the amplitude of fluctuations σ8 using the cluster abundance technique. We derive the MRR relation using GalWCat19, a publicly available galaxy cluster catalog we created from the Sloan Digital Sky Survey-DR13 spectroscopic data set. In the MRR, cluster mass scales with richness as $\mathrm{log}{M}_{200}=\alpha +\beta \mathrm{log}{N}_{200}$. We find that the MRR we derive is consistent with both the IllustrisTNG and mini-Uchuu cosmological numerical simulations, with a slope of β ≈ 1. We use the MRR we derived to estimate cluster masses from the GalWCat19 catalog, which we then use to set constraints on Ωm and σ8. Utilizing the all-member MRR, we obtain constraints of Ωm = ${0.31}_{-0.03}^{+0.04}$ and σ8 = ${0.82}_{-0.04}^{+0.05}$, and utilizing the red member MRR only, we obtain Ωm = ${0.31}_{-0.03}^{+0.04}$ and σ8 = ${0.81}_{-0.04}^{+0.05}$. Our constraints on Ωm and σ8 are consistent and very competitive with the Planck 2018 results.

Where is Carl Sagan when you need him? I know these are scientific journals, but plain language abstracts should be possible.

Luckily, the university released a press release on the study findings. Here is the bottom line:

A UC Merced researcher and her teammates around the world have succeeded in measuring the total amount of matter in the universe for the second time. A new paper in the Astrophysical Journal, titled “Constraining Cosmological Parameters using the Cluster Mass-Richness Relation,” shows that matter makes up 31% of the universe, with the remainder consisting of dark energy — answering one of the most interesting and important questions in cosmology.

Now that wasn’t too hard. If you want to read the paper itself, you can find the details here.

Good luck.

Study Findings: Diverse Organic-mineral Associations in Jezero Crater, Mars

Posted on by onespaceman2000
Image (Credit): NASA’s Mars Perseverance rover selfie with its Ingenuity helicopter in the background. (NASA/JPL-Caltech/MSSS)

Nature abstract of the study findings:

The presence and distribution of preserved organic matter on the surface of Mars can provide key information about the Martian carbon cycle and the potential of the planet to host life throughout its history. Several types of organic molecules have been previously detected in Martian meteorites and at Gale crater, Mars. Evaluating the diversity and detectability of organic matter elsewhere on Mars is important for understanding the extent and diversity of Martian surface processes and the potential availability of carbon sources. Here we report the detection of Raman and fluorescence spectra consistent with several species of aromatic organic molecules in the Máaz and Séítah formations within the Crater Floor sequences of Jezero crater, Mars. We report specific fluorescence-mineral associations consistent with many classes of organic molecules occurring in different spatial patterns within these compositionally distinct formations, potentially indicating different fates of carbon across environments. Our findings suggest there may be a diversity of aromatic molecules prevalent on the Martian surface, and these materials persist despite exposure to surface conditions. These potential organic molecules are largely found within minerals linked to aqueous processes, indicating that these processes may have had a key role in organic synthesis, transport or preservation.

Citation: Sharma, S., Roppel, R.D., Murphy, A.E. et al. Diverse organic-mineral associations in Jezero crater, Mars. Nature (2023).
https://doi.org/10.1038/s41586-023-06143-z

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