If extraterrestrials were to visit Earth, their diet would likely consist of raw materials such as water, nitrogen, and salts, rather than familiar human foods like Reese's Pieces, according to Professor José Miguel Soriano del Castillo, a nutritionist from the University of Valencia.
Writing in The Conversation, Professor del Castillo explained that Earth could present a 'risky buffet' for alien life. Even if aliens share similar basic biology with humans, there's no guarantee that Earth-based foods would be compatible with their digestive systems. Terrestrial proteins might be unusable if their digestive systems utilize different amino acids, and Earth's sugars could be indigestible to their metabolism.
Instead of processed foods, Professor del Castillo posits that aliens would more likely sustain themselves on fundamental elements and compounds. These include water, nitrogen, phosphorus, iron, salts, lipids, microbial biomass, or simple organic molecules.
Potential Alien Diets and Needs
While the exact dietary needs of an alien are impossible to determine without knowing their specific biology, scientists generally believe life requires a source of energy, a liquid medium for chemical reactions, and suitable chemical elements. Earth readily provides these components.
Advanced extraterrestrials might possess the ability to process Earth's organic matter into a form suitable for their own digestive systems. However, Professor del Castillo warns that interstellar visitors would need to be cautious due to potential toxins, pathogens, and allergens present on Earth.
Cows, for example, rely on internal bacteria to digest grass, illustrating the diverse and unique digestive systems found on Earth. This complexity makes it difficult to predict what an alien's natural diet might resemble. The classic notion of UFOs abducting cows might be more plausible, as it would allow aliens to analyze local biology before consumption.
Scientists can estimate the caloric needs of potential alien visitors based on their size. For instance, a 70-kilogram alien might require around 1,700 kilocalories per day, while a 150-kilogram extraterrestrial could need over 3,000 kilocalories for basic sustenance. These figures do not account for the additional energy needed for activities like movement, thinking, or operating machinery.
Beyond Biological Needs
An even more unconventional possibility is that alien life might not require food in the traditional sense. Many scientists speculate that the first extraterrestrial contact may come not from biological beings, but from robotic probes. Highly advanced aliens could potentially transcend their biological forms to become 'post-biological entities' with synthetic bodies.
In such scenarios, 'food' would be replaced by energy sources like electricity, heat, chemical fuel, or nuclear energy. An alien robot, for example, would not consume food but would need to recharge its power source. This concept offers a different perspective on sustenance for non-biological or post-biological extraterrestrial life.
The Fermi Paradox, named after physicist Enrico Fermi, questions the apparent contradiction between the high probability of extraterrestrial civilizations existing and the lack of evidence for, or contact with, such civilizations. Explanations range from the vast distances between stars to the possibility that intelligent alien species deliberately avoid contact, or that advanced civilizations inevitably destroy themselves.