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3 days ago
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Dust devils on Mars leave 'fingerprints' that can guide future Red Planet missions
When you buy through links on our articles, Future and its syndication partners may earn a commission. Martian dust devils are fleeting, but the footprints they leave behind can endure for months. Now, researchers have used those tracks to learn about the whirlwinds and potentially guide future mission planning. As wind swirls across the landscape on both Mars and Earth, it sweeps up ground particles that reveal the dry columns. The whirlwinds dance across the landscape, leaving a path revealed by excavated particles. On the active surface of Earth, such paths are hard to spot. But on the nearly inactive surface of Mars, they can remain for months, long after the devils' minutes-long lifetimes. "Dust devils themselves are difficult to capture in images because they are so short-lived," Ingrid Daubar, a planetary scientist at Brown University and lead author of the study, told by email. "The tracks they leave behind last longer, so we are able to observe them more thoroughly." Dusting off the fingerprints On warm, windy days in Earth's deserts, vortices of sand and debris can form suddenly and move unpredictably. (This author distinctly recalls being "chased" by one such devil in the Mojave Desert as a child in 1990.) Similar conditions on Mars can also produce dust devils. But the whirls on the Red Planet tend to be both wider and taller than their counterparts on Earth, and scientists aren't sure why. Questions like these led Dauber and her colleagues to study images from the High Resolution Imaging Science Experiment (HiRISE) on NASA's Mars Reconnaissance Orbiter — the highest-resolution photos of the planet snapped from space. HiRISE can capture features as small as 3 feet (1 meter). But its detailed perspective comes at a price: Its images cover only a small percentage of the Martian surface and are taken by request, though most latitudes and longitudes are well sampled. Dauber's team studied 21,475 HiRISE images taken between January 2014 and April 2018 — roughly a quarter of the snapshots captured by the instrument as of autumn 2024. Tracks appear in only 798 of those, or just under 4%. Dust devil tracks (DDTs) suggest dust devils are more common at high northern and southern latitudes and are especially active in each hemisphere's summer, peaking in the southern hemisphere's summer. According to the researchers, Mars' significant orbital eccentricity, or deviation from a perfect circle, causes the atmosphere in the southern summer to circulate more energetically, creating conditions ideal for vortex formation. That, combined with less dust accumulation in the North, makes the southern hemisphere summer an almost perfect storm for dust devils. The observations reflect peak DDT preservation more than dust devil formation, the researchers cautioned, but the culmination coincides with the peak observed by NASA's Spirit rover at Gusev crater, along with global observations of the sand spouts. The researchers also realized that DDTs most commonly form and are preserved in regions of mixed sand, rocks and bedrock, with little bright dust, the most common surface type identified on Mars. Bright dust scooped up from the surface leaves behind trails that are dark from the underlying landscape. "The material on the ground is critical to the formation of the DDTs," Dauber said. Dusty missions The first Martian dust devil tracks appeared in images sent back from NASA's Mariner 9 mission in 1972 (although they weren't discovered until the images were analyzed in 2014). But it wasn't until 1998, when higher-resolution images were captured by Mars Global Surveyor, that the tracks could be seriously analyzed. RELATED STORIES —Dust devils on Mars may spark lightning — possibly threatening NASA's Perseverance rover —NASA's Perseverance rover watches as 2 Mars dust devils merge into 1 (video) —Perseverance Mars rover figures out how devils and winds fill the Red Planet's skies with dust Dust has hindered past ground missions. Mars rovers take their energy from the sun via solar panels. Over time, dust builds up on the panels, limiting their efficacy. The blockage has shuttered missions like NASA's Opportunity rover, which explored the surface for 14.5 years. NASA's InSight lander also succumbed to a dust-related death after four years. The high winds that birth dust devils can also revitalize robots, however. Opportunity's twin, Spirit, got a second lease on life after a Martian whirlwind cleaned its solar arrays back in 2005. Understanding where dust devils are most active can help in the selection of landing sites for future missions. High-latitude bands where DDTs and their progenitors occur more frequently could help to scour solar panels and thus enable a more enduring exploration. "It depends on the mission — every mission is unique," Daubar said. There are many requirements for landing sites and exploration, including regions that will allow for a safe touchdown, alongside complex scientific goals. "It could be that there are only a few places where the specific science goals can be achieved, and then perhaps this could be a deciding factor between those sites," she said. A new study of dust devils on Mars was published in May 2025 in the journal Geophysical Research Letters. Solve the daily Crossword
