In its lawsuit, the human rights group said that more than one million Tibetans had been killed or gone missing since China occupied Tibet in 1951.

Tibet's spiritual leader, the Dalai Lama, fled into exile in India after an abortive 1959 uprising against increasingly heavy-handed Chinese rule. China has labelled the Dalai Lama a separatist seeking to use his religious authority to gain independence for Tibet.

The Spanish National Court will hear witnesses before deciding whether to file charges of genocide, crimes against humanity, state terrorism and torture against China's former president Jiang Zemin, the former prime minister Li Peng and five military and security officials in Tibet, some of whom have retired.

Mr Liu said China and Spain had friendly ties and had enjoyed a "smooth development of bilateral relations in recent years".

Around 750 families, or 2,500 people, will have their cases reviewed by a committee made up of government officials and immigrant support groups.

The Education Without Borders Network (RESF), which is campaigning for all the children and families concerned to be given residence rights, dismissed the announcement as a token gesture.

RESF -- which had previously said some 10,000 children were at risk of deportation -- now believes at least 50,000 families to be concerned, based on interior ministry figures, said its spokesman Richard Moyon.

"As many as 100,000 children of illegal immigrants are enrolled in French schools, so this so-called humanitarian gesture will reach a mere one or two percent."

However Sarkozy ruled out a large-scale amnesty for clandestine immigrants with children in the French school system, which he argued would create a new "channel" for illegal immigration.

Anyone is free to register their child at a school in France -- without having to produce identity or residence papers.

France's centre-right government has vowed to step up the deportation of illegal immigrants -- who number 200,000 to 400,000 in the country -- as part of a toughening of immigration policy backed by three-quarters of the public.

To encourage families to leave, the interior ministry recently raised the relocation funds paid to illegal immigrants, from 150 to 2,000 euros (190 to 2,500 dollars) per person, plus 1,000 euros per child under 18.

Since 2004, RESF has blocked dozens of deportations -- which are part of a wider move to tighten immigration rules under Sarkozy's authority.

Schoolteachers, parents and activists in the network say many of the children concerned are well-integrated and thriving in the French school system, and that to deport them would violate the principles of the republic.

RESF also charges that many have been unfairly denied political asylum in France and could face persecution upon their return home.

Since late April, more than 40,000 people have signed an RESF petition against what they denounce as a "childhunt" -- pledging to "sponsor, protect and house" the children and their families, even it if means breaking the law.

Sarkozy announced the scale-back of his deportation plans as the Senate began debating a hotly-contested new immigration law adopted by the National Assembly last month.

The law on "selected immigration" aims to favour skilled workers and cut back on family reunification, while scrapping automatic residence rights for illegal immigrants who have spent 10 years in the country.

Sarkozy strongly denies that his policies are racist -- Africans make up a majority of illegal immigrants in France -- warning that a failure to combat the phenomenon would play into the hands of the xenophobic far-right.

Pioneer 10's sister ship is also being pushed off course, and an analysis of the Galileo spacecraft to Jupiter and the Ulysses solar probe hints that they are affected by a similar anomaly. This has led some physicists to suggest that the Pioneer probes may have exposed a fundamental flaw in our understanding of how objects move through space under the influence of gravity. Turyshev's mission might be the best chance we have to see if our best theory of gravity, Einstein's general theory of relativity, needs an upgrade.

Turyshev will not, however, be launching two replica craft into space. His missions will be virtual ones, in which he will replay the data from the real flights to see if he can detect where and how things started going wrong.

The project nearly failed at the first hurdle. Though the Pioneers have been flying for more than 30 years, the anomaly in their trajectories is based on observations from only a small portion of their journeys: 11.5 years for Pioneer 10 and just 3.75 years for Pioneer 11. Turyshev needed the data for the rest of the flights, but when he went in search of it he found that the magnetic tapes and floppy discs had gone astray. After much searching, all he could find were 400 reels of magnetic tape, stored in boxes under a staircase at JPL. The tapes contained the full 30 years' worth of measurements about the spacecrafts' trajectories, but there was a snag. Years of heat and humidity had started to take their toll on the tapes, and he feared they might have become unreadable.

