Peter M. Higgins

Astrobiologist, University of Toronto, Canada

I'm a Postdoctoral Fellow in the Stable Isotope Lab at the University of Toronto. I examine how thermodynamic principles control whether or not life can survive, grow and/or evolve in various physico-chemical settings. To do so, I develop and employ computational models which: i) assess dynamic habitability, ii) constrain possible biomass levels, and iii) estimate biosignature production and detectability against an abiotic background. The universal nature of these laws allows us to examine environments throughout the cosmos, from deep earth through deep time, to the oceans of icy moons in the outer solar system, and even exoplanets around distant stars.

Postdoc: University of Toronto 2022-
PhD: Astrobiology, University of Edinburgh 2022
MSci: Natural Sciences, Lancaster University 2017

Projects

These are my current research interests. Contact me if you are interested in collaborating or taking on a student project in one of these areas!

NutMEG

NutMEG is a python module for predicting the growth behaviour of microbial organisms in astrobiology. It’s flexibly designed for astrobiologsts to assess habitablility, biomass potential, and biosignature production in a variety of setings.

Check out NutMEG's documentation! [mirror] Or, go straight to the code on GitHub.

Habitability

Image: Higgins (2022) [link]

To be habitable, an environment needs enough energy and nutrients for life to beat out the costs of survival. This is something we can quantify.

For example, at high temperatures or adverse pH it becomes more difficult for life to maintain the structure of important biomolecules like proteins and DNA.

Icy Moons

Image credits: NASA

Enceladus, Europa and Titan have subsurface water oceans and may be habitable. Energy and nutrients for life can be delivered to them via water-rock reactions at their seafloors, or from above through their icy surfaces. Any local ecosysems could be very different to most of life on Earth, as photosynthesis is probably not viable.

Deep Earth & Rocky Crusts

Image: Sherwood Lollar et al. (2024) [link]

Earth’s subsurface is teeming with life, but little is known about the full spectrum and limits of habitability within its diverse and difficult-to-access settings. The deep crust in particular hosts a variety of 'extreme', often-isolated waters that are analogs for putative habitats in other rocky crusts, such as on Mars.

These settings and their habitats are also of interest for economic H2 and He production/storage, CCS, and nuclear waste management.

Biosignatures

Image: Higgins et al. (2024) [link]

One way to identify candidate worlds for life detection missions is to demonstrate, through several lines of evidence, that data we have collected already may contain signs of biology. This can be through metabolic by-products, isotopic fractionation, particular properties of organic chemical species, etc. These signals can also help us work out what else a biosphere, if present, might be doing.

Crucially, analysing biosignatures requires we evaluate how they compare against the 'abiotic background'. Which, on exotic extraterrestrial geologies, can be difficult to constrain.

Exoplanets & Exomoons

Image credits: NASA

Current and future space telescopes will gleam ever-more insight on planets orbiting other stars. However, the challenges of exoplanet astrobiology are very different than those in the solar system, because there is much less world-specific data, but larger sample sizes and planetary diversity. Reliably inferring habitability, biomass and biosignature potential on these extrasolar worlds is going to be a major scientific challenge in the coming decades.

NutMEG

Habitability

Image: Higgins (2022) [link]

To be habitable, an environment needs enough energy and nutrients for life to beat out the costs of survival. This is something we can quantify.

For example, at high temperatures or adverse pH it becomes more difficult for life to maintain the structure of important biomolecules like proteins and DNA.

Icy Moons

Image credits: NASA

Enceladus, Europa and Titan have subsurface water oceans and may be habitable. Energy and nutrients for life can be delivered to them via water-rock reactions at their seafloors, or from above through icy surfaces. Any local ecosysems could be very different to most of life on Earth, as photosynthesis is probably not viable.

Deep Earth & Rocky Crusts

Image: Sherwood Lollar et al. (2024) [link]

Earth’s subsurface is teeming with life, but little is known about the full spectrum and limits of habitability within its diverse and difficult-to-access settings. The deep crust in particular hosts a variety of `extreme', often-isolated waters that are analogs for putative habitats in other rocky crusts, such as on Mars.

These settings and their habitats are also of interest for economic H2 and He production/storage, CCS, and nuclear waste management.

Biosignatures

Image: Higgins et al. (2024) [link]

One way to identify candidate worlds for life detection missions is to demonstrate, through several lines of evidence, that data we have collected already may contain signs of biology. This can be through metabolic by-products, isotopic fractionation, particular properties of organic chemical species, etc. These signals can also help us work out what else a biosphere, if present, might be doing.

Crucially, analysing biosignatures requires we evaluate how they compare against the `abiotic background'. Which, on exotic extraterrestrial geologies, can be difficult to constrain.

Exoplanets & Exomoons

Image credits: NASA

Current and future space telescopes will gleam ever-more insight on planets orbiting other stars. However, the challenges of exoplanet astrobiology are very different than those in the solar system, because we have much less world-specific data, but larger sample sizes and planetary diversity. Reliably inferring habitability, biomass and biosignature potential on these extrasolar worlds is going to be a major scientific challenge in the coming decades.

