ICE SCOUR AT THE BOTTOM OF THE OCEAN

ICE SCOUR AT THE BOTTOM OF THE OCEAN
As the Titanic found out, icebergs can cause a lot of destruction. But it isn’t just ships that can be damaged; close to the coast the seafloor can take a pounding as icebergs are moved around by currents, wind and tides. This “ice scour” occurs along coastlines at high latitudes in water up to about 1,600 feet deep, depending on the size of the iceberg. It disturbs the ocean bottom just as a forest fire or flood disturbs the landscape.
A study by researchers with the British Antarctic Survey adds to the limited knowledge of ice scour. Working in water up to 80 feet deep off the West Antarctic Peninsula, Dan A. Smale and colleagues laid out concrete markers on the seafloor and observed which ones were hit. Smale said the findings, reported in Science, had implications for seafloor biodiversity in the Antarctic. On regional scales, scour may create a continuum of damaged and recovering environments over time, with different species inhabiting each.
The researchers also found that less scour occurred in colder years, when ice was anchored to the coast for longer. That has implications for the future, when warmer conditions may free icebergs to move around longer and scour even more seafloor.

ON JUPITER, A BATTLE OF THE RED SPOTS
Can a planet change its spots? Jupiter, where spots are really just large storms, seems to be in the process of doing so. A small red spot that formed on the surface this year appears to have met its match in the Great Red Spot. Images taken by the Hubble Space Telescope on June 28 and July 8 show that the small spot, which has the misfortune to lie at the same latitude as the great one, has moved from the west side of the giant to the east side.
But more than that, the small spot, known informally as Baby Red Spot, seems to have gotten caught in the maelstrom that is the great spot (which is about 18,000 miles wide and packs winds up to about 400 miles per hour). Baby Red appears to be coming apart and is definitely turning paler.
Spots on Jupiter are thought to turn red when the winds become so powerful that they draw certain gases from deep in the atmosphere that change color when exposed to sunlight. So if Baby Red is losing its color, that probably means its winds are diminishing, its energy being absorbed by the giant spot. Subsuming smaller spots may be one way the great one persists—it has been around for centuries, at least.
A medium-size spot, officially known as Oval BA but often called Red Spot Jr, is also in the images, south of the giant. It has been going strong since 2000 and turned red about two years ago. It is far enough south of the giant to be unaffected by it—for now.

A NEW WAY TO WEIGH ATOMS
Say you’ve got a few atoms of gold or another element and you want to weigh them. There’s no scale in the world sensitive enough to do the job, but you could use a mass spectrometer. That involves stripping electrons off the atoms and sending the resulting ions through a magnetic field.
Physicists at the University of California, Berkeley, have come up with what may well be a better way. They have developed a nanomechanical sensor—a cantilevered carbon nanotube that sways like a diving board. And just as a diving board is affected by the weight of the diver, the nanotube’s vibrations change when gold or other atoms are stuck to it. By measuring the changes, researchers can calculate the mass of a single atom.
The key to the sensor’s sensitivity is its extremely small size, said Kenny Jensen, a doctoral student who describes the device in a paper in Nature Nanotechnology. (His co-authors are Alex Zettl, director of the university’s Center of Integrated Nanomechanical Systems, and Kwanpyo Kim.) The nanotube is only about a billionth of a meter in diameter and 200 billionths of a meter long.
There were many hurdles to overcome, not the least being how to measure the vibrational frequency. The researchers ended up measuring it electrically—sending a radio signal to the nanotube and listening for the vibrations. Zettl said sensors like this had been the subject of much research. “The holy grail has been, can you get down to the molecular or even atomic level, and can you do it at room temperature,” he said. His lab’s device accomplishes this and may be particularly useful for measuring large molecules like proteins, which don’t fare well in mass spectrometry.
(—NYT)