On this day in science history: the earliest recorded confirmed total solar eclipse occurred

In 709 BC, the earliest record of a confirmed total solar eclipse was written in China. From: Ch'un-ch'iu, book I: "Duke Huan, 3rd year, 7th month, day jen-ch'en, the first day (of the month). The Sun was eclipsed and it was total." This is the earliest direct allusion to a complete obscuration of the Sun in any civilisation. The recorded date, when reduced to the Julian calendar, agrees exactly with that of a computed solar eclipse. Reference to the same eclipse appears in the Han-shu ('History of the Former Han Dynasty') (Chinese, 1st century AD): "...the eclipse threaded centrally through the Sun; above and below it was yellow." Earlier Chinese writings that refer to an eclipse do so without noting totality.

Total Solar Eclipse. I, Luc Viatour [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons

Having fascinated mankind for years, the Sun is the star at the centre of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99.86% of the total mass of the Solar System. About three quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron.

The Sun is a G-type main-sequence star (G2V) based on its spectral class. As such, it is informally referred to as a yellow dwarf. It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core. It is thought that almost all stars form by this process.

The Sun is roughly middle-aged; it has not changed dramatically for more than four billion years, and will remain fairly stable for more than another five billion years. After hydrogen fusion in its core has diminished to the point at which it is no longer in hydrostatic equilibrium, the core of the Sun will experience a marked increase in density and temperature while its outer layers expand to eventually become a red giant. It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury and Venus, and render Earth uninhabitable.

The enormous effect of the Sun on Earth has been recognized since prehistoric times, and the Sun has been regarded by some cultures as a deity. The synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today.

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Solar paint offers endless energy from water vapor

Researchers have developed a solar paint that can absorb water vapour and split it to generate hydrogen - the cleanest source of energy.

The paint contains a newly developed compound that acts like silica gel, which is used in sachets to absorb moisture and keep food, medicines and electronics fresh and dry.

Sun with sunspots and limb darkening as seen in visible light with solar filter. By Geoff Elston [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons

But unlike silica gel, the new material, synthetic molybdenum-sulphide, also acts as a semi-conductor and catalyses the splitting of water molecules into hydrogen and oxygen.

Lead researcher Dr Torben Daeneke, from RMIT University in Melbourne, Australia, said: "We found that mixing the compound with titanium oxide particles leads to a sunlight-absorbing paint that produces hydrogen fuel from solar energy and moist air.

"Titanium oxide is the white pigment that is already commonly used in wall paint, meaning that the simple addition of the new material can convert a brick wall into energy harvesting and fuel production real estate.

"Our new development has a big range of advantages," he said. "There's no need for clean or filtered water to feed the system. Any place that has water vapour in the air, even remote areas far from water, can produce fuel."

His colleague, Distinguished Professor Kourosh Kalantar-zadeh, said hydrogen was the cleanest source of energy and could be used in fuel cells as well as conventional combustion engines as an alternative to fossil fuels.

"This system can also be used in very dry but hot climates near oceans. The sea water is evaporated by the hot sunlight and the vapour can then be absorbed to produce fuel.

"This is an extraordinary concept - making fuel from the sun and water vapour in the air."

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On this day in science history: Pioneer 10 crossed the orbit of Pluto

In 1983, Pioneer 10, an American space probe, crossed the orbit of Pluto, the outermost planet, to continue its voyage into the universe beyond our solar system. This space exploration project was conducted by the NASA Ames Research Center in California, and the space probe was manufactured by TRW Inc.

Pioneer 10 was launched on March 2, 1972, by an Atlas-Centaur expendable vehicle from Cape Canaveral, Florida. Between July 15, 1972, and February 15, 1973, it became the first spacecraft to traverse the asteroid belt. Photography of Jupiter began on November 6, 1973, at a range of 25,000,000 kilometres (16,000,000 mi), and a total of about 500 images were transmitted. The closest approach to the planet was on December 4, 1973, at a range of 132,252 kilometres (82,178 mi). During the mission, the on-board instruments were used to study the asteroid belt, the environment around Jupiter, the solar wind, cosmic rays, and eventually the far reaches of the Solar System and heliosphere.

