Never before has a space probe come so close to the pint-sized moon embedded in Saturn’s rings — and when NASA’s Cassini buzzed Pan, the spacecraft revealed what a strange moon it really is.
This is Pan, a 22 mile-wide moon that scoots through Saturn’s rings, orbiting the gas giant once every 13.8 hours. And it’s weird.
Resembling a giant ravioli or some kind of “flying saucer” from a classic alien invasion sci-fi comic, Pan is known as a “shepherd moon” occupying the so-called Encke Gap inside Saturn’s A Ring. This gap is largely free of particles and it has become Pan’s job to hoover up any stray material — the moon’s slight gravity pulls particles onto its surface and scatters others back out into the ring system. This gravitational disturbance creates waves that ripple through the ring material, propagating for hundreds of miles.
On March 7, NASA’s Cassini mission came within 15,268 miles of Pan, revealing incredible detail in the moon’s strange surface. It’s thought that its characteristic equatorial ridge (a trait it shares with another Saturn moon Atlas) is caused by the gradual accumulation of ring material throughout the moon’s formation and with these new observations, scientists will be able to better understand how Pan came to be.
As Cassini rapidly approaches the end of its mission, eventually orbiting through Saturn’s ring plane as a part of its “Grand Finale,” we can expect more of these striking views from orbit before the veteran probe is steered into Saturn’s atmosphere in September, bringing its historic mission to an end.
We always seem to be “overdue” a devastating asteroid impact, but how can we be overdue if asteroids don’t have an impact schedule?
Humans are naturally tuned to seek out patterns in seemingly random events. It’s an evolutionary trait that has helped us become the smart Homo sapiens we are today.
This ability to spot patterns and predict cyclical events continues to dominate our everyday lives. For example, geologists chart seismic activity in hopes of seeing a tell-tail earthquake signal before the “big one” happens; farmers track seasonal cycles in an attempt to predict periods of drought; Wall Street traders use complex numerical models to warn of the next financial crisis (or, indeed, profit from the downturn). Also, astronomers try to find patterns in cosmic occurrences that could pose an existential threat.
We are, of course, talking asteroid impacts — cataclysmic events that have shaped all of the planets in our solar system. Although Earth’s atmosphere is very good at eroding away ancient impact craters, evidence for asteroid impacts in the geological history of our planet is very common. Frankly, it’s perfectly natural to be hit by large asteroids and comets; that’s how planets accrete rocky material, collect water and accumulate organic chemistry for life (on Earth, at least).
But should we get hit by a massive asteroid in the near future, it could be curtains for our civilization. So it sure would be handy if we could somehow use the geologic record of our planet, see how often we get punched, spot a cycle or some kind of pattern, predict then the next impact is likely to happen and — hopefully — plan for the next marauding space rock to make an appearance in our skies! (Whether we’ll be able to do anything about it is an entirely different matter.)
But what could drive periodic asteroid or comet impacts in the first place? One hypothesis claims that the solar system’s “wobble” through the galactic plane may destabilize comets in the Oort Cloud periodically, causing an uptick in massive planetary impacts. Also, the much hyped solar twin, Nemesis, could gravitationally jumble asteroids during its long orbit around the sun. But neither hypothesis stands up to scrutiny and the existence of an extremely dim solar partner is becoming increasingly unlikely.
Regardless, previous studies have suggested that extinction-level impacts (of the magnitude of the one that wiped out, or at least greatly contributed to the extinction of the dinosaurs) occur roughly every 26 million years (the cause of which is open to debate), but researchers from ETH Zurich and Lund University in Sweden now refute this claim.
“We have determined … that asteroids don’t hit the Earth at periodic intervals,” Matthias Meier, of ETH Zurich’s Institute of Geochemistry and Petrology, said in a statement.
After studying precisely-dated impact craters around the world that were formed in the past 500 million years, Meier and Sanna Holm-Alwmark of Lund University dated some 22 craters with dates of impacts known to a precision of one percent.
