Science News: 8/7/12

The Curiosity has landed! Mars, y’all!! And, you know, some other stuff happened too. 

The biggest news of the week is the landing of the Mars rover Curiosity! The rover touched down on the surface of Mars at 1:32 am EDT Monday (Sunday evening for the West Coast dwellers). The rover launched on November 26, 2011, travelling about 350 million miles in 36 weeks to reach its final destination inside Gale Crater. Curiosity’s initial two-year mission is to look for signs of past microbial life on Mars; observations of the crater from orbit show signs of rocks formed in the presence of liquid water. The rover carries ten different scientific instruments, some of which never before sent to Mars, making the Curiosity much larger than the older rovers Spirit and Opportunity. The first pictures were sent back to Earth two hours after the landing; check NASA.gov for the latest news and images as they come in.

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(Click to enlarge and for more info. All images courtesy of NASA/JPL-Caltech; image of descent from orbit also courtesy Univ. of Arizona; image of landing zone also courtesy ESA/DLR/FU Berlin/MSSS)

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Remember how I told you last week that a new study suggested that the moon might have been formed by a glancing blow from a very large object? Well, another study using computer simulations shows that the earth-like composition of the moon could have resulted from a direct impact of an object about the size of Mars, which is smaller than the Earth. A head-on, high-speed collision would have released quite a bit of material from Earth. I’m not sure if we’ll ever be able to know for certain which version of history is correct, but it’s an interesting look at the difficulty of reconstructing past events accurately.

Further experiments at the Large Hadron Collider are lending further credence to last month’s announcement of the existence of the Higgs boson (or at least, of a “Higgs-like” particle). The most recent tests raise the probability that the predicted Higgs boson or a remarkably similar particle is real to 5.9 sigma, meaning there’s only a 1-in-550 million chance that the results are a freak coincidence. Further tests are planned to ensure that the particle seen fits neatly into the proposed Standard Model, or to determine if we need to go looking for more particles like it.

Dinosaur news! Geology can have surprising impacts on evolution. Researchers say the rapid appearance of new dinosaur species in North America around 75 million years ago is due to the rise of two mountain ranges; the Sevier mountains near the present-day Sierra Nevadas, and the Laramide Orogeny, which later grew to be the Rockies we know today. These changes also caused the formation of an inland sea stretching from the Arctic Ocean southward to the present-day Gulf of Mexico, dividing the continent into three large islands and allowing species to evolve rapidly to adapt to their new environments. Another study shows that the meteor impact 65 million years ago may not have been the sole cause of the extinction of the dinosaurs. More than 100,000 years before the meteor, there was a series of huge volcanic eruptions in India that has long been suspected to have adversely affected many species, and scientists have finally found sedimentary rocks of exactly the right age to see their impact. Isotope testing shows an increase of polar temperatures of 7°C following the eruptions, and the die-off of many species in the oceans. The later meteor impact remains the most likely killing blow, but the volcanism and resultant global warming may have already weakened or killed some species.

A drilling project off the coast of Antarctica has found evidence that 53 million years ago the continent was home to palm trees and other species similar to today’s baobabs, macadamia trees, beeches, and conifers. Though the continent had already drifted close to its current position at the South Pole, carbon dioxide levels were much higher than today, leading to higher temperatures across the globe. Evidence from single-celled organisms called Archaea shows that during Antarctic winters temperatures seldom dropped below 10°C (50°F) and summers could reach between 20-25°C (68-77°F).

The oldest known modern tools have been found in a cave in South Africa. Dating to about 44,000 years ago, they predate the previously oldest known tools by 20,000 years and are virtually identical to tools still in use today by indigenous African San bush people. The artifact cache includes arrowheads with traces of the beeswax that was used to affix them to arrows, decorated bones and beads, and most unusually, a notched stick with trace remains of a natural poison that was likely used to apply the poison to arrowheads.

The evolutionary split between brown bears and polar bears may have taken place far earlier than previous estimates. The first attempt to date the emergence of the polar bear as a separate species put their age as only 150,000 years old, and a study earlier this year pushed that back to 600,000 years. The most recent study looks at the full genome of 23 polar bears and, assuming that their genes mutate at the same rate as primates, pushes their origin back to between 4 and 5 million years ago. Some populations that come into contact with brown bears show evidence of interbreeding.

Australian officials are considering removing great white sharks from the list of protected species in the wake of five fatal attacks on humans in less than a year. The sharks were originally listed as protected in 1997, but the attacks have led officials to call for a study to see if their population has rebounded. It’s unlikely that they would be removed from the list if their numbers are still low.

Warmer winters and abundant food mean some humpback whales are slow to leave Antarctic waters to migrate north for breeding. A study of whale populations there between April and June 2009 (late fall/early winter in the southern hemisphere) shows a much higher density than scientists expected.The whales were especially crowded in the bays and inlets of Western Antarctica. If climate change delays the onset of winter and prevents bays from icing over, it could change the whales’ migration patterns and some might even forgo the trip to warmer waters entirely.

A study of the mitochondrial DNA of fruit flies found that certain mutations caused male flies to have shorter lifespans but didn’t affect the females, possibly lending insight into why the females of many species including humans tend to live longer on average. Mitochondrial DNA is only inherited from the mother, so any disadvantage a mutation gave to males wouldn’t affect its chance of being passed on to the next generation. Many other factors are also likely at work, such as hormones and lifestyle differences.

17-year-old Britanny Wenger has won the Google Science Fair with her development of a virtual brain that can detect breast cancer correctly in 99.1% of tests conducted using the least invasive biopsy method. She was only in seventh grade when she started programming artificial neural networks, computer programs that simulate the thought processes of the human brain to detect complex patterns. She’s run 7.6 million trials, and since her network can “learn” from new information it reads, it should actually get more accurate with further use. Wenger is hoping to deploy her program in hospitals and to teach it to detect other cancers in the future.

Cataract surgery, a relatively simple outpatient procedure, can have health benefits that far exceed simply having better vision. A study that looked at the records of 1.1 million Medicare patients aged 65 and older showed that those who had undergone cataract surgery had 16% fewer hip fractures than those who been diagnosed with cataracts and opted not to treat them. The greatest benefit was seen by patients aged 80 to 84, who were 28% less likely to break a hip. Better vision makes people less likely to fall and get injured, and also improves mental health by allowing the elderly to be more independent.

The version of the pertussis (whooping cough) vaccine currently given to children may not be as effective as an older formula that was replaced about 20 years ago. The older version was a whole-cell vaccine, but complaints about high levels of mild side effects (redness and swelling at the injection site, fever) led to its replacement with an acellular version of the vaccine, which boasts a lower incidence of side effects but also may be less effective and whose affects may wear off sooner. A study of children vaccinated in Australia in 1998, the year the new version was rolled out there, shows that children who received the old version were much less likely to later develop pertussis than those who received the new one (or a mix of the two, since three injections are given in the first year of life). Another study in the U.S. shows that preteens who were vaccinated as young children but hadn’t received the last pertussis booster had an unusually highest rate of infection, leading researchers to think it may wear off faster than previously thought. Of course, if all children and adults are fully vaccinated, herd immunity will lesson the odds that those more susceptible to infection will be exposed in the first place.