2.1.2 Analogue sites

Clickable slideshow with 5 slides

Slide 1: Colour Peak, Canada and Mars

Data returned by the NASA Curiosity rover from Gale crater on Mars showed that water may have been present on the red planet 4.1–3.7 billion years ago. Chemical analysis of Colour Peak, a spring system located on Axel Heiberg Island in the High Arctic of Canada (Figure 8) identified a sulfate-rich and hypersaline chemistry similar to that found at Gale crater. Analysis of the microbes in the Colour Peak environment also identified the presence of sulfur oxidising bacteria, that yield energy from sulfur. These are being studied to understand the feasibility of sulfur oxidising bacteria on Mars billions of years ago, and what biosignatures they might leave behind.

Figure 8a) a map showing a roughly diamond shaped island with a white star labelled colour Peak in the centre. Beside this a red circle labelled ‘Gypsum Hill’ and to the south east another red circle is labelled ‘Lost Hammer’. In the top right hand corner of the map is a small map of Canada, showing Axel Heiberg Island within the country's islands in the north.

Figure 8b) the photograph shows land in the foreground and sea in the background. Seven springs are labelled with an arrow on land, with a circle indicating the study area.

Slide 2: Lake Yeguas, Spain and Mars

A series of hypersaline lagoons in the semiarid La Mancha region of Spain is used as an analogue for ancient martian environments where surface water regularly forms then evaporates seasonally resulting in the formation of saturated, salty brines and desiccated salt flats (Figure 9). The drainage networks linked to the La Mancha source river are characterised by weak erosive power, like the basins observed on the surface of Mars. Chemical analysis of the waters of these lagoons also identified a higher concentration of sulfate compared to chloride, similar to Gale crater and Jezero crater, analysed by the Curiosity and Perseverance rovers, respectively. The lagoons are dominated by sulfate reducing bacteria, which yield energy from sulfur and produce sulfide. These are being studied to understand the diversity of life that may exist in similar environments on Mars.

Figure 9 Laguna de las Yeguas captured during the dry winter period. No water was visible on the surface. However, as revealed by our footsteps, just beneath the dry layer, there is moist sediment. A photograph of a dark white flat landscape extending to the horizon. In the foreground are some dark footprints and a geological hammer.

Slide 3: Makgadikgadi Basin, Botswana and Mars

The Makgadikgadi Basin, Earth’s largest inland evaporitic basin in the Kalahari Desert, Botswana, represents an analogue for ancient aqueous environments on Mars. This vast basin, encompassing salt pans (vast plains covered in salt) like Sua (Figure 10) and Ntwetwe, is a remnant of a mega-palaeolake. It is arid to semi-arid, and fed by groundwater and precipitation, resulting in conditions mirroring early Mars, including high UV radiation, extreme salinity, and deposition of salts and clays. The sedimentary beds found across the basin are very similar to deposits observed on Mars. Analysis of the microbes in this environment identified the presence of sulfur oxidising bacteria, the same as Colour Peak, as well as Cyanobacteria that yield energy from sunlight.

Figure 10 View south across the Sua salt pan, Botswana during a sampling campaign in January 2024. The black regions are dried mats of Cyanobacteria. A photograph of a light grey flat landscape extending to the horizon. The surface appears to be sandy, with some black sediments accummulating in places on the surface.

Slide 4: Iceland and icy worlds

Iceland’s active geology and cold climate make it a good analogue site for studying the icy words of the outer Solar System, such as Enceladus (a moon of Saturn) and Europa (a moon of Jupiter), that harbour sub-surface oceans that could be habitable. Its unique combination of glacial, volcanic, and geothermal environments makes it a natural laboratory that can be used to understand the process occurring within these icy worlds. For example, the Geyser system in south-west Iceland, contains a variety of hot springs that might be analogous to hydrothermal conditions on extraterrestrial ocean floors. Sampling aerosols produced at the springs can also provide clues to how particulates form and become dispersed in the plumes that are emitted from Enceladus’ south pole. These particulates have been sampled by the Cassini mission.

Figure 11 The Geyser system of Iceland showing hot springs that are analogues of environments on icy worlds that were sampled during a 2025 field study. A photograph taken at dawn showing a black flat landscape interrupted by pools of water. Some of the pools are bubbling and steam is rising.

Slide 5: Space as an analogue

Even space itself can be used in astrobiological studies. Research carried out on the International Space Station can address fundamental questions regarding the resistance of microbes to extraterrestrial conditions and their probability of surviving when exposed to space conditions including the radiation environment, the vacuum of space, reduced gravity, and extreme temperature fluctuations. Experiments conducted in low Earth orbit (LEO), including involvement from scientists at the Open University, have been performed to expose microbes to conditions over time, even on the scale of years. This showed the profound negative impact of solar radiation on their survival. However, if microbes were embedded in layers of minerals, rock, or grown in thick layers, they often had better survival rates. Many species of extremophile have also shown remarkable resilience in the combined presence of vacuum and radiation. Understanding this survival can shed light on the viability of microbial transfer between planetary bodies and be used to assess risk for planetary protection, informing cleaning strategies for cleanrooms and contamination controls.

Figure 12 Astronaut Patrick G. Forrester worked on the Materials International Space Station Experiment (MISSE) during a spacewalk. MISSE exposed 750 material samples on the ISS Quest Airlock for 18 months. A photograph of an astronaut in a white space suit on a space walk. The astronaut is on his side and is holding a large metal box with different colour and shaped panels.