Ever since it landed on the Red Planet in 2012, the Curiosity rover has showed no signs of slowing down! For the past six years, it has ventured across the Gale Crater, scaled Mount Sharp, and taken numerous drill samples. And in the process, it has found evidence that liquid water (and possibly even life) once existed on the Martian surface.
It has also taken many breathtaking pictures that have catalogued its progress. Last month (on Aug. 9th), the rover took another 360-degree panoramic photo of its location. In addition to showing how the skies were still darkened by the fading dust storm and the rover’s dust-covered body, the picture also captured and the site where the latest drill sample was obtained.
Martian dust storms are a pretty common occurrence, and generally happen whenever the southern hemisphere is experiencing summer. Though they can begin quite suddenly, these storms typically stay contained to a local area and last only about a few weeks. However, on occasion, Martian dust storms can grow to become global phenomena, covering the entire planet.
One such storm began back in May, starting in the Arabia Terra region and then spreading to become a planet-wide dust storm within a matter of weeks. This storm caused the skies over the Perseverance Valley, where the Opportunity rover is stationed, to become darkened, forcing the rover into hibernation mode. And while no word has been heard from the rover, NASA recently indicated that the dust storm will dissipate in a matter of weeks.
The update was posted by NASA’s Mars Exploration Program, which oversees operations for the Opportunity and Curiosity rovers, as well as NASA’s three Mars orbiters (Mars Odyssey, MRO, and MAVEN) and the Insight lander (which will land on Mars in 109 days). According to NASA, the storm is beginning to end, though it may be weeks or months before the skies are clear enough for Opportunity to exit its hibernation mode.
As noted, dust storms occur on Mars when the southern hemisphere experiences summer, which coincides with the planet being closer to the Sun in its elliptical orbit. Due to increased temperatures, dust particles are lifted higher into the atmosphere, creating more wind. The resulting wind kicks up yet more dust, creating a feedback loop that NASA scientists are still trying to understand.
Since the southern polar region is pointed towards the Sun in the summer, carbon dioxide frozen in the polar cap evaporates. This has the effect of thickening the atmosphere and increasing the surface pressure, which enhances the process by helping suspend dust particles in the air. In some cases, the dust clouds can reach up to 60 km (40 mi) or more in elevation.
Planet-wide dust storms are a relatively rare occurrence on Mars, taking place every three to four Martian years (the equivalent of approximately 6 to 8 Earth years). Such storms have been viewed many times in the past by missions like Mariner 9 (1971), Viking I (1971) and the Mars Global Surveyor (2001). In 2007, a similar storm took place that darkened the skies over where Opportunity was stationed – which led to two weeks of minimal operations and no communications.
While smaller and less intense the storm that took place back in 2007, the current storm intensified to the point where it led to a level of atmospheric opacity that is much worse than the 2007 storm. In effect, the amount of dust in the atmosphere created a state of perpetual night over the rover’s location in Perseverance Valley, which forced the rover’s science team to suspend operations.
This is due to the fact that Opportunity – unlike the Curiosity rover, which runs on nuclear-powered battery – relies on solar panels to keep its batteries charged. But beyond suspending operations, the prolonged dust storm also means that the rover might not be to keep its energy-intensive survival heaters running – which protect its batteries from the extreme cold of Mars’ atmosphere.
Luckily, NASA scientists who have been observing the global event indicated that, as of last Monday (July 23rd), more dust was falling out of the planet’s thin air than was being raised into it. This means that the global weather event has reached its decay phase, where dust-raising events either become confined to smaller areas or stop altogether.
Using its Mars Color Imager (MARCI) and Mars Climate Sounder (MCS), NASA’s Mars Reconnaissance Orbiter (MRO) also noted surface features were beginning to reappear and that temperatures in the middle atmosphere were no longer rising – which indicates less solar heating by dust. The Curiosity rover also noted a decline in dust above its position in the Gale Crater on the other side of the planet.
This is certainly good new for the Opportunity rover, though scientists expect that it will still be a few weeks or months before its solar panels can draw power again and communications can be reestablished. The last time communications took place with the rover was on June 10th, but if there’s one thing the Opportunity rover is known for, it’s endurance!
When the rover first landed on Mars on January 25th, 2004, its mission was only expected to last ninety Martian days (sols), which is the equivalent of about 92.5 Earth days. However, as of the writing of this article, the rover has endured for 14 years and 195 days, effectively exceeding its operational lifespan 55 times over. So if any rover can survive this enduring dust storm, its Opportunity!