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3 days ago
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Largest known Martian meteorite on Earth sells for $5.3 million at auction
When you buy through links on our articles, Future and its syndication partners may earn a commission. The largest known Martian meteorite has just been sold at auction for $5.29 million, selling well over the asking price of $2 million to $4 million. The hefty chunk of the Red Planet could help us learn more about our cosmic neighbor — if it's allowed to be properly studied. The meteorite, dubbed Northwest Africa (NWA) 16788, is around twice the size of a basketball and weighs 54 pounds (24.5 kilograms), making it "the largest known piece of Mars ever found on Earth," according to Sotheby's — the auction house responsible for selling the space rock. It is around 70% larger than the previous largest known Martian meteorite, and is described as having a "deep red hue" and a "glassy crust," according to Sotheby's. An anonymous meteorite hunter recovered NWA 16788 from part of the Sahara desert in Niger in November 2023. The space rock was known to scientists before now but has not been studied in detail, meaning it is currently unclear how old the space rock is, according to a 2024 study. "NWA 16788 is a geological time capsule from another world," Sotheby's representatives wrote. "With fewer than 400 Martian meteorites ever recorded, and most no larger than a pebble, this specimen offers the biggest tangible connection to a planet that has captivated humanity for centuries." Related: 32 things on Mars that look like they shouldn't be there The meteorite was sold at a natural history-themed auction held at Sotheby's New York auction house on Wednesday (July 16), along with more than 100 other lots, which included dinosaur fossils, megalodon teeth, Neanderthal tools, rare minerals, a piece of "fossilized lightning" and several other meteorites. Sold at the same auction was the mounted skeleton of a juvenile ceratosaurus, a theropod dinosaur that lived during the late Jurassic period. The skeleton sold for $30.5 million, making it the third most-expensive dinosaur fossil ever sold at auction. The most expensive fossil ever sold was a stegosaurus skeleton named "Apex," which sold for $44.6 million in July 2024. What can we learn from Martian meteorites? Martian meteorites are chunks of the Red Planet that were ejected into space as asteroids and comets smashed into the alien world. Most of these fragments have likely drifted in space for millions, if not billions, of years before eventually falling to Earth. While several Mars rovers have examined rocks on the Red Planet, these robots haven't returned any to Earth so far, and this is unlikely to change due to NASA's recent cancellation of the Mars Sample Return mission, meaning meteorites like NWA 16788 are currently the only way of directly studying Mars' origins on Earth. (A planned Chinese mission could bring Mars samples back to Earth no sooner than 2031.) Martian meteorites on Earth have already led to multiple discoveries: For example, in 2023, researchers discovered a "huge diversity" of organic compounds hiding in a rock that was recovered from Morocco; and in 2024, experts uncovered evidence of ancient water on Mars in a rediscovered meteorite found in a university collection. RELATED STORIES —Single enormous object left 2 billion craters on Mars, scientists discover —A Martian meteorite is going home, in NASA's Perseverance mission launch —Massive Martian meteor impact was largest ever recorded in solar system Researchers have also traced back the likely origins of more than 200 Martian meteorites and found that they can be linked to just five different impact sites on Mars, hinting that the space rocks can be used to study specific Mars locations. Whether or not researchers can learn more about the Red Planet from NWA 16788 depends on whether its new owner allows it to be studied by scientists. Solve the daily Crossword
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3 days ago
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If aliens existed on Mars 3.7 billion years ago, they would have needed umbrellas
