The Guardian

Vast concealed glaciers that extend for tens of miles along the cliff edges and mountain tops of Mars have been spotted by a space probe as it orbits the red planet.

The ice sheets – which are up to half a mile thick – are thought to be the planet's largest reserves of water ice outside the polar caps.

The discovery of such large quantities of ice is encouraging for Nasa scientists, whose strategy for hunting extraterrestrial life is to follow signs of water.

The US space agency's Mars Reconnaissance Orbiter used radar echoes to image gentle slopes at the base of cliffs and mountain ridges that have puzzled scientists since they were first photographed by spacecraft in the 1970s.

The radar images show that the features contain large amounts of water ice. "These results are the smoking gun pointing to the presence of large amounts of water ice at these latitudes," said Ali Safaeinili at Nasa's Jet Propulsion Laboratory in California.

Writing in the journal Science, the researchers describe how they discovered the glaciers in the Hellas Basin region in the southern hemisphere of Mars. Similar features are known to exist in the northern hemisphere.

"Altogether, these glaciers almost certainly represent the largest reservoir of water ice on Mars that's not in the polar caps. Just one of the features we examined is three times larger than the city of Los Angeles, and up to one-half-mile thick, and there are many more," said John Holt at the University of Texas at Austin. "In addition to their scientific value, they could be a source of water to support future exploration of Mars."

The rocky debris on top of the glaciers is thought to have protected the ice from vaporising on contact with the thin atmosphere.

"A key question is how did the ice get there in the first place," said James Head at Brown University. One theory is that ice sheets are able to spread down to mid-latitudes when the planet tilts dramatically on its axis.

The discovery of the hidden glacier came as Nasa announced its shortlist of four landing sites for its next mission to the planet. The Mars Science Laboratory rover is due to blast off in September or October next year.

The four landing sites are Eberswalde, where an ancient river once flowed into a lake; a mountain inside the Gale crater, where the rover could investigate clay deposits; the Holden crater; and the Mawrth valley, an apparent flood channel near the Martian highlands.

• Mars
• Space exploration
• Geology

MyHeritage, the genealogy social networking website, is offering its 27 million global users a "cheek scraper" DNA test for less than £100.

The site is expanding its family research features after linking with US company FamilyTreeDNA to offer the DNA test for an additional payment that will help identify living relatives with common ancestors.

Israeli-based MyHeritage's 27 million registered members, who are mostly in the English-speaking world, use the site to document their family trees and research missing connections or relatives.

A Y-chromosome test identifies paternal descent, while a mitochondrial DNA test shows the maternal line, and both cost $129 (£87). A combined test, for men, is $219.

The DNA test can identify if a member has Native American, African or Jewish ancestors and trace relatives to a migration map of the US.

"Ninety per cent of people are interested in genealogy," said Bennett Greenspan, the president and chief executive of FamilyTreeDNA, which already has records on 220,000 people.

Tests do also not include any medical information, Greenspan added. "That's not to say that generic DNA doesn't have that information, but we do not do medical testing. We are searching for the unaltered DNA that is passed on from father to son," he said.

When FamilyTreeDNA started in 2000, Greenspan said he had to "drag people" into his booth to explain the technology, but testing is now much more mainstream. Now, he said, around 40% of people are interested in DNA testing and understand it.

Greenspan added that the internet had fuelled a massive boom in genealogy as a hobby, because before the web, enthusiasts would need significant time and money to invest in research and travel to track down records including church and census entries internationally.

Asked whether DNA testing within families might unearth some uncomfortable home truths, he said: "The biggest problem is finding out your brother isn't your brother or your father isn't your father. But we don't deal with that.

"The good news is that genealogy is essentially historic, so you'd be more likely to find out that your great grandfather was adopted or that there was false paternity."

Greenspan said two weeks ago one customer had asked for a test result to be reexamined when his results did not match a relative from the early 1800s. "He called me back and said 'cancel the retest' - he'd discovered that his grandmother was already four to five months pregnant when she married," he added.

