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.”
March 7, 2013
Roughly 3.5 billion years ago, Mars began to shift from a wetter, warmer climate to the dry and cold planet we see today. This period of geologic change, known as the Hesperian age, was a turbulent time. The red planet saw widespread volcanic eruptions and catastrophic flooding as melted ice rushed into wide craters, forming lakes. These natural disasters carved a network of basins into its surface called outflow channels, eroding the terrain and reshaping the landscape of the planet. The exact end of this geologic period in Mars’ history is unknown, but scientists give a rough estimate of 3 billion years ago.
Later, many of these outflow channels became covered with lava, burying evidence of Mars’ geologic history. But now, a new map of the planet’s subsurface shows for the first time what one of these buried channels looks like in three dimensions. The findings, published today in the journal Science, reconstruct the Marte Vallis, the largest of the youngest channels on Mars. Marte Vallis is located in the Elysium Planitia region, an expanse of plains along the equator and the youngest volcanic region on the planet.
To create the 3D map, the researchers used data from Shallow Radar, a device that probes for liquid or frozen water underneath Mars’ crust. Known as SHARAD, the technology is on board NASA’s Mars Reconnaissance Orbiter spacecraft, which is currently circling the planet to study its climate. SHARAD’s orbital sounding radar works in much the same way as medical imaging scans. It sends signals to the surface, some of which automatically bounce back to the spacecraft. The signals that don’t readily bounce back can penetrate Mars’ crust and register buried structures before returning to the device. The data appears in two-dimensional cross sections, which are then pieced together to build the 3D representation. In this manner, a deeply grooved set of channels was revealed.
The system of channels, which is somewhere between 10 million to half a billion years old, spans 60 miles in width and stretches for more than 600 miles in length. From what can be seen of Marte Vallis from the surface, the channels are similar in structure to more ancient channel systems traced to the Hesperian, but the lava that had obscured many of their features made it difficult for researchers to make accurate estimates about its depth.
The new data reveals that the scale of erosion for Marte Vallis had indeed been underestimated: the 25-mile-wide main channel is at least twice as deep than earlier approximations indicated. The map shows multiple perched channels which feed into the deeper and wider main channel. These channels once lay along a series of four islands, which floods eroded into teardrop-shaped hills.
The researchers found that the geometry of the features are similar to those of the planet’s oldest channels, which are less obscured by lava, making them easier to study. This also suggests that the Marte Vallis could have been carved entirely by water, says lead study author Gareth Morgan, a geologist at the National Air and Space Museum’s Center for Earth and Planetary Studies. In fact, most Mars scientists accept that outflow channels on Mars were carved by water. Lava also carves out tunnels through thermal erosion heating up the terrain, but Morgan says that this process is implausible for the scale of erosion at the Marte Valle channels. The speed of rushing water is also more efficient at erosion that the flow of lava, which can get stuck on rock, Morgan says. In addition, lava creates tunnels that aren’t as wide—typically only several miles across—so collapsed tunnels couldn’t account for the broad size of the channels.
Using the map, researchers were also able to pinpoint the source of the
floodwater: a now buried portion of the Cerberus Fossae fracture, a series of fissures in the planet’s surface. The researchers posit that water from a reservoir deep below Mars’ surface was released by nearby tectonic or volcanic activity, and it worked quickly to form the channels. These channels would have been a short-lived affair,” Morgan says. “The fracture would have connected this groundwater to the surface. After a short duration of weeks or months, the source would have been exhausted.”
But why was water in that reservoir during a time when the rest of Mars is believed to have been dry? Water, the authors believe, could have collected in aquifers below the surface during the Hesperian. This water hypothetically could have remained stable in liquid form long after the Hesperian ended. Morgan feels that the 3D map could provide more
evidence to support this hypothesis, showing that Mars was wet place in the more recent—as opposed to far ancient—past.
More than 20 similar outflow channels are spread out on the surface of the planet, extending hundreds of miles in length. The most prominent are located in the Chryse Planitia, a circular volcanic plain in the northern hemisphere of Mars. The largest, the Kasei Valles, runs for 1,500 miles along the plain.
Cataclysmic floods like the ones that shaped Mars’ channels aren’t unique to the red planet. Approximately 14,000 years ago, the largest known flood on Earth sprang from Lake Missoula, a prehistoric body of water that existed at the end of the last Ice Age in present-day Montana. The waters eroded part of the landscape of Washington state, forming the Channeled Scablands, a terrain that resembles Martian outflow channels. Marte Vallis’ main channel is estimated to be between 226 and 371 feet deep, a depth that’s comparable to the Channeled Scablands.
So if Mars’ expansive outflow channels were formed by gushing water, the question remains: Where did it all ago?
Some of it vaporized, drifted to the planet’s poles, and precipitated as ice on polar caps, Morgan says. Similar to the ones we have on Earth, the polar ends on the Red Planet are covered in miles-thick layers of ice. The water also could have pooled into shallow areas below the surface, where it also froze—in 2008, NASA’s Phoenix mission confirmed that ice exists in the porous soil that makes up much of the planet’s surface.
