October 4, 2012
One of the strangest facets of modern exploration is that we now have more experience with the surface of Mars than the layer of earth not too far beneath our feet. Nearly everything we know about the mantle—the 1,800-mile-thick semi-molten layer of the planet below the crust—comes indirectly: from computer simulations, mantle-derived rocks that made their way to the surface and observation of earthquake waves that move through the mantle.
The international group of scientists that makes up the Integrated Ocean Drilling Program (IODP), though, hopes that will soon change. As part of a new project, they are planning to drill some 3.7 miles down into the earth beneath the Pacific Ocean to reach the mantle—and bring up samples of mantle rock for the first time in human history. Damon Teagle, a geochemist at the University of Southampton in England and one of the project’s leaders, told CNN that it will be “the most challenging endeavor in the history of earth science.”
The first effort to drill through the crust to the mantle, Project Mohole, reached 600 feet below the sea floor off Mexico before being abandoned in 1966. Subsequent attempts have gone increasingly deeper, and on September 6, the IODP’s drilling vessel, the Chikyu, set a world record by drilling almost 7,000 feet below the seafloor off Japan and bringing up rock samples.
The ambitious new project aims to go nearly three times as deep. IODP scientists have selected three different sites in the Pacific where the crust is thinnest–it was formed relatively quickly at spreading mid-ocean ridges, where new crust crystallizes as the plates move apart. Although drilling from a floating ship out at sea presents many difficulties, going through the oceanic plates that make up the seafloor is a much easier way of getting to the mantle than trying to drill through the continental plates—the ocean crust ranges from four to six miles thick, whereas the continents go 20 to 30 miles down.
Still, penetrating the oceanic crust will be an unprecedented challenge. The project will cost at least $1 billion, some of which still needs to be raised, and drilling will likely take years. The equipment will be lowered down through more than a mile of water, and the stress that the tungsten carbide drill bits encounter as they grind through hard igneous seafloor rock requires that each bit needs to be replaced after just 50 to 60 hours of use.
The extreme narrowness of the hole itself (just 11 inches wide) also increases the difficulty of the operation. “It will be the equivalent of dangling a steel string the width of a human hair in the deep end of a swimming pool and inserting it into a thimble 1/10 mm wide on the bottom, and then drilling a few meters into the foundations,” Teagle said.
As the drill descends, the team will repeatedly retrieve rock cores roughly three inches across and 30 feet long for scientists to study. If the mission is successful in reaching all the way to the mantle, the scientific payoff will be significant, as samples of mantle rock will help geologists better understand the layer that makes up more than 84 percent of the planet’s volume. “[The mantle] is the engine that drives how our planet works and why we have earthquakes and volcanoes and continents,” Teagle said. “We have the textbook cartoons, but detailed knowledge is lacking.”
For Teagle and others, the mission also represents the kind of ambitious, grand project that can inspire generations of young people to get involved in science—like NASA’s Apollo missions and the more recent Curiosity rover. Teagle says that successfully reaching the mantle would be revolutionary and that it will leave a new “legacy of fundamental scientific knowledge.”
August 6, 2012
Hydraulic fracturing (a.k.a. “fracking”) recovery techniques for oil and natural gas are a controversial business. The practice—in which a mix of water, sand and chemicals is injected deep into bedrock at high pressure to create fractures, allowing gas and oil to flow upward—was developed in the late 1990s and has become more and more common across the United States over the past few years, opening up geologic areas such as the Bakken Shale in North Dakota and the Marcellus Shale in Pennsylvania, New York and West Virginia to dramatic increases in gas production.
On the one hand, proponents argue that hydraulic fracturing increases the amount of energy that can be economically produced in the United States, making oil and gas cheaper and reducing our dependency on foreign imports. Opponents, though, note that fracking causes dangerous chemicals to leach into groundwater, releases known carcinogens into the air and increases our contribution to climate change.
Alongside these observed problems, though, a different sort of worry has emerged: the idea that hydraulic fracturing can trigger an earthquake. Scientists have known for decades that injecting fluids into the earth could cause quakes, but we were uncertain just how much of an increase widespread fracking might cause. This past spring, USGS scientists decided that the recent dramatic increase in the number of small quakes in the United States is “almost certainly manmade,” but were unable to conclusively tie it to this particular activity.