When you buy through links on our articles, Future and its syndication partners may earn a commission. Mars was a rainier, wetter place than planetary scientists previously thought, according to a new study of ancient, inverted river channels that span more than 9,000 miles (14,484 kilometers) in the Red Planet's southern Noachis Terra region. "Our work is a new piece of evidence that suggests that Mars was once a much more complex and active planet than it is now, which is such an exciting thing to be involved in," study leader Adam Losekoot of the U.K.'s Open University said in a statement. We've known Mars was once a wet planet ever since the Mariner 9 orbiter mission from the '70s photographed a surface covered in dried-up river channels. These channels were dated back to over 3.5 billion years ago. However, channels cut into the ground are not the only evidence for running water on Mars. When that water ran-off, or evaporated, it left sedimentary deposits. Sometimes we see these in craters that were once lakes filled with water: NASA's Curiosity rover is exploring Gale Crater, which has a central three-mile-tall (five-kilometer-tall) peak covered in sediment. Other times, these sediments were laid down on river beds. Over the eons, the sediments would have hardened, while the river channels and the land around them would have weathered and eroded away. That left the sediments, which are more resistant to erosion, sticking out as tall ridges. Geologists today call them fluvial sinuous ridges, or, more plainly, inverted channels. Now, Losekoot, who is a Ph.D. student, has led the discovery of a vast network of these channels in Noachis Terra based on images and data taken by the High Resolution Imaging Science Experiment (HiRISE) camera and the Context Camera on NASA's Mars Reconnaissance Orbiter, and the Mars Orbiter Laser Altimeter (MOLA) on the defunct Mars Global Surveyor mission. Previously, Noachis Terra had not been given due attention because it lacked the more classical river channels that form more obvious evidence of water. However, by mapping the network of inverted channels, Losekoot realized there was lots of evidence there had once been plentiful water in the region. "Studying Mars, particularly an under-explored region like Noachis Terra, is really exciting because it's an environment which has been largely unchanged for billions of years," said Losekoot. "It's a time capsule that records fundamental geological processes in a way that just isn't possible here on Earth." Some of the inverted channels appear as isolated segments that have survived the elements for billions of years. Others are more intact, forming systems that run for hundreds of miles and stand tens of yards tall. Such a widespread network of inverted channels does not suggest these channels were caused by flash floods, argues Losekoot. Rather, they seem to have formed in stable climatic conditions over a geologically significant period of time during the Noachian–Hesperian transition, which was the shift from one geological era into the next around 3.7 billion years ago. What's particularly intriguing is the most likely source of water to have formed these inverted channels is precipitation — be it rain, hail or snow. Indeed, given the size of the inverted channel network in Noachis Terra, this region of Mars may have experienced lots of rainy days in a warm and wet climate. RELATED STORIES — Carbon dioxide rivers? Ancient Mars liquid may not all have been water — Good news for life: Mars rivers flowed for long stretches long ago — Mars Had Big Rivers for Billions of Years It's more evidence that Mars was once more like Earth than the cold and barren desert it is today. Losekoot presented his findings at the Royal Astronomical Society's National Astronomy Meeting held at the University of Durham in the U.K., which ran between July 7 and July 11. Solve the daily Crossword
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5 days ago
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Happy anniversary, Mariner 4! NASA probe got 1st-ever up-close look at Mars 60 years ago today
When you buy through links on our articles, Future and its syndication partners may earn a commission. "That Mars is habitable by beings of some sort or other is as certain as it is uncertain what these beings may be," wrote Percival Lowell in the early 20th century. While the theories of this well-heeled amateur astronomer might seem fanciful when viewed from 2025, given what was known at the time, a large percentage of the public found Lowell's theories about an inhabited Mars not just credible, but likely. Lowell went so far as to theorize that the planet was straddled by canals, designed and executed by hyper-intelligent beings, that would carry water from the poles to the equator of the apparently arid planet. While other astronomers had their doubts, popular notions of Mars as a colder and drier near-twin of Earth persisted for almost a half century longer, well into the 1960s. In 1953, Wernher von Braun, who would go on to design NASA's giant Saturn V moon rocket, wrote a seminal work called "The Mars Project,' the first comprehensive look at how to send people to the Red Planet. The centerpiece was a number of huge, winged gliders that would land astronauts on Mars by navigating what was then thought to be an atmosphere perhaps half the density of Earth's. More generally, contemporary maps of Mars were still based on observations from telescopes like Lowell's 24-inch refractor up to Mount Palomar's 200-inch giant reflector. But even that latter monster showed only a shimmering red blob of a planet with shifting, indistinct