A year and a half ago, NASA announced that one of its scientists, Felisa Wolfe-Simon, had found a bacterium that could use arsenic instead of phosphorus in its DNA. This revelation, published in Science, had enormous implications for our understanding of what’s necessary for life—we’ve always thought phosphorus was essential and arsenic poisonous, and having that disproven might mean life could exist in environments where it had been thought impossible.
Almost immediately, though, scientists and science journalists began to pick apart this paper. DISCOVER blogger Carl Zimmer rounded up the case against in a Slate article shortly after the paper’s publication. Ever since, he’s kept track of the story’s evolution—including experiments posted by microbiologist Rosie Redfield on her blog that provided evidence against the claim—here on his blog.
All the way along, Wolfe-Simons refused to comment on Redfield’s experiments, saying she would wait until they were published by a peer-reviewed journal. Now, Redfield’s paper and one other paper finding no evidence of arsenic life have been published by Science, the same journal that published the original claim. The researchers found no evidence of arsenic being used in the bacterium’s DNA.
The Xultun scribe’s chamber, with A, B, and C showing the locations of the calculations.
In a small closet-like chamber off a central plaza of the ancient Mayan city of Xultun, a scribe once sat with a paintbrush in hand.
On the north walls of the room, he painted an apparent self-portrait, facing a figure with an elaborate headdress, perhaps a ruler. But on adjacent walls, he and his successors, starting in about 800 C.E., painted and inscribed various astrological calculations. They are very similar to those found in the Dresden Codex, one of the most famous extant Mayan books, which contains numerous astrological and ritualistic cycles and is thought to have been copied from older books sometime between the 11th and 15th centuries. The markings on the scribe’s walls in Xultun, unveiled last week in a paper in Science, represent the earliest known depictions of some of these calculations.
Artist’s concept of the pulsar and its planet. The system could fit into our Sun, represented by the yellow surface.
What’s the News: An international team of astronomers has found an exotic planet possibly made of diamond, located about 4,000 light-years away from Earth. The researchers believe that the unusual planet was once a sun-like star, transformed into its current state by its hungry stellar companion, a millisecond pulsar.
What’s the News: Keeping track of what’s happening inside the body often requires a great deal of equipment outside it: Just think of the tangle of sensors in any hospital room. Now, though, engineers have developed an ultra-thin electrical circuit that can be pasted onto the skin just like a temporary tattoo. Once it’s served its purpose, you can simply peel it off. These patches could be provide a simpler, less restrictive way to monitor a patient’s vital signs, or even let wearers command a computer with speech or other slight movements.
What’s the News: While most people think of dyslexia as primarily a problem with reading, people with dyslexia seem to have trouble processing the spoken language, as well. A new study published last week Science found that people with dyslexia have a harder time recognizing voices than other people do.
Scanning electron micrograph images of the nut (A,B)
and screw (C, D) in the leg joint of a Papuan weevil
What’s the News: Biologists spend lots of time poring over nature’s nuts and bolts. Now, for the first time, they’ve found a biological screw and nut—previously thought to be an exclusively human invention. The legs of beetles called Papuan weevils, researchers report today in Science, have a joint that screws together much like something you’d find in the hardware store.
What’s the News: Scientists—and smokers—have long known that nicotine is an appetite suppressant, but just how it kept hunger at bay remained unclear. Now, researchers have uncovered the neural pathway by which nicotine reduces appetite, in a study published today in Science. This discovery could lead to new drugs that help people quit smoking or lose weight.
Diagram of the new DNA circuit
What’s the News: Researchers have built the most complex DNA-based computer yet, a circuit of 130 strands of DNA that can compute the square root of numbers up to 15. The system, reported today in Science, is made of biological logic gates, which do computations using DNA strands’ natural propensity to zip and unzip. This new method is easily adapted for different calculations and can be automated, meaning it could be used to build much larger circuits.
What’s the News: Mammals’ increased brain size may have come from long-ago natural selection for a better sense of smell, suggests a new study published today in Science. By reconstructing in 3D the skulls of two animals far back on the mammal family tree, the researchers saw that growth of smell-related brain regions accounted for much of the early increase in brain size as mammals developed.
What’s the News: Jupiter’s moon Io is more volcanically active than any other object in our solar system, releasing 30 times more heat than Earth through volcanism. It’s thought that Jupiter’s gravity pulls so hard on the moon and causes so much friction that the resulting thermal energy melts a huge amount of underground rock, feeding Io’s 400 active volcanoes.
For years, astronomers have debated whether Io’s spewing lava comes from isolated pockets of magma or a layer that spans the entire moon. Astronomers have now peered into Io’s interior for the first time, discovering that it has a global sea of magma roughly 30 miles thick. “It turns out Io was continually giving off a ‘sounding signal’ in Jupiter’s … magnetic field that matched what would be expected from molten or partially molten rocks deep beneath the surface,” lead researcher Krishan Khurana told Wired. Read More