Now, the evidence is starting to pile up. A study published today in the Proceedings of the National Academy of Sciences finds a correlation between dozens of small earthquakes in Texas’ Barnett Shale region—the site of intensive hydraulic fracturing activity—and the locations of injection wells used to dispose of the wastes of this process. ”You can’t prove that any one earthquake was caused by an injection well,” says Cliff Frohlich, the University of Texas geologist who conducted the study, “but it’s obvious that wells are enhancing the probability that earthquakes will occur.”
To come to the finding, Frohlich analyzed two years’ worth of data from a network of extremely sensitive seismographs that was installed in the region in 2009. He discovered dozens of small earthquakes that had not been previously reported—and found that all 24 of the quakes for which he was able to establish an accurate epicenter occurred within two miles of an injection well.
One important distinction is that these wells were the disposal sites for waste fluids that had already used to fracture rock, rather than the original wells used to extract the gas. Although the actual gas extraction wells cause many microearthquakes by their very nature (they literally crack the bedrock to release gas and oil), these are far too small to be felt by humans or cause any damage. The fluid disposal wells, though, are more likely to cause earthquakes of significance, because they are sites of injection for a longer duration over time.
The waste fluids may trigger earthquakes by acting as lubricants in pre-existing faults deep underground, allowing masses of rock to slide past each other more easily and relieve built-up pressure. All of the wells that Frohlich found correlated with quakes were home to high rates of injection (more than 150,000 barrels of fluid per month). However, there were other wells in the area with similar rates of injection that did not correlate with increased seismic activity. ”It might be that an injection can only trigger an earthquake if injected fluids reach and relieve friction on a nearby fault that is already ready to slip,” explains Frohlich.
The good news is that all of these earthquakes were still relatively small, with magnitudes of less than 3.0 on the Richter scale, unlikely to cause any damage on the surface. Seismologists, though, are concerned that fluid injection could cause larger quakes if the fluid migrates into older, deeper rock formations beyond the local shale, which are home to larger fault lines. A number of earthquakes that occurred in Ohio last year, including one with a 4.0 magnitude, were linked to disposal of fracking fluids.
Frohlich notes that much more research is needed to help us understand exactly why some wells are more likely to cause earthquakes than others. For those already concerned about fracking, though, his new research adds another major concern to a growing list.
June 22, 2012
Despite claims in the 1890s that Mars was filled with canals teeming with water, research over the past several decades has suggested that in fact, Mars has only a tiny amount of water, mostly near its surface. Then, during the 1970s, as part of NASA’s Mariner space orbiter program, dry river beds and canyons on Mars were discovered—the first indications that surface water may have once existed there. The Viking program subsequently found enormous river valleys on the planet, and in 2003 it was announced that the Mars Odyssey spacecraft had actually detected minute quantities of liquid water on and just below the surface, which was later confirmed by the Phoenix lander.
Now, according to an article published yesterday in the journal Geology, there is evidence that Mars is home to vast reservoirs of water in its interior as well. The finding has weighty implications for our understanding of the geology of Mars, for hopes that the planet may have at some point in the past been home to extraterrestrial life and for the long-term prospects of human colonization there.
“There has been substantial evidence for the presence of liquid water at the Martian surface for some time,” said Erik Hauri, one of the study’s authors. “So it’s been puzzling why previous estimates for the planet’s interior have been so dry. This new research makes sense.”
The research team, led by led by University of New Mexico scientist Francis McCubbin, didn’t even have to go all the way to Mars to find the water—they just closely looked at a pair of meteorites we’ve already had for some time. The Shergotty meteorite, which crashed in Bihar, India in 1865, and the Queen Alexandria Range 94201 meteorite, which landed in Antarctica and was discovered in 1994, were both ejected from Mars roughly 2.5 million years ago. Because they formed due to volcanic activity, when molten Martian mantle was brought to the surface and crystallized, they can tell us a great deal about the planet’s insides.
