Driven by southwesterly winter winds, dust from the White Sands dune field in New Mexico rises thousands of feet from the valley floor and drifts over the snowy peaks of the Sacramento Mountains. Credit: NASA
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It’s clear from this image of why a region in New Mexico, USA is called ‘White Sands.’ The dust plumes in this photograph taken by an astronaut on board the International Space Station show a dust storm in the White Sands National Monument. But this is a huge dust storm. The white dust plumes stretch across more than 120 kilometers (74 miles).
Caused by winds that channel the dust through a low point in the mountains, the vigorous winds are lifting dust particles from the valley floor to more than 1200 meters over the mountains. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite also captured a wider, regional view of the same storm on the same day.
The sand dunes of this national monument are white because they are composed of gypsum, a relatively rare dune-forming mineral. The dunes’ brilliance, especially contrasted against the nearby dark mountain slopes, makes them easily identifiable to orbiting astronauts. The white speck of the dunes was even visible to the Apollo astronaut crews looking back at Earth on the way to the Moon.
This is an artist’s depiction of a 10-kilometer (6-mile) diameter asteroid striking the Earth. New evidence in Australia suggests an asteroid 2 to 3 times larger than this struck Earth early in its life. Credit: Don Davis/Southwest Research Institute.
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Even though the Late Heavy Bombardment is somewhat of a controversial idea, new research has revealed this period of impacts to the Earth-Moon system may have lasted much longer than originally estimated and well into the time when early life was forming on Earth. Additionally, this “late-late” period of impacts — 3.8 billion to 2.5 billion years ago — was not for the faint of heart. Various blasts may have rivaled those that produced some of the largest craters on the Moon, and could have been larger than the dinosaur-killing impact that created the Chicxulub crater 65 million years ago.
“Our work provides a rationale that the last big impacts hit over an extended time,” said William Bottke principal investigator of the impact study team at the NASA Lunar Science Institute’s Center of Lunar Origin and Evolution (CLOE), based at the Southwest Research Institute (SwRI) in Boulder, Colorado.
The evidence for these prodigious impacts comes from bead-like impact ‘spherules’ found in millimeter- to centimeter-thick rock layers on Earth and date from the Archean period of Earth’s history, more recent than the estimated LHB period of 4.1 to 3.8 billion years ago.
“The beds speak to an intense period of bombardment of Earth,” Bottke said. “Their source long has been a mystery.”
The millimeter-scale circles and more irregular gray particles are formerly molten droplets ejected into space when an asteroid hit the early Earth. The image at left is from the Monteville layer in South Africa. Courtesy Bruce Simonson, Oberlin College and Conservatory
The circles seen in the image above are all formerly molten droplets ejected into space when an asteroid struck the Earth about 2.56 billion years ago. The droplets returned to Earth and were concentrated at the base of the Reivilo layer in South Africa.
The spherules still contain substantial extraterrestrial material, such as iridium (176 parts per million), which rules out alternative sources for the spherules, such as volcanoes, according to Bruce Simonson, a geologist from the Oberlin College and Conservatory who has studied these ancient layers for decades.
The timing of these impacts also coincides with a record of large lunar craters being created more recently than 3.8-billion years ago.
At least 12 spherule beds deposited between 3.47 and 1.7 billion years ago have been found in protected areas on Earth, such as in shales deposited on the seafloor below the reach of waves.
From these beds, the team found evidence of approximately 70 impacts on Earth during this time period that were likely larger than the Chicxulub impact.
In their paper, which was published in Nature, the team created a computer model of the ancient main asteroid belt and tracked what would have happened when the orbits of the giant planets changed. They extended the work of the Nice Model, which supports the theory that Jupiter, Saturn, Uranus and Neptune formed in different orbits nearly 4.5 billion years ago and migrated to their current orbits about 4 billion years ago, triggering a solar system-wide bombardment of comets and asteroids called known as the LHB.
