Giant asteroid Vesta ‘resembles planet’

23 March 2012 Last updated at 08:15 ET
By Paul Rincon
Science editor, BBC News website, The Woodlands, Texas


Dawn’s view of the south pole of the giant asteroid Vesta

The giant asteroid Vesta possesses many features usually associated with rocky planets like Earth, according to data from a Nasa probe.

Vesta has been viewed as a massive asteroid, but after studying the surface in detail, scientists are describing it as “transitional”.

The Dawn spacecraft has been orbiting Vesta – one of the Solar System’s most primitive objects – since July 2011.

They have documented many unexpected features on its battered surface.

Mission scientists presented their latest results at the Lunar and Planetary Science Conference (LPSC) in The Woodlands, Texas.

Dawn’s principal investigator, Christopher T Russell, told the meeting that the science team found it hard not to refer to the object as a planet.

He said the rounded asteroid showed evidence of geological processes that characterise rocky worlds like Earth and the Moon.

Getting hammered

Vesta is the second most massive of the asteroids, measuring some 530km (330mi) in diameter. It is dominated by a huge crater called Rheasilvia and bears many other scars left by the hammering it has received at the hands of other asteroid belt denizens.

One important transitional feature of Vesta can be found in its topography, or elevation. Vertical elevation on the Moon or Mars might reach tens of kilometres, but these objects are also very large.

“This means the topography is about 1% of the radius,” Dr Ralf Jaumann, from the German Aerospace Center (DLR), told BBC News, “If you go to Vesta, it is 15%, and if you go to the largest outer asteroid – Lutetia – it is 40%.”

In short, this mathematical relationship between topography and radius (half an object’s diameter), puts Vesta in an intermediate position between small asteroids and rocky planets.

Another aspect concerns the way its surface has been modified, or “processed”, by the many collisions. This is evident in dark material that can be seen in images of its terrain.

The dark material seems to be related to impacts and their aftermath. Scientists think carbon-rich asteroids could have hit Vesta at speeds low enough to produce some of the smaller deposits without blasting away the surface.

Higher-speed asteroids could also have collided with Vesta’s surface and melted the volcanic basaltic crust, darkening existing surface material.

Scientists are confident there has been volcanism on the asteroid during its history. This is because there are hundreds of pieces of Vesta sitting in museums around the world.

They form a particular class of meteorite called the HEDs; more of these objects have fallen to Earth than all the meteorites from the Moon and Mars put together. Studies of HED meteorites have revealed telling chemical signatures of volcanic activity.

Major cover-up

Dave Williams, from Arizona State University, told BBC News: “We know [from the HED meteorites] there were lava flows at some point in history, so I expected there to be at least a few lava flows, maybe a few channels, shields or cones. Looking at all the images in places that have been illuminated thus far, we don’t see any evidence of that.

“That’s because of all the impact processing over Solar System history. It has destroyed all the evidence.”

Mission scientist Brett Denevi, from Johns Hopkins University Applied Physics Laboratory in Maryland, explained why she thought some of the collisions that have pounded Vesta were intense enough to melt its surface.

Referring to observations of a crater called Marcia, in Vesta’s northern hemisphere, Dr Denevi commented: “We think what we’re seeing here is at least a portion of this target rock has melted and flowed. The impact velocities were high enough – at least in this one case.”

She added: “Impact melt hasn’t really been observed on asteroids before. It wasn’t really expected because the speed of collisions in the asteroid belt are pretty low compared with the inner Solar System. So it wasn’t known whether you’d have enough energy to melt the target rock.”

Dawn is set to depart Vesta for an even bigger object – the spherical “dwarf planet” Ceres – in August for an arrival in 2015.

Paul.Rincon-INTERNET@bbc.co.uk and follow me on Twitter

BBC News – Giant asteroid Vesta ‘resembles planet’.

