"Long before it's in the papers"
September 11, 2007

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Alien life… from dust particles?

Aug. 14, 2007
Courtesy The Institute of Physics
and World Science staff

It’s not what life is sup­posed to be made of. It’s def­i­nitely not where life is sup­posed to be found. Yet it looks pret­ty alive, re­search­ers say: it sus­tains it­self, re­pro­duces it­self, in­ter­acts with its neigh­bors and evolves.

It’s a mere com­put­er sim­ula­t­ion of dust, of a type si­m­i­lar to that which floats among stars, ac­cord­ing to the sci­en­tists.

The in­ves­ti­ga­tors de­scribed the strange sim­ulated dust—which takes on the form of cork­screw-shaped par­t­i­cles—in a pa­per pub­lished today in the New Jour­nal of Phys­ics. The find­ings hint at the pos­si­bil­ity that life be­yond earth may not nec­es­sarily use car­bon-based mo­le­cules as its build­ing blocks, as it does on Earth, they said. But the re­search al­so points to a pos­si­ble new ex­plana­t­ion for life on our plan­et, they added.

Life on Earth con­sists of or­gan­ic mo­le­cules, which are simply large com­pounds of car­bon. The no­tion that inor­gan­ic, or non-car­bon based, dust may take on life is noth­ing short of al­ien. The stuff does­n’t even con­tain sil­i­con, which a few sci­en­tists have sug­gested could re­place car­bon as a build­ing block for life (e­ven that idea is mostly rel­e­gat­ed to sci­ence fic­tion to­day.)

In the new re­search, sci­en­tists at the Rus­sian Acad­e­my of Sci­ence in Mos­cow, the Max-Planck In­sti­tute for Ex­tra­ter­res­tri­al Phys­ics in Garch­ing, Ger­ma­ny and the Un­ivers­ity of Syd­ney, Aus­tral­ia, stud­ied mix­tures of inor­gan­ic ma­te­ri­als in a plas­ma. 

Plas­ma is a gas-like sub­stance whose at­oms are stripped of the elec­trons, or elec­tric­ally charged par­t­i­cles, that nor­mally in­hab­it them. This separa­t­ion leads the at­oms to al­so be­come charged, be­cause un­der nor­mal con­di­tions, the elec­tron’s charge can­cels out that of the at­om. Plas­ma is con­sid­ered a fourth state of mat­ter be­yond sol­id, liq­uid and gas.

Un­til now, phys­i­cists as­sumed that there could be lit­tle or­ga­nisa­t­ion in such a cloud of par­t­i­cles. How­ev­er, The Rus­sian Acad­e­my’s V.N. Tsy­tovich and col­leagues found, us­ing a com­put­er mod­el of mo­lec­u­lar dy­nam­ics, that plas­ma par­t­i­cles can un­dergo self-organ­iz­a­tion as charges be­come sep­a­rat­ed. This re­sults in mi­cro­scop­ic strands of sol­id par­t­i­cles that twist in­to cork­screw shapes, or hel­i­cal struc­tures. These hel­i­cal strands are them­selves charged and are at­tracted to each oth­er.

Quite bi­zarre­ly, not only do these hel­i­cal strands in­ter­act in a sur­pris­ing way in which like can at­tract like, they al­so un­dergo changes nor­mally as­so­ci­at­ed with bi­o­log­i­cal molecules, such as DNA and pro­teins, say the re­search­ers. They can, for in­stance, di­vide, or bi­fur­cate, to form two cop­ies of the orig­i­nal struc­ture. These new struc­tures can al­so in­ter­act to in­duce changes in their neigh­bours and they can even evolve in­to yet more struc­tures as less sta­ble ones break down, leav­ing be­hind only the fit­test struc­tures in the plas­ma.

So, could hel­i­cal clus­ters formed from in­ter­stel­lar dust be some­how alive? “These com­plex, self-organized plas­ma struc­tures ex­hib­it all the nec­es­sary prop­er­ties to qual­i­fy them as can­di­dates for inor­gan­ic liv­ing mat­ter,” said Tsy­tovich, “they are au­ton­o­mous, they re­pro­duce and they evolve”.

He adds that the plas­ma con­di­tions needed to form these hel­i­cal struc­tures are com­mon in out­er space. How­ev­er, plas­mas can al­so form un­der more down to earth con­di­tions such as the point of a light­ning strike. The re­search­ers hint that per­haps an inor­gan­ic form of life emerged on the pri­mor­di­al earth, which then acted as the tem­plate for the more fa­mil­iar or­gan­ic mo­le­cules we know to­day.

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Homepage image: Dust surrounds a star (Courtesy NASA)

It’s not what life is supposed to be made of. It’s definitely not where life is supposed to be found. Yet it looks pretty alive, researchers say: it sustains itself, reproduces itself, interacts with its neighbors and evolves. It’s mere computer simulation of dust, of a type similar to that which floats among stars, according to the scientists. The investigators described the strange simulated dust—which takes on the form of corkscrew-shaped particles—in a paper in the research journal New Journal of Physics. The findings hint at the possibility that life beyond earth may not necessarily use carbon-based molecules as its building blocks, as it does on Earth, they said. But the research also points to a possible new explanation for life on our planet, they added. Life on Earth consists of organic molecules, which are simply large compounds of carbon. The notion that inorganic, or non-carbon based, dust may take on life is nothing short of alien. The stuff doesn’t even contain silicon, which a few scientists have suggested could replace carbon as a building block for life (even that idea is mostly relegated to science fiction today.) In the new research, scientists at the Russian Academy of Science in Moscow, the Max-Planck Institute for Extraterrestrial Physics in Garching, Germany and the University of Sydney, Australia, studied mixtures of inorganic materials in a plasma. Plasma is a gas-like substance whose atoms are stripped of the electrons, or electrically charged particles, that normally inhabit them. This separation leads the atoms to also become charged, because under normal conditions, the electron’s charge cancels out that of the atom. Plasma is considered a fourth state of matter beyond solid, liquid and gas. Until now, physicists assumed that there could be little organisation in such a cloud of particles. However, The Russian Academy’s V.N. Tsytovich and colleagues found, using a computer model of molecular dynamics, that particles in a plasma can undergo self-organization as electronic charges become separated. This effect results in microscopic strands of solid particles that twist into corkscrew shapes, or helical structures. These helical strands are themselves electrically charged and are attracted to each other. Quite bizarrely, not only do these helical strands interact in a surprising way in which like can attract like, they also undergo changes normally associated with biological molecules, such as DNA and proteins, say the researchers. They can, for instance, divide, or bifurcate, to form two copies of the original structure. These new structures can also interact to induce changes in their neighbours and they can even evolve into yet more structures as less stable ones break down, leaving behind only the fittest structures in the plasma. So, could helical clusters formed from interstellar dust be somehow alive? “These complex, self-organized plasma structures exhibit all the necessary properties to qualify them as candidates for inorganic living matter,” said Tsytovich, “they are autonomous, they reproduce and they evolve”. He adds that the plasma conditions needed to form these helical structures are common in outer space. However, plasmas can also form under more down to earth conditions such as the point of a lightning strike. The researchers hint that perhaps an inorganic form of life emerged on the primordial earth, which then acted as the template for the more familiar organic molecules we know today.