Mercury's water ice at north pole finally proven

[Cidersomerset]

30 November 2012 Last updated at 12:55

Mercury's water ice at north pole finally proven First hints of water came from radio data two decades ago, which Messenger has now shown to be

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Scientists have finally shown what has been postulated for decades: the planet Mercury holds billions of tonnes of water ice at its north pole.

A report in Science shows evidence from the Messenger spacecraft that craters in constant shadow host water.

A futher pair of Science papers shows that much of the ice is beneath an insulating layer of dark material rich in organic and "volatile" molecules.

The findings may help explain how these ingredients first arrived on Earth.

Messenger was the first spacecraft to orbit Mercury, and since its arrival in March 2011 has been feeding back the best images of the planet that scientists have ever seen.

The principal evidence for water ice comes from the craft's "neutron spectrometer", which can detect the subatomic particle neutrons as they stream from Mercury.

"Neutrons are generated when cosmic rays hit a planet," Sean Solomon, Messenger principal investigator, explained to the Science podcast.

"Hydrogen is the best absorber of neutrons, so a neutron spectrometer looks for the signature of hydrogen near the surface by looking for decrease in the flux of neutrons coming from the planet."

This dip in the neutron count showed vast amounts of hydrogen in specific places at the planet's pole, consistent with deposits of water.

But further measurements using a laser and looking for reflections showed that much of the ice is covered with a layer of dark material tens of centimetres thick.

"The guess is that both the water and the dark material, which we think is organic-rich material, were delivered by the same objects impacting Mercury: some mixture of comets and the kinds of asteroids that are rich in organic and volatile material like water ice," Prof Solomon said.

"These are very common objects in the Solar System, we know many of them have orbits that bring them very close to the Sun."

Prof Solomon said that what Messenger finds not only unlocks secrets about the innermost planet in our Solar System, but could also shed light on those of other planets.

"The surprise that we received on making the first chemical measurements of Mercury was that none of the theories for how Mercury was assembled are correct," he said.

"So we're having to rewrite the books on how Mercury was assembled, and by implication how all the inner planets were assembled.

"The ice at the poles is only a recent chapter in that history but it's one that might be very informative."


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Images captured by Messenger have already revealed surprising details about the planet

http://www.bbc.co.uk/news/science-environment-20553879


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Water-Ice On Mercury - How It Was Found | Video

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Published on 29 Nov 2012 by VideoFromSpace


It has been estimated that there may be up to 1 trillion metric tons of water ice on Mercury. Scientist David Lawerence explains how NASA's MESENGER mission's neutron spectroscopy data contributed to the find.


fullvid..

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Published on 30 Nov 2012 by PBSNewsHour


NASA announced Thursday that the Messenger spacecraft confirmed water ice at Mercury's poles. NASA officials said the ice was likely transported by a comet that crashed into Mercury perhaps tens of millions of years ago.

[Cidersomerset]

Organic material and billions of tonnes of ice found on Mercury


By Adam Mann

30 November 12



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Comments 1

For the first time, scientists have confirmed that the planet Mercury holds at least 100 billion tonnes of water ice as well as organic material in permanently shadowed craters at its north pole.

The findings come from Nasa's Messenger spacecraft, which has been in orbit around the solar system's smallest and innermost planet since 2011. Researchers have suspected that ice could exist in such craters since 1992, when Earth-based radar measurements found bright areas at the planet's polar regions. Craters in this area cast long shadows, which prevent any sunlight from reaching their floors.

Though alternative explanations had been put forward to account for the radar-bright areas, Messenger has provided convincing evidence for water ice on the planet closest to our Sun, where surface temperatures can sometimes reach 425C. The results appeared in three studies on 29 November in Science.

Messenger was able to detect water ice because it carries a neutron spectrometer that looks at energetic neutrons bouncing off Mercury's surface. Water gives off a characteristic neutron signature. The spacecraft measured the area around Mercury's north pole and found this characteristic signature, suggesting that between around 100 billion and nearly one trillion tonnes of water ice was present somewhere in the area. But the neutron spectrometer has fairly low resolution, on the order of hundreds of kilometres, so it can't definitively say if this water is inside the craters. (If it were outside, daytime temperatures would have boiled the water away.)

