May 9, 2013
In September 2009, after decades of speculation, evidence of water on the surface of the Moon was discovered for the first time. Chandrayaan-1, a lunar probe launched by India’s space agency, had created a detailed map of the minerals that make up the Moon’s surface and analysts determined that, in several places, the characteristics of lunar rocks indicated that they bore as much 600 million metric tonnes of water.
In the years since, we’ve seen further evidence of water both on the surface and within the interior of the Moon, locked within the pore space of rocks and perhaps even frozen in ice sheets. All this has gotten space exploration enthusiasts pretty excited, as the presence of frozen water could someday make permanent human habitation of the Moon much more feasible.
For planetary scientists, though, it’s raised a knotty question: How did water arrive on the Moon in the first place?
A new paper published today in Science suggests that, unlikely as it may seem, the Moon’s water originated from the same source as the water that comes out of the faucet when you open a tap. Just as many scientists believe the Earth’s entire supply of water was initially delivered via water-bearing meteorites that traveled from the asteroid belt billions of years ago, a new analysis of lunar volcanic rocks brought back during the Apollo missions indicates the Moon’s water has its roots in these same meteorites. But there’s a twist: Before reaching the Moon, this lunar water was first on Earth.
The research team, led by Alberto Saal of Brown University, analyzed the isotopic composition of hydrogen found in water within tiny bubbles of volcanic glass (supercooled lava) as well as melt inclusions (blobs of melted material trapped in slowly cooling magma that later solidified) in the Apollo-era rocks, as shown in the image above. Specifically, they looked at the ratio of deuterium isotopes (“heavy” hydrogen atoms that contain an added neutron) to normal hydrogen atoms.
Previously, scientists have found that in water, this ratio changes depending on where in the solar system the water molecules initially formed, as water that originated closer to the Sun has less deuterium than water formed further away. The water locked in the lunar glass and melt inclusions was found to have deuterium levels similar to that found in a class of meteorites called carbonaceous chondrites, which scientists believe to be the most unaltered remnants of the nebula from which the solar system formed. Carbonaceous chondrites that fall to Earth originate in the asteroid belt between Mars and Jupiter.
Higher deuterium levels would have suggested that water was first brought on to the Moon by comets—as many scientists have hypothesized—because comets largely come from the Kuiper belt and Oort Cloud, remote regions far beyond Neptune where deuterium is more plentiful. But if the water in these samples represents lunar water as a whole, the findings indicate that the water came from a much closer source—in fact, the same source as the water on Earth.
The simplest explanation for this similarity would be a scenario in which, when a massive collision between a young Earth and a Mars-sized proto-planet formed the Moon some 4.5 billion years ago, some of the liquid water on our planet was somehow preserved from vaporization and transferred along with the solid material that would become the Moon.
Our current understanding of massive impacts, though, doesn’t allow for this possibility: The heat we believe would be generated by such an enormous collision would theoretically vaporize all lunar water and send it off into space in a gaseous form. But there are a few other scenarios that might explain how water was transferred from our proto-Earth to the Moon in other forms.
One possibility, the researchers speculate, is that the early Moon borrowed a bit of Earth’s high-temperature atmosphere the instant it formed, so any water that had been locked in the chemical composition of Earth rocks pre-impact would have vaporized along with the rock into this shared atmosphere after impact; this vapor would have then coalesced into a solid lunar blob, binding the water into the chemical composition of lunar material. Another possibility is that the rocky chunk of Earth was kicked off to form the Moon retained the water molecules locked inside its chemical composition, and later on, these were released as a result of radioactive heating inside the Moon’s interior.
Evidence from recent lunar missions suggests that lunar rocks—not just craters at the poles—indeed contain substantial amounts of water, and this new analysis suggests that water originally came from Earth. So the findings will force scientists to rethink models of how the Moon could have formed, given that it clearly didn’t dry out completely.
March 20, 2013
Update: Since the press release announcing Voyager 1′s exiting the solar system, NASA has clarified that the final indicator of this event—a change in the direction of the magnetic field surrounding the craft—has still not been observed. As was first observed in December 2012, Voyager 1 is in a new outermost region of the solar system called “the magnetic highway,” not true interstellar space. This post has been edited to reflect the clarification.