Luckily, he knew someone who could help. Software engineer Kyong Lee at JPL was able to coax the tapes into revealing their precious data, which he re-recorded on DVD. Last year Turyshev had another stroke of luck when he visited NASA's Ames Research Center in Moffett Field, California. "I had gone to Ames to give a lecture, specifically to interest people in investigating the Pioneer anomaly," he says. He knew that sitting somewhere in the research complex were the project documents, including records from 114 onboard sensors that recorded the spacecrafts' manoeuvres and spin rate, as well as "housekeeping" data. Throughout the Pioneers' three-decade voyages, the craft beamed back this telemetry data to Earth so that engineers on the ground could monitor each spacecraft's vital signs. All this data had been painstakingly stored on floppy discs by mission engineer Larry Kellogg, who figured that it could one day be used to construct a computer program to teach children how a real spacecraft operated.

With access to both the tracking measurements and telemetry data, Turyshev was confident that he had everything he would need to build a virtual model of the spacecraft, and investigate whether a malfunction was causing the anomaly. His optimism was short-lived, though. Straight after the talk, managers at Ames told him they had earmarked the data discs for destruction because they were taking up too much space. The first dumpster had already been delivered and was sitting outside waiting to be filled. In desperation, Turyshev offered to return at the weekend with a truck of his own to collect the material. He had no idea where he was going to store it, but he knew he could not allow this priceless information to be destroyed. In the end, the Ames managers relented, and found a place to store the 60 filing cabinets' worth of data.

The next problem was how to read the obsolete discs. Kellogg introduced Turyshev to Viktor Toth, a C++ programmer and space enthusiast living in Ottawa, Canada. Toth volunteered to write a program that would extract the 40 gigabytes of data from the old floppies and record it onto DVDs. That has now been done, and the data is about to be released to groups throughout the world so that the virtual re-flight of Pioneer can begin.

Several teams will pore through the telemetry data, watching for every firing of the thrusters and every malfunction, no matter how slight. Each event will then be checked against the tracking data, which tells them how fast and in what direction the spacecraft is moving. In this way they will be able to reconstruct, moment by moment, the condition and movement of the spacecraft (see "Anatomy of an anomaly"). The job will take at least a year to complete. There are nearly 95,000 measurements to correlate for Pioneer 10 alone, covering 29 years of the mission during which the spacecraft travelled more than 12 billion kilometres (see Diagram). Nothing similar has ever been attempted before, Turyshev says. "This is the first time in history that a space mission will be reconstructed."
Constant force

The investigators are faced with a painstaking task, as the malfunction they are looking for is likely to be a tiny one. "The leak of a single molecule of gas from the spacecraft will give a momentary acceleration similar in size to the Pioneer anomaly," says Dario Izzo, a mission analyst from the European Space Agency's Advanced Concepts Team in Noordwijk, the Netherlands. Thankfully, the force acting on the craft is a persistent one, so if a malfunction of the spacecraft's systems is the cause it must be long-lived too.

With this in mind, the teams plan to concentrate their attention on the prime suspect for the anomaly: the radioisotope thermoelectric generator (RTG) on each Pioneer probe. The RTGs, which convert heat from the radioactive decay of plutonium-238 into electricity to power the spacecraft, are held on a boom away from the spacecraft's body. Even from here a little waste heat from the generator might reach the probe. This could raise the temperature on one side of it, producing a feeble thrust as the energy radiates away into space. Turyshev has high hopes that the telemetry data will allow the researchers to study the impact of the RTG for the first time. "The plutonium's half-life is 87.7 years, and I believe that we will able to see this decay in the telemetry and account for its effects," he says. Once researchers have done that, and other checks, whatever remains is the Pioneer anomaly. "We may end up with a smaller Pioneer anomaly than at present - or better with nothing at all," Turyshev says.

But what if the teams convince themselves that there is no onboard explanation for the anomaly? Their next step then will be to measure the precise direction in which the force is acting. The best we can say at the moment is that it seems to point back towards the sun, but that is only because the limited measurements and analysis available till now make the Earth's direction virtually indistinguishable from the sun's. Signals from the earlier part of the mission should resolve this, because the difference between the sun's and the Earth's directions should be more noticeable in measurements taken when the spacecraft was closer to Earth. If the anomalous force points towards the Earth, it will mean that it is an artefact of the way the tracking stations on Earth collected the signals, and the mystery of the Pioneer anomaly will be solved.