Publications and Presentations

Publications

Sorted by most recent; several more in review! Last citations scrape: April 11 2024

Reference	Open Access?	Metrics
Sherwood Lollar B.S., Warr O., Higgins P.M. (2024) "The Hidden Hydrogeosphere: The Contribution of Deep Groundwater to the Planetary Water Cycle" Annual Review of Earth and Planetary Sciences 52 DOI: 10.1146/annurev-earth-040722-102252	TBC (est. May 2024)
Higgins P.M., Chen W., Glein C.R., Cockell C.S., Sherwood Lollar B. (2024) "Quantifying Uncertainty in Sustainable Biomass and Production of Biotic Carbon in Enceladus' Notional Methanogenic Biosphere" JGR: Planets 129 (3) e2023JE008166 DOI: 10.1029/2023JE008166	Publisher
Ortega-Arzola E., Higgins P.M., Cockell C.S. (2024) "The minimum energy required to build a cell" Scientific Reports 14 5267 DOI: 10.1038/s41598-024-54303-6	Publisher
Neish C., Malaska M.J., Sotin C., Lopes R.M., Nixon C.A., Affholder A., Chatain A., Cockell C., Farnsworth K.K., Higgins P.M., Miller K.E and Soderlund K.M. (2024) "Organic Input to Titan's Subsurface Ocean Through Impact Cratering" Astrobiology 20 (2) 177-189 DOI: 10.1089/ast.2023.0055	ResearchGate	1
Cockell C.S., Simons M., Castillo-Rogez J., Higgins P.M., Kaltenegger L., Keane J.T., Leonard E.J., Mitchell K.L., Park R.S., Perl S.M., Vance S.D. (2024) "Sustained and comparative habitability beyond Earth" Nature Astronomy 8 30-38 DOI: 10.1038/s41550-023-02158-8	Caltech	2
Seeburger R., Higgins P.M., Whiteford N.P., Cockell C.S. (2023) "Linking Methanogenesis in Low-Temperature Hydrothermal Vent Systems to Planetary Spectra: Methane Biosignatures on an Archean-Earth-like Exoplanet" Astrobiology 23 (4) 415-430 DOI: 10.1089/ast.2022.0127	Publisher	1
Higgins P.M. (2022) "Modelling extraterrestrial habitability, biomass and biosignatures through the bioenergetic lens" The University of Edinburgh DOI: 10.7488/era/2078	ERA	2
Higgins P.M., Glein C.R., Cockell C.S. (2021) "Instantaneous habitable windows in the parameter space of Enceladus' ocean" JGR: Planets 126 (11) e2021JE006951 DOI: 10.1029/2021JE006951	Publisher	12
Cockell C.S., Higgins P.M., Johnstone A.A. (2021) "Biologically available chemical energy in the temperate but uninhabitable Venusian cloud layer: What do we want to know?" Astrobiology 21 (10) 1224-1236 DOI: 10.1089/ast.2020.2280	ResearchGate	13
Cockell C.S., Wordsworth R., Whiteford N.P., Higgins P.M. (2021) "Minimum units of habitability and their abundance in the universe" Astrobiology 21 (4) 481-489 DOI: 10.1089/ast.2020.2350	ResearchGate	13
Gault S.A, Higgins P.M., Cockell C.S., Gillies K. (2021) "A meta-analysis of the activity, stability, and mutational characteristics of temperature-adapted enzymes" Bioscience Reports 41 (4) BSR20210336 DOI: 10.1042/BSR20210336	Publisher	9
Higgins P.M. & Cockell C.S. (2020) "A bioenergetic model to predict habitability, biomass and biosignatures in astrobiology and extreme conditions" J. R. Soc. Interface 17 (171) 20200588 DOI: 10.1098/rsif.2020.0588	Publisher	10

Presentations

Only includes presentation with Pete as first author

AGU Fall Meeting (2023), Oral Presentation: "Uncertainty in Habitability and Sustainable Biomass for a Hypothetical Methanogenic Biosphere on Enceladus".
CIFAR Earth-4D Program Meeting (2023), Poster Presentation: "Probabilistic Habitability Near and Far".
Royal Observatory of Edinburgh Colloquium (2020), Invited Seminar: "Predicting Energy Flow and Biomass in Extreme and Extraterrestrial Environments".
AGU Fall Meeting (2020), Poster Presentation: “Nutrients, Maintenance, Energy and Growth: predicting habitability, biomass and biosignatures from limited datasets”.
AbSciCon (2019), Oral Presentation: “The Energetic Habitability of Enceladus may be Tenuous”.
ASB (2019), Oral Presentation: “The Energetic Habitability of Enceladus may be Tenuous”.
LPSC (2019), ePoster Presentation: “A Power Driven Model for Predicting Microbial Growth in Poorly Characterised Environments”.
EANA (2018), Poster Presentation: “A new model to estimate energy flow and biomass in terrestrial and extraterrestrial environments”.
EANA (2018), Oral Presentation: “A new model to estimate energy flow and biomass in terrestrial and extraterrestrial environments”
Won student contest 2018 for best talk.
GMBN RiP (2018), Poster Presentation: “A new model to estimate energy flow and biomass in terrestrial and extraterrestrial environments”.

Contact

@pm_higgins

pete.higgins[AT]utoronto.ca

Department of Earth Sciences, University of Toronto, M5S 3B1