'Virgin Earth' Material Survived Cataclysmic Cosmic Collision
Through the analysis of a previously unexplained ratio of isotopes, scientists have recovered a geological time capsule of sorts that they believe represents a very different Earth that existed some 4.5 billion years ago. Continue reading →
Billions of years ago, our baby planet was smashed by another planetary body, turning it into a burning ball of molten rock. But according isotopes recovered from deep inside the Earth's mantle, some of the pre-impact material persists to this day, possibly proving that some of our planet survived the cosmic collision intact.
During that epoch of our solar system's evolution, planetary collisions were commonplace and it is thought that a hypothetical Mars-sized body, nicknamed "Theia," hit Earth in a cataclysmic collision some 4.5 billion years ago. The energies released during impact would have totally transformed our planet, obliterating its surface and melting its rocky mantle.
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But the extent of this planetary transformation isn't well understood. Was Earth completed melted? Or have some pockets of material of a primordial Earth persisted to modern day, proving that not all terrestrial material was affected by the Earth-Theia encounter?
"The energy released by the impact between the Earth and Theia would have been huge, certainly enough to melt the whole planet," said geochemist Sujoy Mukhopadhyay of Harvard University and lead scientists of this research. "But we believe that the impact energy was not evenly distributed throughout the ancient Earth. This means that a major part of the impacted hemisphere would probably have been completely vaporized, but the opposite hemisphere would have been partly shielded, and would not have undergone complete melting."
Mukhopadhyay is presenting his team's work at the Goldschmidt geochemistry conference in Sacramento, Calif., this week.
The research focuses on the comparison of noble gas isotopes in the deep mantle compared with the shallow mantle. The Earth's mantle is a silicate rocky shell that extends from the crust to as deep as 1,800 miles (2,900 kilometers) to the Earth's molten outer core. The mantle is differentiated into different mineral layers that provide information about our planet's ancient geochemical past.
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The researchers analyzed ratios of isotopes of Helium (3He) and Neon (22Ne) and found that the ratio was significantly higher in the shallow mantle than it was in the deep mantle. "This implies that the last giant impact did not completely mix the mantle and there was not a whole mantle magma ocean," said Mukhopadhyay in a press release.
In addition, they analyzed the 129-Xenon to 130-Xenon ratio from material transported from the deep mantle to the surface by mantle plumes - again, the ratio was significantly lower in material from the lower mantle when compared to ratios found at the surface. The Xenon ratio is interesting as 129-Xenon is produced by the radioactive decay of 129-Iodine, putting a definite ‘time stamp' on the transported deep mantle material to within the first 100 million years of Earth's early history.
"The geochemistry indicates that there are differences between the noble gas isotope ratios in different parts of the Earth, and these need to be explained," said Mukhopadhyay. "The idea that a very disruptive collision of the Earth with another planet-sized body, the biggest event in Earth's geological history, did not completely melt and homogenize the Earth challenges some of our notions on planet formation and the energetics of giant impacts.
"If the theory is proven correct, then we may be seeing echoes of the ancient Earth, from a time before the collision."
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In other research published in the journal Science last week, isotopic analysis of elements inside moon rock (rock recovered by the Apollo missions from the lunar surface and moon meteorites recovered on Earth) revealed the chemical signature for Theia and geologists have been able to deduce that around 50 percent of the moon is likely composed of material originating from the interplanetary impactor.
There is little doubt that the impact of Theia was was a global event, turning our planet into a burning blob of magma and even spawning the formation of our moon, but it appears that the picture is a little more complex when trying to work out how much of our planet was transformed by the impact.
Deep down in the Earth's mantle, material from a pre-impact world appears to be lurking, providing us with an intriguing geological time capsule of a very alien ‘virgin' Earth.
The face of the Earth changed dramatically in 2013. Natural disasters, war and other human activities left geographic scars that Landsat satellites viewed from their orbits. The Landsat program uses National Aeronautic and Space Administration satellite images to monitor the Earth from space with assistance from the U.S. Geological Survey.
On Nov. 8, 2013, Typhoon Haiyan scourged the Philippines. On the island of Leyte, 315 kilometer- (195 mile-) per-hour winds and a deadly storm surge devastated Talcoban City. NASA's False-color images show the extent of the destruction. In this image from 2004, vegetation shows up as red, urban areas are white and silver and bare ground is tan. Cloud shadows and water appear black.
The typhoon seems to have stripped the vegetation from the hills west of the Talcoban City, although some of this may have resulted from deforestation, noted
. The southeast coast lost even more vegetation, along with buildings. The area near the airport appears to have suffered intense damage. Black patch mark where water left by the storm surge formed pools. Parts of the downtown area appear smudged, which may result from the rubble and debris scattered around the city.