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Huge Sunquakes Triggered by Solar Eruptions

Massive solar wind bursts and magnetic fields can cause ripples on sun’s surface

By Kat Piper
Epoch Times Staff
Created: March 30, 2012
Last Updated: April 4, 2012

Massive bursts of solar wind and magnetic fields from the Sun can cause huge sunquakes, according to new UK research.

The results of the study, led by University College London’s Mullard Space Science Laboratory, are being presented by Dr Sergei Zharkovat at the National Astronomy Meeting 2012 in Manchester on Friday, March 30.

Research over the last 10 years has shown that sunquakes can be produced when solar flares—huge explosions of energy in the Sun’s atmosphere—impact and travel into the Sun. The quakes appear as circular ripples on the surface of the Sun.

The new study shows that eruptions of charged particles and magnetic fields known as Coronal Mass Ejections (CMEs) are also able to produce sunquakes.

“Sunquakes are generated by solar flares, when enormous amounts of energy are released high up in the solar atmosphere. Most of the energy goes up into interplanetary space, but a fraction of this energy travels to the Sun’s surface creating a sonic boom that causes the solar interior to oscillate and produce the ripples,” explained Zharkov in an email.

“I sometimes think of sunquakes as thunder to the flare’s lightning, except imagine a lightning over an ocean that is so strong that it creates a tsunami.”

The researchers studied an eruption that took place on Feb. 15, 2011. They found that sunquakes 1,000 times more powerful than the March 2011 Japanese earthquake were triggered at two ends of the erupting rope of magnetic field. The sudden expansion of the magnetic field as it erupts is thought to play a part in the generation of the sunquakes.

The eruption travelled through our solar system at around 600 kilometres per second (1.34 million miles per hour) towards Earth, causing a geomagnetic storm and aurora when it hit the Earth’s atmosphere.

It is for this reason that study of sunquakes is of interest, especially as solar activity is predicted to increase and peak in 2013.

“Sunquakes themselves do not have [an] impact on Earth as they are acoustic waves travelling inside the Sun. But flares and, accompanying them, Coronal Mass Ejections that we have shown play an important role in generating sunquakes, can and do impact Earth,” Zharkov said.

“Sunquakes now form an integral part for our search for understanding of flare and CME phenomena.”

Flares and CMEs have a direct impact on space weather, so understanding how they form could help in predicting when they are going to occur and planning for possible geomagnetic storms, which can affect satellites and radio and GPS equipment on Earth.

But sunquakes are relatively rare, explained Zharkhov. “Known sunquakes were all generated by string solar flares (X and M class), which occur only during the active part of an [11-year] Solar Cycle. However, only a small fraction of such flares produce sunquakes,” he said.

“There is also a chance, however, that sunquakes are more common than we think; it’s just that our means of detecting them are not yet up to scratch.”

Until recently, observation of sunquakes had been hampered by availability of data. “With the (relatively) new NASA’s Solar Dynamics Observatory satellite providing us with practically continuous high resolution and high cadence observations of the Sun, this problem is now solved,” Zharkov said.

Much like geologists use earthquakes to understand the internal structure of our planet, future research will be focused on using sunquakes to learn more about the internal processes of the Sun, said Zharkov. As scientists still don’t fully understand how sunquakes are generated, research will also continue to look for physical explanations of this solar phenomenon.

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Huge Sunquakes Triggered by Solar Eruptions | Space & Astronomy | Science | Epoch Times.

The hair-raising truth about the Cornish tsunami triggered by under-sea earthquake

By MICHAEL HANLON
UPDATED: 10:23 EST, 17 February 2012

Calm as a mill pond: The normally steady waters around St Michael’s Mount, Cornwall, were hit by the unexpected mini-tsunami

This week, parts of the Cornish coastline were hit by what appears to have been a mini-tsunami. The wave was of no great height, but it was still substantial enough to suck the sea out for 150 feet or more, before surging back in to drench the causeway linking St Michael’s Mount to the mainland near Penzance, and giving tourists a soaking.