Artist's impression of Pioneer 10's flyby of Jupiter, by Rick Guidice [Public domain], via Wikimedia Commons

So, what do we know about Jupiter?

Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, but two and a half times that of all the other planets in the Solar System combined. Jupiter and Saturn are gas giants; the other two giant planets, Uranus and Neptune are ice giants. Jupiter has been known to astronomers since antiquity. The Romans named it after their god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough for its reflected light to cast shadows, and making it on average the third-brightest object in the night sky after the Moon and Venus.

Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, though helium comprises only about a tenth of the number of molecules. It may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rapid rotation, the planet's shape is that of an oblate spheroid (it has a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere. Jupiter has at least 67 moons, including the four large Galilean moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these, has a diameter greater than that of the planet Mercury.

Radio communications were lost with Pioneer 10 on January 23, 2003, because of the loss of electric power for its radio transmitter, with the probe at a distance of 12 billion kilometers (80 AU) from Earth.

Jupiter has been explored on several other occasions by robotic spacecraft, such as the Voyager flyby missions and later, the Galileo orbiter. In late February 2007, Jupiter was visited by the New Horizons probe, which used Jupiter's gravity to increase its speed and bend its trajectory en route to Pluto. The latest probe to visit the planet is Juno, which entered into orbit around Jupiter on July 4, 2016. Future targets for exploration in the Jupiter system include the probable ice-covered liquid ocean of its moon Europa.

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On this day in science history: Sakurai's Object was discovered

In 1996, a bright “new” star was discovered in Sagittarius by Japanese amateur astronomer Yukio Sakurai. It was found not to be a usual nova, but instead was a star going through a dramatic evolutionary state, re-igniting its nuclear furnace for one final blast of energy called the “final helium flash.” It was only the second to be identified in the twentieth century. A star like the Sun ends its active life as a white dwarf star gradually cooling down into visual oblivion. Sakurai's Object had a mass a few times that of the Sun. Its collapse after fusing most of its hydrogen fuel to helium raised its temperature so much higher it began nuclear fusion of its helium remains. This was confirmed using its light spectrum to identify the elements present.

Sakurai's Object By ESO, [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons

Sakurai's Object is a highly evolved post-asymptotic giant branch star which has, following a brief period on the white dwarf cooling track, undergone a helium shell flash (also known as a very late thermal pulse). The star is thought to have a mass of around 0.6 M☉. Observations of Sakurai's Object show increasing reddening and pulsing activity, suggesting that the star is exhibiting thermal instability during its final helium-shell flash.

Prior to its reignition V4334 Sgr is thought to have been cooling towards a white dwarf with a temperature around 100,000 K and a luminosity around 100 L☉. The luminosity rapidly increased about a hundred-fold and then the temperature decreased to around 10,000 K. The star developed the appearance of an F class supergiant (F2 Ia). The apparent temperature continued to cool to below 6,000 K and the star was gradually obscured at optical wavelengths by the formation of carbon dust, similar to an R CrB star. Since then the temperature has increased to around 20,000 K.

The properties of Sakurai's Object are quite similar to that of V605 Aquilae. V605, discovered in 1919, is the only other known star observed during the high luminosity phase of a very late thermal pulse, and Sakurai's Object is modeled to increase in temperature in the next few decades to match the current state of V605.

During the second half of 1998 an optically thick dust shell obscured Sakurai's Object, causing a rapid decrease in visibility of the star, until in 1999 it disappeared from optical wavelength observations altogether. Infrared observations showed that the dust cloud around the star is primarily carbon in an amorphous form. In 2009 it was discovered that the dust shell is strongly asymmetrical, as a disc with a major axis oriented at an angle of 134°, and inclination of around 75°. The disc is thought to be growing more opaque due to the fast spectral evolution of the source towards lower temperatures.

Sakurai's Object is surrounded by a planetary nebula created following the star's red giant phase around 8300 years ago. It has been determined that the nebula has a diameter of 44 arcseconds and expansion velocity of roughly 32 km/s.