imagery. In short, in the mid-20th century, our understanding of Mars was still as much intuition and imagination as fact. That all changed 60 years ago on July 14, 1965, when a small spacecraft sped by the planet at a distance of just 6,118 miles (9,846 kilometers). After the 22 low-resolution TV images made it back to Earth, the Martian empire dreamed of by Lowell and fiction authors like Edgar Rice Burroughs were smashed into red dust. Some of NASA's earliest planetary missions, Mariners 3 and 4 were planned and executed by a group of pioneering scientists at the California Institute of Technology (Caltech) and its associated NASA field center, the Jet Propulsion Laboratory (JPL). NASA was a brand-new agency when the planning for the first Mars flyby was begun a few years earlier, but the core science team had been working together at Caltech for years, and included one of the newest additions to the geology faculty — Bruce Murray, who would later become the fifth director of JPL. Other Caltech professors on the Mariner Mars team were Robert Sharp and Gerry Neugebauer, professors of geology, and Robert Leighton and Victor Neher, both professors of physics. Despite the impressive intellect brought to bear, the project was, by today's standards, a plunge into the unknown. The combined Caltech and JPL team had little spaceflight experience to guide them. There had been just one successful flight beyond lunar orbit — Mariner 2's dash past Venus in 1962 — to build upon. There was no Deep Space Network to track and command the spacecraft, and navigating to Venus was less challenging than the voyage to Mars, which was almost twice as long — some 325 million miles (523 million km). And while the Mariner design was ultimately quite successful, at the time, flying machines in the harsh environment of space was in its infancy. Most failed to achieve their goals. Incredibly, the probe was originally designed, like the Venus-bound Mariner 2 that had recently returned copious "squiggly-line' data from that planet, without a camera. Leighton took exception to this, realizing that a lot of valuable data would be gleaned from visual imagery. He had a long history in optical astronomy and was not about to pass up this opportunity to get a close look at Mars. He also understood a more human side of the mission: Images of the planet could forge a powerful connection between planetary science and the public. Mariner 4 had a twin, Mariner 3, which launched on Nov. 5, 1964. The Atlas rocket that boosted it clear of the atmosphere functioned perfectly (not always the case, given its high failure rate in that era), but the fairing in which Mariner 3 rode became snagged, and the spacecraft, unable to collect sunlight on its solar panels, died within hours, drifting into a heliocentric orbit. After a hurried fix, Mariner 4 launched three weeks later on Nov. 28 with a redesigned fairing. The probe deployed as planned and began the long journey to Mars. But there was more drama in store: The primitive guidance system, oriented by a photocell device that was intended to acquire and track the bright star Canopus, became confused — both by other stars of similar brightness and also by a cloud of dust and paint flecks ejected when the spacecraft deployed. Ultimately, the tracker was able to find Canopus and the journey continued without incident. This star-tracking technology, along with an instrument-laden scan platform and various other design features, was central to planetary missions for decades. Just over seven months later, Mars was in the crosshairs. On July 14, 1965, Mariner's science instruments were activated. These included a magnetometer to measure magnetic fields, a Geiger counter to measure radiation, a cosmic-ray telescope, a cosmic dust detector, and the television camera. This last device had caused no end of consternation. At the time, TV cameras used fragile glass tubes and, with their associated electronics, were slightly smaller than dishwashers. Space-capable TV imagers were not available, and few people had thought to even try designing one. Leighton's team spent countless hours coming up with a low-resolution, slow-scan Vidicon tube — a glass vacuum tube aimed through a toughened telescope — that could withstand the violence of launch and the harsh temperature variations in space. Just a few hours after the science package was put to work, the TV camera began acquiring images. About nine hours later, with the spacecraft heading away from Mars, the on-board tape recorder, which had stored the data from the primitive camera, initiated playback and transmitted the raw images to Earth. And what images they were. The first views arrived at JPL shortly after midnight on July 15. These were initially represented by numeric printouts that had to be interpreted into black-and-white images, but the imaging team was impatient. They cut the numbered paper into strips, pasted them onto a backboard, and played "paint by numbers" with grease markers to create an eerily accurate first look. Once the computer-processed photographs arrived, though they were soft and