River deltas hint at ancient Martian ocean

Similar heights of channel mouths suggest they fed into one body of water.

Jon Cartwright

A huge ocean may have covered almost one-third of the Martian surface.B.Hynek/University of Colorado

Planetary geologists in the United States have analysed data that suggest Mars was once home to a huge ocean of water, covering nearly one-third of its surface. Their evidence, a ring of dry river deltas and valleys all at a similar elevation, adds weight to the idea that the red planet once supported an Earth-like water cycle.

Hints that an ocean once occupied the northern lowlands of ancient Mars first arose in the late 1980s. Scientists examining pictures of the surface claimed to recognize extensive shorelines and vast networks of river valleys and outflow channels feeding in the same direction. Other researchers used thermal physics to imply that such networks could only have been carved by a complete water cycle, fuelled by one or more huge bodies of water.

Not all evidence has supported the idea of a Martian ocean, however. In the late 1990s, researchers studying high-resolution images of the proposed shoreline regions could not find any of the erosion and sediment normally associated with an ocean's edge. Nor have they since found the telltale coastal landforms seen on Earth, such as spits and wave-deposited ridges.

Gaetano Di Achille and Brian Hynek of the University of Colorado in Boulder, whose study could now tip the balance back in favour of an ancient ocean, initially had no interest in the debate. They had been building a database of Martian river deltas and valleys to examine how they might have been eroded by water, but ultimately realized that they had enough data to tackle the bigger picture. "Our research started as kind of a joke," says Di Achille. "We were working on this database of deltas and valleys, and we said: why don't we try to check this ocean hypothesis?"

Elevation issue

Di Achille and Hynek analysed the distribution and elevation of 52 deltas and numerous valley networks along Mars's northern lowlands. Of the deltas, 17 were at a very similar elevation and could not be dismissed as being the mouths of smaller tributaries or feeding isolated basins. A further 12 deltas fitted within the error bars of this average surface elevation, totalling 29 deltas, or 55% of those analysed, that seemed to feed the same body of water. The locations of the end points of the valleys also seemed to be consistent with a possible coastline. The research is published online in Nature Geoscience today¹.

Taylor Perron, a geologist at the Massachusetts Institute of Technology in Cambridge, says that the result "strengthens the argument in favour of oceans" but leaves some issues unresolved. He says that there is enough variability in the delta elevations to suggest that there is not just one level coastline, and that it is "hard to explain" why some valleys end at much higher elevations than the proposed ocean. "One possible explanation is a large-scale deformation of the planet, which warped the landscape, transforming what was once a level shoreline into one with more variable elevations," he says.

Di Achille thinks that this explanation doesn't work, because any widespread deformation should see the deltas' elevations sweep up and down in broad waves along the coastline, rather than narrowly scattered about it as they observed. In any case, he says, the variability in delta elevation on Mars is smaller than that found on Earth, and valleys almost always peter out on dry, higher land, so the question is moot.

Still, there is broad agreement from all sides that Di Achille and Hynek's analysis is not the last word on the existence of an ancient Martian ocean. If it did exist, at some point a dramatic change in climate probably caused it to disappear into the crust, into ice caps and out through the atmosphere. Now, 3.5 billion years later, researchers have the difficult task of finding evidence amid a landscape that has since been blighted by volcanism and cratering.

Caleb Fassett, a geoscientist at Brown University in Providence, Rhode Island, says that the work will "stimulate new thinking" about past conditions on Mars. But he agrees that, as an indirect study, it needs backup from a more definitive method. "Finding further evidence for an ancient ocean besides the topography of Mars would have major implications," he says.

http://www.nature.com/news/2010/100613/full/news.2010.293.html

• References

  1. Di Achille, G. & Hynak, B. M. Nature Geoscience doi:10.1038/NGEO891 (2010).

Rare genetic variants linked to autism - June 09, 2010

The search for the genetic underpinnings of autism spectrum disorder has just yielded a new set of clues. In the largest study to date, the Autism Genome Projectconsortium reports that people with autism have more copy number variants – segments of DNA that have been either duplicated or deleted – in their genes.

The results, published today in Nature, could eventually be used to develop quick diagnostic tests. The consortium was also able to group some of the affected genes into biochemical pathways. These pathways – some of which are clearly linked to brain function -- may then become attractive targets for those who hope to develop drugs to treat the condition.

Autism is a complex disorder. Although the environment is thought to influence the risk of autism, genetics are known to play an important role.

The study included 996 people with autism and another 1,287 people without the disorder, to serve as controls. The researchers focused on rare genetic variants – a shift from previous approaches, which analyzed variants that are commonly seen in the population. (For more on rare variants, see ‘Hunt for genetic causes of diseases causes narrows targets’.)