In the meantime, multiple NASA missions are actively monitoring the storm in support of Opportunity and to learn more about the mechanics of Martian storms. By learning more about what causes these storms, and how smaller ones can merge to form global events, future robotic missions, crewed missions and (quite possibly) Martian colonists will be better prepared to deal with them.
The weather patterns on Mars are rather fascinating, owing to their particular similarities and differences with those of Earth. For one, the Red Planet experiences dust storms that are not dissimilar to storms that happen regularly here on Earth. Due to the lower atmospheric pressure, these storms are much less powerful than hurricanes on Earth, but can grow so large that they cover half the planet.
Recently, the ESA’s Mars Express orbiter captured images of the towering cloud front of a dust storm located close to Mars’ northern polar region. This storm, which began in April 2018, took place in the region known as Utopia Planitia, close to the ice cap at the Martian North Pole. It is one of several that have been observed on Mars in recent months, one which is the most severe to take place in years.
The images (shown above and below) were created using data acquired by the Mars Express‘ High Resolution Stereo Camera (HRSC). The camera system is operated by the German Aerospace Center (DLR), and managed to capture images of this storm front – which would prove to be the harbinger of the Martian storm season – on April 3rd, 2018, during its 18,039th orbit of Mars.
This storm was one of several small-scale dust storms that have been observered in recent months on Mars. A much larger storm emerged further southwest in the Arabia Terra region, which began in May of 2018 and developed into a planet-wide dust storm within several weeks.
Dust storms occur on Mars when the southern hemisphere experiences summer, which coincides with the planet being closer to the Sun in its elliptical orbit. Due to increased temperatures, dust particles are lifted higher into the atmosphere, creating more wind. The resulting wind kicks up yet more dust, creating a feedback loop that NASA scientists are still trying to understand.
Since the southern polar region is pointed towards the Sun in the summer, carbon dioxide frozen in the polar cap evaporates. This has the effect of thickening the atmosphere and increases surface pressure, which enhances the storms by helping to suspend dust particles in the air. Though they are common and can begin suddenly, Martian dust storms typically stay localized and last only a few weeks.
While local and regional dust storms are frequent, only a few of them develop into global phenomena. These storms only occur every three to four Martian years (the equivalent of approximately 6 to 8 Earth years) and can persist for several months. Such storms have been viewed many times in the past by missions like Mariner 9 (1971), Viking I (1971) and the Mars Global Surveyor (2001).
In 2007, a large storm covered the planet and darkened the skies over where the Opportunity rover was stationed – which led to two weeks of minimal operations and no communications. The most recent storm, which began back in May, has been less intense, but managed to create a state of perpetual night over Opportunity’s location in Perseverance Valley.
As a result, the Opportunity team placed the rover into hibernation mode and shut down communications in June 2018. Meanwhile, NASA’s Curiosity rover continues to explore the surface of Mars, thanks to its radioisotope thermoelectric generator (RTG), which does not rely on solar panels. By autumn, scientists expect the dust storm will weaken significantly, and are confident Opportunity will survive.
Understanding how global storms form and evolve on Mars will be critical for future solar-powered missions. It will also come in handy when crewed missions are conducted to the planet, not to mention space tourism and colonization!
Martian dust storms, which occur during the summer season in the planet’s southern hemisphere, can get pretty intense. Over the course of the past few weeks, a global dust storm has engulfed Mars and forced the Opportunity rover to suspend operations. Given that this storm is much like the one that took place back in 2007, which also raged for weeks, there have been concerns over how this development could affect rover operations.
Meanwhile the Curiosity rover managed to snap pictures of the thickening haze caused by the storm. Though Curiosity is on the other side of the planet from where Opportunity is currently located, atmospheric dust has been gradually increasing over it. But unlike Opportunity, which runs on solar power, Curiosity will remain unaffected by the global storm thanks to its nuclear-powered battery, and is therefore in a good position to study it.
As already noted, Martian storms occur during summer in the southern hemisphere, when sunlight warms dust particles and lifts them higher into the atmosphere, creating more wind. The resulting wind kicks up yet more dust, creating a feedback loop that NASA scientists are still trying to understand. Since the southern polar region is pointed towards the Sun in the summer, carbon dioxide frozen in the polar cap evaporates.
