Earth and Moon from 114 Million Miles.Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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A new image to add to the family photo album! The MESSENGER spacecraft is working its way to enter orbit around Mercury in March of 2011, and while wending its way, took this image of the Earth and Moon, visible in the lower left. When the image was taken in May 2010, MESSENGER was 183 million kilometers (114 million miles) away from Earth. For context, the average separation between the Earth and the Sun is about 150 million kilometers (93 million miles). It’s a thought provoking image (every one of us is in that image!), just like other Earth-Moon photos — Fraser put together a gallery of Earth-Moon images from other worlds, and this one will have to be added. But this image was taken not just for the aesthetics.
This image was taken as part of MESSENGER’s campaign to search for vulcanoids, small rocky objects hypothesized to exist in orbits between Mercury and the Sun. Though no vulcanoids have yet been detected, the MESSENGER spacecraft is in a unique position to look for smaller and fainter vulcanoids than has ever before been possible. MESSENGER’s vulcanoid searches occur near perihelion passages, when the spacecraft’s orbit brings it closest to the Sun. August 17, 2010 was another such perihelion, so if MESSENGER was successful in finding any tiny asteroids lurking close to the Sun, we may hear about it soon.
Planet Earth, as seen from Apollo 17 mission. Credit: NASA/)PL
Planet Earth, which we humans and all currently-known forms of life call home, is the third planet from the Sun, and the largest of the terrestrial planets. With a mean radius of 6,371 km (3,958.8 miles), it is slightly larger than Venus (which has a radius of approx. 6,050 km), almost twice the size of Mars (~3,390 km), and almost three times the size of Mercury (~2,440 km).
Basically, Earth is a pretty big world. But just how big if one were to measure it from end to end? If one were to just start walking, how many kilometers (and/or miles) would they have to go before they got back to where they started. Well, the short answer is just over 40,075 km (or just over 24,901 miles). But as always, things get a little more complicated when you look closer.
The collision between "Proto-Earth" and Theia, from which the Earth and Moon were created 4,500-4,400 million years ago. Both planets had a massive iron core when they collided and created the Moon and Earth.
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The Earth and Moon were created as the result of a giant collision between two planets the size of Mars and Venus. Until now it was thought to have happened when the solar system was 30 million years old or approximately 4.5 billion years ago. But new research shows that the Earth and Moon may have formed much later – perhaps up to 150 million years after the formation of the solar system.
“We have determined the ages of the Earth and the Moon using tungsten isotopes, which can reveal whether the iron cores and their stone surfaces have been mixed together during the collision,” said Tais W. Dahl, from the Niels Bohr Institute at the University of Copenhagen in collaboration with professor David J. Stevenson from the California Institute of Technology (Caltech).
The planets in the solar system were created by collisions between planetary embryos orbiting the newborn sun. In the collisions the small planets congealed together and formed larger and larger planets. When the gigantic collision occurred that ultimately formed the Earth and Moon, it happened at a time when both planetary bodies had a core of metal (iron) and a surrounding mantle of silicates (rock). But when did it happen and how did it happen? The collision took place in less than 24 hours and the temperature of the Earth was so high (7000º C), that both rock and metal must have melted in the turbulent collision. But were the stone mass and iron mass also mixed together?
The age of the Earth and Moon can be dated by examining the presence of certain elements in the Earth’s mantle. Hafnium-182 is a radioactive substance, which decays and is converted into the isotope tungsten-182. The two elements have markedly different chemical properties and while the tungsten isotopes prefer to bond with metal, hafnium prefers to bond to silicates, i.e. rock.
It takes 50-60 million years for all hafnium to decay and be converted into tungsten, and during the Moon forming collision nearly all the metal sank into the Earth’s core. But did all the tungsten go into the core?
“We have studied to what degree metal and rock mix together during the planet forming collisions. Using dynamic model calculations of the turbulent mixing of the liquid rock and iron masses we have found that tungsten isotopes from the Earth’s early formation remain in the rocky mantle,” said Tahl.
The new studies imply that the moon forming collision occurred after all of the hafnium had decayed completely into tungsten.
