ABOUT RESEARCH PUBLICATIONS CONTACT

Peter M. Higgins

Astrobiologist, Planetary Scientist, Biogeochemist
Harvard University

I build biogeochemical models that assess whether or not life can survive, grow and/or evolve in various physico-chemical settings. Using spacecraft data as our primary input, we can assess dynamic habitability, constrain possible biomass levels, and test strategies for life detection on other worlds. Back home on Earth, this improves our understanding of biosphere-geosphere coupling and how it impacts strategies for resource management in society's urgent energy transition.

The universal nature of thermodynamics and the flexibility offered by mircobial kinetic models 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.

Kavli-Laukien Fellow: Harvard University 2024-
Postdoc: University of Toronto 2022-2024
PhD: Astrobiology, University of Edinburgh 2022
MSci: Natural Sciences, Lancaster University 2017

Pete

Research Interests

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!

For research updates, follow me on LinkedIn

Evaluating habitability with NutMEG


To be habitable, an environment needs to provide enough energy and nutrients for life to beat out the costs of survival. This is something that can be quantified (Higgins & Cockell 2020). Every organism has its own specific habitability requirements. A major theme of my research is working out who can survive where, how they make it happen, and what they do to their surroundings in that process.

NutMEG is an open-source python module we developed 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.

Key research questions:

  • Can we infer habitability from the geophysical and chemical data returned by spacecraft?
  • What adaptations are needed to survive in different environments?
NutMEG logo


Click the logo to check out the docs, or go straight to the code on GitHub.

Water processes in Earth's deep crust


Image: Sherwood Lollar et al. (2024)

Finding life and resources in planetary crusts


I explore the habitability, carbon cycling, and biological producitivty in some of Earth's oldest, slowest biospheres. The subsurface of our home planet is teeming with life, but little is known about the full spectrum of microbial activity that is happening in its diverse and difficult-to-access settings. The deep crust in particular hosts a variety of 'extreme', isolated waters that are analogs for putative habitats in other rocky crusts (e.g., on Mars).

As well as acting as a Rosetta stone for understanding how biology could work on other worlds, this research is also important for society back home. Understanding how microbial activity operates in the deep biosphere also helps us estimate how life interacts with important subsurface repositories for human society, including for economic hydrogen and helium, CCS, and nuclear waste management (Sherwood Lollar et al., 2024; Higgins, Song et al., 2025).

Key research questions:

  • How much biomass is there in the deep subsurface?
  • Are subsurface resource repositories viable on Earth, or other worlds?

Searching for life on icy worlds and exoplanets


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 (e.g., Higgins et al., 2021; Affholder & Higgins et al., 2025). Any local ecosysems could be very different to most of life on Earth, as photosynthesis is probably not viable.

I use models like NutMEG to ask what signs of life might be detectable on ocean worlds with future spacecraft and observatories. By exploring possible biological signals and their interaction/coexistence with the abiotic background, we're able to infer what proposed future observations can—and cannot—actually tell us (Higgins et al., 2026).

We build similar models for exoplanets. Reliably inferring exoplanet habitability, biomass and biosignature potential is going to be a major scientific challenge in the coming decades, and biogeochemical models have an important role to play (Seeburger et al., 2023)

Key research questions:

  • How can life be sustained on these worlds?
  • What are the possible abiotic and biotic contributions to observations?

Icy Moons of the Solar System


Image credits: NASA

Evaluating habitability with NutMEG

NutMEG logo
Key research questions:
  • Can we infer habitability from the geophysical and chemical data returned by spacecraft?
  • What adaptations are needed to survive in different environments?

To be habitable, an environment needs to provide enough energy and nutrients for life to beat out the costs of survival. This is something that can be quantified (Higgins & Cockell 2020). Every organism has its own specific habitability requirements. A major theme of my research is working out who can survive where, how they make it happen, and what they do to their surroundings in that process.

NutMEG is an open-source python module we developed 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.

Finding life and resources in planetary crusts

Water processes in Earth's deep crust

Image: Sherwood Lollar et al. (2024)

Key research questions:
  • How much biomass is there in the deep subsurface?
  • Are subsurface resource repositories viable on Earth, or other worlds?

I explore the habitability, carbon cycling, and biological producitivty in some of Earth's oldest, slowest biospheres. The subsurface of our home planet is teeming with life, but little is known about the full spectrum of microbial activity that is happening in its diverse and difficult-to-access settings. The deep crust in particular hosts a variety of 'extreme', isolated waters that are analogs for putative habitats in other rocky crusts (e.g., on Mars).