“We analyzed two meteorites that had very different processing histories,” Hauri said. “One had undergone considerable mixing with other elements during its formation, while the other had not.” For both of the meteorites, the team looked specifically at the amount of water molecules locked inside crystals of the mineral apatite and used this as a proxy for how much water was contained in the original rock on Mars that produced the meteorites. To determine the precise amount of water, they used a technology called secondary ion mass spectrometry, which shoots a focused beam of ions at the sample and measures the amount of ions that bounce off of the surface.
The amount of water in the meteorites suggested that the Martian mantle contains somewhere between 70 and 300 parts per million of water—an amount strikingly similar to Earth’s own mantle. Because both the samples contained roughly the same water content despite their different geological histories on Mars, the researchers believe that the planet incorporated this water long ago, during the early stages of its formation. The paper also provides us with an answer for how underground water may have made its way to the Martian surface: volcanic activity.
Earlier this week, we discussed how solar radiation is among the many problems that face potential human colonization of Mars, but finding a huge underground store of water inside the planet would still go a long way towards making settlement a legitimate possibility. In the long-term, drilling for underground water may be cheaper and easier than, say, trying to melt surface ice, or subsisting off the tiny amount of surface water that we know is present.
Additionally, the finding is getting an entire separate crowd excited: those who are hoping to find fossil or other evidence that Mars once supported life. The fact that water has apparently existed on the planet for such a long time makes the odds of life originating there just a little less scant.
All this from a pair of meteorites that crashed on our planet over a century ago. Just imagine what we might learn during future missions to Mars, such as NASA’s unmanned space laboratory, Curiosity, which will land on Mars on August 5th.
Still, it won’t be easy. Watch this NASA video to learn about the riskiest part of the whole mission—the seven minutes between when the rover hits the top of the Martian atmosphere and when it touches down.
May 31, 2012
About 74,000 years ago, in what is now Indonesia, Mount Toba violently erupted. The volcanic explosion sent some 700 cubic miles of magma into the air and deposited an ash layer roughly 6 inches thick over all of South Asia.
The eruption—which was an estimated 100 times larger than the largest in modern times, the 1815 Mount Tambora eruption—altered global climate patterns significantly, likely triggering a period of rapid cooling. The effect on ecosystems around the world was dramatic, and it may have nearly led to the extinction of the human species—some genetic studies suggest that the human population went through a bottleneck around that time, with as few as 1,000 breeding pairs of our ancestors surviving the devastating volcanic winter.
Yesterday, scientists from Vanderbilt University and the University of Chicago published a study in the journal PLoS ONE that has an ominous conclusion. Their findings indicate that the underground magma pools that fuel such supervolcanoes—pancake-shaped reservoirs that are typically 10 to 25 miles in diameter and one half to three miles deep—erupt much more quickly than previously thought. The research team says that once these enormous subterranean magma reservoirs form, they are unlikely to stay dormant for very long—they may be capable of sitting quietly for just thousands or even hundreds of years before erupting.
“Our study suggests that when these exceptionally large magma pools form, they are ephemeral, and cannot exist very long without erupting,” said Guilherme Gualda, the Vanderbilt University professor who directed the study, in a press release. ”The fact that the process of magma body formation occurs in historical time, instead of geological time, completely changes the nature of the problem.”
Hundreds of years may seem like a long time when compared to the length of a human life, but a century is just a blip when viewed in terms of geologic time. Most geologic events—the formation of mountains and the movement of tectonic plates, for example—typically occur on the order of hundreds of thousands or millions of years. So the fact that these underground magma pools can only lay dormant for mere centuries is stunning when viewed in the context of conventional beliefs about geology.
Gualda’s research team arrived at the conclusion by studying Bishop Tuff, a rock formation in eastern California that formed as a result of a supervolcano eruption some 760,000 years ago. Using advanced methods for analyzing the date of magma formation, the researchers concluded that the subterranean reservoir developed sometime between 500 and 3,000 years before the eruption. The resulting event covered more than half of North America with a layer of volcanic ash.
