Zaragoza (Spain), February 23: The quest to uncover the origins of life beyond Earth remains one of the most fascinating scientific pursuits. While Earth is currently the only known planet capable of sustaining life, scientists continue their search for ‘LUCA’ (Last Universal Common Ancestor), the ancestral cell from which all known living organisms are believed to have evolved.
The Search Beyond Earth
As humanity dreams of colonizing Mars, scientific perspectives about the Red Planet have evolved significantly. The ‘Perseverance’ and ‘Curiosity’ rovers have identified compounds and minerals on Mars, suggesting that life-supporting conditions might have once existed there. However, concrete evidence of life remains elusive.
Currently, Mars resembles a barren, red desert with no visible signs of life. Prospects of finding life on other nearby planets are even slimmer. Mercury, being too close to the Sun, is a scorched rock, while Venus has a dry and toxic atmosphere. The remaining planets in our solar system are either gas giants or too distant from the Sun to support life.
Therefore, scientists are focusing on the moons of Jupiter and Saturn, particularly Europa and Enceladus, respectively. These moons are believed to harbor vast oceans beneath their icy surfaces, potentially containing organic molecules essential for life. These molecules might not resemble stereotypical extraterrestrial beings but could manifest as simple, single-celled organisms similar to Earth’s prokaryotes.
Exploring Extremes for Life
Before the 1960s, the idea of life existing on remote moons or extreme environments seemed impossible. It was believed that life could only thrive under moderate conditions—water, temperatures between 0 to 40 degrees Celsius, neutral pH, low salinity, and a stable energy source such as sunlight.
However, in the mid-20th century, microbiologist Thomas D. Brock discovered bacteria thriving in the boiling hot springs of Yellowstone National Park, where temperatures exceed 70 degrees Celsius. Although not directly related to extraterrestrial research, this discovery broadened the scientific understanding of life's adaptability.
Since then, extremophiles—organisms that thrive in extreme conditions—have been found in various harsh environments on Earth. These include the cracks of polar ice, deep-sea high-pressure zones, highly acidic environments like Rio Tinto, and even in extreme salinity, as seen in the Dead Sea. Some extremophiles are also resistant to high levels of radiation.
Life on Mars: Closer Than Expected?
Surprisingly, potential Martian life forms might already reside within us. During the 1980s, Australian physicians Barry Marshall and Robin Warren discovered Helicobacter pylori, a bacterium thriving in the highly acidic environment of the human stomach. This bacterium not only survives but also causes gastric ulcers, challenging the belief that such acidic conditions were uninhabitable for microorganisms.
The discovery led to the 2005 Nobel Prize in Medicine, showcasing how life can adapt to extreme conditions. The bacterium uses flagella to navigate stomach fluids, break through protective mucus, and adhere to the stomach lining. It creates a microenvironment conducive to its survival by breaking down urea into ammonia and carbon dioxide, neutralizing stomach acids locally.
The Promise of Extremophiles in Space Exploration
The study of extremophiles offers hope that life might exist on other celestial bodies within the solar system or among the 5,500 known exoplanets. While life elsewhere might not mirror Earth's complex ecosystems, it could manifest as resilient microorganisms capable of surviving under extreme conditions.
As Carl Sagan famously said in ‘Contact’, “The universe is a pretty big place. If it’s just us, it seems like an awful waste of space.” The search for life continues, fueled by discoveries on Earth and the tantalizing possibility that our universe might harbor life in the most unexpected places.
