martes, 20 de diciembre de 2016

The birth of a 'spider' on Mars: NASA reveals timelaspe showing how strange cracks form

'Spidersrange from tens to hundreds of yards, are found in south polar region They are carved through years of erosion as seasonal carbon dioxide thawsNow, NASA has spotted what could be theinfant versionsof these features

The Martian south pole is dotted with strange networks of branching troughs known as ‘spiders,’ each carved through years of erosion as seasonal carbon dioxide thaws.

Now, NASA scientists have spotted what could be the ‘infant versions’ of these features.

Using the Mars Reconnaissance Orbiter, researchers have detected cumulative channel growth from one Martian spring to another for the first time.

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HOW THEY FORM

Researchers have thought that during the spring, sunshine penetrates the ice and warms the ground underneath.

This causes some carbon dioxide on the bottom of the sheet to that, turning into gas.

The gas, in turn, becomes trapped and pressure increases until a crack forms in the ice sheet.

Then, the gas erupts out, and that beneath the ice rushes toward the vent, gathering particles of sand and dust, eroding the ground.

The process also supplies the geyser with particles, which fall back to the surface, downwind, and create dark spring fans.

The sites spotted near the south pole are at spring-fan sites, and have persisted and grown through three Mars years, and formed branches resembling the spidery terrain.

The researchers say sand may ‘jump start’ the process of carving a channel in the ground.

A ‘spider’ on Mars can range in size from tens to hundreds of yards, and are only found in the south polar region, according to NASA.

They typically feature a central pit, with multiple channels branching out – like the body and legs of a spider.

The researchers have monitored their changes for the past decade using MRO’s High Resolution Imaging Science Experiment (HiRISE) camera, but now, they may have caught a glimpse at how these spiders form.

‘We have seen for the first time these smaller features that survive and extend from year to year, and this is how the larger spiders get started,’ said Ganna Portyankina of the University of Colorado, Boulder.

‘These are in sand-dune areas, so we don’t know whether they will keep getting bigger or will disappear under moving sand.’

It’s thought that dunes contribute to the formation of ‘baby spiders,’ but the researchers say they also may prevent some from developing to their full potential.

The researchers estimate it would require erosion over a thousand Martian years to sculpt a typical spider.

‘Much of Mars looks like Utah if you stripped away all vegetation, but ‘spiders’ are a uniquely Martian landform,’ said co-author Candice Hansen of the Planetary Science Institute, Tuscon, Arizona.

While carbon-dioxide ice – ‘dry ice’ – doesn’t occur naturally on Earth, it covers the ground on Mars during winter in the areas around both poles.

Each spring, dark fans mark these areas.

A ¿spider¿ on Mars can range in size from tens to hundreds of yards, and are only found in the south polar region, according to NASA. They typically feature a central pit, with multiple channels branching out ¿ like the body and legs of a spider

Researchers have thought that during the spring, sunshine penetrates the ice and warms the ground underneath.

This causes some carbon dioxide on the bottom of the sheet to that, turning into gas.

The gas, in turn, becomes trapped and pressure increases until a crack forms in the ice sheet.

Then, the gas erupts out, and that beneath the ice rushes toward the vent, gathering particles of sand and dust, eroding the ground and supplying the geyser with particles.

These particles fall back to the surface, downwind, and create the dark spring fans.

Observing this process has proved challenging, and though researchers have spotted the appearance of small furrows on the sand in the north, these disappeared within a year.

The sites spotted near the south pole, however, are also at spring-fan sites, and have persisted and grown through three Mars years, and formed branches resembling the spidery terrain.

‘There are dunes where we see these dendritic [or branching] troughs in the south, but in this area, these is less sand than around the north pole,’ Portyankina said.

‘I think the sand is what jump starts the process of carving a channel in the ground.’

The researchers speculate that the spiders may require ground that’s soft enough to be carved, but not too loose.

‘The combination of very high-resolution imaging and the mission’s longevity is enabling us to investigate active processes on mars that produce detectable changes on time spans of seasons or years,’ said MRO Deputy Project Scientist Leslie Tamppari of NASA’s Jet Propulsion Lab.

‘We keep getting surprises about how dynamic Mars is.’ 

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