“Our results show that metal core and rock are unable to emulsify in these collisions between planets that are greater than 10 kilometers in diameter and therefore that most of the Earth’s iron core (80-99 %) did not remove tungsten from the rocky material in the mantle during formation” said Dahl.
The result of the research means that collision that created the Earth and the Moon may have occurred as much as 150 million years after the formation of the solar system, much later than the 30 million years that was previously thought.
Titan's thick haze. Image: NASA/JPL/Space Science Institute.
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Models of the Sun’s evolution indicate it was as much as 30 percent less luminous during Earth’s early history than it is now. But, somehow the surface of the planet was warm enough for primordial life to emerge. A new study and a look at Saturn’s moon Titan has provided clues for how the Sun could have kept the early Earth warm enough. Scientists say a thick organic haze that enshrouded early Earth several billion years ago may have been similar to the haze that covers Titan and would have protected emerging life on the planet from the damaging effects of ultraviolet radiation, while warming the planet, as well.
Eric Wolf from the University of Colorado-Boulder and his team believe the organic haze was made up primarily of methane and nitrogen chemical byproducts created by reactions with light. If the particles clumped together in larger, complex structures, an arrangement known as a fractal size distribution, then the smallest particles would interact with the shortwave radiation, while the larger structures made out of the smaller particles would affect longer wavelengths. Not only would the haze have shielded early Earth from UV light, it would have allowed gases like ammonia to build up, causing greenhouse warming and perhaps helped to prevent the planet from freezing over.
Other researchers including Carl Sagan have proposed possible solutions to this “Early Faint Sun” paradox, which generally involved atmospheres with powerful greenhouse gases that could have helped insulate the Earth. But while those gases would have blocked the radiation, it wouldn’t have warmed Earth enough for life to form.
“Since climate models show early Earth could not have been warmed by atmospheric carbon dioxide alone because of its low levels, other greenhouse gases must have been involved,” said Wolf. “We think the most logical explanation is methane, which may have been pumped into the atmosphere by early life that was metabolizing it.”
Lab simulations helped researchers conclude that the Earth haze likely was made up of irregular “chains” of aggregate particles with greater geometrical sizes, similar to the shape of aerosols believed to populate Titan’s thick atmosphere. The arrival of the Cassini spacecraft at Saturn in 2004 has allowed scientists to study Titan, the only moon in the solar system with both a dense atmosphere and liquid on its surface.
During the Archean period there was no ozone layer in Earth’s atmosphere to protect life on the planet, said Wolf. “The UV shielding methane haze over early Earth we are suggesting not only would have protected Earth’s surface, it would have protected the atmospheric gases below it — including the powerful greenhouse gas, ammonia — that would have played a significant role in keeping the early Earth warm.”
The researchers estimated there were roughly 100 million tons of haze produced annually in the atmosphere of early Earth during this period. “If this was the case, an early Earth atmosphere literally would have been dripping organic material into the oceans, providing manna from heaven for the earliest life to sustain itself,” said team member Brian Toon, also from CU-Boulder.
“Methane is the key to make this climate model run, so one of our goals now is to pin down where and how it originated,” said Toon. If Earth’s earliest organisms didn’t produce the methane, it may have been generated by the release of gasses during volcanic eruptions either before or after life first arose — a hypothesis that will requires further study.
This new study will likely re-ignite interest in a controversial experiment by scientists Stanley Miller and Harold Urey in the 1950s in which methane, ammonia, nitrogen and water were combined in a test tube. After Miller and Urey ran an electrical current through the mixture to simulate the effects of lightning or powerful UV radiation, the result was the creation of a small pool of amino acids — the building blocks of life.
“We still have a lot of research to do in order to refine our new view of early Earth,” said Wolf. “But we think this paper solves a number of problems associated with the haze that existed over early Earth and likely played a role in triggering or at least supporting the earliest life on the planet.”