Posted by Heidi Ledford on June 09, 2010 

http://blogs.nature.com/news/thegreatbeyond/2010/06/rare_genetic_variants_linked_t.html

THOSE of us who support the careful and well-regulated use of animals for scientific and medical advancement are well aware that it remains controversial. Animal experiments are essential for the development of new medicines, and for safety testing, but are vocally opposed by some.

So it is with growing concern that we read the latest in a string of scientific papers highlighting problems with the way animal research is conducted. The accusation is that animal experiments are too often poorly designed, conducted, reported and reviewed.

Not only does this give ammunition to the opposition, it allows some to claim that animal studies are a misleading guide to what might happen in humans, and also that animals are suffering needlessly in useless experiments.

The use of animals is a privilege, and must always be undertaken responsibly. We must therefore face up to these criticisms and assess what needs to be done.

One of the papers causing concern is an analysis of more than 1350 animal experiments on the treatment of stroke (PLoS Biology, vol 8, p e1000344). The authors used statistical tools to predict that a further 214 experiments had been conducted but the results never published - the so called "file drawer problem".

That is 1 in 7 studies that never see the light of day. The authors concluded that this publication bias has probably distorted the collective findings of the published studies, as research usually remains unpublished because it failed to find any positive effect of a treatment.

Although the results cannot necessarily be applied across all animal research, it is nonetheless cause for concern. The danger is that humans may be put at risk because potential new medicines are moved into clinical trials prematurely.

Another paper reveals perhaps an even bigger problem. The authors chose 217 animal studies at random and analysed their quality in terms of experimental design, statistical analysis and reporting of results. Only 59 per cent of the studies stated the objective of the study and the number and types of animals used. More than 80 per cent failed to say whether the researchers used randomisation or blinding - standard tools in much biomedical research (PLoS One, vol 4, p e7824).

There have been other papers suggesting that many animal studies are poorly designed, using too few animals to be statistically valid, for example.

One note of caution is that animal studies are highly diverse. Most are part of basic or applied medical research, but animals are also used in pre-clinical safety testing, veterinary development, environmental studies and various types of fundamental research. It would be wrong to suggest that these different types of research should be designed and analysed the same way.

Even so, these various problems need to be tackled. Doing so will require a willingness to confront the issues and improve practices.

The first area that needs to be dealt with is publication bias. The non-publication of negative results is a serious problem in many fields of research. Reducing it in animal research would bring clear benefits, not least ensuring a sound basis to move from animal studies into clinical trials.

The recognition of publication bias in clinical trials involving humans led to the introduction of registration systems to keep track of all relevant trials. It is not inconceivable that we might move towards a similar registration system for animal studies. Initiatives are already under way in some fields of research, with stroke studies a notable example. Collaboration would need to be international, since the missing papers could come from anywhere.

Journals can help. One prominent publication, the British Medical Journal, now welcomes studies with negative results as long as their research questions are important and relevant. Open-access online publishing also presents opportunities for wider access to the buried data.

Another area where weaknesses exist and improvements are needed is the way animal studies are written up in journals - failure to report the number of animals used, for example. The UK National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) has been working with scientists, journal editors and research funders to develop guidelines. These will set out the basic information that should be included, based on successful guidelines for reporting human clinical research developed by an international group of biomedical researchers and journal editors calledCONSORT.

The design and statistical analysis of individual experiments also need to be improved. While there are plenty of well-conducted studies out there, ideally every research project - whether using animals or not - should be well-designed and the results analysed using the most appropriate statistical method.

Funders have a role to play here by checking experimental design. Regulatory authorities could also require the panels who evaluate proposed projects to include sufficient statistical expertise. This measure has been included in the newly revised European Union regulations on animal experiments.

Many of the initiatives in these areas come from researchers themselves. Far from accepting the status quo, they strive to achieve better scientific results. With effort and education, these difficult issues should be eminently solvable.

Animal research remains a small but vital part of the biomedical research endeavour. Let's make sure we get it right so that the greatest good is achieved for the least harm to animals.

Simon Festing is chief executive of Understanding Animal Research, a London-based organisation which seeks to promote understanding and acceptance of the need for humane animal research

http://www.newscientist.com/article/mg20627635.500-dont-waste-lab-animals.html

By Katherine Harmon   

MORE PIECES FOR AUTISM: The roots of autism seem to be nearly as variable as the individuals who have it, and new large genetic studies are continuing to turn up new genomic links.
ISTOCKPHOTO/SATURATED

http://www.scientificamerican.com/article.cfm?id=autism-genetic-complexity