Scientists have discovered a remarkable undersea field of hot springs and gigantic chimneys, unlike anything seen before, and named it Lost City. Geologist Deborah Kelley led an expedition to analyze Lost City, obtaining results that have prompted reconsideration of how life on Earth first emerged and of where extraterrestrial life might also exist.
Around most hydrothermal vents, the seawater is extremely acidic and reaches temperatures over 400 degrees Celsius. But at Lost City, the water is alkaline and no hotter than 90 degrees Celsius. And unlike other hydrothermal vents, those at Lost City are situated on seafloor consisting mainly of rock called peridotite. Seawater reacts with the peridotite, producing energy-rich gases such as hydrogen and methane.
Some scientists speculate that these gases could have fostered the emergence of life on Earth. A famous experiment conducted in 1952 showed that sparks discharging through energy-rich gases produce many organic compounds, including amino acids, which are components of all living things. However, geologists later concluded that these gases were probably not concentrated enough in Earth's early atmosphere to form such compounds. But the gases are far more concentrated in the Lost City waters.
Billions of years ago, could vents resembling those at Lost City have produced the organic compounds required for life? Hydrothermal fluids at Lost City contain certain organic compounds. And on early Earth, peridotite probably comprised most of the seafloor, making conditions like those at Lost City far more common than they are today.
Lost City also teems with microbes such as methanogens, which metabolize hydrogen and generate methane. Each step in the geothermal process that generates methane is replicated in the biochemical pathways of these methanogens. This suggests that on early Earth, the methanogens' primordial ancestors at sites like Lost City may have simply co-opted each of the geochemical steps for themselves, producing the first biochemical pathways, which their descendents have inherited.
The Lost City findings also suggest that extraterrestrial life could exist on any planet or moon containing peridotite and liquid water. Evidence of these components is strongest on Mars and on Jupiter's moon Europa, and researchers have detected methane in the Martian atmosphere. Whether the methane comes from microbes or chemical reactions remains uncertain.