The potential effects of a supervolcano eruption in modern times are truly terrifying to behold. The eruption in Mount Tambora in Indonesia, which produced less than 1 percent of the volume of lava and ash of a supervolcano, caused 1815 to become known as “The Year Without a Summer” in North America and Europe. Volcanic ash suspended in the atmosphere blocked enough sunlight from reaching earth so that crop production was severely interrupted, causing famines and food riots in from Switzerland to China.
If the formation and eruption of giant magma pools capable of producing supervolcanoes truly happens as quickly as indicated in the study, it means we ought to take an entirely different approach in preparing for such cataclysms, the researchers report. Thankfully, it is believed that no magma pools of this size are present on earth at this time. But since they can form and erupt so rapidly, the authors recommend that we continually monitor geologic hot spots to detect the earliest signs of formation.
It might be impossible to prevent such natural disasters, but experts agree that preparation and advance warning are the best bet for mitigating the destruction they might bring. Centuries might be short when viewed in terms of geologic time, but they are long for human civilizations—long enough that, if we knew the location of a massive underground magma pool, we might even be able to intentionally avoid building cities and development in the area above it. This wouldn’t prevent the massive level of damage a supervolcano would bring, but it would reduce the destruction to some degree.
May 22, 2012
In 2007, new images of Mars wowed astronomers and the general public with something out of the pages of a sci-fi comic: extraterrestrial caves. Photos produced by orbiting satellites showed evidence of “skylights” into underground caverns, and thermal imaging indicating that these caves remained at a constant temperature day and night. In recent years, caves and related structures have also been discovered on our moon and on Jupiter’s moon Titan. The concept of extraterrestrial caves has plainly moved from fiction to reality, and scientists are eager to start exploring.
Why is the scientific world so excited about extraterrestrial caves? For many, they represent the next frontier in the search for extraterrestrial life. For others, they are our best bet for someday constructing and maintaining habitable colonies on other planets.
In October 2011, an interdisciplinary group of geologists, cave explorers, earth scientists, astrobiologists and other researchers met in New Mexico for the first time to discuss the science and implications of caves on other planets. Published earlier this month in the journal Eos, the results of the meeting give us a tantalizing hint of what discoveries may come during our lifetimes as space missions begin exploring these hidden crevices throughout the solar system.
Caves are a remarkably promising location to begin looking for life, the scientists report. Because they are isolated and protected from the surface, they can provide a diverse range of microenvironments—and the greater number of different habitats, the greater the chance life will happen to evolve in one of them. The study of caves here on earth has shown us that many unusual (and in some cases, downright bizarre) life forms can evolve in caves, and many of these result from the abundance of sulfur, metals and other chemicals that are likely to be available in caves on other planets as well.
The group of researchers also theorized about possible means of exploring caves on other planets and moons. Although images produced by satellites and other spacecraft can sometimes reveal the existence of caves, new technologies are clearly necessary to actually explore their interiors and extract samples that might contain life. Exploration and mapping could hypothetically be undertaken by either human or robotic means, although the latter seems more realistic at this point.
Ground-based exploration vehicles, such as the Mars rovers, could be equipped to enter and navigate caves, but the group noted that such devices would require better autonomous decision-making. Robotic explorers would need to be able to avoid hazards and make decisions about what data to collect without communicating with earth, since the cave walls and ceilings could block the transmission of radio signals.
The scientists even considered how caves can foster human exploration of other moons and planets. They might, for example, be good places to look for ice and other resources that would help groups of humans explore and perhaps even inhabit far-flung extraterrestrial bodies. They could also provide physical protection for colonies and experiments. Close study of caves on earth—their geologic context, the means by which they formed, the microenvironments they provide and other factors—will help us know what to expect in planning cave excursions elsewhere.
Although all of this cave talk sounds a bit like it belongs in a summer Hollywood blockbuster rather than the proceedings of an academic conference, consider this: Exploration of the ocean floor and the moon were both predicted in science fiction before being taken seriously by the scientific establishment. After technology caught up with the human imagination, these ideas didn’t seem so far-fetched.
It may take decades or longer, but it appears as though exploration of extraterrestrial caves is on the same track. What’s more uncertain, though, is what marvels we’ll find when we get there.