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On this day in science history: Jupiter orbiter Galileo launched

In 1989, the Galileo space orbiter was released from the STS 34 flight of the Atlantis orbiter. Then the orbiter's inertial upper stage rocket pushed it into a course through the inner solar system. The craft gained speed from gravity assists in encounters with Venus and Earth before heading outward to Jupiter. During its six year journey to Jupiter, Galileo's instruments made interplanetary studies, using its dust detector, magnetometer, and various plasma and particles detectors. It also made close-up studies of two asteroids, Gaspra and Ida in the asteroid belt. The Galileo orbiter's primary mission was to study Jupiter, its satellites, and its magnetosphere for two years. It released an atmospheric probe into Jupiter's atmosphere on 7 Dec 1995.

Jupiter and its shrunken great red spot. By NASA, ESA, and A. Simon (Goddard Space Flight Center) [Public domain], via Wikimedia Commons

Jupiter's mass is 2.5 times that of all the other planets in the Solar System combined—this is so massive that its barycenter with the Sun lies above the Sun's surface at 1.068 solar radii from the Sun's center. Jupiter is much larger than Earth and considerably less dense: its volume is that of about 1,321 Earths, but it is only 318 times as massive. Jupiter's radius is about 1/10 the radius of the Sun, and its mass is 0.001 times the mass of the Sun, so the densities of the two bodies are similar. A "Jupiter mass" (MJ or MJup) is often used as a unit to describe masses of other objects, particularly extrasolar planets and brown dwarfs. So, for example, the extrasolar planet HD 209458 b has a mass of 0.69 MJ, while Kappa Andromedae b has a mass of 12.8 MJ.

Theoretical models indicate that if Jupiter had much more mass than it does at present, it would shrink. For small changes in mass, the radius would not change appreciably, and above about 500 M⊕ (1.6 Jupiter masses) the interior would become so much more compressed under the increased pressure that its volume would decrease despite the increasing amount of matter. As a result, Jupiter is thought to have about as large a diameter as a planet of its composition and evolutionary history can achieve. The process of further shrinkage with increasing mass would continue until appreciable stellar ignition is achieved as in high-mass brown dwarfs having around 50 Jupiter masses.

Although Jupiter would need to be about 75 times as massive to fuse hydrogen and become a star, the smallest red dwarf is only about 30 percent larger in radius than Jupiter. Despite this, Jupiter still radiates more heat than it receives from the Sun; the amount of heat produced inside it is similar to the total solar radiation it receives. This additional heat is generated by the Kelvin–Helmholtz mechanism through contraction. This process causes Jupiter to shrink by about 2 cm each year.  When it was first formed, Jupiter was much hotter and was about twice its current diameter.

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Methane muted: How did early Earth stay warm?

For at least a billion years of the distant past, planet Earth should have been frozen over but wasn't. Scientists thought they knew why, but a new modeling study from the Alternative Earths team of the NASA Astrobiology Institute has fired the lead actor in that long-accepted scenario.

Humans worry about greenhouse gases, but between 1.8 billion and 800 million years ago, microscopic ocean dwellers really needed them. The sun was 10 to 15 percent dimmer than it is today - too weak to warm the planet on its own. Earth required a potent mix of heat-trapping gases to keep the oceans liquid and livable.

For decades, atmospheric scientists cast methane in the leading role. The thinking was that methane, with 34 times the heat-trapping capacity of carbon dioxide, could have reigned supreme for most of the first 3.5 billion years of Earth history, when oxygen was absent initially and little more than a whiff later on. (Nowadays oxygen is one-fifth of the air we breathe, and it destroys methane in a matter of years.)

Full structural formula of the methane molecule

"A proper accounting of biogeochemical cycles in the oceans reveals that methane has a much more powerful foe than oxygen," said Stephanie Olson, a graduate student at the University of California, Riverside, a member of the Alternative Earths team and lead author of the new study published September 26 in the Proceedings of the National Academy of Sciences. "You can't get significant methane out of the ocean once there is sulfate."

Sulfate wasn't a factor until oxygen appeared in the atmosphere and triggered oxidative weathering of rocks on land. The breakdown of minerals such as pyrite produces sulfate, which then flows down rivers to the oceans. Less oxygen means less sulfate, but even 1 percent of the modern abundance is sufficient to kill methane, Olson said.

