World Science
New clues for finding alien life
Climate change sparked rise of the lizards
Technology delivers net through TV aerial
Indigenous burn control a myth: study
Galapagos whales hold pollutant mystery
Bicycle scheme reveals rider behaviour
Frog bladder holds a surprise
Relocating species to ensure survival
Plant growth could slow warming: NASA
Astronomers find planet with a diamond heart
Free radicals not such a bad thing
Ants lay trail to complex problem-solving
Imagine more, eat less: study
'Stealth fungus' seeks, destroys crops
Saturn rings born from Titanic collision
New thinking on asteroid belt
Hungry Maoris burned forests to grow food
Ocean may contain nuclear powered microbes
Voyager reaches edge of solar system
Medical science examines urban myths
Clusterwinks bask in the afterglow
Cyclone batters Saturn for five years
Arctic icecap 'safe' from runaway melting
Fearless woman helps unlock anxiety puzzle
CO2 gets Martian sand dunes moving
Sand dunes surrounding the North Pole of Mars are on the move, powered by carbon dioxide, a finding that has surprised planetary scientists.

Until now, it was though the dunes of the vast northern plains were thought to be frozen in time and cemented in place by water ice.

Now a report in the journal Science claims high resolution imaging by NASA's Mars Reconnaissance Obiter (MRO) spacecraft shows these dunes are dynamic and moving.

Dr Candice Hansen from the Planetary Science Institute in Tucson, Arizona, says knowing how Mars is changing helps our understanding of basic planetary processes.

According to Hansen, scientists thought the dunes were fairly static, shaped long ago when winds on the planet's surface were much stronger than today.

"The before and after pictures show a surprising number of changes in the higher latitude dunes," says Hansen.

She says the changes are caused by the periodic deposition and sublimation of carbon dioxide.

"A seasonal layer of frozen carbon dioxide blankets the region in winter, changing directly back to gas in spring, causing the sand to avalanche down in dark streaks, forming new alcoves and debris aprons on about 40 per cent of dunes."

Hansen says the other surprising discovery was the impact of the Martian wind.

"Scars of past avalanches were covered over in a single year by winds strong enough to move sand. That's a surprise because most of our climate models didn't predict strong winds and our experience with the landers at lower latitudes tells us winds are rare."

She says the winds indicate there's a lot going on weather-wise near the poles.
Different processes in the south

Hansen says the processes occurring in the Southern Hemisphere are different to those in the north.

"Things are different because there's less sand, most of which is confined to craters", she says. "Water ice solidifies the core of dunes and dry ice provides a seasonal cover."

"And the planet's highly elliptical orbit makes southern winters longer and colder, so seasonal ice covers the dunes for longer, allowing the grains to get bigger and more compacted."

Despite these differences, Hansen was surprised water ice has so little impact in the Northern Hemisphere.

"It's far less than originally thought and not enough to cement the dunes in place," she says.

Hansen plans to continue studying the dunes during several Martian years to see if there are any differences during that time.

"There appears to be a difference in the weather in a subsequent winter after a dust storm, so we want a longer time history to puzzle out those differences."

Reefs reeling from Queensland floods
Public asked to define a galaxy
Polygamy produces more virile offspring
Sleep best time to reinforce memory
Some Himalayan glaciers advancing: study
Massive coal fires caused Great Dying
Kid's self-control predicts health, wealth
Fish in groups decide quicker, better
One-clawed dino found in China
Conservationist and marine photographer recognised
Awards for medical research pioneers
Tough conditions favour giants
Bat uses carnivorous plant as a toilet
Telescope spots 'oldest galaxy' yet seen
Scientists unravel probiotics gut defence
Humans came out of Africa via Arabia: study
Bovine bellies yield biofuel clues
Saturnian moon's ocean full of gas
Sun rises on next solar generation
New test targets 'mad cow' disease
Dogs sniff out cancer in stool
Great drying reveals clues to big wet
Ant genome may reveal survival secrets
Dud mates stress out female finches
Kepler dramatically boosts exoplanet count
Scientists grow blood vessels
CO2 gets Martian sand dunes moving
Team makes nanosheet breakthrough
Music thrills trigger reward chemical
Lunar water may have come from comets
Birds falling from the sky 'not unusual'
NASA spots hot, Earth-like planet
Lifespan of early humans, Neanderthals same
Echidnas' unusual mating habits revealed
Funky frogs sniff out danger
La Nina lives up to predictions
Cuckoos ramp up effort in 'arms war'
Lensing putting universe out of focus
Penguins to shrug off flipper band
Device may silence ringing in the ears
Scientists find tiny 'dawn runner' dinosaur
'Goldilocks' planet lost in translation
Smoking causes gene damage in minutes
Climate matched Europe's ups and downs
Accuracy gave bows the early upper hand
Chemistry comes from the genes
Researchers aim to resurrect mammoth
Smaller corals take the heat
Blood drug could save crash victims
Gaps in flood knowledge: experts
Malaria parasite caught in the act
White blood cell protein aids melanoma
Visit Statistics