Where will you be when the lights go out? Earth Hour 2010 will take place on Saturday, March 27 at 8:30 pm local time. Even though it will spark a tirade of controversy just asking folks to turn off their lights for one hour, let’s see who would rather fight than turn off a switch. In 2009 hundreds of millions of people around the world showed their support and Earth Hour 2010 will continue to be a global call to action to every individual, every business and every community. A call to stand up, to show leadership and be responsible for our future. Do you have what it takes to make such a simple gesture?
Then let’s rock the house…
Earth Hour started in 2007 in Sydney, Australia when 2.2 million homes and businesses turned their lights off for one hour to make their stand against climate change. A year later Earth Hour had become such a global force that more than 50 million people in 35 countries showed their support by switch off for a simple 60 minutes. Icons stood in dark silence as Sydney Harbour Bridge, The CN Tower in Toronto, The Golden Gate Bridge in San Francisco, and Rome’s Colosseum, all did their part as symbols of hope for the future.
Can you still use your imagination? Can you? Then imagine Earth Hour from space…
This year China’s Forbidden City heads up a list of some of the world’s most iconic landmarks that have confirmed their participation in Earth Hour – including The Great Pyramids of Giza and the Sphinx. They will be joined by Italy’s Trevi Fountain in Rome and Leaning Tower of Pisa, Big Ben and Houses of Parliament in London, Edinburgh Castle in Scotland, India Gate and Red Fort in Delhi, Victoria Falls in Zimbabwe, Bosphorous Bridge in Istanbul, Hohensalzburg Castle in Salzburg, and Independence Angel in Mexico City. They join a comprehensive list of the world’s great man-made marvels and natural wonders, including the Eiffel Tower, Brandenburg Gate, Hiroshima Peace Memorial, Empire State Building, London Eye, Table Mountain, Christ the Redeemer statue, Sydney Opera House and the world’s tallest building, Burj Khalifa, which will plunge into darkness for Earth Hour
Before you say “Why bother?” or “My contribution won’t make a difference.”, then think on this… Earth Hour has truly managed to raise our awareness of climate change issues. But there’s more to it than switching off your lights for one hour once a year. It’s all about giving people a voice on the future of our planet and working together. Even if you’d rather fight than flick the switch… you are participating. Whether you are an individual, a business, a school or a city, you can show your support for Earth Hour by turning off your lights at 8.30 pm on March 27 wherever you are on the planet. No one is saying you can’t use your computer or watch television. Bake a pizza and eat it by candlelight with your family! All it takes is the guts to show you understand and care enough to take action.
Researchers in Antarctica got a surprise visit from a creature in a borehole 185 meters (600 feet) below the Antarctic ice, where there is usually no light. A Lyssianasid amphipod, a shrimp-like creature can be seen swimming in this video. A NASA team had lowered a small video camera to get the first-ever photograph of the underside of an ice shelf when the curious little 7 cm (3- inch) shrimp stopped by to check out the equipment. Scientists say this could challenge the idea of where and how forms of life can survive. Anyone else thinking Europa? Continue reading “Unexpected Life Found Under Antarctic Ice”
The Goddard Space Flight Center has a Flickr account showcasing a series of images of our own home planet. Called “Blue Marble,” these spectacular images are the most detailed true-color image of the entire Earth to date. Using a collection of satellite-based observations, scientists and visualizers stitched together months of observations in 2001 of the land surface, oceans, sea ice, and clouds into a seamless, true-color mosaic of every square kilometer (.386 square mile) of our planet. Your tax dollars at work, these images are freely available to educators, scientists, museums, and the public. This record includes preview images and links to full resolution versions up to 21,600 pixels across.
Our blue marble. Credit: NASA
Compare these new images to the original “Blue Marble” photograph, below, taken by the Apollo 17 crew in 1968. The original Blue Marble by Apollo 17.
This view of Earth comes from NASA's Moderate Resolution Imaging Spectroradiometer aboard the Terra satellite.
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Yikes! Just how big was the magnitude 8.8 earth quake in Chile? One scientist says the shaking may have affected the entire planet by shifting Earth on its axis. This possibly may have shortened the length of a day on Earth by about 1.26 microseconds. Using a complex model JPL research scientist Richard Gross computed how Earth’s rotation should have changed as a result of the Feb. 27, 2010 quake. If his figures are correct, the quake should have moved Earth’s figure axis (the axis about which Earth’s mass is balanced) by 2.7 milliarcseconds (about 8 centimeters, or 3 inches).