Then, using a technique known as circular spectral analysis (CSA), they attempted to find the approximate-26 million year period in this set of craters. They found no such period.
Interestingly, Meier and Holm-Alwmark also found that some of the impact craters were of the same age, hinting at a common source. “Some of these craters could have been formed by the collision of an asteroid accompanied by a moon,” said Meier. “But in other cases, the impact sites are too far away from each other for this to be the explanation.”
One interesting example is the apparent close similarity in age of the famous 66 million-year-old, 110 mile-wide Chicxulub Crater in Mexico (that has been linked with the extinction of the dinosaurs) and the 15 mile-wide Boltysh Crater in the Ukraine. As pointed out by the researchers, although a definitive explanation for this coincidence isn’t immediately clear, the two impactors may have originated from a collision in the asteroid belt, sending fragments to Earth, hitting the planet within a very short period of one another.
And it’s these kinds of clustering impacts that the researchers have identified as being potential problems with previous statistical studies — they assumed each impact is distinct, when in fact, they happened at the same time, possibly skewing results and creating a pattern when, in fact, there wasn’t one.
“Our work has shown that just a few of these so-called impact clusters are enough to suggest a semblance of periodicity,” said Meier.
I have little doubt that these new findings will be disputed, spawning more studies pointing to other statistical techniques and a bigger impact crater data set, but it is interesting to think that, as far as extinction-level impact events go, there really may be no pattern to their occurrence.
We know that a doomsday asteroid is out there, and it will hit us, but it has a random impact date that is only known to our planet’s geological future.
Evidence is mounting around the cryovolcanic history of the solar system’s innermost dwarf planet — and its most recent eruptions may have happened within the last four million years.
Since NASA’s Dawn mission arrived at dwarf planet Ceres in 2015, we’ve been treated to some wonderfully detailed images of the small world’s pockmarked terrain. Understanding the underlying processes of what is believed to be an ice-filled celestial body, however, is taking some time to decipher. But with more observations comes more understanding and planetary scientists are getting close to realizing what lies beneath those craters and, possibly, unlocking the secrets behind a very icy and very alien phenomenon we have no experience of in our terrestrial lives.
That phenomenon is cryovolcanoes. And Ceres seems to have them.
The most startling feature on Ceres is Occator Crater. This 57 mile-wide feature is the result of a massive impact tens of millions of years ago. Large craters on small worlds isn’t necessarily a strange thing in our battered solar system, but what is strange about Occator is the very bright feature (and small bright patches surrounding it) in the crater’s center. Even before Dawn arrived in orbit and only fuzzy images of Ceres were available, hopes were high that this bright anomaly in the otherwise gray Cererian landscape could be indicative of ices or some mineral compound that was formed by the presence of water.
Cryovolcanoes — or, simply, ice volcanoes — are hypothetical features that are believed to be common throughout the outer solar system. These ice volcanoes are thought to erupt in a similar fashion to the volcanoes we have on Earth, but instead of molten rock, these volcanoes erupt ice-cold volatiles — like water, methane or ammonia. Dwarf planet Pluto, for example, has features that look like cryovolcanoes, as does Saturn’s moon Titan and Jupiter’s moon Ganymede. These locations are extremely cold and known to contain large quantities of methane and water, so internal heating (caused by radioactive decay or tidal processes) melt the ices and force them to the surface. When they vent through the crust, gases are released and the liquids quickly freeze and sublimate.
Around these vents, cryovolcanoes will grow, and if Ceres really does have its own ice volcanoes, this will be the closest planetary body to the sun (and Earth) known to have them.
Now, in research headed by the Max Planck Institute for Solar System Research (MPS) in Göttingen, Germany, scientists using Dawn data have, for the first time, taken a stab at dating the age of the bright material in the center of Occator Crater and realized that the location has likely been the site of many cryovolcanic eruptions in the recent past.