MyHeritage is available in 34 languages including Arabic, Farsi, Mandarin and Brazilian Portuguese.

Its founder and chief executive, Gilad Japhet, said the site was home to 5m family trees, featuring 280m names. Japhet claimed a 10% success rate in matching living relatives from different trees, using technology that detects similarities in names and family structures. The site also has facial recognition technology to identify people in photos.

"We can build on those paper records and on people's memories – but now we can also use real biology to complete those family trees. You can find relatives from centuries ago, but also use the site to keep in touch with your family today," Japhet added.

Both MyHeritage and FamilyTreeDNA are keen to emphasise that records are not shared or published and are held securely.

"There's a trade-off here. There's an entire family tree that wants to be discovered – if only your family could see it," Japhet said.

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• Digital media
• Internet
• Genetics

Scientists have unravelled the genetic makeup of the woolly mammoth by analysing hairs plucked from carcasses recovered from the Siberian permafrost.

The feat was hailed as a milestone in genetic science yesterday and represents the first time an extinct animal has had its genome sequenced.

The first draft of the genetic code shows mammoths split into two groups about 2m years ago. One group became extinct about 45,000 years ago, while the other is thought to have lived on to as recently as 10,000 years ago.

"It has now become feasible to sequence a complete extinct animal, which is quite amazing," said Stephan Schuster, who led the research at Penn State University.

The achievement is an indication of the rapid progress in genetics. In 2003, the 13-year effort to read the human genome was completed at a cost of $2.6bn. The mammoth genome was read at one laboratory in less than a year and cost just over $1m.

Schuster's team gathered hair samples from 18 woolly mammoths and pieced together 3.3bn pairs of letters that make up about 70% of the animal's genetic code, the journal Nature reported.

By comparing the mammoth's DNA with that of the African elephant, the scientists identified sections of genetic code that may explain how the beasts adapted to harsh Arctic conditions. All elephants originated in Africa, but split into different species around 6.5m years ago. One group migrated to tropical Asia, while the mammoth headed for temperate Europe and eventually the Arctic.

Schuster said genetic diversity was very low in the two groups of mammoths. That may explain why the animals suddenly became extinct after enduring successive ice ages. The changing climate could have depleted their populations, leaving them vulnerable to disease and hunting when humans arrived in their regions about 23,000 years ago.

Analysis of the mammoth genome reveals it differs from the African elephant by only 0.6%. That is about half the difference between humans and chimpanzees, which split from a common ancestor at around the same time. The greater genetic gulf between humans and chimps suggests primates have evolved faster, probably because apes have historically been preyed on more than mammoths.

"It's an absolute first to have a genome sequence of an extinct animal, that's really a milestone," said Michael Hofreiter at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

Ultimately, scientists want to compare the genomes of mammoths that lived at different times to see how the species evolved. "Within the next decade, that is what people will go for. It's what evolutionary biologists dream of: seeing evolution in action," said Hofreiter.

The publication of the mammoth's genome is unlikely to lead to the resurrection of the beasts through cloning. While most of the genetic code is known, scientists do not have the technological knowhow to make chromosomes.

Next year, scientists are expected to reveal the full genetic code of our most recent ancestor, neanderthal man.

• Genetics

An iron age gold collar worth more than £350,000 that was found by an amateur metal detectorist in a muddy field in Nottinghamshire was described yesterday as the best find of its kind in half a century.

"I was only in the field because a customer kept me late," Maurice Richardson, a tree surgeon from Newark, said yesterday. "Normally I'd never want to go into this field because a plane crashed there in the last war, and the whole place is littered with bits of metal."

The first beep from his detector was indeed a chunk of wartime scrap metal, but as he bent down to discard it, his machine gave a louder signal. Expecting to find a bigger chunk of fuselage, he instead discovered the 2,200-year-old collar.

The piece, a near twin of one already in the British Museum, was the most spectacular of 1,257 finds reported over the last three years. Treasure reports have increased every year since the Portable Antiquities scheme was set up to record finds by the public in England and Wales.