Olson and her Alternative Earths coauthors, Chris Reinhard, an assistant professor of earth and atmospheric sciences at Georgia Tech University, and Timothy Lyons, a distinguished professor of biogeochemistry at UC Riverside, assert that during the billion years they assessed, sulfate in the ocean limited atmospheric methane to only 1 to 10 parts per million - a tiny fraction of the copious 300 parts per million touted by some previous models.

The fatal flaw of those past climate models and their predictions for atmospheric composition, Olson said, is that they ignore what happens in the oceans, where most methane originates as specialized bacteria decompose organic matter.

Seawater sulfate is a problem for methane in two ways: Sulfate destroys methane directly, which limits how much of the gas can escape the oceans and accumulate in the atmosphere. Sulfate also limits the production of methane. Life can extract more energy by reducing sulfate than it can by making methane, so sulfate consumption dominates over methane production in nearly all marine environments.

The numerical model used in this study calculated sulfate reduction, methane production, and a broad array of other biogeochemical cycles in the ocean for the billion years between 1.8 billion and 800 million years ago. This model, which divides the ocean into nearly 15,000 three-dimensional regions and calculates the cycles for each region, is by far the highest resolution model ever applied to the ancient Earth. By comparison, other biogeochemical models divide the entire ocean into a two-dimensional grid of no more than five regions.

"Free oxygen [O2] in the atmosphere is required to form a protective layer of ozone [O3], which can shield methane from photochemical destruction," Reinhard said. When the researchers ran their model with the lower oxygen estimates, the ozone shield never formed, leaving the modest puffs of methane that escaped the oceans at the mercy of destructive photochemistry.

With methane demoted, scientists face a serious new challenge to determine the greenhouse cocktail that explains our planet's climate and life story, including a billion years devoid of glaciers, Lyons said. Knowing the right combination other warming agents, such as water vapor, nitrous oxide, and carbon dioxide, will also help us assess habitability of the hundreds of billions of other Earth-like planets estimated to reside in our galaxy.

"If we detect methane on an exoplanet, it is one of our best candidates as a biosignature, and methane dominates many conversations in the search for life on Mars," Lyons said. "Yet methane almost certainly would not have been detected by an alien civilization looking at our planet a billion years ago - despite the likelihood of its biological production over most of Earth history."

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Rosetta’s comet contains ingredients for life

Ingredients crucial for the origin of life on Earth, including the simple amino acid glycine and phosphorus, key components of DNA and cell membranes, have been discovered at Comet 67P/Churyumov-Gerasimenko.

The possibility that water and organic molecules were brought to the early Earth through impacts of objects like asteroids and comets have long been the subject of important debate.

While Rosetta's ROSINA instrument already showed a significant difference in composition between Comet 67P/C-G's water and that of Earth, the same instrument has now shown that even if comets did not play as big a role in delivering water as once thought, they certainly had the potential to deliver life's ingredients.

ESA/Rosetta/NAVCAM, CC BY-SA IGO 3.0 [CC BY-SA 3.0-igo (http://creativecommons.org/licenses/by-sa/3.0-igo)], via Wikimedia Commons

While more than 140 different molecules have already been identified in the interstellar medium, amino acids could not be traced. However, hints of the amino acid glycine, a biologically important organic compound commonly found in proteins, were found during NASA's Stardust mission that flew by Comet Wild 2 in 2004, but terrestrial contamination of the collected dust samples during the analysis could not be ruled out. Now, for the first time, repeated detections at a comet have been confirmed by Rosetta in Comet 67P/C-G's fuzzy atmosphere, or coma.

The first detection was made in October 2014, while most measurements were taken during the perihelion in August 2015 - the closest point to the Sun along the comet's orbit while the outgassing was strongest. "This is the first unambiguous detection of glycine in the thin atmosphere of a comet," says Kathrin Altwegg, principal investigator of the ROSINA instrument at the Center of Space and Habitability of the University of Bern and lead author of the study. The results are now being published in Science.