Turyshev's effort comes at a time of growing interest in the anomaly. Two years ago, when ESA asked researchers to submit ideas for missions to launch between 2015 and 2025, several of the proposals were for experiments to investigate the Pioneer anomaly. This led Izzo and his team at ESA to analyse various strategies to study it. "If I had the money I would launch a mission just to study the gravitational field of the outer solar system," he says. The central component of the mission would be a small sphere of precisely known mass with a highly reflective surface. The sphere would move as gravity dictates, along a trajectory known as a geodesic. A conventional spacecraft would follow, firing a laser beam at the sphere's reflective surface to track its movements. As well as investigating the Pioneer anomaly, such a mission would be the most precise test yet of general relativity.
Planetary puzzle

Izzo concedes, though, that this is probably not going to happen, at least not as the dedicated mission he would like. "I have to be realistic," he says, and that means piggybacking the mission onto something that will tour the outer solar system. He and his collaborator Andreas Rathke at EADS Astrium in Germany propose doing this on ESA's next mission to Jupiter or one of the other outer planets.

Not everyone thinks the Pioneer anomaly deserves the attention it is getting. Lorenzo Iorio of the Italian National Institute for Nuclear Physics in Bari points out that if the anomaly is due to gravity, then it should act on the planets as well as spacecraft. Yet the outer planets are moving entirely as expected, Iorio says, so the anomaly must arise from a fault with the Pioneer craft. Another doubter is Daniel Whitmire, an astronomer at the University of Louisiana, Lafayette. In a study in 2002 of the behaviour of comets from the farthest realms of the solar system, he failed to observe any strange gravitational effects. He is also quick to dismiss a suggestion by Gary Page of George Mason University in Fairfax, Virginia, that the unexplained disappearance of an asteroid called 1995SN55 occurred because it was pulled off course by the same forces that act on the Pioneer craft. None of this persuades Izzo to give up the hunt. "There are many complicating factors and uncertainties in planetary orbits that will mask the Pioneer anomaly," he says.

The achievements of Pioneers 10 and 11 as the first missions to visit Jupiter and Saturn are already being overshadowed by the mystery of their unexpected trajectory through deep space, but with the stakes so high, even those who found the Pioneer anomaly are determined to remain sceptical. "I'm trying to remain open-minded," Turyshev says. "That is why I want to reanalyse the data from the full Pioneer 10 and 11 missions to see if we can explain the anomaly with things that were happening on the spacecraft." If after that the anomaly persists, it might be time to start thinking the unthinkable: that two distant spacecraft have provided the first clear evidence for a breakdown in Einstein's theory of gravity.

Stuart Clark is a science journalist based in the UK.

From issue 2554 of New Scientist magazine, 03 June 2006, page 46

Drawn with calcium carbonate, and using the bumps in the wall to give form to the face, it features two horizontal lines for the eyes, another for the mouth and a vertical line for the nose. "The portrait of this face is unique," said Jean Airvaux, a researcher at the French Directorate of Cultural Affairs. "We have other drawings, but they are more recent. Here, it could be the oldest representation of a human face."

Archaeologists are particularly interested in the Vilhonneur cave because there are several drawings, including one of a hand in cobalt blue, along with animal and human remains.

Jean-François Baratin, the regional director of archaeology in western France, said that there were only two known examples of prehistoric caves from this era containing both bones and drawings. The other is at Cussac in the Dordogne.

The discovery was made by M Jourdy in November, but kept secret until February while the site was sealed. The results of a scientific analysis were made public on Friday.

M Baratin said ribs, a thigh bone and a tibia taken from the floor of the cave had been dated by scientists in Miami, as were the drawings. These turned out to be about 11,000 years older than the renowned paintings at Lascaux in the nearby Dordogne.Michel Boutant, chairman of the local Charente department council, said: 'The face reminded me of a Modigliani portrait."

The two biggest storms in the solar system are about to go bump in the night, in plain view of backyard telescopes.

