Ripples testify to 14th century collision

During the 1300s, the Black Death was savaging Europe, England and France were locked in the Hundred Years' War and Chaucer was penning his Canterbury Tales. Meanwhile, more than a billion kilometers away, a comet careened toward Saturn and disintegrated, dropping dusty clouds of debris on the giant planet's iconic rings, creating rippled cometary footprints.

The ripples from that cataclysmic event can still be detected today, electrical engineer Essam Marouf reported October 4 during the joint meeting of the European Planetary Science Congress and the American Astronomical Society's Division for Planetary Sciences.

Marouf, a professor at San Jose State University in California and a member of the Cassini science team, described how the probe beamed radio waves back to Earth through the innermost part of Saturn's C ring, a tenuous inner band in the planet's ring system. The radio waves revealed what Marouf calls a "very unusual kind of addition" to the normal ring structure. "There were highly regular little wiggles that rippled over hundreds of kilometers in a very specific pattern," Marouf says.

A strange geological process is at work in a remote corner of northern Chile's Atacama Desert, and it was discovered thanks to one scientist's upset stomach.

University of Arizona geologist Jay Quade were traveling through the area when Quade's sour stomach forced them to stop their truck at a lifeless expanse of boulders in the Atacama that they had passed before without noticing anything unusual.

While the others wandered off to see the sites, as geologists are wont to do, Quade climbed under the truck to get out of the beating sunlight. That's when Quade noticed something very unusual about the half-ton to 8-ton boulders near the truck: they appeared to be rubbed very smooth about their midsections.

The most common agent of such erosion is water - not something readily found in the bone-dry Atacama.

About the only other thing that came to Quade's mind was earthquakes, he said in a statement. Over the approximately two million years that these rocks have been sitting on their sandy plain perhaps they were jostled by seismic waves that caused them to gradually grind against each other and smooth their sides. It made sense, but Quade never thought he'd be able to prove it.

There are many weird viruses on this planet, but none weirder-in a fundamentally important way-than a group known as the giant viruses.

For years, they were hiding in plain sight. They were so big-about a hundred times bigger than typical viruses-that scientists mistook them for bacteria. But a close look revealed that they infected amoebae and built new copies of themselves, as all viruses do. And yet, as I point out in A Planet of Viruses, giant viruses certainly straddle the boundary between viruses and cellular life. Flu viruses may only have ten genes, but giant viruses may have 1,000 or more. When giant viruses invade a host cell, they don't burst open like other viruses, so that their genes and proteins can disperse to do their different jobs. Instead, they assemble into a "virus factory" that sucks in building blocks and spits out large pieces of future giant viruses. Giant viruses even get infected with their own viruses. People often ask me if I think viruses are alive. If giant viruses aren't alive, they sure are close.

A team of British engineers is set to begin a journey to a lake hidden beneath nearly 2 miles of Antarctic ice.

The explorers depart next week for Antarctica on the first stage of an ambitious scientific mission to collect water and sediment samples from a lake buried beneath 1.8 miles (3 kilometers) of solid ice. This mission will hopefully yield new knowledge about the evolution of life on Earth and other planets, and will provide vital clues about the Earth's past climate.

Transporting nearly 80 tons of equipment, the "advance party" will make a journey almost 10,000 miles (16,000 km) from the United Kingdom to the subglacial Lake Ellsworth on the West Antarctic Ice Sheet. It is one of the most remote and hostile environments on Earth, with temperatures that hover at minus 13 degrees Fahrenheit (minus 25 degrees Celsius). Their task is to prepare the way for the "deep-field" research mission that will take place next year, when the team of scientists and engineers will live in tents, spending around three months working above the lake.

A genetic mutation possibly linked to malarial resistance may have helped drive the evolution of the genus Homo, humans' ancient ancestor, a new study finds.

The mutation tweaked one type of sugar molecule, Neu5Gc, produced by early hominids, the first great apes. About 2 million or 3 million years ago, just as human ancestors Homo ergaster and Homo erectus emerged in Africa, a genetic mutation halted the production of this molecule, and the prehuman immune system began to recognize it as a threat. As a result, researchers find, some hominids would no longer have been able to mate and produce offspring with other populations, potentially driving early humans apart from other apes.

"Over time, this incompatibility would reduce and the eliminate individuals with Neu5Gc," study researcher Pascal Gagneux of the University of California, San Diego, said in a statement.

Cells communicate with other cells using sugar molecules that stud the outsides of their membranes. One type of sugar molecule is sialic acid, which is found on all animal cells.

Mars Express was able to accomplish what so many other spacecraft have tried and failed by using a SPICAM(2) spectrometer

The search for water on Mars has been ongoing for quite some time now, with Mars rovers like NASA's Spirit and Opportunity being two examples of those who have found clues that point to a once-tropical past on the dusty red planet billions of years ago.