This has the effect of thickening the atmosphere and increasing the surface pressure, which enhances the process by helping suspend dust particles in the air. In some cases, the dust clouds can reach up to 60 km (40 mi) or more in elevation. Though they are common and can begin suddenly, Martian dust storms typically stay contained to a local area and last only about a weeks.
By contrast, the current storm has lasted for several weeks and is currently covering an area that would span North America and Russia combined. While smaller than the storm that took place back in 2007, this storm has intensified to the point where it created a perpetual state of night over the rover’s location in Perseverance Valley and led to a level of atmospheric opacity that is much worse than the 2007 storm.
When dust storms occur, scientists measure them based on their opacity level (tau) to determine how much sunlight they will prevent from reaching the surface. Whereas the 2007 storm had a tau level of about 5.5, this most recent storm reached an estimated tau of 10.8 earlier this month over the Perseverance Valley – where Opportunity is located.
The intensity of the storm also led Bruce Canton, deputy principal investigator of the Mars Color Imager (MARCI) camera onboard NASA’s Mars Reconnaissance Orbiter (MRO), to declare that the storm has officially become a “planet-encircling” (or “global”) dust event. Above the Gale Crater, where Curiosity is located, the tau reading is now above 8.0 – the highest ever recorded by the mission.
While the storm has some worried about the fate of Opportunity, which is Mars’ oldest active rover (having remained in operation for over 14 years), it is also an chance to address one of the greatest questions scientists have about Mars. For example, why do some storms span the entire planet and last for months while others are confined to small areas and and last only a week?
The animation (shown above) consists of a series of daily photos captures by Curiosity’s Mast Camera (Mastcam), which show the sky getting hazier over time. While taking these pictures, Curiosity was facing the crater rim, about 30 km (18.6) away from where it stands inside the crater. This sun-obstructing wall of haze is about six to eight times thicker than normal for this time of season.
Nevertheless, Curiosity’s engineers – which are based at NASA’s Jet Propulsion Laboratory in Pasadena, California – have studied how the growing dust storm could affect the rover’s instruments and concluded that it poses little risk. Ironically enough, the largest impact will be on the rover’s cameras, which require extra exposure time due to the low lighting conditions.
As Jim Watzin, the director of NASA’s Mars Exploration Program at the agency’s headquarters in Washington, explained in a NASA press release earlier this month:
“This is the ideal storm for Mars science. We have a historic number of spacecraft operating at the Red Planet. Each offers a unique look at how dust storms form and behave – knowledge that will be essential for future robotic and human missions.”
However, all dust events, regardless of size, help to shape the Martian surface. As such, studying their physics is critical to understanding the Martian climate, both past and present. As Rich Zurek, the chief scientist for the Mars Program Office at NASA’s Jet Propulsion Laboratory, indicated:
“Each observation of these large storms brings us closer to being able to model these events – and maybe, someday, being able to forecast them. That would be like forecasting El Niño events on Earth, or the severity of upcoming hurricane seasons.”
The ability to understand the causes and dynamics of Martian dust storms would not only lead to a better understand of how weather works on other planets, it would also be of immense importance if and and when humans begin traveling to the Red Planet on a regular basis. For instance, if SpaceX really does intend to bring tourists to Mars in the future, said tourists will want to avoid booking during “storm season”.
And if humans should choose to someday make Mars their home, they will need to know when planet-spanning dust storms are coming, especially since their habitats will likely be relying on wind and solar power. In the meantime, NASA and other space agencies will continue to monitor this storm and the Opportunity rover is expected to come through (fingers crossed!) unscathed!
The latest discovery came on Thursday, May 7th, when NASA announced that the Curiosity rover had once again discovered organic molecules. This time, however, the molecules were found in three-billion-year-old sedimentary rocks located near the surface of lower Mount Sharp. This evidence, along with new atmospheric evidence, are another indication that ancient life may have once existed on the Red Planet.
As Thomas Zurbuchen, the associate administrator for the Science Mission Directorate at NASA Headquarters, explained in a recent NASA press release:
“With these new findings, Mars is telling us to stay the course and keep searching for evidence of life. I’m confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet.”
In the first paper, the authors indicate how Curiosity’sSample Analysis at Mars (SAM) suite detected traces of methane in drill samples it took from Martian rocks. Once these rocks were heated, they released an array of organics and volatiles similar to how organic-rich sedimentary rocks do on Earth. On Earth, such deposits are indications of fossilized organic life, which may or may not be the case with the samples examined by Curiosity.