This image shows a representation of how the giant planets have migrated to the current orbits, destabilizing the extension of the primordial asteroid belt closest to Mars. This drove numerous big impactors onto orbits where they could hit the terrestrial planets, though over a long enough time span that this drawn-out barrage may have lasted more than a billion years. The frequency of these impacts on Earth was enough to reproduce the known impact spherule beds. Image Courtesy David Kring, Center for Lunar Science and Exploration, and the Lunar and Planetary Institute
The new computer model shows that the innermost portion of the asteroid belt could have become destabilized, delivering numerous big impacts to Earth and Moon over longer time periods.
Have there been any previous indications about this period of impacts?
“The problem is that we have almost no Archean rocks,” Bottke told Universe Today. “The oldest terrestrial craters, Sudbury and Vredefort, are 1.85 and 2.02 billion years old. The spherule beds are our only window into impacts prior to this time.”
Also, Bottke said, the number of people who look for impact spherules is almost equally scarce. “People such as Bruce Simonson, Don Lowe, Gary Byerly, and Frank Kyte, have been carrying on a long, lonely quest to try to get people to consider the implications of their work, which are deeply profound, in my opinion,” Bottke said.
As for finding evidence of this later period of impacts on the Moon, Bottke said the problem there is the lack of solid ages for most impact events.
“This means it is difficult say anything definitive about the timing of major impacts,” Bottke said. “We are working this problem now with Michelle Kirchoff, who is counting craters on top of large lunar craters. This can be done now that we have LRO data.” (Listen to a podcast interview of Kirchoff on the 365 Days of Astronomy.)
Still, Bottke said, without using “fancy dynamics,” they can address some issues.
“Studies in the post-Apollo era suggested that the Moon has four 160-300 km craters that formed after Orientale, whose age is 3.7-3.8 billion years ago and (i.e., K/T-sized events or larger),” he said. “Crater counts from the Galileo mission and Apollo-era geologic analyses suggest at least one of these events took place near 3.2-3.5 billion years ago. If we account for the gravitational cross section of the planets, we know that for every lunar event, we should get about 20 on the Earth. So, from this argument alone, one should get a lot of big impacts on the Earth after the formation of Orientale.”
The new study fits with the available constraints about impacts on the Moon as well as finding the right distribution of spherule beds on Earth.
The best way to confirm everything, however, Bottke said, would be if more lunar rocks from various locations were available for study.
In honor of Earth Day, enjoy this beautiful timelapse compiled by science educator James Drake, who put together one of the first ISS flyover videos. This video was created from images produced by the Russian geostationary Electro-L Weather Satellite, and the images are some of the largest whole disk images of our planet, as the satellite is orbiting at about 40,000 km. Each image is 121 megapixels, and the resolution is 1 kilometer per pixel. They are taken every half hour in four different wavelengths of light — three visible, and one infrared. The infrared light is reflected by forests and vegetation, which appear orange in these images. Enjoy!
See more at Drake’s Planet Earth web page, including a zoomable, full resolution image of Earth, as well as other image downloads.
Solar flares pose a major hazard to electronics and infrastructure in Low Earth Orbit, but they may have played a role in kick-starting life on Earth. Credit: NASA/SDO/J. Major
This big! The M1.7-class flare that erupted from active region 1461 on Monday, April 16 let loose an enormous coronal mass ejection many, many times the size of Earth, making this particular writer very happy that our planet was safely tucked out of aim at the time… and 93 million miles away.
The image above was obtained by NASA’s Solar Dynamics Observatory’s AIA 304 imaging instrument on Monday during the height of the event. I rotated the disk of the Sun 90 degrees to get a landscape look over the eastern limb, cropped it down and then added an Earth image to scale — just to show how fantastically huge our home star really is.
This MERIS image of Spain and Portugal could be Envisat's last. (Chelys/EOsnap)
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The European Space Agency’s venerable Envisat satellite may have sent back its final image, according to recent news from the Agency.