Another possibility, Morgan says, is that the ancient water again escaped deep underground, forming a large reservoir that awaits its chance to flood again.
February 6, 2013
Space added several stunning new images to its photo album this week, including the one above of spiral galaxy M106, located 23.5 million light-years away in the constellation Canes Venatici, Notice something?
The image, released yesterday, actually contains two spirals overlain on each other. One is the cloudy, blue-white spiral with a yellow core. The core itself is a composite of images take by the Hubble Space Telescope‘s Advanced Camera for Surveys, Wide Field Camera 3, and Wide Field Planetary Camera 2 detectors. Spiraling outward, the cloudy arms also come from Hubble, but were colorized with ground-based images captured from relatively small telescopes (12.5-inch and 20-inch) as they imaged from dark, remote sites in New Mexico. The telescopes, owned by photo-astronomers Robert Gendler and R. Jay GaBany, helped these astronomy enthusiasts fill in gaps left by Hubble’s cameras. The images were meticulously assembled into a mosaic by Gendler, a physician by training, to form the base spiral of the photo illustration above.
But what about the second spiral? Emanating at odd angles is a glowing red swirl, known as the “anomalous arms” of M106, These arms, captured by Hubble imagery and GaBany’s telescope, are enormous streamers of irradiated hydrogen gas molecules which glow red when seen through special filters. This begs the question–what’s cooking the hydrogen?
The answer is…a black hole! As astronomer Phil Plait blogs in Slate, “Every big galaxy has a supermassive black hole in its core. The Milky Way has one, and it has about 4 million times the mass of the Sun. The black hole at M106’s heart is about 30 million times the mass of our Sun. Besides being heftier it’s also actively feeding, gobbling down material swirling around it (our own galaxy’s black hole is quiescent; that is, not eating anything at the moment).”
While this photo shows stars at the brink of death within M106, another photo released yesterday shows the environment of stars at their birth:
Tinged an eerie green–like smoke from a witch’s brew–the new image from NASA’s Wide-field Infrared Survey Explorer (WISE) was taken after zooming in on bright dot in the “sword” of the constellation Orion. Visible to the naked eye as a single fuzzy star (also known as M42), the dot is actually a cluster of stars, surrounded by the Orion nebula. Here, stars are born.
The image captures the infrared nimbus formed as newborn stars are compressed from vast clouds of gas and heat the wisps that remain. White regions are the hottest part of these stars’ first dust bath, while greens and reds show lukewarm dust. Carving holes through the dust are massive stars–newly formed–such as the one seen at the picture’s center.
The Orion nebula is a site of star formation close to the Earth, giving scientists the opportunity to study its characteristics and hypothesize on how our Sun was born five billion years ago, perhaps from a similar cloud of dust. The white orbs seen here are less than 10 million years old.
The images of the death and birth of stars–both hauntingly beautiful–showcase the evolving nature of space. Mirrored by our own cycles of life and death, the pictures help to link our daily grind with the vastness beyond Earth.
February 5, 2013
The discovery of planets beyond our solar system, along with recent efforts to catalog them, has fueled the search for rocky planets similar to Earth that may have conditions suitable for life. For the past 20 years, many scientists have focused on locating “super-Earths“–planets heavier than Earth but with masses quite a bit below that of Neptune or Uranus–in the so-called “habitable zone” of their stars. Within this zone, it is theoretically possible for a planet with the right atmospheric pressures to maintain liquid water on its surface.
In early January, astronomers working on NASA’s Kepler Mission announced the discovery of KOI 172.02 (KOI for Kepler Object of Interest), an exoplanet candidate that is about 1.5 times the radius of Earth, orbiting in the habitable zone of a G-type star slightly cooler than our Sun. If confirmed, the planet, which orbits its sun every 242 days, is “our first habitable-zone super Earth around a sun-type star,” astronomer Natalie Batalha, a Kepler co-investigator at NASA’s Ames Research Center, told Space.com. Batalha and colleagues hail KOI 172.02 as the exoplanet most like Earth, and thus is a prime candidate for hosting life, they expect.
But don’t get too excited–new research suggests that most of these super-Earths may never support life because they are permanently encased in hydrogen-rich atmospheres. The findings, released yesterday in the Monthly Notices of the Royal Astronomical Society, show that these super-Earths may actually be mini-Neptunes. Further, these exoplanets will likely never evolve to look like Mercury, Venus, Earth, or Mars–the rocky planets of our inner solar system.
Led by Helmut Lammer of the Austrian Academy of Sciences’s Space Research Institute (IWF), researchers examined how radiation from the stars Kepler-11, Gliese 1214 and 55 Cancri would effect on the upper atmospheres of the super-Earths orbiting too close to their host stars to be in the habitable zone. These super-Earths have sizes and masses that indicate they have rocky interiors surrounded by hydrogen-rich atmospheres–atmospheres that were likely captured early in the planet’s history from the clouds of dust and gas that formed the systems’ nebulae.
Using a model that simulates the dynamic properties of planetary atmospheres, the researchers showed how the extreme ultraviolet light from the host stars heat up the exoplanets’ atmospheres, and as a result, the atmospheres expand several times the radius of each planet, allowing gases to escape. But not fast enough.