In Jordan, a city now appears where there was only desert in 2009. That city, the Zaatari refugee camp (shown here in a
image from July of 2013), is the the size of Fargo, North Dakota, and exemplifies the human suffering caused by the Syrian civil war. The camp opened in 2012 and grew to become Jordan's fourth largest city with approximately 115,000 people by December 2013, according to the
Back in May of 2009, the site of the Zaatari refugee camp (shown here) held only arid scrub land on the border between Jordan and Syria. The humanitarian crisis caused by the conflict in Syria continues to grow worse, Valerie Amos, under secretary general and emergency relief coordinator for the U.N. Security Council, told journalists on December 3, reported the
While a typhoon may have caused much of the vegetation loss in and around Tacloban, the loss of rainforest in the Peruvian Amazon (shown here) bore the signature of human activity. In July 2013, Clinton Jenkins, remote sensing scientist at North Carolina State University, received a tip about deforestation near Tamshiyacu in northeastern Peru, reported
. Landsat satellite imagery proved that approximately 100 hectares (247 acres) of forest had been cleared per week. The total deforestation equaled at least 1000 hectares (3.86 square miles).
Landsat images from 2012 show intact forest in the region. Jenkins estimated that approximately 300,000 tons of trees and other biomass were cut down. That loss of forest equated to the emission of 150,000 tons of carbon dioxide. "Landsat imagery is essential for environmental monitoring because it is free, easy to access, and quickly available after the satellite passes over an area," Jenkins told NASA. "Satellites are the only way to monitor these areas because they are so large and so difficult to access."
On June 11, 2013, the
started in a suburb of Colorado Springs, Colorado. The blaze torched 486 homes by the time firefighters contained the inferno nine days later, reported
. A drought that started in 2012 contributed to the intensity of the fire. A heat wave also gripped the area, which resulted in parched trees prone to burn. In this image from June 2013, the burn scar left by the inferno mars the Black Forest Reserve and nearby residential areas.
Although drought and heat contributed to the intensity of the Black Forest fire, the toll on people's homes resulted from a dramatic increase in housing development in the area. In the 60s, there were fewer than 100 homes in the area. By 2013, Colorado's Black Forest held 1,603 houses. In this image, from 1985, note the lack of squiggling suburban roads seen as tan lines in the 2013 image. "Most wildland fire policies to date have focused on reducing wildfire risk by removing trees and forest fuels, but we need a paradigm shift," Tania Schoennagel, wildfire expert at the University of Colorado-Boulder, told
. "We need to start focusing on limiting residential development in fire-prone forests and working hard to create fire-resistant communities in the wildland-urban interface to minimize future losses."
While satellite imagery shows the current chaos of war in Syria, the site of the Battle of Gettysburg now appears tranquil and pastoral. In this
image from May of 2013, fresh spring fields cut the land into a jigsaw puzzle, where 160,000 Americans once squared off to cut each other down. The battle raged from July 1-3, 1863, leaving approximately 8,000 dead and more than 27,000 wounded. This year marked the 150th anniversary, or seven score and ten years ago, of the battle that inspired President Lincoln's famous speech, the Gettysburg Address. The green patches of Little and Big Round Top Hills mark where Union forces surveyed the battlefield from a higher vantage point than the Confederates, which gave the Yankees a geographic advantage. "How soft your fields so green, can whisper tales of gore, Of how we calmed the tides of war," as Led Zeppelin said in Immigrant Song.
Pine Island Glacier
The leading edge of the Pine Island Glacier in Antarctica shattered between November 9-11 and created an iceberg 35 kilometers by 20 kilometers (21 by 12 miles), known as B-31, according to the
. Currents around Antarctica will decide the eventual fate of the newborn glacier (shown here on Nov. 13, 2013). The chunk of ice may bob around in Pine Island Bay for years, or it may drift out into the oceans surrounding Antarctica, reported
. Two major currents swirl around the frozen continent. One, the "coastal counter current" flows counterclockwise, while the larger, wider "circumpolar current" flows clockwise.
Pine Island Glacier
The Pine Island glacier moved seaward at approximately 4 kilometers per year. Icebergs break off from the glacier every five or six years, reported NASA. However, Iceberg B-31 is roughly 50 percent larger than previous icebergs that have snapped off from the Pine Island Glacier. This image shows the glacier as a rift started to form in late October that would eventually result in iceberg B-31.
As Iceberg B-31 begins its course through the ocean, ships plow though the waves far to the north. The clouds that formed in the ships' wakes distinguish the routes of the vessels as seen in this
image from Jan. 15, 2013. The particles in ships' exhaust serve as seeds for the clouds. Water vapor condenses onto the particles and creates long, thin clouds off the western coast of North America.