In the center of Occator, a pit measuring around 7 miles wide can be found, likely formed during the massive impact approximately 30 million years ago. But around the edges of that pit are mountains, some 750 meters high, and in the center is a cracked dome measuring 400 meters high and nearly 2 miles wide. This bright dome is called Cerealia Facula and surrounding it appears to be material that was spewed from a cryovolcanic vent. Analysis has shown that this material contains salts that were formed in the presence of water from Ceres’ interior and then deposited onto the surface. The minerals around Cerealia Facula has been dated to only four million years, meaning that there has been cryovolcanic eruptions long after the Occator impact punctured Ceres’ crust.
“The age and appearance of the material surrounding the bright dome indicate that Cerealia Facula was formed by a recurring, eruptive process, which also hurled material into more outward regions of the central pit,” said Andreas Nathues, lead investigator of Dawn’s Framing Camera. “A single eruptive event is rather unlikely.” As noted in an MPS news release, Jupiter moons Callisto and Ganymede have similar features that are also believed to be related to cryovolcanic eruptions.
“The large impact that tore the giant Occator crater into the surface of the dwarf planet must have originally started everything and triggered the later cryovolcanic activity,” added Nathues.
Previous imagery of haze inside Occator Crater has led to the suspicion that ices remain on the surface today; the haze could be vapor from sublimating water ice exposed on the surface having been forced to the surface from Ceres’ interior. Evidence for this haze has been supported by other studies and appears to vary throughout the day as one would expect — increased sunlight would accelerate sublimation (ice turning from a solid to a vapor without passing through the liquid phase).
If volatiles are still being extruded through this vent today, this would seem to indicate that, in addition to the cryovolcanic eruptions in the last four million years, some form of activity continues to this day. Add this to the recent discovery of organic material on Ceres’ surface, this small world has become a very big asset for planetary science.
For more on Ceres’ icy eruptions, check out one of my last DNews videos:
Around 3.5 billion years ago — when basic life was just gaining a foothold on Earth — the Tharsis region on Mars was swamped with vast floods that scar the landscape to this day.
Mars wears its geological history like a badge of honor — ancient craters remain unchanged for hundreds of millions of years and long-extinct volcanoes look as if they were venting only yesterday. This is the nature of Mars’ thin, cold atmosphere; erosional processes that rapidly delete Earth’s geological history are largely absent on the Red Planet, creating a smorgasbord of features that provide planetary scientists with an open book on Mars’ ancient past.
In this latest observation from the European Mars Express mission, a flood of biblical proportions has been captured in all its glory. But this flood didn’t happen recently, this flood engulfed a vast plain to the north of the famous Valles Marineris region billions of years ago.
It is believed that a series of volcanic eruptions and tectonic upheavals in the Tharsis region caused several massive groundwater releases from Echus Chasma, a collection of valleys some 100 kilometers (62 miles) long and up to 4 kilometers (2.5 miles) deep. These powerful bursts of water carved vast outflow channels into the adjacent Lunae Planum, contributing to the formation of the Kasei Valles outflow channels, releasing water into the vast Chryse Planitia plains which acted as a “sink.” Smaller “dendritic” channels can be seen throughout the plain, indicating that there were likely many episodic bursts of water flooding the region.
In the middle of what was likely a powerful, vast and turbulent flows of water is Worcester Crater that was created before the Tharsis floods and, though its crater rim stands to this day and retains its shape, it was obviously affected by the flow of water, with a “tail” of sediment downstream.
Also of note are smaller “fresh” craters that would have appeared long after the flooding took place, excavating the otherwise smooth outflow channels. These younger craters have tails that seem to be pointed in the opposite direction of the flow of water. These tails weren’t caused by the flow of water, but by the prevailing wind direction.
From orbital observations by our armada of Mars missions, it is well known that these channels contain clays and other minerals associated with the long-term presence of water. Although the Red Planet is now a very dry place, as these beautiful Mars Express images show, this certainly hasn’t always been the case.