“Our results indicate that, although material in the atmosphere of these planets escapes at a high rate, unlike lower mass Earth-like planets many of these super-Earths may not get rid of their nebula-captured hydrogen-rich atmospheres,” Lammer said in a statement.
If their model is correct, its implications spell doom for life on exoplanets further out, in the ‘habitable zone.’ Although temperatures and pressures would allow liquid water to exist, gravity and an inability for their suns to blow off their atmospheres would forever preserve their thick hydrogen-rich atmospheres. Thus, they probably could not sustain life.
Scientists may have to wait until 2017–after the European Space Agency launches the Characterising Exoplanets Satellite (CHEOPS)–before they can learn whether these findings stand the test of time. CHEOPS. Until then, the search for exoplanets with conditions ripe for life has gotten a lot harder.
December 14, 2012
The year 2012 was a major one for science. We saw scientists develop a new type of drug to combat HIV, figure out how to store digital data in DNA—fitting an astonishing 700 terabytes of information into a single gram of it—and even invent a coating for the inside of condiment bottles that could eliminate our stuck-ketchup-headaches once and for all (though, admittedly, this one is a little less groundbreaking than the others). Yet a few milestones in particular—discoveries, technological feats, realizations, and inventions—stand out:
1. The Higgs Boson: The landmark discovery by the European Organisation for Nuclear Research (CERN) of the once-mythical particle might be the most significant scientific discovery of our lifetimes, but it’s also one of the most surprising. Stephen Hawking, the Einstein of our time, famously bet Michigan physicist Gordon Kane $100 that it would never be found.
In an interview with The Atlantic, physicist Lawrence Krauss explained why so many experts had agreed with Hawking, arguing that the existence of the Higgs—a particle (and associated field) that makes certain types of elementary particles behave as though they had mass—was just too convenient, as it was originally posited simply to explain away an apparent difficulty in an otherwise appealing theory in theoretical physics.
The theory seeks to unite all physical forces under the same set of rules. But how can electromagnetic forces–governed by massless photons–fit under the same theoretical umbrella as the weak force, which is governed by bosons with discernible mass that control radioactive decay? Efforts to answer this conundrum gave birth to the Higgs boson. Krauss noted,”It seemed too easy…It seemed to me that introducing an invisible field to explain stuff is more like religion than science…Great, I invented invisible hobgoblins to make things right.”
Incredibly, in this case, it turned out the hobgoblins were real.
2. Earth-Like Planets: 2012 featured a ton of exoplanet discoveries, but the sighting of HD 40307g was without a doubt the most unexpected and exciting. The planet, bigger than earth but not so large as to be a gas giant, seems to orbit in its sun’s “goldilocks zone” (not too hot and not too cold), making it potentially capable of hosting liquid water, considered a prerequisite for life as we know it.
Even better, it’s just 42 light-years away: distant by human standards, but fairly close by compared many of the astronomical objects, making future projects to observe the planet much more feasible.
3. Curiosity Reaches Mars: Okay, the mission itself wasn’t too surprising—it’s been in the works since 2004—but what was so astonishing was the sudden surge of public interest in the rover and in space exploration as a whole. For decades following the manned Apollo missions of the 1960s and 70s, general enthusiasm for space science had slowly ebbed. After Curiosity’s successful landing, though, it surged. Among other things, video of NASA engineers celebrating the feat went viral and the official Curiosity twitter account garnered some 1.2 million followers.
People are so interested in Curiosity‘s exploits, in fact, that even an engineer’s throwaway line about “a discovery for the history books” pumped up expectations so much that we were bound to be disappointed by the actual finding: that early Martian soil samples seem to be representative of what we know of the planet as a whole, and that its chemistry is complex enough to have potentially once supported life. Bigger news might come over the next few years, but as project scientist John Grotzinger said, “Curiosity’s middle name is patience.”
4. Climate Change Is Even Worse Than We Thought: After decades of warnings from scientists that our greenhouse gas emissions will soon wreak havoc with the climate, we’re now starting to see the consequences—and they sure aren’t pretty. As a whole, experts are saying that the even the most frightening climate scenarios have proved to be too conservative in their analysis of how rising carbon dioxide concentrations will alter precipitation patterns, drive ocean acidification, lead to more powerful storms and, in general, make most parts of the planet grow warmer.
One silver lining might be that the public is now starting to acknowledge climate change as a present-day problem, rather than a hypothetical trend that could take effect in the future. Sadly, this has come only after record-breaking heat waves, droughts and the tragic impacts of Hurricane Sandy. Although the most recent international climate talks in Doha accomplished little, there are hopes that this shift in opinion could lead to a long-awaited change in policy sometime soon.
5. A New Way to Desalinate Seawater: With world populations expected to keep growing and potable water projected to grow more scarce over the coming century, a practical and cheap means of desalinating sea water is one of materials science’s holy grails. In July, MIT researchers announced the development of a new method of desalinization using one-atom-thick sheets of graphene, a pure carbon substance. Their method could be far cheaper and less energy-intensive than existing systems—potentially providing a way to solve many of the world’s water problems once and for all.