Earth’s figure axis is not the same as its north-south axis; they are offset by about 10 meters (about 33 feet). By comparison, Gross said the same model estimated the 2004 magnitude 9.1 Sumatran earthquake should have shortened the length of day by 6.8 microseconds and shifted Earth’s axis by 2.32 milliarcseconds (about 7 centimeters, or 2.76 inches).
Gross said that even though the Chilean earthquake is much smaller than the Sumatran quake, it is predicted to have changed the position of the figure axis by a bit more for two reasons. First, unlike the 2004 Sumatran earthquake, which was located near the equator, the 2010 Chilean earthquake was located in Earth’s mid-latitudes, which makes it more effective in shifting Earth’s figure axis.
Second, the fault responsible for the 2010 Chiliean earthquake dips into Earth at a slightly steeper angle than does the fault responsible for the 2004 Sumatran earthquake. This makes the Chile fault more effective in moving Earth’s mass vertically and hence more effective in shifting Earth’s figure axis.
Gross said the Chile predictions will likely change as data on the quake are further refined.
Zonal swishing in the Earth's outer core (Credit: Akira Kageyama, Kobe University)
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Why does the Earth’s magnetic field ‘flip’ every million years or so? Whatever the reason, or reasons, the way the liquid iron of the Earth’s outer core flows – its currents, its structure, its long-term cycles – is important, either as cause, effect, or a bit of both.
The main component of the Earth’s field – which defines the magnetic poles – is a dipole generated by the convection of molten nickel-iron in the outer core (the inner core is solid, so its role is secondary; remember that the Earth’s core is well above the Curie temperature, so the iron is not ferromagnetic).
But what about the fine structure? Does the outer core have the equivalent of the Earth’s atmosphere’s jet streams, for example? Recent research by a team of geophysicists in Japan sheds some light on these questions, and so hints at what causes magnetic pole flips.
About the image: This image shows how an imaginary particle suspended in the liquid iron outer core of the Earth tends to flow in zones even when conditions in the geodynamo are varied. The colors represent the vorticity or “amount of rotation” that this particle experiences, where red signifies positive (east-west) flow and blue signifies negative (west-east) flow. Left to right shows how the flow responds to increasing Rayleigh numbers, which is associated with flow driven by buoyancy. Top to bottom shows how flow responds to increasing angular velocities of the whole geodynamo system.
The jet stream winds that circle the globe and those in the atmospheres of the gas giants (Jupiter, Saturn, etc) are examples of zonal flows. “A common feature of these zonal flows is that they are spontaneously generated in turbulent systems. Because the Earth’s outer core is believed to be in a turbulent state, it is possible that there is zonal flow in the liquid iron of the outer core,” Akira Kageyama at Kobe University and colleagues say, in their recent Nature paper. The team found a secondary flow pattern when they modeled the geodynamo – which generates the Earth’s magnetic field – to build a more detailed picture of convection in the Earth’s outer core, a secondary flow pattern consisting of inner sheet-like radial plumes, surrounded by westward cylindrical zonal flow.
This work was carried out using the Earth Simulator supercomputer, based in Japan, which offered sufficient spatial resolution to determine these secondary effects. Kageyama and his team also confirmed, using a numerical model, that this dual-convection structure can co-exist with the dominant convection that generates the north and south poles; this is a critical consistency check on their models, “We numerically confirm that the dual-convection structure with such a zonal flow is stable under a strong, self-generated dipole magnetic field,” they write.
This kind of zonal flow in the outer core has not been seen in geodynamo models before, due largely to lack of sufficient resolution in earlier models. What role these zonal flows play in the reversal of the Earth’s magnetic field is one area of research that Kageyama and his team’s results that will now be able to be pursued.
Launch Complex 41: Atlas rocket was rolled from VIF at left to pad at right on Feb 9, 2010. Credit: Ken Kremer
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(Editor’s Note: Ken Kremer is at the Kennedy Space Center for Universe Today covering the launch of SDO and Endeavour.)