Storm #1 is the Great Red Spot, twice as wide as Earth itself, with winds blowing 350 mph. The behemoth has been spinning around Jupiter for hundreds of years.

Storm #2 is Oval BA, also known as "Red Jr.," a youngster of a storm only six years old. Compared to the Great Red Spot, Red Jr. is half-sized, able to swallow Earth merely once, but it blows just as hard as its older cousin.

The two are converging. Closest approach: the 4th of July, according to Amy Simon-Miller of the Goddard Space Flight Center who has been monitoring the storms using the Hubble Space Telescope.

"There won't be a head-on collision," she says. "The Great Red Spot is not going to 'eat' Oval BA or anything like that." But the storms' outer bands will pass quite close to one another-and no one knows exactly what will happen.

Amateur astronomers are already monitoring the event. Christopher Go of the Philippines took the picture above using his 11-inch telescope on May 28th. "The distance between the storms is shrinking visibly every night," he says.

Similar encounters have happened before, notes JPL's Glenn Or ton, a colleague of Simon-Miller. "Oval BA and the Great Red Spot pass each other approximately every two years." Previous encounters in 2002 and 2004 were anti-climatic. Aside from some "roughing" around the edges, both storms survived apparently unaltered.

This time might be different. Simon-Miller and Orton think Red Jr. could lose its red color, ironically, by passing too close to the Great Red Spot.

Red Jr./Oval BA wasn't always red. For five years, 2000 to 2005, the storm was pure white like many other small "white ovals" circling the planet. In 2006 astronomers noticed a change: a red vortex formed inside the storm, the same color as the powerful Great Red Spot. This was a sign, researchers believed, that Oval BA was intensifying.

The color of the Great Red Spot itself is a mystery. A popular theory holds that the storm dredges up material from deep inside Jupiter's atmosphere, lifting it above the highest clouds where solar ultraviolet rays turn "chromophores" (color-changing compounds) red. A beefed-up Oval BA could suddenly do the same.

Bumping up against the Great Red Spot, however, could weaken Oval BA, turning it white again. Simon-Miller explains: "We believe the Great Red Spot will push Oval BA toward a southern jet stream, which is blowing against the oval's counterclockwise rotation." This would slow Oval BA's spin, possibly reversing the process that reddened it in the first place.

What will actually happen? "We'll see," she says. That's what telescopes are for.

Rutledge first joined the physics department at the university in 1963. He was department chairman there from 1964 to 1982. He retired from teaching in 1992.

Rutledge first gained national notoriety through an organization he launched in 1973 called "Project Identification." The project was a response to a flurry of UFO sightings near Piedmont, Mo. Over the next six years, Rutledge and crews of students, scientists and amateur enthusiasts spent 150 nights scanning the skies in Franklin County with cameras, audio recorders, telescopes and tools measuring electromagnetic field disturbances. The efforts were funded in part by the St. Louis Globe-Democrat.

In 1980 he published a book also called "Project Identification," which took a scientific approach to cataloguing the UFO activity. He tracked the velocity, distance and size of the objects he caught on video and said he was careful not to let his own hypotheses get in the way of the data.

"I don't want to scare anyone and the one way not to do that is by trying to explain these phenomena," said Rutledge in 1979.

"I treat reports of UFOs like bottles of medicine without labels. I can't use the medicine without the label, but I can put it on the shelf until I get a label for it."

In 1989, Rutledge claimed to have seen 164 UFOs during his life. At the end of this research he claimed to have 700 photographs of UFOs either taken by him personally or by associates.

His fame as a passionate investigator of the unexplained led him to be a featured expert on CNN and quoted in a Time-Life book on UFOs and an astrology textbook. He was also a lively interview subject featured on the radio talkshow circuit.

His unfulfilled dream, though, was to come face to face with an extraterrestrial.

"I've seen just about everything there is to see, but I haven't seen one of those little creatures," he said in an interview in 1988.

Dr. Art Soellner, a friend and colleague in the physics department, remembered Rutledge's ability to simplify complex science.

"What I remember most was that he was a very good teacher," said Soellner. "He had a way of working with the students that stood out. I had an office behind his classroom, and he was teaching a physical science general education course, which usually means a lot of students aren't too interested. But he got them involved and I could often hear he got good chuckles out of them."

