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March 18, 2011 10:07 pm
Planetary scientists have issued their official wish list for unmanned space missions to explore the solar system over the next decade. Top priority of the report from the US National Academy of Sciences is robotic exploration of Mars. The second mission on the list is a visit to Jupiter’s icy moon Europa and its subsurface ocean – seen as one of the most promising environments in the solar system for supporting life. Third priority would be a mission to investigate the interior structure, atmosphere and composition of the outer planet Uranus, one of the least understood large bodies in the solar system.
The 400-page report is the result of a thorough review of the options by 17 senior planetary scientists. It will carry great weight with its sponsor, the US space agency Nasa. But whether it turns out to be a practical guide for Nasa to plan future missions – or a fantasy list – depends on how much money the agency receives from the US Congress for space science.
Latest signals from the Washington budgetary process are not encouraging. The report was prepared on the basis of Nasa’s 2011 budget, which has still not been enacted as a result of the Obama administration’s fiscal standoff with Congress. The proposed 2012 budget gives considerably less money to space science. “Our recommendations are science-driven, and they offer a balanced mix of missions – large, medium and small – that have the potential to greatly expand our knowledge of the solar system,” says Steven Squyres of Cornell University, who chaired the academy’s review panel. “However, in these tough economic times, some difficult choices may have to be made.”
The report says that if Nasa does not have enough money to support its three big favoured missions, then one or more of these should be delayed, scaled back or cancelled, so that the agency can continue to fund a steady stream of smaller, less expensive missions. Candidates for these include returning a sample from a comet to earth, probing Saturn’s atmosphere, landing on the surface of Venus, visiting more asteroids and putting a network of geophysical observatories on to the moon. The most expensive of the three top priorities is the Jupiter Europa Orbiter, for which an independent estimate put the price at $4.7bn. Its cost needs to come down substantially, by reducing the spacecraft’s capabilities and possibly getting the European Space Agency to contribute more, the review says.
But the Planetary Society, a leading lobby group for space science, fears that there will be no mission beyond Mars. “This is not just the loss of an American flagship mission, it is a loss to planet Earth,” says Louis Friedman, the society’s former director.
Making scents: how foxes mark territory
Thirty years of data about the movement of urban foxes has led to a new mathematical model of animal territories – which could have applications well beyond behavioural ecology.
The study at Bristol University models the complex system of individual-level interactions that determine animals’ transient territorial boundaries.
The size of a territory depends on how long the fox can exert its control before intruders cross the boundaries into its space. This involves a trade-off between two factors: the time required for a fox to move between its own boundaries and the period during which it can maintain its scent trail within the territory.
When a disease called sarcoptic mange killed most of Bristol’s foxes in the 1990s, Professor Stephen Harris noticed that as the animals in one territory died, their healthy neighbours moved in and took over within three or four days. He assumed that this was because the scent marks of the original owners were no longer fresh.
The study, published in PLoS Computational Biology, shows how important it is for a fox to renew its scent marks, further demonstrating the transient nature of territories, and contradicting the belief that scent marks serve as a longer-term indicator of boundaries.
Lead author Luca Giuggioli says the model may also “shed light on the processes responsible for the formation of territorial boundaries in early human hunter-gatherer societies, and eventually help predict how the size of modern-day countries will evolve.”
His colleague Jonathan Potts adds: “Our theoretical framework might also inspire designs in collective robotics. From very simple rules, the individuals divide space into territories, and if one individual should fail, its territory is taken over,” he says. “Building an army of territorial robots that move according to these rules could be an efficient and robust way to deal with dangerous tasks over a wide spatial area, such as clearing minefields.”
Were humanity’s first steps in the Kalahari?
The idea that modern humans originated in Africa and then migrated out to Asia and Europe more than 60,000 years ago has been conventional scientific wisdom for decades. It has been less clear where in Africa Homo sapiens first evolved from earlier hominid species.
Most palaeontologists have assumed that our ancestors originated in east Africa, on the basis of fossil and archaeological evidence, but the largest genomic analysis of the continent’s hunter-gatherer populations carried out so far strongly suggests the region of origin was actually southern Africa.
That conclusion emerges from a study published in Proceedings of the National Academy of Sciences of genetic variation in 27 African populations, including all the continent’s remaining hunter-gatherer groups.
The international team led by Marcus Feldman of Stanford University looked for changes in 650,000 chemical “letters”’ of the genetic code. They found that the “click-speaking” bushmen of the Kalahari desert in southern Africa had substantially more genetic variation than other groups including the “click-speaking” hunter-gatherer peoples of east Africa, the Hadza and Sandawe in Tanzania.
The genetic diversity of the bushmen – greater than any other group on earth in relation to their numbers – is a strong indicator that they are the closest representatives alive today of the source population from which all modern humans evolved.
Why your mother’s diet sets you up for life
Some people have long argued that you are what you eat – and a group of scientists has now provided a new twist that suggests you are also significantly what your mother ate, writes Andrew Jack. Researchers at Cambridge University showed that pregnant female rats which were malnourished by restricting their protein intake gave birth to offspring more likely to develop type 2 diabetes.
The findings, published in Proceedings of the National Academy of Sciences, demonstrated that the gene Hnf4a, already known to play an important role in the development of the pancreas and the production of insulin, was regulated by maternal diet, exacerbating modifications to DNA.
“It is remarkable that maternal diet can mark our genes so they remember events in very early life,” said Miguel Constancia, senior co-author on the paper. Jeremy Pearson, associate medical director at the British Heart Foundation, which jointly funded the study, said: “A mother’s diet may sometimes alter the control of certain genes in her unborn child. It’s no reason for expectant mothers to be unduly worried. This research doesn’t change our advice that pregnant women should try to eat a healthy, balanced diet.”
Of course the study was conducted in rats, so there are questions about how far the same effect would be translated into humans. But if mother already knows best, she now knows a little bit more about precisely why eating sensibly makes sense.
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