indistinct, and spectroscopic and other measurements were still inexact, the combined data turned our notions about the true nature of the Red Planet on their head. Within hours, Mars had descended from Lowell's fever dreams to cold, harsh reality. Quick calculations told the story — Mars was a frigid, desert world, and those who still held to Lowell's dreams of a possible Martian empire had to concede defeat. The planet was a moon-like desert, a place of intense cratering and wide empty plains. The final blow came shortly after the flyby, when Mariner directed its radio signal through the limb of the Martian atmosphere. The atmospheric density was found to be about 1/1000th that of Earth. For the dreamers, Mars died on that day in 1965. Related Stories: — Mariner 4: NASA's 1st successful Mars mission — Mars: Everything you need to know about the Red Planet — Mars missions: A brief history But for the gathered Caltech team savoring the fuzzy pictures from Mariner 4's sprint, this was a victory. After the discovery of Venus' true nature, when a planet thought to be a swampy, humid world was revealed as a hellish place of intense pressure and searing temperatures, Mars seemed almost welcoming. And the inclusion of a TV camera on the mission added a human touch that transcended the numbers, bringing the fourth planet into living rooms worldwide. When discussing the mission a few years later, Leighton related one touching letter he received from, of all people, a milkman. It read, "I'm not very close to your world, but I really appreciate what you are doing. Keep it going." A soft-spoken Leighton said of the sentiment, "A letter from a milkman… I thought that was kind of nice." After its voyage past Mars, Mariner 4 maintained intermittent communication with JPL and returned data about the interplanetary environment for two more years. But by the end of 1967, the spacecraft had suffered close to 100 micrometeoroid impacts and was out of fuel. The mission was officially ended on Dec. 21. Since then, a multitude of spacecraft have rocketed Marsward from a variety of nations. The path to Mars is still challenging, and the U.S. leads in successes. From the Viking Mars orbiters and landers of the 1970s through the Curiosity and Perseverance rovers, which are still operating today, the Red Planet has crept from the dreadful waste seen by Mariner 4 to a place once covered in shallow oceans and with a possibly temperate atmosphere. And while we have never found any signs of Percival Lowell's high-society Martians, we may soon live in their stead.
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11-07-2025
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Water on Mars Probably Doesn't Explain These Weird Streaks
For years, scientists have been looking for signs of liquid water just beneath the surface of Mars. The problem, though, is that the observations from various orbiting probes have been maddeningly ambiguous, sparking a lot of debate. New research recently published in Nature Communications may have dried up one of the most intriguing lines of evidence for subsurface water: it found that long streaks of material on the sides of slopes and crater walls is likely not from seeping liquid but from disturbed dry dust. Does it even make sense to look for liquid water anywhere on Mars? When we look to Mars today, we see a desiccated, frozen world. No liquid water exists aboveground, and what water we do find is frozen solid, mostly at the poles. [Sign up for Today in Science, a free daily newsletter] There's tantalizing evidence of liquid water in the Red Planet's distant past, however. Scientists have spied the sinuous courses of long-lost rivers, as well as the ancient shorelines of vanished lakes and seas carved in the world's rocks, and minerals formed in aqueous environments are relatively commonplace on the surface. That wet phase of Martian history was billions of years ago, however, and all that water has since evaporated away into space or seeped deep underground. But here and there on modern-day Mars, we still see what might be evidence for liquid water lurking just beneath the Martian surface. One of the most perplexing hints of hydration are a handful of slope streaks: narrow, long and sometimes bright but usually dark features that are commonly located near the tops of crater walls and scarps. Many are straight, and some wind a bit, but they do very much look like what you'd expect if water leaked out from behind the slope and caused a small flow downhill. These streaks were first discovered in Viking data from the 1970s. The images were low-resolution and fuzzy by today's standards, but the advent of more advanced orbiters provided sharper views of these features. The streaks tend to be only a few dozen to a couple of hundred meters wide, but they can be a kilometer long. They're seen in dusty equatorial regions and relatively persistent: once formed, they fade over years and decades. In the late 2000s similar markings were discovered. Called recurring slope lineae (or RSLs), they look much like slope streaks but are usually found in rocky