Soellner also recalled that Rutledge was integral in building up the physics department at the university from a faculty of four when he was first hired to nine when he left.

During the past three years Rutledge had been suffering from Alzheimers. He is survived by his wife, Ruth. They were married for 52 years and have five children.

tgreaney@semissourian.com

A team of Greek and British scientists probing the secrets of the Antikythera Mechanism has managed to decipher ancient Greek inscriptions unseen for over 2,000 years, members of the project say.

"Part of the text on the machine, over 1,000 characters, had already been deciphered, but we have succeeded in doubling this total," said physician Yiannis Bitsakis, part of a multi-disciplinary team of researchers from universities in Athens, Salonika and Cardiff, the Athens National Archaeological Museum and the Hewlett-Packard company.

"We have now deciphered 95 percent of the text," he told AFP.

Scooped out of a Roman shipwreck located in 1900 by sponge divers near the southern Greek island of Antikythera, and kept at the Athens National Archaeological Museum, the Mechanism contains over 30 bronze wheels and dials, and is covered in astronomical inscriptions.

Probably operated by crank, it survives in three main pieces and some smaller fragments.

"(The device) could calculate the position of certain stars, at least the Sun and Moon, and perhaps predict astronomical phenomena," said astrophysicist Xenophon Moussas of Athens University.

"It was probably rare, if not unique," he added.

The rarity of the Antikythera Mechanism precluded its removal from the museum, so an eight-tonne 'body scanner' had to be assembled on-site for the privately-funded project, which used three-dimensional tomography to expose the unseen inscriptions.

The first appraisal of the Mechanism's purpose was put forward in the 1960s by British science historian Derek Price, but the scientists' latest discovery raises more questions.

"It is a puzzle concerning astronomical and mathematical knowledge in antiquity," said Moussas. "The Mechanism could actually rewrite certain chapters in this area."

"The challenge is to place this device into a scientific context, as it comes almost out of nowhere... and flies in the face of established theory that considers the ancient Greeks were lacking in applied technical knowledge," adds Bitsakis, also of Athens University.

The researchers are also looking at the broader remains of the Roman ship -- believed to have sunk around 80 BC -- for clues to the Mechanism's origin.

One theory under examination is that the device was created in an academy founded by the ancient Stoic philosopher Poseidonios on the Greek island of Rhodes.

The writings of 1st-century AD Roman orator and philosopher Cicero -- himself a former student of Poseidonios -- cite a device with similarities to the Mechanism.

"Like Alexandria, Rhodes was a great centre of astronomy at the time," said Moussas. "The boat where the device was discovered could have been part of a convoy to Rome, bearing treasure looted from the island for the purpose of a triumph parade staged by Julius Caesar."

The new findings are to be discussed at an international congress (www.antikythera-mechanism.gr) scheduled to be held in Athens in November.

© 2006 AFP

The central mystery has fascinated philosophers for thousands of years; that the universe seems to contain two completely different kinds of thing. On the one hand are bodies and brains - physical objects that we can touch and measure; on the other are conscious experiences - private and subjective feelings that we cannot get at directly. We can ask people what they are experiencing, record their words, and measure what happens in their brains, but somehow this doesn't seem to capture the "what it's like" of subjective experience.

Right now, for me, the sky is a very faint pale blue streaked with early morning wisps of delicate pink. But how can science measure this? We can't even tell whether you and I are having the same experience when we both say we are seeing blue. My pale blue might be your bright orange. This "what it's like for me", is what philosophers call "qualia"; the intrinsic properties of the experiences themselves. So the mystery is this - how can a few pounds of living neurons inside a skull create qualia? No one knows.

No one knows, but at least now they are arguing about it. When I started my research, more than 30 years ago, no serious scientist would even admit to an interest in consciousness, and I was very much on my own. I had had many strange experiences and was obsessed with trying to understand them, but the science simply wasn't there to do the job. Then, gradually, I found I was in the midst of a hot topic. Brain scanning and other advances in neuroscience meant we could at last peek inside a living brain, but how could we find consciousness there?

