Plasma blobs hint at new form of life

19:00 17 September 03

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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.


David Cohen

Galileo set for deep impact on Jupiter

16:48 18 September 03

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The NASA spacecraft Galileo is set to crash into Jupiter on Sunday, sacrificing itself for the sake of alien life. But there should be some rewards for astronomers, too. In its final hour, the spacecraft may discover whether a Jovian moon is disintegrating, and explore Jupiter's outermost atmosphere for the first time.

Since its launch in 1989, Galileo has orbited Jupiter for nearly eight years - far longer than the two-year mission that was originally planned. It has made discovery after discovery about the giant planet and its moons.

One suggestion was to keep Galileo in orbit as a long-term observatory, but with little fuel left aboard the craft, NASA decided to make a quick end of it. So they have aimed it at Jupiter and at 0655 GMT on 21 September Galileo will hit the planet's atmosphere and disintegrate.

The main reason the Galileo team gives for destroying the craft is to ensure that there is no chance of it contaminating any of Jupiter's moons. "There had been talk of putting it in a 60-year orbit - parking it there to study comets, for example," says Claudia Alexander, head of the team at NASA's Jet Propulsion Laboratory that will oversee the final plunge.

But no one could guarantee that the orbit would be stable. The complex gravitational effects of Jupiter and its moons are hard to predict, and the strong magnetic field around the planet could change a small spacecraft's course.

"There was a not insignificant chance that the orbit would be perturbed," says Alexander. If so, the spacecraft would probably still have hit Jupiter in the end. But there is just a chance that it would hit Europa, Ganymede or Callisto, which probably hold liquid water, and possibly life.

Nuclear waste

Alexander points to two risks if Galileo had hit one of the moons. First, its instruments are powered by a generator that uses heat from the decay of plutonium to generate electricity. "You don't want to contaminate the environment with nuclear waste," she says.

And it is just possible that terrestrial microbes could have survived on board, as they seem to have done on satellites and space probes. The possibility that terrestrial organisms could have arrived on a crashing spacecraft might confuse the results of any future mission searching for life.

But some scientists say these fears are overplayed. "I am not too worried about contamination," says William McKinnon, a planetary scientist at Washington University in St Louis, Missouri.

Jupiter's moons are subject to ionising radiation from cosmic rays and the planet's radiation belts, he points out. "I tend to think that Europa gets so zapped by radiation that bacteria wouldn't survive."

Star scanner

During Galileo's final plunge, Alexander hopes to make two unique measurements. On its last pass by the inner moon Amalthea in November 2002, Galileo saw nine bright objects whose size and origin are still a mystery.

They may be part of a new ring around Jupiter - a string of rocks rather than the circlets of fine dust that constitute the known rings - or they may just be a local grouping around Amalthea. Either way, they may have originated on Amalthea itself.

On Sunday, JPL scientists will try to use the spacecraft's star scanner to find out more about these rocks. It is a crude camera designed for navigation, but it might still be good enough to measure the locations, motions and even size of the rocks, and work out where they came from and where they are going.

After that, Galileo will press deep into Jupiter's most intense radiation belt. If can survive for just half an hour or so past Amalthea, down to within 40,000 kilometres of Jupiter's cloud tops, the radiation may start to decline.

"After that it will be plain sailing - and we will learn some interesting things," says Alexander. Galileo's last act could be to discover the transition between the Jovian atmosphere and space - an unexplored realm called the exosphere. No one knows what to expect here.

A full version of this story, plus a history of the mission, appears in New Scientist print edition, on sale from 18 September

Row erupts over asteroid press scare

13:59 18 September 03

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Astronomers have been so horrified by press scares over asteroids that they are toning down the scale they use to rate the threat posed in an attempt to discourage journalists from covering potential collisions. The most prominent recent furore involved asteroid QQ47, which briefly had a one-in-a-million chance of crashing into our planet in 2014.

The Torino Scale

False alarms

Binzel himself is so upset by the press coverage of asteroid scares that he is toning down the scale's wording. Instead of "requiring careful monitoring", a category-1 event will now be described as "normal".

Brian Marsden of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, worries that the public will stop taking the asteroid threat seriously if false alarms continue. He says altering the scale is not enough: "It's time we got rid of it."

At the moment, newly discovered "threats" tend to start higher on the scale, when astronomers still have little information on them, and then drop down as further observations rule out the hazard. Marsden says incorporating a measure of how long the asteroid has been tracked would help prevent false alarms.