NASA’s nearly $1 Billion hi tech sun probe, the Solar Dynamics Observatory or SDO, was rolled out today (Feb 9) to Launch Pad 41 on a rainy day here in Florida at 1 day from blast off. SDO will be carried aloft atop an Atlas V rocket at 10:26 AM EST on Feb 10 at Cape Canaveral Air Force Station. The launch window extends for 1 hour. The current weather prediction is only 40% “GO”. The primary concerns for launch day are ground winds with gusts and thick clouds.
NASA’s SDO sun explorer is encapsulated inside 4 meter payload fairing and is bolted atop Centaur Upper Stage of Atlas V rocket at Launch Complex 41. Umbilical lines at right carry cryogenic propellants, electrical power and purge gases. Credit: Ken KremerAt the Kennedy Space Center, I was thrilled to watch the rocket rollout to the pad this morning as part of a NASA Media event along with Universe Today Senior Editor Nancy Atkinson. We were accompanied by a group of SDO managers and science investigators from across the country. The rollout started from inside the 30 story gantry known as the VIF, or Vertical Integration Facility, and ended at the launch pad. It took approximately 35 minutes for the twin “trackmobiles” to push the Atlas rocket about 1800 ft along railroad tracks.
Atlas V booster is 12.5 ft in diameter and 106.5 ft in length. Centaur Upper Stage is 10 ft in diameter and 41.5 ft long. SDO payload fairing is 14 ft in diameter. Total Vehicle height is about 189 ft. Credit: Ken KremerThis afternoon I traveled directly inside the highly restricted security zone which surrounds Launch Complex 41 for a photo shoot to observe the assembled Atlas V rocket and SDO spacecraft directly at the pad. Fantastic experience despite the rainstorm.
SDO, Atlas V and Ken in ditch below rocket less than 24 hours from blast off. Credit: Ken Kremer
SDO project scientist Dean Pesnell told me in an interview today that “SDO will acquire movies of the entire surface of the Sun on a 24/7 basis with 10 times greater resolution than High Definition. That’s about equivalent in size to an IMAX movie”. The three science instruments will collect a staggering 1.5 terabytes of data per day which is equivalent to downloading 500,000 songs. The data will be beamed back continuously to two dedicated ground stations in New Mexico which were specially constructed for SDO. There are no on board recorders due to the huge volume of data.
“It’s perfect timing to launch and study the sun as it starts the rise to a solar maximum,” according to Pesnell. “The sun patiently waited for us to be ready to launch as we waited for a launch opportunity. After a long period of inactivity, Sun spots recently started appearing at the North Pole. And they also just started at the South Pole”.
“SDO was conceived by the scientists around 1996 and formally approved by NASA in 2002”, Prof. Phillip Scherrer said to me. He is the Principal Investigator for the Helioseismic and Magnetic Imager (HMI) instrument.
“The primary mission phase will last 5 years and hopefully extend out to 10 and perhaps even longer. The longevity depends on the health of the science instruments. Remember SOHO was projected to last 2 years and has now operated for over 15 years ! “
HMI will study the origin of solar variability and attempt to characterize and understand the Sun’s interior and magnetic activity.
Both HMI, and the Atmospheric Imaging Assembly, or AIA, will allow scientists to see the entire disc of the sun in very high resolution — 4,096 by 4,096 mm CCDs. In comparison, a standard digital camera uses a 7.176 by 5.329 mm CCD sensor.
AIA also will image the outer layer of the sun’s atmosphere, while the Extreme ultraviolet Variability Experiment, or EVE, measures its ultraviolet spectrum every 10 seconds, 24 hours a day.
We are now less than 12 hours from launch of SDO, NASA’s “New Eye on the Sun”.
Read my earlier SDO reports, including from on site at the KSC launch pads for both SDO and STS 130.
Atlas rocket has been rolled to pad 41 on Feb 8, 2010 and is locked in place surrounded by four lightening masts. Credit: Ken KremerAtlas V rocket begins the 1800 ft rollout from VIF to Pad 41. Credit: Ken Kremer