However, this evidence is bolstered by the fact that Curiosity has also found evidence that the Gale Crater was once an ancient lakebed. In addition to water, this lakebed contained all the chemical building blocks and energy sources that are necessary for life. As Jen Eigenbrode of NASA’s Goddard Space Flight Center, and the lead author of the first study, explained:
“Curiosity has not determined the source of the organic molecules. Whether it holds a record of ancient life, was food for life, or has existed in the absence of life, organic matter in materials holds chemical clues to planetary conditions and processes… The Martian surface is exposed to radiation from space. Both radiation and harsh chemicals break down organic matter. Finding ancient organic molecules in the top five centimeters of rock that was deposited when Mars may have been habitable, bodes well for us to learn the story of organic molecules on Mars with future missions that will drill deeper.”
In the second paper, the team described how Curiosity’s SAM suite also detected seasonal variations in methane in the Martian atmosphere. These results were obtained over the course of nearly three years on Mars, which works out to almost six Earth years. While the team admits that water-rock chemistry could have generated the methane, they cannot rule out the possibility that it was biological in origin.
In the past, methane and organic molecules have been detected in Mars’ atmosphere and in drill samples, the former of which appeared to spike unpredictably. However, these new results indicate that within the Gale Crater, low levels of methane peak during the warm summer months and drop in the winter months every year. As Chris Webster, a researcher from NASA’s Jet Propulsion Laboratory (JPL) and the lead author of the second paper, explained:
“This is the first time we’ve seen something repeatable in the methane story, so it offers us a handle in understanding it. This is all possible because of Curiosity’s longevity. The long duration has allowed us to see the patterns in this seasonal ‘breathing.'”
To find this organic material, Curiosity drilled into sedimentary rocks (known as mudstone) in four areas in the Gale Crater. These rocks formed over the course of billions of years as sediments were deposited at the bottom of the ancient lake by flowing water. The drill samples were then analyzed by SAM, which used its oven to heat the samples to over 500 °C (900 °F) to release organic molecules from the powdered rock.
These results indicate that some of the drill samples contained sulfur (which could have preserved the organic molecules) as well as thiophenes, benzene, toluene, and small carbon chains – such as propane or butene. They also indicated organic carbon concentrations of about 10 parts per million or more, which is consistent with carbon concentrations observed in Martian meteorites and about 100 times what has been previously detected on Mars’ surface.
While this does not constitute evidence of past life on Mars, these latest findings have increased confidence that future missions will find more organics, both on the surface and slightly beneath the surface. But above all, they have bolstered confidence that Mars may have once had life of its own. As Michael Meyer, the lead scientist for NASA’s Mars Exploration Program, summarized:
“Are there signs of life on Mars? We don’t know, but these results tell us we are on the right track.”
In the coming years, additional missions will also be searching for signs of past life, including NASA’s Mars 2020 rover and the European Space Agency’s ExoMars rover.The Mars 2020 rover will also leave samples behind in a cache that could be retrieved by a future crewed mission for sample-return analysis. So if there was life on Mars (or, fingers crossed, still is) we are sure to find it soon enough!
And be sure to check out this video of this latest discovery by Curiosity, courtesy of NASA’s Jet Propulsion Laboratory:
In fact, back in January of 2018, the rover had spent a total of 2,000 Earth days on Mars. And as of March 22nd, 2018, NASA’s Mars Curiosity rover had reached its two-thousandth Martian day (Sol) on the Red Planet! To mark the occasion, NASA released a mosaic photo that previews what the rover will be investigating next (hint: it could shed further light on whether or not Mars was habitable in the past).
The image (shown at top and below) was assembled from dozens of images taken by Curiosity‘s Mast Camera (Mastcam) on Sol 1931 (back in January). To the right, looming in the background, is Mount Sharp, the central peak in the Gale Crater (where Curiosity landed back in 2012). Since September of 2014, the rover has been climbing this feature and collecting drill samples to get a better understanding of Mars’ geological history.
In the center of the image is the rover’s next destination and scientific target. This area, which scientists have been studying from orbit, is rich in clay minerals, which indicates that water once existed there. In the past, the Curiosity rover found evidence of clay minerals on the floor of the Gale Crater. This confirmed that the crater was a lake bed between 3.3 and 3.8 billion years ago.
Mount Sharp, meanwhile, is believed to have formed from sedimentary material that was deposited over a period of about 2 billion years. By examining patches of clay minerals that extend up the mountain’s side, scientists hope to gain insight into the history of Mars since then. These include how long water may have persisted on its surface and how the planet made the transition to the cold and desiccated place it is today.