The wave rolled up the estuaries and rivers from Mounts Bay in the West to Plymouth in the east, sending small boats rolling on their keels.

If that isn’t strange enough, witnesses said it was preceded by a surge of static electricity. ‘People’s hair stood on end,’ said a National Trust guide on the Mount.

Others reported the air going unnaturally still, with a dense, warm clamminess settling over land and sea before the wave struck.

Of course, the Cornish tsunami on Monday morning was tiny compared to the one that devastated Japan earlier this year. But the reports raise a tantalising question; might we have found one of the great holy grails of seismology — a reliable way of predicting earthquakes which could save thousands of lives?

Experts suggest that the Cornish tsunami was caused by either a small earthquake or an undersea landslide off the Irish coast 250 miles away.

One theory is that the resulting rock vibrations could generate a powerful electrical charge, strong enough to travel all the way along the seabed to land, up the beach, and reach the top of a tourist’s head.

‘It’s called the Piezoelectric Effect,’ says Chris Shepherd of the Institute of Physics, explaining that quartz crystals, present in the ancient rocks in and around Cornwall, could generate a high voltage if squeezed. ‘It’s the same effect used in gas lighters on your cooker.’

Intriguingly, something similar but far more dramatic seems to have taken place several days before the Japanese earthquake.

After studying data sent by satellites over the Pacific Ocean, NASA scientists at the Goddard Space Flight Centre in Maryland have discovered that there was a sudden and dramatic pulse of heat high in the atmosphere over the epicentre of the quake 72 hours before it struck.

The heat pulse was associated with an equally dramatic increase in electrical charge in the air. Similar effects were reported, retrospectively, before the Haiti earthquake in 2007.

Just what was happening is something of a mystery. A persistent conspiracy theory doing the rounds on the internet links recent big earthquakes and secret radio experiments allegedly being carried out by the Pentagon.

Far more likely, however, is a little-understood phenomenon called the ‘Lithosphere-Atmosphere-Ionosphere Coupling mechanism’.

The theory is that in the days before an earthquake, the great stresses that have built up cause the release of large amounts of radioactive radon gas from deep in the Earth.

The radioactivity from this gas ionises the air on a large scale, electrifying it and heating it up. So could something like this, on a smaller scale, have explained the weird phenomena seen in Cornwall this week?

Perhaps what we saw was a combination of the piezoelectric effect and the release of radon gas — large quantities of which are present in Cornish rocks.

It is still very much a mystery. Dr Simon Boxall, an oceanographer who was out at sea on a small boat off the coast of Falmouth when the tsunami struck, thinks the wave had nothing to do with an earthquake at all, but instead was something called a ‘seiche’.

‘I’m 99 per cent certain,’ he says, pointing out that seismographs of the British Geological Survey did not seem to have detected any earth-shaking at all before the wave struck.

A seiche is a freak wave which can be caused by an area of very low or high pressure crossing an area of water.

If the speed at which the weather system is moving is just right, the sea underneath can ‘resonate’ like a wine glass ringing when you rub the rim in the right way, and a single big wave can come seemingly from nowhere.

‘The static had nothing directly to do with the wave, but it did have a lot to do with the low-pressure system,’ Dr Boxall insists, adding that southern England was hit by a number of powerful thunderstorms later that day.

‘The air would have been charged with static.’

Whatever the explanation, we may be getting tantalisingly close to finding a way to predict earthquakes — something dismissed as a pseudoscience until very recently.

For centuries there have been reports of lightning, static and even fireballs in the sky associated with earthquakes together with, of course, persistent reports that animals are able to sense that something is about to happen and flee to higher ground.

These reports are now being taken more seriously.

More than a third of a million people perished in the Indian Ocean tsunami, and 25,000 more in Japan this year.

If satellites — or even the hairs on the back of your neck — could be used to predict disasters like these hours or even days ahead, millions of lives could be saved in years to come.

The hair-raising truth about the Cornish tsunami triggered by under-sea earthquake | Mail Online.