Since the dawn of the Space Age, our manned missions and unmanned probes have reached the Moon, asteroids and other planets. But only now do we have confirmation that a human-made object has reached a new milestone: The Voyager 1 space probe is at the furthermost edge of the solar system.
According to a paper recently accepted for publication by the journal Geophysical Research Letters, data transmitted by probe—which is now more than 11 billion miles away from the Sun—reveal that it has exited the heliosphere. The heliosphere (also called the heliosheath) is the region of space influenced by the solar wind and is commonly accepted as the outer border of the solar system. Thirty-five years, 6 months and 15 days after its launch, the spacecraft will soon enter the second phase of its mission—studying the interstellar medium that exists between our galaxy’s star systems.
Bill Webber of New Mexico State and F.B. McDonald of the University of Maryland (who has passed away since the paper was written) came to the conclusion after analyzing radiation data transmitted by Voyager 1 last August 25. The probe’s sensors detected that the levels of radiation from cosmic rays that had come from the Sun dropped to less than 1 percent of what they’d been previously, while radiation from galactic cosmic rays (which originate from beyond the solar system) doubled in intensity.
Although there is no exact boundary that defines the edge of the solar system, the point at which the Sun’s cosmic rays and galactic cosmic rays meet indicates the edge of the region dominated by our Sun’s solar wind, and thus the outside border of our star’s system. Webber says that the sudden change in radiation indicates Voyager 1 passed this point.
“Within just a few days, the heliospheric intensity of trapped radiation decreased, and the cosmic ray intensity went up as you would expect if it exited the heliosphere,” he said in a press release issued by the American Geophysical Union today. He also noted that it’s possible the probe hasn’t reached true interstellar space, but rather a separate, not-yet-understood region that lies in between our solar system and the interstellar medium.
Since its launch in 1977, the spacecraft has conducted a grand tour of the solar system, passing by and photographing Jupiter and Saturn and providing us with some of the first-ever close-ups of the gas giants. Voyager 2, a twin probe, visited Jupiter, Saturn, Uranus and Neptune, and is still firmly within the solar system for now, 9.4 billion miles away from the Sun.
In 2005, Voyager 1 entered the heliosheath (the region in which the solar wind begins to slow down due to encountering the interstellar medium), and last October, researchers reported that it may have left the heliosphere altogether. Soon afterward, though, scientists cautioned that it may not have exited the heliosphere’s outer boundary, because a shift in the direction of the magnetic field had not yet been detected.
Despite the announcement alongside the new paper, this may still be the case—Voyager 1 may have finally exited the heliosphere, but not yet entered interstellar space per se. According to NASA, “A change in the direction of the magnetic field is the last critical indicator of reaching interstellar space and that change of direction has not yet been observed.” Thus, the probe is in an unexpected region in between the heliosphere and interstellar space, previously referred to as a magnetic highway.
Either way, though, it’s still in the starting stages of its journey, set to spend millennia—yes, millenia—traveling through the interstellar medium, though it will probably not be able to record or send back data after around 2025.
After an estimated 40,000 years, it will come relatively close (within a light year) to another star—and at that point, could serve as something of a time capsule. The Voyager 1 carries a Golden Record, designed to present a virtual snapshot of humankind to other life forms, contains everything from images of DNA and the Taj Mahal to recordings of whale sounds and Chuck Berry’s “Johnny B. Goode.”
As Timothy Ferris wrote in Smithsonian last May when he reflected on the 35th anniversary of the Voyager mission, “The Voyagers will wander forever among the stars, mute as ghost ships but with stories to tell…Whether they will ever be found, or by whom, is utterly unknown.”
February 12, 2013
This Friday afternoon at approximately 2:26 Eastern time, an asteroid roughly half the size of a football field (147 feet) in diameter will pass extremely close to the Earth—just 17,200 miles from our planet’s surface. That said, there’s no need to worry, as NASA scientists confirmed with certainty nearly a year ago that the asteroid will not make an impact and poses absolutely no threat.
