Hold the Old Lace, Please

So some NASA scientists trained bacteria from a lake in California to eat the element arsenic instead of phosphorus. That may not sound like a big deal -- if you're a bacterium, your life is pretty darn dull anyway, so why would it matter what you ate.

However, phosphorus is one of the "pick six" of elements thought to be essential for life as we know it (sometimes scientists abbreviate that LAWKI). Find a place without it or any of the other five -- carbon, oxygen, nitrogen, hydrogen and sulfur -- and you find a place which, up until this experiment, was thought to be guaranteed to be without life. Science fiction has frequently suggested life that replaces carbon with silicon, but swapping the phosphorus out for arsenic was not really on most folks' radar.

But the researchers theorized that arsenic, which is just below phosphorus on the periodic table, might take its place in critters that could already tolerate high levels of that element. So they dug some out of the mud of a salty, arsenic-heavy lake and fed them more arsenic to see what would happen. The bacteria survived and grew, although they were different from normal, phosphate-eating bacteria. They also, judging by their growth rates, would rather have phosphates in their diet along with the arsenic.

The fact that life can exist and continue without one of the basic elements previously considered essential for it means that satellites and probes sent to other planets may wind up overlooking living critters whose chemistry is different than ours. It also gives some weight to a realization that many people have when they get old enough to start examining the world around them and weighing it against what seems sane and rational:

Life is weird.