If you’re like me, you hang off every news release and new photo from our tenacious Mars rover Curiosity. The awesome one-ton, six-wheeled robot is, after all, exploring a very alien landscape. But if there’s one thing I’ve learned from the mission, Mars is far from being a truly alien place. Sure, we can’t breath the thin frigid air, but we can certainly recognize similar geological processes that we have on Earth, and, most intriguingly, regions that would have once been habitable for life as we know it. This doesn’t mean there was life, just that once upon a time parts of Gale Crater would have been pretty cozy for terrestrial microbes. Personally, I find that notion fascinating.
But, way back in May, I noticed something awry with our beloved rover’s wheels. Curiosity’s beautiful aircraft-grade aluminum wheels were looking rather beaten up. Punctures had appeared. Fearing the worst I reached out to NASA to find out what was going on. After a friendly email exchange with lead rover driver Matt Heverly, I felt a lot more at ease: The damage was predicted; dings, scratches, even holes were expected to appear in the thinnest (0.75 mm thick) aluminum between the treads. On Mars, after all, there is no asphalt. Also, erosion is a slower-paced affair in the thin winds and dry environment — sharp, fractured rocks protrude, embedding themselves into the wheels at every slow turn.
Then, on Friday, in a news update on Curiosity’s progress, JPL scientists mentioned that they would be commanding the rover to drive over a comparatively smooth patch to evaluate the condition of the wheels as their condition is getting worse. But isn’t that to be expected? Apparently not to this degree. “Dents and holes were anticipated, but the amount of wear appears to have accelerated in the past month or so,” said Jim Erickson, project manager for the NASA Mars Science Laboratory at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
So what are we looking at here?
All of the wheels are exhibiting wear and tear, but this particular ‘rip’ in aluminum is by far the most dramatic. But what does that mean for Curiosity? We’ll have to wait and see once JPL engineers have assessed their condition. Although this kind of damage has inevitably been worked into the the structural equations for the wheels’ load-bearing capabilities, whichever way you look at it, damage like this is not good — especially as Curiosity hasn’t even roved three miles yet.
But in the spirit of Mars exploration, Curiosity will soldier on regardless of how rough the red planet treats her.
Read more in my coverage on Discovery News, a location you’ll find me during most daylight (and many nighttime) hours:
“It’s kind of like landing on the moon. It’s a milestone in history. Like all science, it’s exploration. It’s new knowledge.” — Donald Gurnett.
After endless speculation, guesswork and data interpretation over the past year, it’s official: Voyager 1 is now an interstellar mission. It’s the first man-made object to leave the heliopause and enter the interstellar medium. This is history.
It’s always fascinating to see evidence of active geological processes on Mars. And with the help of the armada of robots in orbit and roving the Red Planet, there are plenty of opportunities to see the planet in action.
Take this recent image from the High-Resolution Imaging Science Experiment (HiRISE) camera aboard NASA’s Mars Reconnaissance Orbiter (MRO) for example. In this striking scene — which is a little over one kilometer wide — the bright trails of rocks that have rolled down a sloping crater rim after being dislodged from the top are visible from space. The rocks have obviously bounced on their way, leaving dotted impressions as they rolled. Some have reared in wide arcs, following the topography of the landscape. Others have hit other rocks on their way down, dislodging them, creating secondary cascades of smaller boulders.
“The many boulder tracks in this image all seem to emanate from a small alcove near the rim of the crater,” describes HiRISE Targeting Specialist Nicole Baugh. “They spread out downslope and finally terminate near the crater floor. A high-contrast stretch of the area where the tracks stop shows lots of boulders, some still at the ends of the tracks.”
A rough estimate from the high-resolution imagery suggests some of these Mars boulders are over a meter wide. Future Mars astronauts beware: don’t camp out at the bottom of Martian hills! There’s no vegetation to hold big rocks in place or slow their speed. As previous observations of Mars “avalanches” suggest, weathering through the expansion of water ice (frost action) and/or rapid vaporization of carbon dioxide ice likely trigger pretty extreme downfalls of debris. It would be a bummer to travel all the way to Mars, survive the ravages of solar radiation, a daring descent and landing only to get flattened by a wayward chunk of rock when you set up camp.