Glycine is very hard to detect due to its non-reactive nature: it sublimates at slightly below 150°C, meaning that little is released as gas from the comet's surface or subsurface due to its cold temperatures. "We see a strong correlation of glycine to dust, suggesting that it is probably released from the grains' icy mantles once they have warmed up in the coma, perhaps together with other volatiles," says Altwegg. At the same time, the researchers also detected the organic molecules methylamine and ethylamine, which are precursors to forming glycine. Unlike other amino acids, glycine is the only one that has been shown to be able to form without liquid water. "The simultaneous presence of methylamine and ethylamine, and the correlation between dust and glycine, also hints at how the glycine was formed," says Altwegg.

Another exciting detection by ROSINA made for the first time at a comet is of phosphorus. It is a key element in all living organisms and is found in the structural framework of DNA and RNA.

"The multitude of organic molecules already identified by ROSINA, now joined by the exciting confirmation of fundamental ingredients like glycine and phosphorus, confirms our idea that comets have the potential to deliver key molecules for prebiotic chemistry," says Matt Taylor, Rosetta project scientist of the European Space Agency ESA. "Demonstrating that comets are reservoirs of primitive material in the Solar System, and vessels that could have transported these vital ingredients to Earth, is one of the key goals of the Rosetta mission, and we are delighted with this result."

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The above post is reprinted from materials provided by University of Bern. Note: Materials may be edited for content and length.

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Mercury's journey across Sun under way

Skywatchers across the globe are observing Mercury transit the Sun, the little planet's third such pass of 14 it will make this century.

Mercury's sojourn between Earth and our star lasts from 11:12 until 18:42 GMT.

It will not make another transit until 2019 and then 2032.

The event is impossible - and dangerous - to view with the naked eye or binoculars, but astronomy groups worldwide are offering the chance view it through filtered telescopes.

Live views from space and ground telescopes are also available online.

They show Mercury as a tiny black circle, smaller but darker than many sunspots, slowly traversing the Sun's giant yellow disc.

Mercury in colour by NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington. Edited version of Image:Mercury in color - Prockter07.jpg by jjron (cropped to square). (NASA/JPL [1]) [Public domain], via Wikimedia Commons

Mercury spins around the Sun every 88 days, but its orbit is tilted relative to the Earth's. It is that discrepancy which makes it relatively rare for the three bodies to line up in space.

From western Europe, north-western Africa and much of the Americas, Mercury's seven-and-a-half-hour glide across the Sun will be visible in its entirety. A further swathe of the planet will catch part of the transit, depending on local sunrise and sunset times.

The only land masses to miss out completely are Australasia, far eastern Asia and Antarctica.

Because Mercury is so small - just one-third as big as Earth and, from our perspective, 1/150th of the Sun's diameter - its transit can only be glimpsed under serious magnification; the "eclipse glasses" used by thousands of people to view last year's solar eclipse will be useless.

And to avoid permanent eye damage, any telescope must be fitted with a solar filter before being trained on the Sun. The British Astronomical Association explains on its website how amateur stargazers can enjoy the spectacle safely.

Open University's Prof David Rothery said the celestial event would not present any novel scientific opportunities - but was special nonetheless.

"From this transit, we're unlikely to learn anything we don't already know," he told BBC Inside Science. "But what a wonderful event for showing people Mercury. It's a hard planet to see.

"Historically, transits were of immense importance."

In the 1700s, for example, it was observations of Mercury and Venus slipping across the Sun that allowed astronomers, led by Edmund Halley, to pin down the dimensions of the known Solar System.

Prof Rothery is a Mercury expert and a leading scientist on the European Space Agency's BepiColombo mission to the diminutive planet, which will launch in 2017 or 2018.

Mercury has already been visited by two Nasa probes: Mariner 10 flew past in 1974 and 1975 and Messenger spent four years in orbit until its planned crash landing in 2015.

Messenger spent four years in orbit taking images and measurements of Mercury

"[Messenger] told us an awful lot. It really told us we don't understand Mercury - because there's a lot of things which just don't stack up," Prof Rothery said.

"It's an airless body, with lots of craters... But there's been a long history of volcanic activity, fault activity - and the composition, that began to be revealed by Messenger, is weird.