Nevertheless, the proximity of the asteroid’s path is noteworthy: it will come within a distance 2 times the Earth’s diameter, passing us by even closer than some geosynchronous satellites that broadcast TV, weather and radio signals. As Phil Plait writes in his comprehensive post on the asteroid over at Slate, “This near miss of an asteroid is simply cool. It’s a big Universe out there, and the Earth is a teeny tiny target.”
The asteroid—likely made of rock and referred to as 2012 DA14 by scientists—was first spotted last February by astronomers at Spain’s Observatorio Astronómico de La Sagra. Asteroids, like planets, orbit the Sun, and this one passed us by on its last orbit as well, but at a much greater distance—it came within roughly 1.6 million miles last February 16. After this year’s near miss, the rock’s orbit will be altered significantly by the influence of Earth’s gravity, and scientists calculate that it won’t come near us again until the year 2046 at the soonest.
On Friday, though, it will pass by Earth between 18:00 and 21:00 UTC (1-4 p.m. Eastern time, or 10 a.m.-1 p.m. Pacific) and come closest at roughly 19:26 UTC (2:26 p.m. Eastern, 11:26 a.m. Pacific). That means that observers in Eastern Europe, Asia and Australia get to see its closest pass at nighttime, whereas those in North America, Western Europe and Africa will have to wait until after sunset, when the asteroid has already begun to move away.
For all observers, the asteroid will be too small to see with the naked eye, though it should be viewable with binoculars or a telescope. Universe Today has the technical details on where exactly to spot the asteroid in the sky. A number of observatories and organizations will also broadcast video streams of the asteroid live, including NASA.
A fly-by like the one on Friday isn’t particularly rare in terms of mere proximity. There are seven closer asteroid passes on record—in 2011, a tiny asteroid set the record for near misses by coming within 3300 miles of Earth, and in 2008, an even smaller one actually made contact with the atmosphere, burning up over Africa.
Both of those rocks, though, were less a meter across.What distinguishes this asteroid is that it’s passing close by and theoretically large enough to cause major damage if an impact were to occur. While an asteroid of this size passes this closely roughly every 40 years on average, a collision with an object this size only happens once every thousand years or so.
What kind of damage would that impact wreak? For a comparison, many are noting the Tunguska event, an explosion over a remote area Russia in 1908 that was likely caused by an asteroid of similar size burning up in the atmosphere. The explosion knocked down more than 80 million trees covering an area of some 830 square miles; scientists estimate it released more than 1,000 times as much energy as the nuclear bomb dropped on Hiroshima and triggered shock waves that would have registered a 5.0 on the Richter scale.
Of course, unlike in 1908, we now have the power to observe approaching asteroids well ahead of time—and might have the ability to prevent potential collisions. Bill Nye is among those who argue that this event should serve as a wake-up call for the importance of investing in asteroid-detecting infrastructure, such as observatories and orbiting telescopes. The B612 Foundation supports this mission, and advocates for the development of technologies that could slightly alter the path or speed of an approaching object to avoid an impact.
This time, at least, we’re lucky. But Ed Lu, a former astronaut and head of B612, says this event should not be taken lightly. ”It’s a warning shot across our bow,” he told NPR. “We are flying around the solar system in a shooting gallery.”
January 3, 2013
Last year, noted meteorite collector Jay Piatek traveled to Morocco and bought a single stone, less than a pound in weight, that had been discovered in the country some time earlier. When he passed it on to researchers at the University of New Mexico to perform a mineral analysis, they found something unexpected.
The meteor seemed to have originated on Mars, but the rock’s composition didn’t exactly match any of the well-studied meteorites from there found previously. When the researchers compared it to data from soil and rock samples obtained by Curiosity and other recent Martian rovers, though, they realized that rather than originating in the planet’s mantle, as the others had, it appeared to have come from the Martian crust.