His colleague John Remo also believes the Torino and related Palermo scales have got it wrong. "They are scare indexes," he says. "They tend to create anxiety." Rather than quantify the damage an asteroid will cause on impact, Remo says it would be more positive to rate how difficult an asteroid would be to deflect into a safe orbit.

But despite disagreements over how best to avoid crying wolf too often, astronomers insist keeping the data secret is not an option. "I hope people take away the idea that if there is actual news, it will be out in the open," says Binzel.

Anil Ananthaswamy

Giant star caught swallowing three planets

12:20 17 September 03

NewScientist.com news service

A giant star has been caught in the act of swallowing three planets, one after the other, with each "meal" accompanied by a massive eruption.

"It has been suggested in the past that stars might engulf planets in this way, but we believe we have actually caught this action for the first time," says Alon Retter of the University of Sydney, Australia.

The star, known as V838 Monocerotis, is about 20,000 light years from Earth. In January 2002, it temporarily became the brightest star in the Milky Way, 600,000 times more luminous than the Sun. At the time, astronomers struggled to explain the spectacular explosion.

Retter and colleague Ariel Marom believe their new analysis of light emissions from the star indicates that it was a red giant that expanded and successively swallowed three relatively massive planets in quick succession. The time between the first and the last engulfment was only about two months.

"In principle, that explanation seems OK," says John Lattanzio, director of the Centre for Stellar and Planetary Astrophysics at Monash University. But he says the star was too hot to have been a red giant. "It was probably one that was on its way there - that could fit the parameters."

Existing models of what will happen when our Sun expands to become a red giant, in about one billion years, suggest that Venus and Mercury will both be engulfed. The likely fate of the Earth is unclear. "Our work suggests that once one planet is engulfed, there is an eruption, and then further expansion - so it might suggest that Earth will indeed be swallowed. But this will need to be checked carefully with the models," Retter says.

Twin peaks

The light analysed from V838 Monocerotis shows that after a short but gradual decline in luminosity following January's outburst, the star suddenly increased in brightness again in early February. The phenomenon was repeated a third time in March.

Retter and Marom found that each of the three maximum peaks in brightness were followed by secondary, weaker peaks. This repeating pattern suggests each event had the same cause, says Retter. The data also reveals the presence of large amounts of lithium and barium, which astronomers had proposed might indicate that a star had swallowed a planet.

Initially it was suggested that the first explosion was some kind of nova outburst, but this was hard to match to the observations. Other researchers suggested that two stars had collided.

"But again, this cannot explain the complicated light curve," Retter says "Our explanation, that the star swallowed three planets, fits all the observational features of the star."

Retter and Marom describe their analysis in a letter accepted by the Monthly Notices of the Royal Astronomical Society.

Emma Young, Sydney

Coolest thing in the Universe revealed

16:32 12 September 03

NewScientist.com news service

The coolest thing in the Universe is now a cloud of sodium atoms in a laboratory in Cambridge, Massachusetts.

Physicists from the MIT-Harvard Centre for Ultra-Cold atoms have chilled 2500 sodium atoms to within half a billionth of a degree of absolute zero, the temperature at which atomic oscillation slows to a standstill.

"Nothing in the Universe that we know of is naturally this cold" says Aaron Leanhardt, who led the research. Even deep space is six billion times hotter.

"The old record for 'lowest manmade temperature' was published in the journal Nature, so hopefully publishing our result in Science will be considered good enough for acceptance as a Guinness world record" he says.

Spreading out

To cool the atoms, the team trapped them by balancing gravitational and magnetic fields then allowed the gas to expand. In a gas, temperature is a measure of the average speed of the atoms. When the gas expands the atoms spread out and slow down - lowering the temperature.

In this experiment, the atoms had an average speed of only one millimetre per second by the time the temperature had fallen to 450 picokelvin.

Atomic clocks measure time against the frequency of nuclear transitions inside atoms. When atoms are hot, their motion causes the frequency to fluctuate. Colder atoms could therefore lead to more accurate time-keepers.

Also, when atoms are this cold they all settle into the same quantum state - forming a peculiar type of matter known as a Bose Einstein Condensate. These are used to study quantum effects.

The team's next set of experiments, however, will look at what happens when the ultra-cold atoms crash into a wall kept a room temperature. Will they stick, or bounce?

Journal reference: Science (vol 301, p 1513)

Jenny Hogan