"There's very little iron at the surface but it must have a ginormous iron core, because it generates a magnetic field - which Venus, Mars and the Moon don't."

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Iron meteorites 'buried in Antarctica' by the Sun

New research suggests there could be a layer of iron-rich meteorites hidden just under the Antarctic ice.

The churning of glaciers spews many space rocks out on to the surface in Antarctica, but compared to elsewhere on Earth, few of them are made of iron.

Based on modelling and lab experiments, scientists say the missing metallic rocks might be burying themselves, by melting the ice as sunlight heats them.

To prove their idea, the team now wants to look for the rocks themselves.

"The study is proposing a hypothesis - these samples should be there. We just have to go and locate them," said Dr Katherine Joy from the University of Manchester, a co-author of the paper published in Nature Communications.

Antarctica is known by meteorite specialists as a fruitful hunting ground, because the rocks are collected from their landing sites by glacial flows and transported to concentrated dumping-grounds.

"The great thing about Antarctica is they fall on the ice, and then the ice progressively moves away from the plateau. And where it hits these barriers, along the Transantarctic Mountains, the ice gets moved up," Dr Joy told the BBC.

"So this continuous conveyor belt has delivered meteorites from the interior fall sites to the 'meteorite stranding zones' for the past couple of million years or so."

Iron meteorites. By Waifer X (originally posted to Flickr as 090423-1080887) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Among this Antarctic haul, however, researchers have noticed that iron-rich meteorites - whether partly or wholly made of the metal - are surprisingly scarce, compared to the percentage collected in other places around the world.

Dr Joy and her colleagues think they may have discovered why.

They froze two small meteorites of similar size and shape, one made of iron and the other rocky and non-metallic, inside blocks of ice. A special lamp was trained on the ice from above, to mimic the rays of the Sun.

Both meteorites, on repeated trials, melted their way downward through the ice block. But because the metal conducts heat more efficiently, the iron meteorite sank further, faster.

The researchers then expanded that observation using a mathematical simulation. Their model showed that this Sun-driven burrowing would be enough to cause iron-rich rocks to sink so much during the long summer days that, over the course of the year, it would account fairly precisely for the lack of iron space rocks welling their way to the surface of the Antarctic "stranding zones".

"The idea is, they never make it to the surface. They're forever trapped, 50-100cm or so below the ice," Dr Joy explained.

That means, if the team's findings are to be believed, that the hunt is on.

As Dr Joy's Manchester colleague Geoffrey Evatt put it: "The challenge is now set - to be the first team to locate this reserve of meteorites and retrieve samples from it."

Of all the meteorites gathered from Antarctica, only a handful - so far - have been pulled out from beneath the ice. This is mostly for practical reasons, Dr Joy said.

"When it's very cold... picking up the sample in a controlled way is difficult enough with things sitting on the surface. To access ones that are subsurface - nobody's really tried to do that so far."

So it will not be easy, but the team hopes that radar and metal detectors might help target the search. And the potential rewards are high.

"Every meteorite we find tells us something new about the Solar System," Dr Joy said.

Some are carbon-rich or rocky remnants from long before any planet clumped together; others - like iron and rocky-iron meteorites - offer clues from a more intermediate stage, when baby planets with cores, mantles and crusts were trying to form.

"The iron group represents meteorites that were once the cores and the internal structures of different planetesimals.

"We think there were probably hundreds of these early planets, that formed in the solar system but never really got big enough and were broken up in collision events."

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Carbon emissions 'postpone ice age'

The next ice age may have been delayed by over 50,000 years because of the greenhouse gases put in the atmosphere by humans, scientists in Germany say.

They analysed the trigger conditions for a glaciation, like the one that gripped Earth over 12,000 years ago.

The shape of the planet's orbit around the Sun would be conducive now, they find, but the amount of carbon dioxide currently in the air is far too high.

Earth is set for a prolonged warm phase, they tell the journal Nature.

"In theory, the next ice age could be even further into the future, but there is no real practical importance in discussing whether it starts in 50,000 or 100,000 years from now," Andrey Ganopolski from the Potsdam Institute for Climate Impact Research said.

