Psychologists categorise the human desire to seek further knowledge or eliminate uncertainty as epistemic curiosity, fuelling questions such as “Are we alone?“, “Is there life in the universe?” – two age-old questions asked by scientists, philosophers, and general man alike. While scientific evidence of life beyond Earth’s atmosphere remains elusive, popular culture has long fuelled our imagination with images of intellectually sophisticated green antagonists and sprawling alien civilisations. However, the scientific search for extraterrestrial life began not with grandiose visions of intergalactic societies, but with humble investigations into the microbial ecosystems in some of Earth’s most extreme environments.
In 1977, a pivotal finding was uncovered by a group of marine geologists led by Dr. R. Ballard: the unearthing of naturally formed structures protruding from the Pacific Ocean seabed. These structures, known as hydrothermal vents, were found to be erupting chemically rich hot water into the cold depths of the Galapagos Rift. Although initially deemed uninhabitable, subsequent biological surveys revealed a thriving ecosystem teeming with over 800 (and still counting) species, defying preconceptions of what constitutes a habitable environment.
Microorganisms were found to be converting the chemicals and minerals from the vents,
such as carbon dioxide, into palatable organic compounds that larger organisms were consuming symbiotically. Life had seemingly adapted to overcome the harsh conditions of this environment – demonstrating a marine habitat in which its tenants were thriving. In an equal exchange, chemosynthesis processes supported minimal photosynthesis to combat the lack of sunlight, and microbes exchanged food production as currency for the protective shelter of their hosts.
So, how does this relate to finding life elsewhere in the universe? If life could adapt and flourish in such extreme conditions on Earth, the search for extraterrestrial life in our solar system should extend to environments previously deemed inhospitable, potentially out of the perceived habitable zone. Dr. Ballard’s discoveries paved the way for the concept of extremophiles (organisms thriving in conditions once considered untenable), thereby facilitating the hypothesis that extraterrestrial life, in whatever cellular form, could be within our universe.
This theory has been investigated through the modelling of Enceladus. A 2017 study conducted at Stanford University, utilising data from the Cassini spacecraft, explored the potential habitability of Enceladus’ subsurface water ocean, driven by organic and inorganic carbon – a fundamental component of life. While searching for extraterrestrial life involves considering various environmental factors such as phosphorus abundance and atmospheric temperature, Enceladus stands out as a compelling candidate to initiate exploration.
Building upon the foundational insights uncovered by Dr. Ballard’s team and leveraging previous mission concepts such as the Large Ultraviolet Optical Infrared Surveyor (LUVOIR) and Habitable Exoplanet Observatory (HabEx), NASA is charting new frontiers through the Habitable Worlds Observatory (HWO), in search of evidence indicating the presence of extraterrestrial life. The HWO sees advancements in identifying biosignatures (chemicals indicative of habitability in the atmosphere, such as oxygen and methane) and is uniquely tailored to detecting and characterising exoplanets, especially those with habitable qualities.
Supported by the endorsement of the National Academies’ Pathways to Discovery in Astronomy and Astrophysics in the 2020s, the development of the HWO marks one small (well, giant) leap for mankind in our pursuit to discover signs of life beyond Earth’s corner of the solar system and, in turn, find out if we are truly alone in the universe. With the Nancy Grace Roman Space Telescope (a forthcoming space mission from the HWO aimed at surveying vast expanses of the broader universe) set to launch by May 2027, NASA is laying the groundwork for its next flagship astrophysics mission.
Ending by aptly quoting science-fiction writer Arthur C. Clark, “Two possibilities exist: Either we are alone in the Universe, or we are not. Both are equally terrifying“, but with the advances happening at the Habitable Worlds Observatory, we are closer to finding out either way. Watch this space.
