Science News

Headlines
. Exploring the moon, dwarf planets and asteroids from Vesta to Ceres
. The long flights of dragonflies
. How about gold that grows on trees?
. The Koala males have a deep voice
. Hot never looked so cool: vanadium dioxide
. Ultra-small movies, starring molecules

For more details, read on

. From Vesta towards Ceres
In September, the American space agency NASA launched the Lunar Atmosphere and Dust Environment Explorer (LADEE), a robotic mission to the moon (see inner cover for photo). It entered lunar orbit on October 6, 2013 and is successfully communicating with Earth using laser pulses. It has recently been joined in its orbit around the moon by the Chinese moon mission Chang'e 3, also an unmanned mission.
In the meanwhile, NASA's "Dawn" mission, launched in 2007, was aimed at Vesta, one of the largest asteroids in the solar system and the brightest asteroid visible from Earth. After studying Vesta for a year, Dawn is now headed towards the dwarf planet Ceres. Ceres is the largest asteroid and the only dwarf planet in the inner Solar System.
Dawn reached the bright asteroid Vesta (discovered by the German doctor of medicine and amateur astronomer Heinrich Olbers in 1807) in July 2011. The pictures from Dawn suggest that Vesta may also have been a planet in the making, with many similarities to the rocks and material found on the Moon. On a full moon night one can usually see "rays" emanating from the crater Tycho (see picture), craters on Vesta also have rays like these.
After orbiting Vesta for a year, in July 2012, Dawn's rockets were fired to move it to a new orbit which will reach the dwarf planet, Ceres (discovered by the Italian priest, mathematician and astronomer Giuseppe Piazzi in 1801), in February 2015.
Like Earth, Ceres has denser material at the core and lighter minerals near the surface. Astronomers believe that water ice may be buried under Ceres' crust because its density is less than that of the Earth's crust, and because the dust-covered surface bears evidence of water-bearing minerals. Ceres could even boast frost-covered polar caps.
Astronomers estimate that if Ceres were composed of 25 percent water, it may have more water than all the fresh water on Earth. Ceres' water, unlike Earth's, is expected to be in the form of water ice located in its mantle.

. The long flights of dragonflies
Bird migration is well known and familiar to most of us, but birds are not the only creatures that depart from cool climates in search of warmer ones in autumn, and the reverse in the spring. Monarch Butterflies are also well-known long-distance migrants, but so are many other insects, including other species of butterflies, moths, locusts and dragonflies.
Migration by dragonflies has been recorded sporadically for several centuries. European records of this date back to 1494. Since 1998, there has been extensive research on this. Most swarms are sighted between late July and mid-October, with a peak in September. Most of the large flights occur along lakeshores and coastlines. Massive swarm migrations go with northerly winds following the passage of cold fronts.
The Common Green Darner (Anax junius) is the predominant species in the majority of these flights. About 16 to 18 species are regular migrants, with some making annual seasonal flights while others are more sporadic. The Common Green Darner, weighing about one gram, travels more than 600 km over a two-month migration. There are interesting similarities between bird and dragonfly migration behaviour. Like migrating birds, dragonflies stop over at feeding spots occasionally to refuel along the way. 
In fact, during migration Common Green Darners often spend as much or more time feeding as they do making long flights. On average in North America they migrate in a southward direction every three days, covering roughly 50-70 km in 5-7 days. Common Green Darners migrate exclusively during the day, regardless of wind direction, but only after two nights of successively lower temperatures. Like many migrating songbirds and hawks, dragonflies appear to avoid flights over extensive open water, even if it means going miles out of their way. 
Dragonflies begin their adult lives in autumn with very little fat, undeveloped ovaries and functional but incompletely-developed flight muscles. They quickly increase muscle mass and fat stores -- more so than local breeding dragonflies that don't migrate -- and some species periodically lay eggs in ponds along their migratory route during their southward flight. 

. How about gold that grows on trees?
A group of geochemists from Western Australia has announced finding tiny grains of the precious metal in the leaves of eucalyptus trees.
If you're picturing gold leaves glittering in the sun, forget it. The specks of leaf-bound gold are only one-fifth the width of a human hair and just about as long. In fact, to find these nano-nuggets the team had to use a very powerful set of X-ray eyes called the synchrotron.
The leaves are not worth mining. Still, the greenery can lead to real riches How? The leaves can point to where mining teams might want to drill in search of a potentially rich seam of gold. Or of some other mineral -- because sources of any rare mineral spotted in tree leaves may highlight ore hiding deep below the surface.
Geologists have actually known for years about the value of using plant or animal material to explore for buried minerals. The process is called biogeochemical prospecting. 
What is interesting is how trees move and concentrate such a metal, they bring it up from such a depth as a 10-storey building.
But plants aren't the only ones to do this. Termites need moist material to hold their big mounds together. In desert regions those insects have been known to bore 40 meters (131 feet) down, for example in Botswana. And occasionally they drag gold back up along with the mud they were seeking. 
Non-digging animals can help too. Kangaroos, for example, eat plants that may have taken up gold. 
Bringing gold to light is just accidental for the plants, insects and kangaroos. It can prove a huge stroke of luck for geologists, however. After all, why dig and drill to look for gold if the local flora and fauna can do the dirty work for you? 

. The Koala males have a deep voice
Scientists have just turned up a second set of vocal cords in koalas. These bonus vocal cords allows males to hit tones 20 times lower than would be expected from an animal its size.
The size of an animal's voice box and its flapping vocal cords dictate the range of pitches that an animal can make. For a typical 8-kilogram male koala, its voice should fall within the high-pitch range of any animal choir. Yet the male's mating songs include very low bellows -- tones usually created only by elephant-sized mammals. Although these tones may make a female koala swoon, to the human ear, the low-pitched sounds resemble only a string of belches and snorts.
A team of scientists wanted to probe how the serenading males reach those deep bass tones. They dissected the voice boxes of 10 male koalas. They found that koalas possess a unique, second set of vocal flaps. The bonus ones reside outside of the voice box. Their placement allows them to belt out those low, low tones. These extra vocal cords make the koala quite unusual, both in terms of its anatomy and its acoustics -- those sounds it makes, according to a recent issue of Current Biology.

. Hot never looked so cool!
The hotter it gets, the more it glows. This rule applies to stove-tops and light bulbs alike. But it does not hold true for everything. Scientists report finding a rule-breaker -- one that appears to cool down even as its temperature climbs. A material like this could be used to build objects that can fool infrared cameras, the kind that see heat, rather than visible light. It may also help scientists design heating and cooling systems that will use less energy. 
Not all materials respond to changing temperatures in the same way. As their temperatures rise or fall, some substances change the way they respond to light or electricity. That's true for vanadium dioxide. At temperatures below 70 degrees Celsius, this material acts like an insulator. That means electricity can't easily pass through it.
Above 70C, things change. The compound suddenly becomes a conductor. Electricity now readily passes through it. Scientists don't know exactly why vanadium dioxide does this. But its behaviour gave physicists at Harvard University an idea: perhaps that switch in the compound's electrical properties would also change how much it glows. As the material's temperature climbed from 60 to 74 °C, it gave off increasing amounts of radiation. That means it glowed brighter and brighter. Then something strange happened. Even as the compound's temperature continued to rise, its glow began to diminish.
This means the material hides its true temperature, by appearing cooler as it continues to warm. Scientists don't yet know how the material rearranges its structure to pull off this trick.

Compiled from several sources