"It's a fabulous thing, the best Iron Age find in 50 years," said JD Hill, head of the British Museum's iron age department. "When I first saw a picture of it I thought somebody was pulling my leg because it is so like the Sedgeford torc in our collection that it must have been made by the same hand.

"What is fascinating about it is that it turned up where no torc should be - to put it mildly, the Newark region is not known for major high-status iron age finds. This wasn't in a grave, wasn't on a hilltop - it opens up a whole new chapter of the history of this area."

Richardson has been metal detecting, not entirely to the delight of his wife, since he first spent £70 on a detector instead of buying a carpet for their new house just after they were married 40 years ago.

He should now have enough money for new wall-to-wall after sharing the reward with the landowner.

Unusually, the torc has been acquired by his local museum in Newark, after heroic fundraising efforts. Most such finds go to national museums. Sarah Dawes, head of leisure and culture at Newark and Sherwood district council, said: "I took one look and rang my chief executive to say, sit tight, don't leave the office, we've got something to tell you."

For archaeologists, professional and amateur, the greater treasure announced yesterday was the reprieve of the Portable Antiquities scheme itself. Last year there was an outcry in the profession when the scheme almost became collateral damage in swingeing cuts imposed by the government.

• Heritage
• Archaeology

The hedge that launched a thousand neighbourly disputes could have contributed to the mysterious disappearance of one of Britain's best loved birds, scientists said today.

The dramatic 20-year decline of house sparrows in towns and cities, a study has suggested, is because of the popularity of ornamental plants such as leylandii, the removal of trees, and the conversion of front gardens for parking. The loss of woody shrubs and trees leaves too few insects in summer for the birds to feed their chicks.

Experts have called for a return to "lazy" gardening in suburbia to reverse the decline, by using fewer pesticides and leaving grass and weeds to grow. Local authorities could also help, by reversing policies to chop down trees and remove shrubs from parks and green spaces.

Dr Will Peach of the RSPB, who led the study, said: "Sparrows need insects in the summer, and lots of them. The trend towards paving of front gardens and laying decking in the back, and the popularity of ornamental plants from other parts of the world, has made many gardens no-go areas for once common British birds. Many of the things we can do to help just mean being lazy, doing nothing and allowing the garden to be a bit scruffy."

House sparrows have declined in Britain by 68% since 1977. Numbers started to fall in towns and cities in the mid-1980s and the species has almost vanished from central London. Significant drops have also been recorded in Bristol and Edinburgh, and other cities around Europe such as Dublin, Hamburg, Prague and Moscow, although Paris and Berlin seem to have bucked the trend, with house sparrows faring better.

The new study looked at house sparrows in Leicester and surrounding villages. During the three-year research project, the number of birds there dropped by 28%, with many chicks dying within four days of hatching. The study, published in the journal Animal Conservation, linked these deaths to diet, with chicks that ate few insects having poor rates of survival. In contrast, those reared where aphids were abundant were more likely to survive.

Peach said: "Each pair of house sparrows must rear at least five chicks every year to stop their numbers falling. But in our study, too many chicks were starving in their nests."

He added: "If the birds nested in areas rich in insects, they did much better. Where there were too few insects, young house sparrows were likely to die. Young house sparrows need insects, rather than seeds, peanuts or bread, to survive."

Adult house sparrows collect most insect prey for their young from deciduous woody vegetation, trees and grassland, but rarely use evergreen or ornamental shrubs.

Kate Vincent, who worked on the study as a PhD project at De Montfort University in Leicester, said: "This is one of the most mysterious and complex declines of a species in recent years. The study highlights that sparrow chicks are hatching but they aren't surviving. This is partly down to the loss of green spaces within British cities through development on green space, tree removal and the conversion of front gardens for parking."

Phil Grice, senior ornithologist at Natural England, said: "This study highlights the importance of using native varieties of plants in our urban green spaces, which support large numbers of insects that are important in the diet of house sparrows, and a range of other birds that we love to see in our gardens."

