Mercury has made a rare transit in front of the Sun, the third such pass of 14 the planet will make this century.
The little planet’s sojourn between Earth and the Sun lasted from 11:12 until 18:42 GMT.
Mercury will not make another transit until 2019 and then 2032.
The event was impossible – and dangerous – to view with the naked eye or binoculars, but astronomy groups worldwide were offering the chance view it through filtered telescopes.
Live views from space and ground telescopes were 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 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 was visible in its entirety.
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.
To avoid permanent eye damage, any telescope must be fitted with a solar filter before being trained on the Sun.
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.
Chinese and the US researchers suggest that the innermost core of the Earth has another, distinct region at its center.
The team believes that the structure of the iron crystals there is different from those found in the outer part of the inner core.
The findings are reported in the journal Nature Geoscience.
Without being able to drill into the heart of the Earth, its make-up is something of a mystery.
Scientists use echoes generated by earthquakes to study the core, by analyzing how they change as they travel through the different layers of our planet.
Prof. Xiaodong Song, from the University of Illinois at Urbana-Champaign said: “The waves are bouncing back and forth from one side of the Earth to the other side of the Earth.”
He and his colleagues in China say this data suggests that the Earth’s inner core – a solid region that is about the size of the Moon – is made up of two parts.
The seismic wave data suggests that crystals in the “inner inner core” are aligned in an east-to-west direction – flipped on their side, if you are looking down at our planet from high above the North Pole.
Those in the “outer inner core” are lined up north to south, so vertical if peering down from the same lofty vantage point.
Prof. Xiaodong Song said: “The fact we are discovering different structures at different regions of the inner core can tell us something about the very long history of the Earth.”
The core, which lies more than 5,000km down, started to solidify about a billion years ago – and it continues to grow about 0.5mm each year.
The finding that it has crystals with a different alignment, suggests that they formed under different conditions and that our planet may have undergone a dramatic change during this period.
Mountain-size asteroid 2004 BL86 will pass in the vicinity of Earth on January 26, 2015.
The space rock is roughly a third of a mile across.
By comparison, most near-Earth asteroids have diameters no larger than 50 to 100 ft.
But the asteroid is going by at a very safe distance of 745,000 miles. That’s about three times as far away as the Moon.
Asteroid 2004 BL86 is the largest known space rock predicted to come this close to Earth until 2027.Because it’s relatively large, 2004 BL86 will brighten rapidly as it approaches Earth.
Astronomers predict it will become about 9th magnitude for several hours as it passes closest to us. This is still much too faint to be seen by eye, and it is beyond the reach of most binoculars.
However, the asteroid should be bright enough to follow with a 3- or 4-inch-diameter telescope as it moves among the stars.
Observers in the Americas, Europe, and Africa can track down the asteroid during its brightest time: from 8 p.m. EST on Monday evening, January 26, until about 1 a.m. EST on January 27.
During this time 2004 BL86 will be heading northward through the dim constellation Cancer. It skims the eastern edge of a star cluster called the Beehive (or Messier 44) from about midnight to 12:30 a.m. EST.
The asteroid’s closest approach to Earth actually occurs hours earlier, around 11 a.m. EST on the 26th.
However, at that time it’s predicted to be somewhat dimmer, about magnitude 10, because Earth will see only a portion of its illuminated side.
The asteroid brightens, despite the increasing distance, because we’re seeing its face become more fully illuminated.
The space rock will be moving about 2.5° per hour while crossing Cancer. That’s fast enough that you’ll be able to see it moving in real time in a telescopic view whenever it passes close to a background star.
Evidence of the world that crashed into the Earth billions of years ago to form the Moon has been found after researchers analyzed the lunar rock brought back by Apollo astronauts .
Analysis of lunar rock shows traces of the “planet” called Theia.
The researchers claim that their discovery confirms the theory that the Moon was created by just such a cataclysmic collision.
The study has been published in the journal Science.
The accepted theory since the 1980s is that the Moon arose as a result of a collision between the Earth and Theia planet 4.5 billion years ago.
The accepted theory since the 1980s is that the Moon arose as a result of a collision between the Earth and Theia planet 4.5 billion years ago
Theia was named after a goddess in Greek mythology who was said to be the mother Selene the goddess of the Moon. It is thought to have disintegrated on impact with the resulting debris mingling with that from the Earth and coalescing into the Moon.
It is the simplest explanation, and fits in well with computer simulations. The main drawback with the theory is that no one had found any evidence of Theia in lunar rock samples.
Earlier analyses had shown Moon rock to have originated entirely from the Earth whereas computer simulations had shown that the Moon ought to have been mostly derived from Theia
Now a more refined analysis of Moon rock has found evidence of material thought to have an alien origin.
According to the lead researcher, Dr. Daniel Herwartz, from the University of Goettingen, no one has found definitive evidence for the collision theory, until now.
But the difference, some say, could be explained by material absorbed by the Earth after the Moon formed.
Dr. Daniel Herwartz measured the difference in what is called the isotopic composition of the oxygen contained in rocks on Earth and Moon rock. This is the ratio of different forms of oxygen.
Studies of meteorites from Mars and the outer solar system show that these ratios are markedly different -rather like a fingerprint.