The Curiosity science team is eager to analyze rock samples pulled from the clay-bearing rocks seen in the center of the image, and not just because of the results they could provide. Recently, the science team developed a new drilling technique to compensate for the failure of a faulty motor (which allows the drill to extend and retract). When the rover begins to drill again, it will be the first time since December 2016.
All told, the rover has spent a total of about 2055 Earth days (5 years and 230 days), which means Curiosity now ranks third behind the Opportunity (5170 days; 5031 sols) and the Spirit rovers (2269 days; 2208 sols) in terms of total time spent on Mars. Since it arrived on Mars in 2012, Curiosity has also traveled a total distance of 18.7 km (11.6 mi) and studied more than 180 meters (600 feet) vertical feet of rock.
But above all, Curiosity‘s greatest achievement has been the discovery that Mars once had all the necessary conditions and chemical ingredients to support microbial life. Based on their findings, Curiosity‘s international science team has concluded that habitable conditions must have lasted for at least millions of years before Mars’ atmosphere was stripped away.
Finding the evidence of this, and how the transition occurred, will not only advance our understanding of the history of Mars, but of the Solar System itself. It also might provide clues as to how Mars could be made into a warmer, wetter environment again someday!
Since it landed on Mars in 2012, the Curiosity rover has used its drill to gather samples from a total of 15 sites. These samples are then deposited into two of Curiosity’s laboratory instruments – the Sample Analysis at Mars (SAM) or the Chemistry and Mineralogy X-ray Diffraction (CheMin) instrument – where they are examined to tell us more about the Red Planet’s history and evolution.
Unfortunately, in December of 2016, a key part of the drill stopped working when a faulty motor prevented the bit from extending and retracting between its two stabilizers. After managing to get the bit to extend after months of work, the Curiosity team has developed a new method for drilling that does not require stabilizers. The new method was recently tested and has been proven to be effective.
The new method involves freehand drilling, where the drill bit remains extended and the entire arm is used to push the drill forward. While this is happening, the rover’s force sensor – which was originally included to stop the rover’s arm if it received a high-force jolt – is used to takes measurements. This prevents the drill bit from drifting sideways and getting stuck in rock, as well as providing the rover with a sense of touch.
The test drill took place at a site called Lake Orcadie, which is located in the upper Vera Rubin Ridge – where Curiosity is currently located. The resulting hole, which was about 1 cm (half an inch) deep was not enough to produce a scientific sample, but indicated that the new method worked. Compared to the previous method, which was like a drill press, the new method is far more freehand.
“We’re now drilling on Mars more like the way you do at home. Humans are pretty good at re-centering the drill, almost without thinking about it. Programming Curiosity to do this by itself was challenging — especially when it wasn’t designed to do that.”
This new method was the result of months of hard work by JPL engineers, who practiced the technique using their testbed – a near-exact replica of Curiosity. But as Doug Klein of JPL, one of Curiosity’s sampling engineers, indicated, “This is a really good sign for the new drilling method. Next, we have to drill a full-depth hole and demonstrate our new techniques for delivering the sample to Curiosity’s two onboard labs.”
Of course, there are some drawbacks to this new method. For one, leaving the drill in its extended position means that it no longer has access to the device that sieves and portions rock powder before delivering it to the rover’s Collection and Handling for In-Situ Martian Rock Analysis (CHIMRA) instrumet. To address this, the engineers at JPL had to invent a new way to deposit the powder without this device.
Here too, the engineers at JPL tested the method here on Earth. It consists of the drill shaking out the grains from its bit in order to deposit the sand directly in the CHIMRA instrument. While the tests have been successful here on Earth, it remains to be seen if this will work on Mars. Given that both atmospheric conditions and gravity are very different on the Red Planet, it remains to be seen if this will work there.
This drill test was the first of many that are planned. And while this first test didn’t produce a full sample, Curiosity’s science team is confident that this is a positive step towards the resumption of regular drilling. If the method proves effective, the team hopes to collect multiple samples from Vera Rubin Ridge, especially from the upper side. This area contains both gray and red rocks, the latter of which are rich in minerals that form in the presence of water.
Samples drilled from these rocks are expected to shed light on the origin of the ridge and its interaction with water. In the days ahead, Curiosity’s engineers will evaluate the results and likely attempt another drill test nearby. If enough sample is collected, they will use the rover’s Mastcam to attempt to portion the sample out and determine how much powder can be shaken from the drill bit.
