There’s an old acronym in exobiology: LAWKI — Life As We Know It. That’s what we search for off-planet, because we know what its characteristics are and can postulate environments in which it might plausibly exist. NASA’s announcement today is interesting because it turns out that we’ve discovered a new form of life that is not LAWKI not in space but here on Earth.
Up until now, it has been assumed that DNA-based lifeforms cannot function without the vital element phosphorus, which is one of the six needed for cells to function (the others are carbon, oxygen, hydrogen, nitrogen, and sulfur). Thus, it had been presumed that environments lacking this element would lack life as well and so would not be fruitful places to look for it.
The breakthrough is the apparent discovery of microbes in Mono Lake (a very salty lake east of Yosemite National Park in California) that can substitute arsenic for the function normally played by phosphorus. One of the reasons that arsenic is a poison is that organisms have trouble telling the difference between it and phosphorus, due to its chemical nature. These new lifeforms apparently require only trace amounts of phosphorus — the “holy grail” will be if we find some able to do without it completely.
So this is a Life As We Didn’t Know It (LAWDKI), and it will change the thinking of exobiologists about where to look for life in the rest of the universe. It will also teach us to broaden our thinking about what life’s requirements really are, which may ultimately help in the development of artificial life. You can read more here.