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SCIENCE UPDATE
Red planet: a water world?
Liquid water, not anything else, carved the canyons, valleys and outflow plains of Mars, according to the latest research.
A rival theory, that liquid carbon dioxide or rocks supported by CO2 gas could have made the surface features, does not work, according to Dr Neil Coleman of the US Nuclear Regulatory Commission.
It could put an end to the “White Mars” hypothesis that favoured CO2 and made the prospect for life on Mars more remote.
Vast lakes of water accumulating under sheets of ice until they overflowed crater and canyon walls is the way many Martian features formed, says Dr Coleman.
Neil Coleman has studied some of the most dramatic and significant scenery on Mars, the enormous outflow channels of Chryse Planitia.
Chryse Planitia may once have been an ocean. Today it is a huge plain where many of Mars’ largest outflow channels converge. It was also Viking 1’s landing site in 1976.
But what caused the outflow channels? Many scientists say obviously running water, but in recent years a few researchers have questioned this saying that liquid carbon dioxide might be responsible.
The “White Mars” hypothesis contends that gaseous or liquid carbon dioxide carried debris down Martian slopes and eroded the features some attribute to fluvial processes.
Advocates of the theory say it solves many problems with the water model, such as where the water came from and where it went.
Neill Coleman’s work, published in the Journal of Geophysical Research, is, he believes, conclusive evidence that water, not carbon dioxide, is to blame.
Dr Coleman says his latest study shows that nowhere is the evidence for vast quantities of running water clearer than the outflow channels of Chryse Planitia.
Consider the associated Kasei Valles, he suggests, it is a system of intertwined flood-carved channels more than 2,000km long that begins in near the equator in Echus Chasma and ends in Chryse Planitia.
He says that the White Mars theory is “inconsistent with studies of terrestrial and Martian mass movements” because “put simply rocks can ‘float’ on air, but not for long”.
This means that only water had the stamina to carve large-scale Martian features like Kasei Valles.
This latest research indicates that the outflow channels may have been carved by lakes of water trapped under ice that burst through crater walls and flowed downhill in torrents. Only a liquid like water, says Dr Coleman, could have slowly accumulated under ice cover, and ultimately filled a basin until it overflowed.
Water-carved channels are good for the prospect for life on Mars hanging on at the present having been formed in the Martian oceans of three billion years ago.
Arteries grown in the lab
New blood vessels grown from a patient’s own muscle cells are a step nearer after a genetic success in a US laboratory.
The arteries could be used in many operations which currently mean surgeons have to insert plastic tubing to form new vessels. However, it is still likely to be several years before trials in humans can begin, say experts.
A human blood artery is not simply a tube, it is made of a complex sandwich of muscle, lining cells and connective tissue that can expand and contract to regulate blood flow.
The normal formation of new blood vessels in the body is also complicated, with “smooth muscle cells” migrating to surround a lining of epithelial cells.
When scientists tried to replicate this process in the laboratory, however, the smooth muscle cells could not grow to form fully functional arteries because they did not have enough life in them to perform all the necessary cell divisions.
A human cell can only divide a finite number of times, and the muscle cells being used by the researchers simply ran out of time. Researchers from Duke University Medical Center in the US believe they have found a way around this, with a secret taken from cancerous cells.
Some tumours manage to cheat this limit because they have the genetic ability to perform many more divisions.
One of the genes responsible for this “immortality” is called hTERT.
The Duke researchers introduced hTERT into smooth muscle cells, and found that this time, they could grow fully functional arteries.
Dr Laura Niklason, who led the research, said: “We found that the resulting cells not only proliferated long beyond their normal lifespan, but retained characteristics of normal smooth muscle cells.
“We were able to engineer mechanically robust human arteries, a crucial step toward creating arteries for bypass patients.”
It is unlikely that an artificial artery would find favour with surgeons carrying out coronary artery bypass grafts.
The lengths of blood vessel needed are small, and good results can be achieved with veins or arteries extracted from the legs or chest of the patient.
However, where arteries in the legs have hardened and become blocked, a longer section of new artery would be needed, and it is at this point that plastic alternatives are generally used.
New class of stem cells discovered
Scientists with University Health Network have discovered a new class of human stem cells that rapidly grow when implanted in the bone marrow of mice. The findings, available today in an advance online publication of the international scientific journal Nature Medicine, are a major advancement in human stem cell research with possible significant clinical implications for designing more effective cancer therapies.
“This is an exciting discovery because for the first time we have found human stem cells that rapidly rebuild a blood system,” said Dr. John Dick, lead author of the study, senior scientist with UHN, and a professor in the University of Toronto’s Department of Molecular and Medical Genetics. “The potential is that it may allow transplant patients to quickly regain their blood cells, which are critical to their immune system.”
Further study is needed to see if the new stem cells can be separated in larger batches and to refine the method of delivery. “Implanting stem cells directly into bone is a more complex and difficult procedure than the traditional intravenous method,” said Dr Dick. — Dawn ScienceDotcom Report
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