arXiv subjects

Emily G. Mitchell

Publications and source records attributed to Emily G. Mitchell.

3 recordsLinked to original sources

arXiv2026

Ecological modelling of hycean worlds

New observations are opening the possibility of characterising habitable environments in exoplanetary systems, with the recent example of the candidate hycean world K2-18 b. This motivates an exploration of the possible ecological conditions on such planets to better interpret biosignatures as well as understand the nature of potential life. On Earth, the Lotka-Volterra equations have been used to model numerous coupled populations within ecosystems, from interactions between large vertebrates, to systems with multiple microbial species. In this work, we apply the Lotka-Volterra equations to the ecology of habitable exoplanets for the first time, focusing on hycean worlds. We simulate scenarios in a vertical water column with between 1-5 bacterial species that thrive in anoxic environments on Earth, i.e. similar to predicted hycean conditions. We find that a wide range of ecological diversity is possible for microbial populations under hycean conditions. We demonstrate that dominating phototrophic bacteria at the top of a water column out-compete deeper dwelling phototrophic bacteria, analogous to bacterial blooms on Earth. Incorporating microbial viruses (bacteriophages) within our models can cause ecosystem collapse depending on the time of their introduction, and such phage inclusion can be beneficial to ecological diversity. Finally, our work shows that bacterial populations inhabiting tidally locked exoplanets may be more stable due to constant illumination of the ocean, but can have lower peak population densities in such cases when compared to seasonal scenarios. Our work provides an initial step towards understanding the possible ecological diversity on habitable worlds beyond Earth.

astro-ph.EP↗

arXiv2025

Prospects for biological evolution on Hycean worlds

Recent detections of carbon-bearing molecules in the atmosphere of a candidate Hycean world, K2-18 b, with JWST are opening the prospects for characterising potential biospheres on temperate exoplanets. Hycean worlds are a recently theorised class of habitable exoplanets with ocean covered surfaces and hydrogen-rich atmospheres. Hycean planets are thought to be conducive for hosting microbial life under conditions similar to those in the Earth's oceans. In the present work we investigate the potential for biological evolution on Hycean worlds and their dependence on the thermodynamic conditions. We find that a large range of evolutionary rates and origination times are possible for unicellular life in oceanic environments for a relatively marginal range in environmental conditions. For example, a relatively small (10 K) increase in the average ocean temperature can lead to over twice the evolutionary rates, with key unicellular groups originating as early as $\sim$1.3 billion years from origin of life. On the contrary, similar decreases in temperatures can also significantly delay the origination times by several billion years. This delay in turn could affect their observable biomarkers such as dimethylsulfide, which is known to be produced predominantly by Eukaryotic marine phytoplankton in Earth's oceans. Therefore, Hycean worlds that are significantly cooler than Earth may be expected to host simpler microbial life than Earth's oceans and may show weaker biosignatures, unless they orbit significantly older stars than the Sun. Conversely, Hycean worlds with warmer surface temperatures than Earth are more likely to show stronger atmospheric biosignatures due to microbial life if present.

astro-ph.EP↗

arXiv2022

Object oriented data analysis of surface motion time series in peatland landscapes

Peatlands account for 10% of UK land area, 80% of which are degraded to some degree, emitting carbon at a similar magnitude to oil refineries or landfill sites. A lack of tools for rapid and reliable assessment of peatland condition has limited monitoring of vast areas of peatland and prevented targeting areas urgently needing action to halt further degradation. Measured using interferometric synthetic aperture radar (InSAR), peatland surface motion is highly indicative of peatland condition, largely driven by the eco-hydrological change in the peatland causing swelling and shrinking of the peat substrate. The computational intensity of recent methods using InSAR time series to capture the annual functional structure of peatland surface motion becomes increasingly challenging as the sample size increases. Instead, we utilize the behavior of the entire peatland surface motion time series using object oriented data analysis to assess peatland condition. In a Gibbs sampling scheme, our cluster analysis based on the functional behavior of the surface motion time series finds features representative of soft/wet peatlands, drier/shrubby peatlands and thin/modified peatlands align with the clusters. The posterior distribution of the assigned peatland types enables the scale of peatland degradation to be assessed, which will guide future cost-effective decisions for peatland restoration.

stat.AP↗