Because they contain no light, Messenger's cameras can't see right inside the permanently shadowed regions. But the spacecraft carries a useful workaround tool. To map its height above the surface, the probe uses an altimeter that shoots a ten-nanosecond infrared laser pulse at the ground and intercepts the returning beam.

"We can measure the energy that comes back from the laser," said planetary scientist Gregory Neumann of Nasa's Goddard Spaceflight Centre, and lead author on one of the Science studies. Though the number of photons coming back is slight, "we could expect to see glints of brightness from surface water ice".

Early results from Messenger presented a puzzle. Not only were there no bright spots in the permanently shadowed craters where radar measurements suggested ice, the surface was actually much darker than Mercury's average colour. "We were really surprised by this," said Neumann.

The spacecraft continued to search, examining more and more craters. Finally, the laser spotted some dazzling crater floors that were two to four times brighter than the rest of Mercury's surface. This was finally good evidence for the long-sought water ice. By modeling the temperature in and around different craters, scientists were able to determine the northernmost craters stayed cold enough over millions of years to hold onto water ice.

But what about the strange dark craters? Radar measurements suggested ice, but Messenger wasn't confirming the result. The temperature models showed that these craters corresponded exactly to regions that would sometimes receive a small amount of scattered sunlight. This itsy bit of energy would heat the frozen water's surface enough to sublimate it away. Dark organic compounds dissolved in the ice got left behind as residue and would slowly form a black cover, about 19 to 28 centimetres thick, which protected any remaining ice from getting vaporised by random sunbeams.

The organic material is likely made of hydrocarbons like methane and ethane, commonly found in comets and asteroids. "At room temperature it would be kind of gooey stuff, to use the technical term," said planetary scientist Sean Solomon of Columbia University, who leads the Messenger team. Because the layer is relatively thin, it's invisible to radar.

The Messenger team now thinks it has a good story to explain how these polar cold traps work. Every once in a while, a comet or asteroid hits Mercury and gets annihilated. The vaporised material either floats out into space or gets blasted away by the Sun but any that finds its way into a permanently shadowed region will settle down. Molecule by molecule, water and other compounds build up inside the craters. Those that never see a ray of sunlight contain mostly clean water ice. But if even a tiny amount of light intrudes, it may heat up the water and cause it to recede below a layer of organic material.

"These look like really good results, and I think they are very convincing," said planetary scientist Johannes Benkhoff from the Institute of Planetary Research in Germany, who is the lead scientist on the European Space Agency's BepiColombo mission, which is expected to orbit Mercury in 2022. Messenger will provide many follow-up opportunities for this later mission, which will have its own neutron spectrometer to map the water ice regions with greater resolution.

In addition to being an astounding result, the finding can help scientists better understand the history of Earth. Mercury is a terrestrial planet like our own and the ice provides evidence for geologically recent delivery of water and carbon-rich material to the inner solar system from comets and asteroids. This process very likely happened billions of years in the past, when the Earth first formed, creating our planet's oceans and possibly seeding them with the material to produce life.

"There's now this record on Mercury, a place where we least expected to find it, of this process," said Solomon. "It gives us a window to understanding this delivery system."

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Source: Wired.com
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http://www.wired.co.uk/news/archive/2012-11/30/ice-organic-material-on-mercury

Story
Written by Adam Mann
Edited by Liat Clark

Photo
NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

[ghostrider]

Now because NASA says it people will believe what we all here already know. We are not alone in the universe. There is atmosphere on other planets in our neighborhood, the sky of mars is blue (water) , The moon has water and atmoshphere, two planets close to us have what we have, ... hmmmmm ? if they have water and a blue sky and ice, and they are close to us, could they have cities and people ????? an airport ?? runways?? maybe that those strange lines seen from sat photos. hmmmm...could they have trees ?? underground bases ?? fema camps ? chemtrailing ? War ?? I'm writing this way for the new people to peak their curiosity to look a little deeper, and prove it true or not to themselves not just what someone tells them.