Now, the European Space Agency's Mars Express spacecraft has discovered that Mars' atmosphere holds water vapor in a supersaturated state.

Mars Express was able to accomplish what so many other spacecraft have tried and failed by using a SPICAM(2) spectrometer. While other spacecraft have used tools that concentrate only on surface data, which only analyzes the horizontal component of the Martian atmosphere, SPICAM(2) utilizes solar occultation to observe the vertical component of the atmosphere, which is critical for understanding Mars' hydrological cycle. Solar occultation studies light from the Sun in Martian atmosphere during sunrise and sunset.

Supersaturation is the vapor of a compound that has a higher pressure than the vapor pressure of that compound. Earth's atmosphere is considered saturated because water vapor condenses when the temperature drops below dew point, and the atmosphere cannot contain any more moisture at that point. This excess water turns into a liquid around dust and particles that are suspended, causing precipitation, but sometimes the low availability of dust and particles can slow condensation and leave excess water vapor in its gaseous state. This is supersaturation.

As it turns out, supersaturation is common on Mars. In fact, Mars Express found that the levels of supersaturation on Mars were 10 times higher than those on Earth.

"This ability of water vapor to exist in a highly supersaturated state would, for example, allow to supply the southern hemisphere of Mars with water, far more efficiently than models currently predict," said Franck Montmessin, a researcher at the Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS, CNRS / UPMC / UVSQ).

This research could contribute to the overall understanding of the planet's low amount of water today as opposed to its abundance of water billions of years ago.

This study was published in Science.

The largest virus yet discovered has been isolated from ocean water pulled up off the coast of Chile.

Called Megavirus chilensis, it is 10 to 20 times longer than the average virus.

It just beats the previous record holder, Mimivirus, which was found in a water cooling tower in the UK in 1992.

Scientists tell the journal PNAS that Megavirus probably infects amoebas, single-celled organisms that are floating free in the sea.

The particle measures about 0.7 micrometers (thousandths of a millimetre) in diameter.

"It is bigger than some bacteria," explained Professor Jean-Michel Claverie, from Aix-Marseille University, Marseille, France.

For the first time, researchers have detected ocean-like water in a comet - new evidence supporting the theory comets delivered a significant portion of Earth's oceans.

"Life would not exist on Earth without liquid water, and so the questions of how and when the oceans got here is a fundamental one," says Ted Bergin, an astronomy professor at the University of Michigan. "It's a big puzzle and these new findings are an important piece."

The findings are reported in the journal Nature.

Bergin is a co-investigator on HiFi, the Heterodyne Instrument for the Infrared on the Hershel Space Observatory. With measurements from HiFi, the researchers found that the ice on a comet called Hartley 2 has the same chemical composition as our oceans. Both have similar D/H ratios. The D/H ratio is the proportion of deuterium, or heavy hydrogen, in the water. A deuterium atom is a hydrogen with an extra neutron in its nucleus.

A giant sea monster, the likes of the mythological kraken, may have swum Earth's ancient oceans, snagging what was thought to be the sea's top predators - school bus-size ichthyosaurs with fearsome teeth.

The kraken, which would've been nearly 100 feet (30 meters) long, or twice the size of the colossal squid, Mesonychoteuthis, likely drowned or broke the necks of the ichthyosaurs before dragging the corpses to its lair, akin to an octopus's midden, according to study researcher Mark McMenamin, a paleontologist at Mount Holyoke College in Massachusetts.

There is no direct evidence for the beast, though McMenamin suggests that's because it was soft-bodied and didn't stand the test of time; even so, to make a firm case for its existence one would want to find more direct evidence.

McMenamin is scheduled to present his work Monday (Oct. 10) at the annual meeting of the Geological Society of America in Minneapolis.

On December 12, 2010, something very unusual happened to asteroid Scheila. For a short period of time, its appearance changed dramatically and it even developed a comet-like tail. Now a group of international scientists headed by Fernando Moreno of the Instituto de Astrofísica de Andalucía in Granada, Spain have created a computer model which may explain this weird activity... an impact.

In results revealed October 7th in Nantes, France at the joint meeting of the European Planetary Science Congress and the American Astronomical Society's Division for Planetary Sciences, the team explained their theory of how this innocent asteroid may have been crashed into by a smaller object. Moreno and his team plotted the brightness curve of Scheila's newly developed "tail" - watching how it declined over a period of weeks. Their conclusion was that Scheila was either responsible for bumping into an uncatalogued object - or the object bumped into it causing a debris trail.

"The model we used involves a very large number of particles ejected from Scheila." explains Moreno. "We took into account gravity from the Sun, pressure radiation on the ejected particles, and Scheila´s gravity, which has a strong effect on the particles in its vicinity owing to its large mass."