I’ve always had a special joy for surveying HiRISE observations; it’s a very privileged window to this alien landscape that, in actuality, has many similar geological processes we find on Earth. And so here we have a collection of boulders that, somehow, became dislodged and stormed down from the rim of a crater. If we saw such an event in person, we might note the unnatural bounce these boulders have in the roughly one-third Earth gravity. But we’d also have to find shelter fast, as just like rolling boulders on Earth, those things will flatten you.
It’s been a looooong time since I last updated Astroengine.com, so first off, apologies for that. But today seems as good a time as any to crank up the ‘engine’s servers as the White House has rubber-stamped a manned NASA mission to an asteroid! However, this isn’t what the President originally had in mind in 2009 when he mandated the US space agency with the task of getting astronauts to an asteroid by the mid-2020’s.
In a twist, it turns out that NASA will be basing their manned asteroid jaunt on a 2011 Keck Institute study. To cut a long story short (you can read the long story in my Discovery News article on the topic: “NASA to Hunt Down and Capture an Asteroid“), NASA will launch an unmanned spacecraft to hunt down a small space rock specimen, “lasso” it (although “bagging” it would be more accurate) and drag the wild asteroid to park it at the Earth-moon Lagrangian point, L2. Then we can treat it like a fast food store; we can fly to and from, chipping off pieces of space rock, return samples to Earth and do, well, SCIENCE!
Overall, this robotic capture/manned exoplration of an asteroid saves cash and “optimizes” the science that can be done. It also lowers the risk associated with a long-duration mission into deep space. By snaring an asteroid in its natural habitat and dragging it back to the Earth-moon system, we avoid astronauts having to spend months in deep space. The EML2 point is only days away.
But when watching the exciting NASA video after the news broke today, I kept thinking…
But that wasn’t the only thing I was thinking. I was also thinking: what’s the point? It’s flashy and patriotic, but where’s the meat?
The human component of this asteroid mission has now been demoted to second fiddle. Sure, it will utilize NASA’s brand new Orion spacecraft and be one of the first launches of the Space Launch System (SLS), but what will it achieve? Astronauts will fly beyond Moon orbit, dock with the stationary space rock and retrieve samples as they please, but why bother with astronauts at all?
It is hoped that the robotic asteroid bagging spacecraft could launch by 2017 and, assuming a few years to steer the asteroid to EML2, a human mission would almost certainly be ready by the mid-2020s. But by that time, sufficiently advanced robotics would be available for unmanned sample retrieval. Heck, as telepresence technology matures, the EML2 point will be well within the scope for a live feed — light-time between Earth and the EML2 point will only be a few seconds, perhaps a little more if communications need to be relayed around the Moon. Robotics could be controlled live by a “virtual astronaut” on Earth — we probably have this capability right now.
The most exciting thing for me is the robotic component of asteroid capture. The advances in asteroid rendezvous and trajectory modification techniques will be cool, although scaling the asteroid bagging technique up (for large asteroids that could actually cause damage should they hit Earth) would be a challenge (to put it mildly). At a push, it may even be of use to a theoretical future asteroid mining industry. The rationale is that if we can understand the composition of a small asteroid, we can hope to learn more about its larger cousins.
The human element seems to be an afterthought and purely a political objective. There will undoubtedly be advancements in life support and docking technologies, but it will only be a mild taster for the far grander (original) NASA plan to send a team of astronauts into deep space to study an asteroid far away from the Earth-Moon system. The argument will be “an asteroid is a stepping stone to Mars” — sadly, by watering down the human element in an already questionable asteroid mission, it’s hard to see the next step for a long-duration spaceflight to Mars.
From this logic, we may as well just keep sending robots. But that wasn’t the point, was it?