"The important thing is that it is an illustration that we have a geological power now. We can change the natural sequence of events for tens of thousands of years," he told BBC News.

The Earth seen from space

Earth has been through a cycle of ice ages and warm periods over the past 2.5 million years, referred to as the Quaternary Period.

This has seen ice sheets come and go. At its maximum extent, the last glaciation witnessed a big freeze spread over much of North America, northern Europe, Russia and Asia.

In the south, a vast expanse of what are now Chile and Argentina were also iced up.

A fundamental parameter determining what dips Earth into an ice age is the changing nature of its orbit around the Sun.

The passage around the star is not a perfect circle and over time our planet's axis of rotation also rocks back and forth.

These movements alter the amount of solar radiation falling on the Earth's surface, and if a critical threshold is reached in mid latitudes in the Northern Hemisphere then a glaciation can be initiated.

Dr Ganopolski colleagues confirm this in their modelling but show also the role played by the concentration of greenhouse gases in the atmosphere.

And one of their findings is that Earth probably missed the inception by only a narrow margin a few hundred years ago, just before the industrial revolution took hold.

"We are now in a period when our (northern) summer is furthest from the Sun," the Potsdam researcher explained.

"Under normal circumstances, the interglacial would be terminated, and a new ice age would start. So, in principle, we are in the perfect conditions from an astronomical point of view. If we had a CO2 concentration of 240 parts per million (200 years ago) then an ice age could start, but luckily we had a concentration that was higher, 280ppm." Today, industrial society has taken that concentration to over 400ppm.

The team says that an interglacial climate would probably have been sustained anyway for at least 20,000 years, and, very probably, for 50,000 years, even if CO2 had stayed at its eighteenth century level.

But the almost 500 gigatonnes of carbon that has been released since the Industrial Revolution means we will likely miss the next best astronomical entry point into a glaciation, and with a further 500 gigatonnes of emissions the "probability of glacial inception during the next 100,000 years is notably reduced", the scientists say in their Nature paper.

Add a further 500 Gt C on top of that and the next ice age is virtually guaranteed to be delayed beyond the next 100,000 years.

Commenting on the study, Prof Eric Wolff from the University of Cambridge, UK, said: "There have been previous papers suggesting that the next ice age is many tens of thousands of years away, and that the combination of seasonal solar energy at the latitude where an ice sheet would form, plus CO2, is what determines the onset of an ice age. But this paper goes much further towards quantifying where the limits are.

"It represents a nice confirmation that there is a relatively simple way of estimating the combination of insolation and CO2 to start an ice age," he told the Science Media Centre.

And Prof Chris Rapley, from University College London, added: "This is an interesting result that provides further evidence that we have entered a new geological [Epoch] - 'The Anthropocene' - in which human actions are affecting the very metabolism of the planet."

For more information visit:

http://www.bbc.co.uk/news/science-environment-35307800

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Europe and Russia mission to assess Moon settlement

The European and Russian space agencies are to send a lander to an unexplored area at the Moon's south pole.

It will be one of a series of missions that prepares for the return of humans to the surface and a possible permanent settlement.

The spacecraft will assess whether there is water, and raw materials to make fuel and oxygen.

BBC News has obtained exclusive details of the mission, called Luna 27, which is set for launch in five years' time.

The mission is one of a series led by the Russian federal space agency, Roscosmos, to go back to the Moon.

These ventures will continue where the exploration programme that was halted by the Soviet Union in the mid 1970s left off, according to Prof Igor Mitrofanov, of the Space Research Institute in Moscow, who is one of the lead scientists.

"We have to go to the Moon. The 21st Century will be the century when it will be the permanent outpost of human civilisation, and our country has to participate in this process," he told BBC News.

But unlike efforts in the 1960s and 70s, when the Soviet Union was working in competition with the US and other nations, he added, "we have to work together with our international colleagues".

Full moon: Gregory H. Revera

Bérengère Houdou, who is the head of the lunar exploration group of at Esa's European Space Research and Technology Centre (Estec), just outside Amsterdam, has a similar strategy.

"We have an ambition to have European astronauts on the Moon. There are currently discussions at international level going on for broad cooperation on how to go back to the Moon."