Air pollution and traffic could also affect house sparrow numbers, the scientists suggested, so efforts to boost insect numbers by planting "native deciduous shrubs and trees" should be concentrated away from busy roads. They said: "Such advice needs to be targeted at the owners of private gardens and could be incorporated into local authority green space management plans."

Peach said gardeners could plant honeysuckle, wild roses, hawthorn or fruit trees to help house sparrows. The RSPB has launched a new scheme, Homes for Wildlife, to help people encourage wildlife in their gardens. It recommends areas of wildflowers or long grass in summer, native shrubs and a small pond.

• Wildlife
• Endangered species
• Gardening advice
• Conservation
• Biodiversity

Scientists have decoded the genome of the woolly mammoth by analysing hairs plucked from carcasses recovered from the Siberian permafrost.

The feat was hailed as a milestone in genetic science yesterday and is the first time an extinct animal has had its genome sequenced.

"It's an absolute first to have a genome sequence of an extinct animal, that's really a milestone," said Michael Hofreiter at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

The first draft of the genetic code reveals that mammoths split into two groups around 2m years ago. One of the groups became extinct around 45,000 years ago, while the other is thought to have lived on, to as recently as 10,000 years ago.

The achievement is a startling sign of the rapid progress genetics has made in recent decades. In 2003, scientists announced that the 13-year effort to read the human genome had finally been completed, at a cost of around $2.6 billion. The mammoth genome was read at one laboratory in less than a year at a cost of just over $1m.

"It has now become feasible to sequence a complete extinct animal, which is quite amazing," said Stephan Schuster, who led the research at Penn State University in the US.

Schuster's team gathered hair samples from 18 woolly mammoths and pieced together 3.3bn pairs of letters that make up around 70% of the animal's genetic code, according to a report in the journal Nature.

By comparing the mammoths' DNA with that of the African elephant, the scientists identified sections of genetic code that may explain how the beasts adapted to harsh Arctic conditions. African and Asian elephants evolved larger ears than the mammoth to help them cool down, but mammoths are also thought to have evolved differences in their metabolism and the way they stored fat.

All elephants originated in Africa, but split into different species around 6.5 million years ago. One group migrated to tropical Asia, while the ancestors of the mammoth headed for temperate Europe and eventually the Arctic.

Schuster said genetic diversity was very low in the two groups of mammoth, indicating that they were all very closely related. That may explain why the animals suddenly went extinct after enduring traumatic climatic swings through successive ice ages. The changing climate could have depleted populations, leaving them vulnerable to diseases or hunting when humans arrived in the region around 23,000 years ago.

Analysis of the mammoth genome reveals it differs from the African elephant by only 0.6%. That is about half the difference between humans and chimpanzees, which split from a common ancestor at around the same time. The greater genetic gulf between humans and chimps suggests primates have evolved faster, probably because historically apes have been preyed on more than mammoths.

The mammoths managed to adapt to the chilly environment in which they found themselves by growing long hair, even after their ancestors had lost theirs.

Ultimately, scientists want to compare the genomes of mammoths that lived at different times to see how the species evolved over thousands of years. "Within the next decade, that is what people will go for. It's what evolutionary biologists dream of – seeing evolution in action," said Hofreiter.

The publication of the mammoth's genome is unlikely to lead to the resurrection of the beasts through cloning. While most of their genetic code is known, scientists do not have the technological know-how to make their chromosomes in the laboratory.

Theoretically, it would be possible to recreate a mammoth by genetically modifying an elephant embryo to carry all of the 400,000 important genetic differences that exist between the species. With today's technology, however, scientists can only make one genetic change at a time.

Next year, scientists are expected to reveal the full genetic code of our own most recent ancestor, the Neanderthal. Genetic differences between Neanderthals and modern humans could reveal why humans came to be the dominant species on Earth.

• Genetics
• Evolution
• Zoology

Sarah Boseley on the stem cell transplant of an organ

Thousands of 12- and 13-year-old girls will be lining up outside their school medical offices this term, some of them shivering, stomachs lurching, waiting for a jab in the arm that it is hoped will prevent them suffering cervical cancer - a particularly unpleasant form of the disease which kills more than 900 women a year in the UK.