Most intriguingly, when they analyzed the basaltic breccia rock even more closely, they discovered it contained a large quantity of water molecules locked in its crystalline structure. While previous studies of Martian meteorites have suggested the presence of water on the red planet, this sample’s analysis, published today in Science, revealed that it contained 10 times more water than any Martian meteorite examined before.
The discovery of the water molecules in the rock at concentrations of 6000 parts per million could indicate the presence of liquid water sometime during Mars’ history. “The high water content could mean there was an interaction of the rocks with surface water either from volcanic magma, or from fluids from impacting comets during that time,” study co-author Andrew Steele of the Carnegie Institute said in a statement.
Apart from the presence of water, the researchers say that information they’ve gleaned over the course of a year-long analysis of the meteor—the first ever linked to the Martian crust—could significantly impact our understanding of the planet’s geology as a whole. The meteorite is primarily composed of chunks of basalt cemented together, indicating that it formed from rapidly cooling lava, likely on the planet’s crust. While we’ve found meteorites from the Moon that match this composition, we haven’t seen anything like it from Mars previously.
Already, the researchers determined that the specimen is roughly 2.1 billion years-old, formed during Mars’ Amazonian epoch, a time period from which we had no previous rock samples. “It is the richest Martian meteorite geochemically,” Steele said. “Further analyses are bound to unleash more surprises.”
December 31, 2012
NASA has big plans for manned travel in deep space. Although missions haven’t been officially announced yet, experts speculate that the agency plans to establish a space station on the far side of the moon sometime in the next decade, a stepping stone towards landing on an asteroid in 2025 and potentially trying to reach Mars sometime around 2033.
Getting to Mars, though, would require astronauts to endure a round-trip (or possibly one-way) journey that could be as long as three years—which could be particularly worrisome given the results of a study on the health effects of cosmic radiation published today in PLOS ONE. Although we’ve known for some time that the radiation experienced by space travelers could pose problems over the long term, this new study is the first to establish a link with an increased chance of Alzheimer’s disease and dementia.
The researchers, a group from NASA and the University of Rochester, came to the finding by testing a specific type of cosmic radiation—high-mass, high-charged (HZE) iron particles—on mice. This kind of radiation is of particular concern, because its high speed (a result of the force of the exploding stars it’s originally expelled from, light-years away) and large mass mean that it’s tricky to protect against.
Here on Earth, we’re largely protected from it and other types of radiation by our planet’s atmosphere and magnetic field, but even a short time in deep space means much higher levels of exposure, and we haven’t yet figured out how to construct a shield that effectively blocks it. ”Because iron particles pack a bigger wallop it is extremely difficult from an engineering perspective to effectively shield against them,” M. Kerry O’Banion, the paper’s senior author, said in a statement. “One would have to essentially wrap a spacecraft in a six-foot block of lead or concrete.”
After producing radioactive particles that generate this type of radiation using a particle accelerator at the Brookhaven National Laboratory on Long Island, the researchers exposed the mice to varying doses of the radiation, including levels comprable to what astronauts would experience on a mission to Mars. The breed of mice they used has been the subject of numerous studies on dementia and Alzheimer’s, so scientists have a relatively good understanding of how rapidly the disease and related symptoms develop over time.
But when the researchers put the mice through a series of behavioral tests—seeing if they were capable of remembering objects or specific locations—those that had been exposed to greater levels of radiation were far more likely to fail, demonstrating signs of neurological impairment far more early in life than is typical in the breed. Additionally, autopsies of these mice revealed that their brains contained higher levels of beta amyloid, the “plaque” considered a hallmark of Alzheimer’s disease.
This result doesn’t mean we have to abandon dreams of deep space travel—or even that this kind of radiation definitively leads to accelerated neurological degeneration—but it does show that cosmic radiation is going to be a graver concern the longer space missions get. Ingenious engineering has addressed many of the difficulties of space flight, but this remains a problem to be solved.
“These findings clearly suggest that exposure to radiation in space has the potential to accelerate the development of Alzheimer’s disease,” O’Banion said. “This is yet another factor that NASA, which is clearly concerned about the health risks to its astronauts, will need to take into account as it plans future missions.”