The problem got me hooked, and so I gave up my university job to read all I could on the subject and write a textbook; a project that left me well informed but even more baffled. Everyone seemed to disagree. So I decided that I needed to ask the experts what they meant - face to face. I travelled the world talking to some of the world's finest thinkers and put together a book, Conversations on Consciousness.

Perhaps the key thinker in this debate is the young Australian philosopher David Chalmers. I caught up with him in Tucson Arizona where, for many years, he has organised the famous "Toward a Science of Consciousness" conferences. He said that scientists researching vision, memory, thinking or emotions were just tackling "easy problems". Even if they solved all those there would still be something else left to explain - consciousness itself - and this he called the "hard problem".

The phrase stuck, and now Chalmers's hard problem has become something of a Holy Grail for consciousness studies. Scientists and philosophers are falling over themselves to become the one who solves the hard problem. The trouble is, no one knows how to set about solving it.

At one extreme are those who think a revolution in physics is the answer. The Tucson anaesthetist Stuart Hameroff is one such theorist. "Every day," he told me, "I put patients to sleep and wake them up and it's still incredible. You wonder - where do they go?" He has teamed up with the British mathematician, Sir Roger Penrose, to argue that the brain is a quantum computer and the conscious self depends on quantum effects in the microtubules - tiny tubular structures inside every cell of the body. They are convinced that this is the way forward, but no one else I talked to shared their enthusiasm.

Far more common are the neuroscientists who think that if we just get on with the "easy problems" we will eventually solve the hard one. Pre-eminent among these is the late Francis Crick, who won the 1962 Nobel prize for discovering the structure of DNA. Aged 60 and after nearly half a century of work in biology, he changed tack totally - turning his attention from the mystery of heredity to that of consciousness.

Shortly before his death from cancer in 2004, an 88-year-old Crick invited me to his home in Southern California. Within minutes, he was demanding that I come up with a crucial experiment. When I tried my best, he dismissed it out of hand. "All that's nonsense," he said, "because it's based on pure psychology and you're not talking about neurons."

Crick had no time for the speculations of psychologists or philosophers - all they do is argue, he said, and never make discoveries. He was convinced that what we need to do is put the hard problem aside and get on with studying the neural correlates of consciousness; that is, measure what is going on inside the brain when a person has a conscious experience. In this light, he looked for the consciousness neurons - the parts in the brain that are active when someone has a conscious experience.

He likens the hard problem to an ancient conundrum - the nature of life itself. Back in the 19th century, biologists were convinced that they would find a special "life force" that breathed life into plants and animals and departed at their death. Of course, no such force was ever found, Crick himself contributing to its demise. The answer turned out to be that when you understand how living things work, you realise they don't need any special force at all. Could the same be true for consciousness?

Pat and Paul Churchland certainly think so, and the pair, who are both professors of philosophy at the University of California, San Diego, take a strong line on Chalmers and his hard problem. "I don't see how you can tell, by looking at a problem, how difficult it is," says Pat. "There are many examples where people thought a problem was unsolvable, and turned out to be wrong." For the Churchlands, there is no "mystery of consciousness". For them, when we grasp how the brain's visual system processes colour information, the problem of qualia will be solved.

The most extreme view, however, is posited by Tufts University professor, Daniel Dennett.In his book Consciousness Explained, he denies the existence of qualia and says that there is no such thing as "consciousness itself". Dennett believes that if we start from our intuitions about consciousness then we are doomed to failure. For example, he argues, some people may feel as though they have a little conscious self somewhere inside their head, which is the subject of the stream of experiences. He believes that the brain possesses no central controller; no inner screen where the images could appear; and no one inside to experience them. There is no magic process that somehow turns ordinary nerve activity into conscious experiences. We must, he told me, throw out all of these perfectly natural, but misguided ways of thinking about consciousness.

But how? Turning your intuitions inside out is terribly hard, but if Dennett is right then most of the others I spoke to are completely wrong. Quantum physics will not help one jot, and no one will ever find Crick's "consciousness neurons".

I would love to pop into the Tardis, jump forward a few years, and see who turns out to be right. For now at least, consciousness looks set to remain one of our greatest mysteries.

Susan Blackmore will be speaking about 'Conversations on Consciousness' on Saturday 10 June at the Cheltenham Science Festival (www.cheltenhamfestivals.com; 01242 227 979)