There is every sign that takeup of the vaccine will not be universal. In a pilot study, 20% of parents did not give permission for their daughter to have the jab - whether from apathy or anxiety. Girls are being told that if they feel strongly, they can go to their GP and get vaccinated anyway, but that will surely be rare. And takeup will certainly slump for the boosters, months later.

In spite of a health service information campaign and assiduous marketing by the two firms who vied for the NHS contract - the British company GlaxoSmithKline (the winner) and Merck - many people seem to know little about the vaccine, and the usual worries have already surfaced. Is it safe? Does it have side-effects? The legacy of MMR will run for many years.

In the US, websites have started up and the anti-vaccine rumour machine has been grinding away for a while now. Some of the doubts are reasonable - we cannot know what the long-term effect of the jab will be, because it has been tested for less than seven years so far, though the chief worry is that the protection will wear off. Others, such as alarming side-effects, are not well substantiated.

But while Britain and the US are dithering and doubting, there is an urgent need for the vaccine. The real damage done by this horrible disease is in the developing world. There are about 500,000 cases worldwide every year, and more than half the women die. About 80% of the deaths are in poor countries.

These countries don't have screening programmes. They don't have the surgery and radiotherapy to treat cervical cancer, either. The women who die are often mothers and breadwinners, leaving struggling families. A simple vaccine - two or three injections for every girl - could transform their prospects.

But Merck charges $360 for the three-dose vaccine course, presumably needing to recoup the $100m it is said to have spent on marketing in the US on top of development costs. GlaxoSmithKline will have struck a deal at a lower price in Britain to win the NHS contract, but this is still out of reach for countries in Africa and Asia. Merck is not insensitive to this potentially damaging issue and has committed itself to giving away enough vaccine to immunise a million women in the developing world. But the anticipated demand, should an affordable vaccine become available, is for the immunisation of 58 million girls in 60 countries by 2020.

Enormous hopes were building right up until the end of last month. Gavi, the Global Alliance for Vaccination and Immunisation - set up with the help of Bill and Melinda Gates - was expected to support global rollout of the cervical cancer vaccine. It didn't happen. In the face of global financial meltdown, there were nerves about the chances of raising enough money for a programme that will have to begin in schools - it can't just be added to the infant immunisation schedule.

Gavi will return to the issue. It has negotiated a cost in principle from the drug companies of less than $10 a head, of which governments would pay just 30 cents. A big new funding campaign among donor countries would still be needed, even at this price. But when we are spending so much vaccinating girls whose risk of cancer is really pretty low, surely offering the same chance to girls whose lives could genuinely be saved is a no-brainer?

sarah.boseley@guardian.co.uk

• Cancer
• Infectious diseases
• Health
• NHS
• International aid and development

They give Action Man a certain ruggedness and bestow instant testosterone on movie heroes, but according to psychologists, facial scars can also make men more attractive to the opposite sex.

Men with mild facial scars were typically ranked as more appealing by women who were looking for a brief relationship, though they were not considered better as marriage material, a study found.

In the same experiments, women with facial scars were judged to be as attractive as those without, the researchers said.

Psychologists at the universities of Liverpool and Stirling asked 115 women and 64 men to rate the attractiveness of eight opposite sex strangers. Half were asked to look at original face shots, while the other half viewed images that had been digitally manipulated to add scars to their cheeks, jawbones or foreheads.

While facial scars made no difference to the perceived attractiveness of women, scarred men ranked 5.7 percentage points higher in the appeal ratings than those with undamaged skin.

"A large scar is unlikely to make you more attractive, but there are some scars that women do seem to find appealing. There's the whole James Bond thing, where a person is attractive but probably not the best marriage material," said Robert Burriss, a psychologist at the University of Liverpool who led the study.

The study appears in the journal Personality and Individual Differences.

• Reproduction
• Human behaviour
• Psychology