Here At Home - A Clue To Life On Mars

Bacteria found in a North Carolina 
lake may have the answers, reports Biplab Das 

Scientists may soon abandon extravagant space projects designed to look for life on Mars and other planets because a team from the National Space Science and Technology Centre in Huntsville has found a new species of bacteria in Northern Carolina's Mono Lake - a salty, alkaline water body in an enclosed volcanic basin - which could offer clues to the kind of life that may thrive on the red planet. 

Richard Hoover, an astrobiologist at Nasa's Marshall Space Flight Centre in Huntsville, and Dr. Elena Piktu, a microbiologist with the Centre for Space Plasma and the Aeronomy Research Laboratory at the University of Alabama, led the research team. The National Space Science and Technology Centre project is a joint effort between the Marshall Space Flight Centre and Alabama University. The results of the study have been published in the May 2003 issue of the International Journal of Systematic and Evolutionary Microbiology. 

The newly found bacteria have been named Spirochaeta americana. These bacteria loathe oxygen and Mono Lake has been their home for millions of years. Hoover and Piktu isolated the bacteria from the oxygen-deprived mud of the lake. The bug is a long, thin bacterium known as extremophile - an organism that can survive in some of earth's most unforgiving conditions. 

Of the vast numbers of bacteria, only about 6,000 species have been identified. Of these, only a small fraction are extremophiles. Like the newly found species, several other Spirochaeta are extremophiles. "The environment these bacteria inhabit would be distinctly inhospitable to many other life forms, including humans," said Piktu. For survival, humans and many other earthly animals need oxygen. But oxygen is a deadly gas for bugs like Spirochaeta. 

This can encourage scientists who look for alien life forms that might exist beyond our home planet. "Since other bodies of the solar system lack our oxygen-rich atmosphere, micro-organisms that thrive without oxygen are good candidates for astrobiology research," said Hoover. 

For years, astrobiologists have advocated that extreme environments on earth can harbour life forms, which could be models for studying alien life. This notion lured scientists to acid pools, super-heated volcanic vents, glaciers, nuclear reactor waste, at high pressure and absolute darkness in deep-sea abysses and in rocks far beneath the earth's crust - conditions are lethal to other living organisms. 

Such a lethal environment also prevails in Mono Lake where the new species of Spirochaeta thrives. It is a terminal lake through which water does not flow. Instead, water enters the lake from hot alkaline springs, rainfall and streams. Evaporation is the only way for water to escape the lake. As water evaporates, it leaves behind a thickening broth of chemicals. What is more, the activity of myriad types of micro-organisms has made the lake water heavily toxic and twice as salty as seawater and extremely alkaline. 

These bugs are very elusive. Since the discovery of the first species of the genus Spirochaeta in 1835, only 13 other species of these bugs have been detected worldwide. For Hoover and Piktu, finding the new species of Spirochaeta is like winning a jackpot. "These extremely thin and graceful bacteria move with elegant motion. Their cell walls are very delicate and it is difficult to keep them alive for long periods in the laboratory," said Piktu. 

Because these micro-organisms love mineral rich salty water, they are of great interest to astrobiologists. "The goal of astrobiology is to discover whether life exists exclusively here on earth or is widely distributed throughout the universe," Hoover said. "By studying micro-organisms found in earth's extreme places like Mono Lake, we can better understand how life might exist on Mars." But Hoover is sure of one thing. "If, or when, we find life on other planets, our first discoveries will probably be micro-organisms."