UPDATE 1:That whole thing I said in my Al Jazeera English op-ed about being blinkered on the organics explanation for the “big” news on Monday? Well, case in point, as tweeted by @MarsToday on Sunday night, perhaps Curiosity has discovered further evidence for perchlorates on Mars. I have no clue where this information is sourced, and I’m not going to speculate any more, but if perchlorates have been discovered in Gale Crater, it would support the findings of NASA’s 2008 Mars Phoenix lander findings of perchlorate and possible liquid water brine in the arctic regions of the Red Planet. Place your bets…
Over the last bizarre few days, a key NASA scientist (almost) spilled the beans on a “historic” discovery by the Mars Science Laboratory (MSL) rover Curiosity. Then, speculation ran wild. Had NASA’s newest Mars surface mission discovered organics? Feeling the need to stamp out the glowing embers of organic excitement ahead of the Dec. 3 AGU press conference, NASA said that there would be no big announcement on Monday. But then the agency went even further, issuing a terse statement to point out that the speculation is wrong. “At this point in the mission, the instruments on the rover have not detected any definitive evidence of Martian organics,” said NASA.
So now we’re left, understandably, wondering what lead MSL scientist John Grotzinger was referring to. I think it’s safe to assume that he wasn’t misquoted by the NPR journalist who happened to be sitting in his office when the MSL team was receiving data from the mission’s Sample Analysis at Mars (SAM) instrument. And if we take NASA’s damage-controlling statements at face value, Grotzinger was just getting excited for all the data being received from the rover — after all, the entire mission is historic.
As a science media guy with a background in science, I totally ‘get’ what the MSL team are going through. Scientists are only human and whether or not Grotzinger was getting excited for a specific “historic” find or just getting generally excited for all the “historic” data streaming from the rover, is irrelevant. Perhaps he should have been more careful as to the language he used when having an NPR reporter sitting in the same room as him, but that’s academic, I’m pretty sure that if I was leading the most awesome Mars mission in the history of Mars missions I’d be brimming over with excitement too. The scientific process is long and can often seem labored and secretive to the media and public — rumors or a few slipped words from scientists is often all that’s needed to spawn the hype. But for the scientific process to see its course, data needs to be analyzed, re-analyzed and theories need to be formulated. In an announcement as important as “organics on Mars,” the science needs to be watertight.
However, I can’t help but feel that, in NASA’s enthusiasm to “keep the lid” on speculation, that they are setting themselves up for a backlash on Monday.
If the AGU press conference is just “an update about first use of the rover’s full array of analytical instruments to investigate a drift of sandy soil,” as the NASA statement says, won’t there be any mention of organics? Will this be a similar announcement to the sampling of Mars air in the search for methane? The upshot of that Nov. 2 press conference was that the Mars air had been tested by SAM and no methane (within experimental limits) had been discovered… yet. But this was a sideline to the announcement of some incredible science as to the evolution of the Martian atmosphere.
This time, although there may not be “definitive,” absolute, watertight proof of organics, might mission scientists announce the detection of something that appears to be organics… “but more work is needed”? It’s a Catch 22: It’s not the “historic” news as the experiment is ongoing pending a rock-solid conclusion; yet it IS “historic” as the mere hint of a detection would bolster the organics experiments of the Viking landers in the 1970s and could hint at the discovery of another piece of the “Mars life puzzle.” And besides, everything Curiosity does is “historic.”
In NASA’s haste to damper speculation, have they cornered themselves into not making any big announcements on Monday? Or have they only added to the speculation, bolstering the media’s attention? Besides, I get the feeling that the media will see any announcement as a “big” announcement regardless of NASA scientists’ intent. Either way, it’s a shame that the hype may distract from the incredible science the MSL team are carrying out every single day.