One possibility is that Theia was formed very close the Earth and so had a similar composition. If that was the case it raises the possibility that the assumption that each planet in the current Solar System has a markedly different fingerprint that needs to be revisited.
It is well known that Earth is unique as the only planet in the solar system which can sustain life.
However, in other respects, Earth may not be quite as unusually as is often thought.
Astronomers studying Titan, Saturn’s largest moon, have described it as “a weirdly Earth-like place” when it comes to geology.
Titan boasts landscapes shaped by the flow of rivers – though they are rivers of liquid methane, not of water.
And, like Earth, the surface of Titan is surprisingly free of craters, implying that geological activity is constantly reshaping the moon, as also happens here.
The icy landscape of Titan was first discovered by Earth-bound researchers in 2004, when the Cassini-Huygens spacecraft which orbits Saturn first broke through the moon’s atmosphere.
Astronomers studying Titan, Saturn's largest moon, have described it as "a weirdly Earth-like place" when it comes to geology
Scientists had previously been unable to see the amazing rivers which carve out channels in the moon’s surface, as its atmosphere is so thick with methane and nitrogen that the landscape is not visible from Earth.
Intrigued by the discovery of the methane rivers, researchers from MIT and the University of Tennessee at Knoxville wanted to investigate the history of Titan’s geology.
However, despite the visible river networks, the astronomers found less erosion than they had expected, given that Titan has been orbiting Saturn for four billion years.
Similarly, when they looked for craters which could have been caused by meteorites, there were far fewer than on most other moons in the solar system.
In fact, the number of craters was more reminiscent to the situation on Earth, where plate tectonics and volcanic explosions have covered up much of the impact of foreign bodies on the planet.
“Earth’s continents are always eroding or being covered with sediment,” said Taylor Perron, assistant professor of geology at MIT.
“That may be the case on Titan, too.”
Discovering which factors were responsible for shaping Titan’s landscape could be a challenge, as the satellite images do not give a good impression of the ups and downs of the moon’s terrain.
“It’s almost like we were thrown back a few centuries, before there were many topographic maps, and we only had maps showing where the rivers are,” Taylor Perron added.
Despite the challenges, Taylor Perron said he expected the similarities between Titan and Earth would give scientists an ongoing insight into how the moon’s surface has changed over millennia.
“It’s a weirdly Earth-like place, even with this exotic combination of materials and temperatures.
“And so you can still say something definitive about the erosion. It’s the same physics.”
Australian scientists, who have made an overall study of temperature and pressure conditions of Mars, say that a greater percentage of the Red Planet is habitable than Earth.
Scientists from the Australian National University say that 3% of Mars could sustain life, while just one per cent of Earth’s volume contains life – from the core to upper atmosphere.
However, the researchers say that most Earth-like organisms would need to retreat underground to survive on Mars.
Astrobiologist Charley Lineweaver told AFP: “What we tried to do, simply, was take almost all of the information we could and put it together and say <<is the big picture consistent with there being life on Mars?>>” And the simple answer is yes… There are large regions of Mars that are compatible with terrestrial life.”
Life could exist on Mars, scientists say, largely because there is a huge amount of water there in the form of ice, found at the polar regions.
But the pressure on the planet is so low that water would vaporize on the surface.
Below ground, however, there is sufficient pressure for water to be kept in a liquid state, which would enable microbes to thrive.
And while the surface temperature is not ideal for life, being an extremely chilly -65C, below ground it would be much warmer thanks to heat from the planet’s core.
Charley Lineweaver added that his study, which analyzed decades of data, was “the best estimate yet published of how habitable Mars is to terrestrial microbes”.
His findings were published today in Astrobiology.
Australian scientists, who have made an overall study of temperature and pressure conditions of Mars, say that a greater percentage of the Red Planet is habitable than Earth
Scientists will learn a great deal more about Mars’s ability to sustain life when the rover Curiosity lands on the surface next August.
NASA’s earlier Viking rovers concluded 35 years ago that there was no sign of life, but scientists hope Curiosity’s more sophisticated equipment will reveal more.
It will be “the largest and most complex piece of equipment ever placed on the surface of another planet”, said Doug McCuistion, director of NASA’s Mars exploration programme.
Curiosity rover is expected to land on Mars on August 5, 2012, after travelling nearly 354 million miles from our planet.
One of the chief tasks of the $2.5billion mission will be to discover the source of the methane gas scientists have detected in the Martian air.
It will also fire a laser beam with the energy of a million lightbulbs at the surface of the red planet to see whether or not it could have supported life.
The international team of space explorers that launched the Mars Science Laboratory is relying on the instrument to look for biological signs on the distant world.
The ChemCam will fire a powerful laser pulse, vaporising some Mars dust and examining the spectrum of light shining through it.
The robust system is one of 10 instruments mounted on the mission’s rover vehicle.
When ChemCam fires its extremely powerful laser pulse, it will vaporize an area the size of a pinhead.
The system’s telescope will peer at the flash of glowing plasma created by the vaporized material and record the colours of light contained within it.
These spectral colours will then be interpreted by a spectrometer, enabling scientists to determine the elemental composition of the vaporized material.