southern areas. They tend to fade over the course of a Martian year (which is about twice as long as our Earthly year) and recur annually in the same spots during summer in Mars's southern hemisphere. RSLs are narrower than slope streaks, only a few meters wide, but also look very much like flow features. Is this evidence of liquid water on Mars today? I remember, when these were first found, watching an associated NASA press conference and speculating with some colleagues that these could be from water frozen all winter but thawed by the spring and summer sun sending cascades of material downslope. It's cold on Mars, well below water's standard freezing point, but if the water were briny, it might stay liquid even in those frigid temperatures. (Salts are nature's antifreeze.) And we do have plenty of evidence for water ice frozen just beneath the surface in many locations on Mars, even down to midlatitudes. If RSLs really are triggered by water, they could be the best places to search for extant Martian life (and potential oases for any future human explorers as well). That's exciting! But is it true? A problem with previous studies was the lack of a consistent, global database of streaks to investigate. To alleviate that issue, the authors of the new study examined more than 86,000 images from the Context Camera aboard NASA's Mars Reconnaissance Orbiter. This instrument takes images of the Red Planet's surface in long swaths about 30 kilometers wide. In the new study, the researchers used a machine-learning algorithm to find streaks in the images. The algorithm identified about half a million streaks: roughly 13,000 bright and 484,000 dark. After accounting for streaks missed by the algorithm and other factors such as branching or overlapping streaks, the scientists estimate there could be as many as 140,000 bright and nearly two million dark streaks in the dataset. This is the first global, consistent database of Martian streaks, inviting deeper—and easier—analysis. Next, the authors cross-referenced their streak database to others that instead track things such as temperature, wind and hydration across the surface of Mars. What they found supports a dry formation for RSLs and slope streaks alike. For example, if the slope streaks are caused by sunlight-warmed water ice, you'd expect to find them forming overwhelmingly in slopes that face the sun. The researchers found only a weak tie to sunward-facing slopes, however. Another water-based expectation would be to find streaks where the temperature fluctuations are high, but instead they're typically found in locations where temperatures are relatively stable. And although Mars isn't exactly humid, there is some water vapor in the air, so streaks formed by wet cascades should occur mostly in slopes with higher humidity. But the study found them mostly in drier areas instead. Interestingly, the more ephemeral RSLs do tend to favor sunward-facing slopes but, like the more longer-lived streaks, aren't found in areas with high temperature fluctuations or levels of humidity, again implying they aren't caused by water. The scientists did find high correlations of slope streaks with regions that have higher wind speeds and lots of dust deposition—Mars is largely covered with a very fine-grained dust that's high in iron oxide (rust), giving it its characteristic ochre coloring. These results point more toward a dry origin for the streaks. They are also found streaks near younger craters, where the ground is more disturbed and can trigger dust flows more easily. For instance, the researchers cataloged some streaks next to a fresh 140-meter crater that formed when a relatively small meteorite hit the surface of Mars just a few years ago. That location has steep slopes and quite a bit of dust; other craters with flatter slopes and less dust exhibit fewer streaks. Interestingly, some fossae (Latin for 'trenches'), locations where there may be ongoing underground volcanic activity, had streaks. The scientists didn't find a correlation with marsquake activity, but in their paper they note that the data there are limited because of a lack of long-term seismometers on the planet. Still, this implies streaks may be caused when a sharp energetic event happens on or near the surface, such as a quake or an impact that dislodges dust that then cascades down slopes. While all this isn't necessarily conclusive, a dry origin for the streaks does currently seem like the better bet. While that's disappointing from the standpoint of looking for native life or supporting our own when we visit, it's still an interesting result. The total estimated annual flux of dust from slope streaks suggests that they may move an amount of material equivalent to several global dust storms on Mars per year! (Actual global dust storms occur every few years on Mars.) These streaks are important geological features of the planet—and we should understand more about them before setting up shop there. As for life on Mars, whether extant or eons dead, we'll keep looking. Mars is dry now, but it was very likely once very wet, so hope springs eternal.