On April 8, ESA lost communication with the Earth-observation satellite, preventing reception of data as it passed over the Kiruna station in Sweden. Although it’s been confirmed that the satellite is still in orbit, the recovery team has not been able to re-establish contact.
The image above, showing part of the Iberian peninsula, was from the last data to be received from Envisat before it fell silent.
Radar image of Envisat. (Fraunhofer Institute for High Frequency Physics and Radar Techniques.)
Launched in March 2002, Envisat has been helping researchers examine our planet for over ten years — five years longer than its original mission duration. It has completed more than 50,000 orbits and returned thousands of images, as well as a wealth of data about the land, oceans and atmosphere.
Envisat data was instrumental in over 4,000 projects from 70 countries.
Germany’s Tracking and Imaging Radar captured an image of the satellite, revealing that it is still intact and in a stable orbit. Still, all attempts at recovery have so far been unsuccessful.
A contingency agreement with the Canadian Space Agency on Radarsat will be activated to fulfill user requirements if Envisat cannot be brought back online.
An impact between a Mars-sized protoplanet and early Earth is the most widely-accepted origin of the Moon. Did smaller impacts seed the formation of continents? (NASA/JPL-Caltech)
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Recent research on lunar samples has shown that the Moon may be made of more Earth than green cheese — if by “green cheese” you mean the protoplanet impactor that was instrumental in its creation.
It’s an accepted hypothesis that Earth’s moon was created during an ancient, violet collision between our infant planet and a Mars-sized world called Theia, an event that destroyed Theia and sent part of Earth’s crust and upper mantle into orbit as a brief-lived ring of molten material. This material eventually coalesced to form the Moon, and over the next 4.5 billion years it cooled, became tidally locked with Earth, accumulated countless craters and gradually drifted out to the respectable distance at which we see it today.
Theia’s remains were once assumed to have been a major contributor to the material that eventually formed the Moon. Lunar samples, however, showed that the ratio of oxygen isotopes on the Moon compared to Earth were too similar to account for such a formation. Now, further research by a team led by scientists from The University of Chicago shows that titanium isotopes — an element much more refractive than oxygen — are surprisingly similar between the Moon and Earth, further indicating a common origin.
“After correcting for secondary effects associated with cosmic-ray exposure at the lunar surface using samarium and gadolinium isotope systematics, we find that the 50Ti/47Ti ratio of the Moon is identical to that of the Earth within about four parts per million, which is only 1/150 of the isotopic range documented in meteorites,” wrote University of Chicago geophysicist Junjun Zhang, lead author of the paper published in the journal Nature Geoscience on March 25.
If the Moon is more Earth than Theia, then what happened to the original impacting body? Perhaps it was made of heavier stuff that sunk deeper into the Moon, or was assimilated into Earth’s mantle, or got lost to space… only more research will tell.
But for now, you can be fairly sure that when you’re looking up at the Moon you’re seeing a piece of Earth, the cratered remnants of a collision that took place billions of years ago.
Photo by Expedition 30 crew during a night pass over Moscow on March 28, 2012.
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Tracing a bright star upon the Earth, the lights of Russia’s capital city blaze beyond the solar panels of the International Space Station in this photo, captured by the Expedition 30 crew on the night of March 28, 2012.
As an electric-blue dawn flares around Earth’s northeastern limb, the green and purple fire of the Aurora Borealis shimmers and stretches away to the northwest above a pale yellow line of airglow.
Traveling at 17,500 miles an hour (28,163 km/hr), the ISS was approximately 240 miles (386 km) above the Russian city of Volgograd (formerly Stalingrad) when this photo was taken.
The disintegrated Wilkins Ice Shelf in April 2009. (Chelys/EOSnap)
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A paper published in the journal Science in August 1981 made several projections regarding future climate change and anthropogenic global warming based on manmade CO2 emissions. As it turns out, the authors’ projections have proven to be rather accurate — and their future is now our present.