As well as acting as a Rosetta stone for understanding how biology could work on other worlds, this research is also important for society back home. Understanding how microbial activity operates in the deep biosphere also helps us estimate how life interacts with important subsurface repositories for human society, including for economic hydrogen and helium, CCS, and nuclear waste management (Sherwood Lollar et al., 2024; Higgins, Song et al., 2025).

Searching for life on icy worlds and exoplanets

Icy Moons of the Solar System

Image credits: NASA

Key research questions:
  • How can life be sustained on these worlds?
  • What are the possible abiotic and biotic contributions to observations?

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 (e.g., Higgins et al., 2021; Affholder & Higgins et al., 2025). Any local ecosysems could be very different to most of life on Earth, as photosynthesis is probably not viable.

I use models like NutMEG to ask what signs of life might be detectable on ocean worlds with future spacecraft and observatories. By exploring possible biological signals and their interaction/coexistence with the abiotic background, we're able to infer what proposed future observations can—and cannot—actually tell us (Higgins et al., 2026).

We build similar models for exoplanets. Reliably inferring exoplanet habitability, biomass and biosignature potential is going to be a major scientific challenge in the coming decades, and biogeochemical models have an important role to play (Seeburger et al., 2023)

Publications

Sorted by most recent; more in review! * denotes equal contributers; ★ denotes student authors

Reference Open Access? Metrics
Davila A., Hoehler T., Shkolyar S., et al., (2026) "The Abiotic Background: Challenges and Opportunities for Life Detection" Astrobiology doi: 10.1177/15311074261484864. Publisher
Higgins P.M., Chen W., Warr O., Fifer L.M., Kang W., Cockell C.S., Sherwood Lollar B. (2026) "A framework for evaluating biosignature potential against the abiotic baseline on ocean worlds" Nature Astronomy doi: 10.1038/s41550-026-02893-8. SharedIt; or arXiv
Nixon C.A., Birch S., Chatain A., Cockell C., Farnsworth K.K., Higgins P.M., Le Mouélic S., Lopes R., Malaska M.J., Melwani Daswani M., Miller K.E., Neish C.D., Podlaha O.G., Radebaugh J., Schurmeier L.R., Schoenfeld A., Soderlund K.M., Solomonidou A., Sotin C., Teanby N.A., Tokano T., Vance S.D. (2026) "Terrestrial Analogs to Titan for Geophysical Research" Reviews of Geophysics 64, e2025RG000909. doi: 10.1029/2025RG000909. Eos spotlight Publisher
*Miller K.E., *Melwani Daswani M., *Sotin C., Cockell C.S., Neish C., Malaska M.J., Farnsworth K.K., Nixon C., Soderlund K.M., Higgins P.M., Affholder A., Lopes R.M.C. (2026) "Titan’s refractory core evolution: Implications for organics in its subsurface ocean" Icarus 449 116961 DOI: 10.1016/j.icarus.2026.116961 Publisher
*Higgins P.M., *Song M., Warr O., Sherwood Lollar B. (2025) "Natural H2 and Sulfate Production via Radiolysis in Low Porosity and Permeability Crystalline Rocks" JGR: Biogeosciences 130 (86) e2025JG008863 DOI: 10.1029/2025JG008863 Publisher
*Affholder A., *Higgins P.M., Cockell C.S., Neish C., Soderlund K.M., Malaska M.J., Farnsworth K.F., Lopes R.M.C., Nixon C.A., Melwani Daswani M., Miller K.E., Sotin C. (2025) "The viability of glycine fermentation in Titan's subsurface ocean" Planetary Science Journal 6 (86) 28 DOI: 10.3847/PSJ/adbc66. Press Release Publisher
Cockell C.S., Hallsworth J.E., McMahon S., Kane S.R., Higgins P.M. (2024) "The concept of life on Venus informs the concept of habitability" Astrobiology 24 (6) 628-634 DOI: 10.1089/ast.2023.0106 ResearchGate
Sherwood Lollar B., 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 52 443-466 DOI: 10.1146/annurev-earth-040722-102252 Publisher
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 24 (2) 177-189 DOI: 10.1089/ast.2023.0055. Press Release ResearchGate
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. Press Release Caltech
★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
Higgins P.M. (2022) "Modelling extraterrestrial habitability, biomass and biosignatures through the bioenergetic lens" The University of Edinburgh DOI: 10.7488/era/2078 ERA
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
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
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
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
Higgins P.M. and 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

Contact

@petermhiggins

phiggins@fas.harvard.edu

Department of Earth and Planetary Sciences, 20 Oxford St, Harvard University, MA 02138, USA