Meanwhile, in deep space, a little probe launched 35 years ago is edging into the interstellar medium and NASA’s Voyager Program team are also holding an AGU press conference on Monday. Although there have been no NPR journalists getting the scoop from mission scientists, it’s worth keeping in mind that Voyager 1 really is about to make history. In October, I reported that the particle detectors aboard the aging spacecraft detected something weird in the outermost reaches of the Solar System. As Voyager 1 ventures deep into the heliosheith — the outermost component of the heliosphere (the Sun’s sphere of influence) — it detected inexplicable high-energy particles. The theory is that these particles are being accelerated by the magnetic mess that is the outermost reaches of the Solar System. But there is growing evidence in particle detections and magnetometer readings that the probe may have just left the Solar System, completely escaping the heliosphere.
A big hint is in the following graphs of data streaming from Voyager 1. The first plot shows the increase in high-energy cosmic ray particle counts. These high-energy particles typically originate from beyond the heliosphere. The bottom plot shows lower-energy particles that originate from the solar wind. Note how the lower-energy particle counts fell off a cliff this summer, and how the high-energy particles have seen a marked increase at around the same period:
So, in light of the media-centric Curiosity debate over what is “historic” and what’s not “historic” enough to be announced at conferences, I’m getting increasingly excited for what the Voyager team have got to say tomorrow. It’s inevitable that Voyager 1 will leave the Solar System, but will NASA call it at the AGU? Who knows, but that would be historic, just without the hype.
There’s no better method to understand how something works than to build it yourself. Although computer simulations can help you avoid blowing up a city block when trying to understand the physics behind a supernova, it’s sometimes just nice to physically model space phenomena in the lab.
So, two Caltech researchers have done just that in an attempt to understand a beautifully elegant, yet frightfully violent, solar phenomenon: coronal loops. These loops of magnetism and plasma dominate the lower corona and are particularly visible during periods of intense solar activity (like, now). Although they may look nice and decorative from a distance, these loops are wonderfully dynamic and are often the sites of some of the most energetic eruptions in our Solar System. Coronal loops spawn solar flares and solar flares can really mess with our hi-tech civilization.
In an attempt to understand the large-scale dynamics of a coronal loop, Paul Bellan, professor of applied physics at Caltech, and graduate student Eve Stenson built a dinky “coronal loop” of their own (pictured top). Inside a vacuum chamber, the duo hooked up an electromagnet (to create the magnetic “loop”) and then injected hydrogen and nitrogen gas into the two “footpoints” of the loop. Then, they zapped the whole thing with a high-voltage current and voila! a plasma loop — a coronal loop analog — was born.
Although coronal loops on the sun can last hours or even days, this lab-made plasma loop lasted a fraction of a second. But by using a high-speed camera and color filters, the researchers were able to observe the rapid expansion of the magnetic loop and watch the plasma race from one footpoint to the other. Interestingly, the two types of plasma flowed in opposite directions, passing through each other.
The simulation was over in a flash, but they were able to deduce some of the physics behind their plasma loop: “One force expands the arch radius and so lengthens the loop while the other continuously injects plasma from both ends into the loop,” Bellan explained. “This latter force injects just the right amount of plasma to keep the density in the loop constant as it lengthens.” It is hoped that experiments like these will ultimately aid the development of space weather models — after all, it would be useful if we could deduce which coronal loops are ripe to erupt while others live out a quiescent existence.
It’s practical experiments like these that excite me. During my PhD research, my research group simulated steady-state coronal loops in the hope of explaining some of the characteristics of these fascinating solar structures. Of particular interest was to understand how magnetohydrodynamic waves interact with the plasma contained within the huge loops of magnetism. But all my research was based on lines of code to simulate our best ideas on the physical mechanisms at work inside these loops. Although modelling space phenomena is a critical component of science, it’s nice to compare results with experiments that aim to create analogs of large-scale phenomena.
The next test for Bellan and Stenson is to create two plasma loops inside their vacuum chamber to see how they interact. It would be awesome to see if they can initiate reconnection between the loops to see how the plasma contained within reacts. That is, after all, the fundamental trigger of explosive events on the Sun.