One of the first acts of the new head of the European Space Agency, Johann-Dietrich Wörner, was to state that he wants international partners to build a base on the Moon's far side.

The initial missions will be robotic. Luna 27 will land on the edge of the South Pole Aitken (SPA) basin. The south polar region has areas which are always dark. These are some of the coldest places in the Solar System. As such, they are icy prisons for water and other chemicals that have been shielded from heating by the Sun.

According to Dr James Carpenter, Esa's lead scientist on the project, one of the main aims is to investigate the potential use of this water as a resource for the future, and to find out what it can tell us about the origins of life in the inner Solar System.

"The south pole of the Moon is unlike anywhere we have been before," he said.

"The environment is completely different, and due to the extreme cold there you could find large amounts of water-ice and other chemistry which is on the surface, and which we could access and use as rocket fuel or in life-support systems to support future human missions we think will go to these locations."

Back in the heady days of the Apollo missions, it seemed almost inevitable that those astounding but brief trips to the Moon would be followed by something more permanent. But the notion of colonies soon proved to be science fantasy. After the last of 12 astronauts left their boot prints in the lunar dust in 1972, the US government and taxpayers collectively declared, "been there, done that". America had scored a dazzling point over the Soviet Union but at eye-watering cost, so the final three planned Apollo missions were cancelled.

For a while, our nearest neighbour in space seemed rather unappealing. But then, over recent years, came a series of discoveries about the lunar dust itself, suggesting that the Moon holds water and minerals that could conceivably help support a settlement, if anyone has the appetite to pay for it. So a new batch of missions is under way. China seems to be particularly eager, launching increasingly capable robotic craft that could pave the way for human flights, sometime in the 2030s.

In all probability, the next boots on the Moon will be Chinese. One of China's leading space scientists told me how he even envisages opening lunar mines to extract valuable resources such as Helium-3. Throughout history, humanity has gazed at the Moon through different eyes. In the 1960s, it was the scene for Cold War rivalry. Now it is seen as a potential staging-post for longer journeys and as a rock waiting to be dug up and exploited.

Prof Mitrofanov says that there are scientific and commercial benefits to be had by building a permanent human presence on the lunar surface.

"It will be for astronomical observation, for the utilisation of minerals and other lunar resources and to create an outpost that can be visited by cosmonauts working together as a test bed for their future flight to Mars."

Esa and its industrial collaborators are developing a new type of landing system able to target areas far more precisely than the missions in the 1960s and 70s. 

The so-called "Pilot" system uses on-board cameras to navigate and a laser guidance system which is able to sense the terrain while approaching the surface and be able to decide for itself whether the landing site is safe or not, and if necessary to re-target to a better location.

Europe is also providing the drill which is designed to go down to 2m and collect what might be hard, icy samples. According to Richard Fisackerly, the project's lead engineer, these samples might be harder than reinforced concrete and so the drill will need to be extremely strong.

"We are currently looking at the technologies we would need to penetrate that type of material and are looking at having both rotation and hammering functions. The final architecture has yet to be decided - but this combination of rotation, hammering and depth is a step beyond what we have already flown or is in development today," he told BBC News.

Esa will also provide the onboard miniaturised laboratory, called ProSPA. It will be similar to the instrument on the Philae lander, which touched down on the surface of Comet 67P last year. But ProSPA will be tuned to searching for the key ingredients with which to make water, oxygen, fuel and other materials that can be exploited by future astronauts.

The instrument will help scientists discover out how much of these critical resources are under the surface, and, crucially, whether they can be extracted easily.

Europe's participation in the mission is due to receive final approval at a meeting of ministers in late 2016. It has the strong support of Esa and Roscosmos hierarchy, and the scientists involved in Luna 27 are confident that it is not a question of if but when humans go back to the lunar surface.

"This whole series of missions feels like the beginning of the return to the Moon but it is also starting something new in terms of overall exploration of the Solar System," says Mr Fisackerly.

For more information visit:-

http://www.bbc.co.uk/news/science-environment-34504067

http://www.prlabs.co.uk/lab-supplies.php?N=oxygen-emptied-cylinder&Id=60499