arXiv subjects

Nicoletta La Rocca

Publications and source records attributed to Nicoletta La Rocca.

3 recordsLinked to original sources

arXiv2026

Assessing the Climate and Habitability of Tidally Locked Rocky Exoplanets

Tidally locked exoplanets orbiting M dwarf stars are prime targets in the search for habitable worlds, yet their complex climate dynamics challenge conventional models of habitability. We homogeneously estimated the liquid-water habitability of exoplanets with the highest up-to-date Earth-similarity index. We modified the climate model PLASIM to apply it to tidally locked exoplanets across a range of parameters. We systematically classified and compared potentially habitable exoplanets and selected among the ones featuring the highest Earth-similarity index in the conservative sample of the Habitable Wolds Catalog, both relative to each other and as a function of atmospheric pressure. Our analysis revealed three main climate regimes: Snowball, Hot, and Eyeball planets-the latter having a warm and habitable substellar region with T > 273 K and a localized hydrological cycle. Although surface temperature generally increases with pressure, Eyeball planet climates remain stable in a wide pressure range. Complex atmospheric dynamics govern the behavior of the climate, highlighting the need for detailed climate simulations to guide future observations.

astro-ph.EP↗

arXiv2026

White Paper on Phototrophic Biosignatures: Research Priorities for the Search for Life on Other Worlds

Photosynthesis is of prime interest in the telescopic search for life beyond the Solar System, because, on Earth, oxygenic photosynthesis produces two strong "biosignatures," global scale signs of life that can be seen from space: atmospheric oxygen and the Vegetation Red Edge (VRE). The VRE is the spectral reflectance signature of plant leaves, characterized by a step-like increase in reflectance from the red to the near-infrared. The absorption in the red is due to chlorophyll $\textit{a}$ (Chl $\textit{a}$). While Chl $\textit{a}$ dominates our planet, the Earth harbors diverse phototrophic organisms in niche environments possessing other pigments that produce edge-like spectral features across the UV-VIS-NIR, naturally suggesting diverse signatures that could be found on other planets where phototrophic life is adapted to other stars. However, the astrobiology community is very much at an early stage in its ability to constrain the probability that an observation of another planet has detected a sign of photosynthetic life. This white paper identifies critical research questions to advance to a predictive capability the search for phototrophic biosignatures. These questions pertain to the origins, key features, diversity, and potential for alternative adaptations in fundamental aspects of light harvesting; the electron transfer pathway in photosynthesis; rhodopsin-based proton-pumping; and carbon fixation. We discuss the need to constrain how evolution and ecology affect the scaling up of these molecular mechanisms to be potentially detectable by a direct imaging mission. The research questions and recommendations presented here are cross-linked to those posed by the NASA Astrobiology Strategy 2015, and to the Focus Areas of the upcoming NASA Decadal Astrobiology Exploration Strategy (DARES).

astro-ph.IM↗

arXiv2023

Oxygenic photosynthetic responses of cyanobacteria exposed under an M-dwarf starlight simulator: Implications for exoplanet's habitability

Introduction: The search for life on distant exoplanets is expected to rely on atmospheric biosignatures detection, such as oxygen of biological origin. However, it is not demonstrated how much oxygenic photosynthesis, which on Earth depends on visible light, could work under spectral conditions simulating exoplanets orbiting the Habitable Zone of M-dwarf stars, which have low light emission in the visible and high light emission in the far-red/near-infrared. By utilizing cyanobacteria, the first organisms to evolve oxygenic photosynthesis on our planet, and a starlight simulator capable of accurately reproducing the emission spectrum of an M-dwarf in the range 350-900 nm, we could answer this question. Methods: We performed experiments with the cyanobacterium Chlorogloeopsis fritschii PCC6912, capable of Far-Red Light Photoacclimation (FaRLiP), which allows the strain to harvest far-red in addition to visible light for photosynthesis, and Synechocystis sp. PCC6803, a species unable to perform this photoacclimation, comparing their responses when exposed to three simulated light spectra: M-dwarf, solar and far-red. We analysed growth and photosynthetic acclimation features in terms of pigment composition and photosystems organization. Finally, we determined the oxygen production of the strains directly exposed to the different spectra. Results: Both cyanobacteria were shown to grow and photosynthesize similarly under M-dwarf and solar light conditions: Synechocystis sp. by utilizing the few photons in the visible, C. fritschii by harvesting both visible and far-red light, activating the FaRLiP response.

astro-ph.EP↗