Superbugs from Hell - Evolution Re-Visited

The biggest impacts would have blasted away the Earth's atmosphere and swathed the globe in incandescent rock vapour. The heat pulses were fierce enough to boil the oceans dry and sterilise the exposed land to a depth of half a mile or more. Not even superbugs could survive such cataclysmic episodes unprotected. Yet, paradoxically, there are traces of relatively advanced life in ancient rocks from Greenland dated at over 3.85 billion years - a time before this massive cosmic bombardment had abated. But if the 'comfort zone' of heat-loving microbes was deep enough, they could shelter from the cosmic barrage in the torrid strata of the Earth's crust, beyond the reach of even the fiercest heat pulses.

Superbugs on Mars

Photo - NASA Mars today is a frozen desert « yet dried-up channels and crater erosion hints that the Red Planet was once warmer and drier, with rivers and possibly oceans. Was this, too, a cradle of life?

If the theory is right, and life did begin deep within the Earth, it may also have got going beneath the surfaces of other planets too. Mars is an obvious candidate. When two Viking space probes landed there in 1977 they scooped up some dirt to test for biological activity. No clear evidence was found, and most scientists pronounced the Red Planet dead. With hindsight, this outcome wasn't surprising, since the surface of Mars is a freeze-dried desert bathed in ultra-violet radiation that would prove lethal to almost all known organisms. However, beneath the hostile surface, conditions may be more congenial for life. Geothermal heat will have melted the permafrost to create reservoirs of liquid brine similar to those beneath the Earth's sea bed. So there might be superbugs lurking below the harsh Martian terrain.

Although today Mars is cold and dry, in the remote past it was warm and wet, and not unlike Earth. It had rivers and glaciers and possibly a large ocean. Life may well have spread to the planet's surface and briefly flourished in the Martian spring, before the atmosphere leaked away and the temperature plunged. It's possible these ancient organisms left fossils in the surface rocks, where they may be discovered by forthcoming missions to the Red Planet.

Photo - NASA. The infamous "microbes from Mars". Magnified 100,000 times the interior of a meteorite from Mars (coloured red) reveals intriguing bug-like shapes (blue). Researchers are stilling arguing whether these are indeed fossilised bacteria.

A few years ago, some scientists claimed to find fossilised microbes within a Martian meteorite collected in Antarctica. Although the jury is still out on that, it no longer seems so fanciful to speculate that Mars has, or at least once had, some form of life.