The paper, written by a team of atmospheric physicists led by the now-controversial James Hansen at NASA’s Institute for Space Studies at Goddard Space Flight Center, was recently rediscovered by researchers Geert Jan van Oldenborgh and Rein Haarsma from the Royal Netherlands Meteorological Institute (KNMI). Taking a break from research due to illness, the scientists got a chance to look back through some older, overlooked publications.
“It turns out to be a very interesting read,” they noted in their blog on RealClimate.org.
Even though the paper was given 10 pages in Science, it covers a lot of advanced topics related to climate — indicating the level of knowledge known about climate science even at that time.
“The concepts and conclusions have not changed all that much,” van Oldenborgh and Haarsma note. “Hansen et al clearly indicate what was well known (all of which still stands today) and what was uncertain.”
Within the paper, several graphs note the growth of atmospheric carbon dioxide, both naturally occurring and manmade, and projected a future rise based on the continued use of fossil fuels by humans. Van Oldenborgh and Haarsma overlaid data gathered by NASA and KNMI in recent years and found that the projections made by Hansen et al. were pretty much spot-on.
If anything, the 1981 projections were “optimistic”.
Data from the GISS Land-Ocean Temperature Index fit rather closely with the 1981 projection (van Oldenborgh and Haarsma)
Hansen wrote in the original paper:
“The global temperature rose by 0.2ºC between the middle 1960’s and 1980, yielding a warming of 0.4ºC in the past century. This temperature increase is consistent with the calculated greenhouse effect due to measured increases of atmospheric carbon dioxide. Variations of volcanic aerosols and possibly solar luminosity appear to be primary causes of observed fluctuations about the mean rend of increasing temperature. It is shown that the anthropogenic carbon dioxide warming should emerge from the noise level of natural climate variability by the end of the century, and there is a high probability of warming in the 1980’s. Potential effects on climate in the 21st century include the creation of drought-prone regions in North America and central Asia as part of a shifting of climate zones, erosion of the West Antarctic ice sheet with a consequent worldwide rise in sea level, and opening of the fabled Northwest Passage.”
Now here we are in 2012, looking down the barrel of the global warming gun Hansen and team had reported was there 31 years earlier. In fact, we’ve already seen most of the predicted effects take place.
The retreat of Pedersen Glacier in Alaska. Left: summer 1917. Right: summer 2005. Source: The Glacier Photograph Collection, National Snow and Ice Data Center/World Data Center for Glaciology.
And that’s not the only prediction that seems to have uncannily come true.
“In light of historical evidence that it takes several decades to complete a major change in fuel use, this makes large climate change almost inevitable,” Hansen et al wrote in anticipation of the difficulties of a global shift away from dependence on carbon dioxide-emitting fossil fuels.
“CO2 effects on climate may make full exploitation of coal resources undesirable,” the paper concludes. “An appropriate strategy may be to encourage energy conservation and develop alternative energy sources, while using fossil fuels as necessary during the next few decades.”
As the “next few decades” are now, for us, coming to a close, where do we stand on the encouragement of energy conservation and development on alternative energy sources? Sadly the outlook is not as promising as it should be, not given our level of abilities to monitor the intricate complexities of our planet’s climate and to develop new technologies. True advancement will rely on our acceptance that a change is in fact necessary… a hurdle that is proving to be the most difficult one to clear.
Read van Oldenborgh and Haarsma’s blog post here, and see the full 1981 paper “Climate Impact of Increasing Carbon Dioxide” here. And for more news on our changing climate, visit NASA’s Global Climate Change site.
Tip of the anthropogenically-warmer hat to The Register.
Earth just doesn’t make crust like it used to… at least, not according to new research by a team of scientists in the UK.
Researchers with the Universities of Bristol, St Andrews and Portsmouth have studied elements trapped within zircon samples gathered from all over the planet to peer billions of years back in time at how Earth’s crust was being produced.
