Plasma blobs hint at new form of life
Physicists have created blobs of gaseous plasma that can grow, replicate and communicate - fulfilling most of the traditional requirements for biological cells. Without inherited material they cannot be described as alive, but the researchers believe these curious spheres may offer a radical new explanation for how life began.
Most biologists think living cells arose out of a complex and lengthy evolution of chemicals that took millions of years, beginning with simple molecules through amino acids, primitive proteins and finally forming an organised structure. But if Mircea Sanduloviciu and his colleagues at Cuza University in Romania are right, the theory may have to be completely revised. They say cell-like self-organisation can occur in a few microseconds.
The researchers studied environmental conditions similar to those that existed on the Earth before life began, when the planet was enveloped in electric storms that caused ionised gases called plasmas to form in the atmosphere.
They inserted two electrodes into a chamber containing a low-temperature plasma of argon - a gas in which some of the atoms have been split into electrons and charged ions. They applied a high voltage to the electrodes, producing an arc of energy that flew across the gap between them, like a miniature lightning strike.
Sanduloviciu says this electric spark caused a high concentration of ions and electrons to accumulate at the positively charged electrode, which spontaneously formed spheres (Chaos, Solitons & Fractals, vol 18, p 335). Each sphere had a boundary made up of two layers - an outer layer of negatively charged electrons and an inner layer of positively charged ions.
Trapped inside the boundary was an inner nucleus of gas atoms. The amount of energy in the initial spark governed their size and lifespan. Sanduloviciu grew spheres from a few micrometres up to three centimetres in diameter.
Split in two
A distinct boundary layer that confines and separates an object from its environment is one of the four main criteria generally used to define living cells. Sanduloviciu decided to find out if his cells met the other criteria: the ability to replicate, to communicate information, and to metabolise and grow.
He found that the spheres could replicate by splitting into two. Under the right conditions they also got bigger, taking up neutral argon atoms and splitting them into ions and electrons to replenish their boundary layers.
Finally, they could communicate information by emitting electromagnetic energy, making the atoms within other spheres vibrate at a particular frequency. The spheres are not the only self-organising systems to meet all of these requirements. But they are the first gaseous "cells".
Sanduloviciu even thinks they could have been the first cells on Earth, arising within electric storms. "The emergence of such spheres seems likely to be a prerequisite for biochemical evolution," he says.
Temperature trouble
That view is "stretching the realms of possibility," says Gregoire Nicolis, a physical chemist at the University of Brussels. In particular, he doubts that biomolecules such as DNA could emerge at the temperatures at which the plasma balls exist.
However, Sanduloviciu insists that although the spheres require high temperature to form, they can survive at lower temperatures. "That would be the sort of environment in which normal biochemical interactions occur."
But perhaps the most intriguing implications of Sanduloviciu's work are for life on other planets. "The cell-like spheres we describe could be at the origin of other forms of life we have not yet considered," he says. Which means our search for extraterrestrial life may need a drastic re-think. There could be life out there, but not as we know it.
