How the first life on Earth survived its biggest threat — water
On 18 February next year, a NASA spacecraft will plummet through the Martian atmosphere, fire its retro-rockets to break its fall and then lower a six-wheeled rover named Perseverance to the surface. If all goes according to plan, the mission will land in Jezero Crater, a 45-kilometre-wide gash near the planet’s equator that might once have held a lake of liquid water.
Among the throngs of earthlings cheering on Perseverance, John Sutherland will be paying particularly close attention. Sutherland, a biochemist at the MRC Laboratory of Molecular Biology in Cambridge, UK, was one of the scientists who lobbied NASA to visit Jezero Crater, because it fits his ideas about where life might have originated — on Mars and on Earth.
The choice of landing site reflects a shift in thinking about the chemical steps that transformed a few molecules into the first biological cells. Although many scientists have long speculated that those pioneering cells arose in the ocean, recent research suggests that the key molecules of life, and its core processes, can form only in places such as Jezero — a relatively shallow body of water fed by streams.
That’s because several studies suggest that the basic chemicals of life require ultraviolet radiation from sunlight to form, and that the watery environment had to become highly concentrated or even dry out completely at times. In laboratory experiments, Sutherland and other scientists have produced DNA, proteins and other core components of cells by gently heating simple carbon-based chemicals, subjecting them to UV radiation and intermittently drying them out. Chemists have not yet been able to synthesize such a wide range of biological molecules in conditions that mimic seawater. [Continue reading…]