Zircon, a mineral found in granite, can be dated with precision and is thus an accurate measure for geologic timescales.
What they found was that 65% of our planet’s current crust had already existed 3 billion years ago. Since rocks older than 2.5 billion years are rare on Earth today, this means that some process began to take place that either reworked — or destroyed — a large portion of the older crust, and changed how new crust was formed.
During the first 1.5 billion years of Earth’s history, the team reports, the rate of crust formation was high — approximately 3 cubic kilometers was added to the continents each year. After that the rate dropped substantially, falling to about 0.8 cubic kilometers per year for the next 3 billion years — right up to the present day.
The cause is yet unknown, but it may be the result of the onset of plate tectonics driven by subduction — the process by which sections of Earth’s crust (“plates”) slide beneath other sections, sinking into the underlying mantle to be liquefied into magma by pressure and heat. New crust is created when the magma rises again where the plates separate… Earth’s current “conveyor belt” of crust formation.
Whatever process was in place prior to 3 billion years ago, it was much more efficient at creating crust.
“Such a sharp decrease in the crustal growth rate about 3 billion years ago indicates a dramatic change in the way the continental crust was generated and preserved,” said Dr. Bruno Dhuime of the University of Bristol’s School of Earth Sciences. “This change may in turn be linked to the onset of subduction-driven plate tectonics and discrete subduction zones as observed at the present day. The next challenge is to determine which tectonic regime shaped the Earth’s crust in the planet’s first 1.5 billion years before this change.”
The team’s paper “A Change in the Geodynamics of Continental Growth 3 Billion Years Ago” (Bruno Dhuime, Chris J. Hawkesworth, Peter A. Cawood, Craig D. Storey) was published March 16 in Science.
Read more on the University of Bristol’s press release here.
Earth may not have formed quite like once thought (Image: NASA/Suomi NPP)
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Researchers from The Australian National University are suggesting that Earth didn’t form as previously thought, shaking up some long-standing hypotheses of our planet’s origins right down to the core — literally.
Ian Campbell and Hugh O’Neill, both professors at ANU’s Research School for Earth Sciences, have challenged the concept that Earth formed from the same material as the Sun — and thus has a “chondritic” composition — an idea that has been assumed accurate by planetary scientists for quite some time.
Chondrite meteorites are composed of spherical chondrules, which formed in the solar nebula before the asteroids. (NASA)
Chondrites are meteorites that were formed from the solar nebula that surrounded the Sun over 4.6 billion years ago. They are valuable to scientists because of their direct relationship with the early Solar System and the primordial material they contain.
“For decades it has been assumed that the Earth had the same composition as the Sun, as long the most volatile elements like hydrogen are excluded,” O’Neill said. “This theory is based on the idea that everything in the solar system in general has the same composition. Since the Sun comprises 99 per cent of the solar system, this composition is essentially that of the Sun.”
Instead, they propose that our planet was formed through the collision of larger planet-sized bodies, bodies that had already grown massive enough themselves to develop an outer shell.
This scenario is supported by over 20 years of research by Campbell on columns of hot rock that rise from Earth’s core, called mantle plumes. Campbell discovered no evidence for “hidden reservoirs” of heat-producing elements such as uranium and thorium that had been assumed to exist, had Earth actually formed from chondritic material.
“Mantle plumes simply don’t release enough heat for these reservoirs to exist. As a consequence the Earth simply does not have the same composition as chondrites or the Sun,” Campbell said.
The outer shell of early Earth, containing heat-producing elements obtained from the impacting smaller planets, would have been eroded away by all the collisions.
“This produced an Earth that has fewer heat producing elements than chondritic meteorites, which explains why the Earth doesn’t have the same chemical composition,” O’Neill said.
The team’s paper has been published in the journal Nature. Read the press release from The Australian National University here.