It’s been a time of milestones for Mars rovers lately! Last month (on January 26th, 2018), NASA announced that the Curiosity rover had spent a total of 2,000 days on Mars, which works out to 5 years, 5 months and 21 days. This was especially impressive considering that the rover was only intended to function on the Martian surface for 687 days (a little under two years).
But when it comes to longevity, nothing has the Opportunity rover beat! Unlike Curiosity, which relied on a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) for power, the solar-powered Opportunity recently witnessed its five-thousandth sunrise on Mars. This means that the rover has remained in continuous operation for 5000 sols, which works out to 5137.46 Earth days.
This five-thousandth sunrise began on Friday, Feb. 16th, 2018 – roughly 14 Earth years (and 7.48 Martian years) after the rover first landed. From its position on the western rim of the Endeavour Crater, the sunrise appeared over the basin’s eastern rim, about 22 km (14 mi) away. This location, one-third of the way down “Perseverance Valley”, is more than 45 km (28 mi) from Opportunity’s original landing site.
This is especially impressive when you consider that the original science mission was only meant to last 90 sols (92.47 Earth days) and NASA did not expect the rover to survive its first Martian winter. And yet, the rover has not only survived all this time, it continues to send back scientific discoveries from the Red Planet. As John Callas, the Opportunity Project Manager at NASA’s Jet Propulsion Laboratory, explained in a NASA press release:
“Five thousand sols after the start of our 90-sol mission, this amazing rover is still showing us surprises on Mars… We’ve reached lots of milestones, and this is one more, but more important than the numbers are the exploration and the scientific discoveries.”
For instance, the rover has provided us with 225,000 images since its arrival, and revealed that ancient Mars was once home to extensive groundwater and surface water. Beginning in 2008, it began working its way across the Endeavour Crater in order to get a glimpse deeper into Mars’ past. By 2011, it had reached the crater’s edge and confirmed that mineral-rich water once flowed through the area.
At present, researchers are using Opportunity to investigate the processes that shaped Perseverance Valley, an area that descends down the slope of the western rim of Endeavour Crater. Here too, Opportunity has learned some fascinating things about the Red Planet. For instance, the rover has conducted observations of possible “rock stripes” in the valley, which could be indicative of its valley’s origin.
These stripes are of interest to scientists because of the way they resemble rock stripes that appear on mountain slopes here on Earth, which are the result of repeated cycles of freezing and thawing on wet soil. On Mauna Kea, for example, soil freezes every night, but is often dry due to the extreme elevation. This causes soils that have high concentrations of silt, sand and gravel to expand, pushing the larger particles up.
These particles then form stripes as they fall downhill, or are moved by wind or rainwater, and cause the ground to expand less in this space. This process repeats itself over and over, creating a pattern that leads to distinct stripes. As Opportunity observed, there are slopes within the Perseverance Valley where soil and gravel particles appear to have formed into rows that run parallel to the slope, alternating between rows that have more and less gravel.
In the case of the Perseverance Valley’s stripes, scientists are not sure how they formed, but think they could be the result of water, wind, downhill transport, other processes, or a combination thereof. Another theory posits that features like these could be the result of changes in Mars tilt (obliquity) which happen over the course of hundreds of thousands of years.
“One possible explanation of these stripes is that they are relics from a time of greater obliquity when snow packs on the rim seasonally melted enough to moisten the soil, and then freeze-thaw cycles organized the small rocks into stripes. Gravitational downhill movement may be diffusing them so they don’t look as crisp as when they were fresh.”
Having the chance to investigate these features is therefore quite the treat for the Opportunity science team. “Perseverance Valley is a special place, like having a new mission again after all these years.” said Arvidson. “We already knew it was unlike any place any Mars rover has seen before, even if we don’t yet know how it formed, and now we’re seeing surfaces that look like stone stripes. It’s mysterious. It’s exciting. I think the set of observations we’ll get will enable us to understand it.”
Given the state of the Martian surface, it is a safe bet that wind is largely responsible for the rock stripes observed in Perseverance Valley. In this respect, they would be caused by sand blown uphill from the crater floor that sorts larger particles into rows parallel to the slope. As Robert Sullivan, an Opportunity science-team member of Cornell University, explained:
“Debris from relatively fresh impact craters is scattered over the surface of the area, complicating assessment of effects of wind. I don’t know what these stripes are, and I don’t think anyone else knows for sure what they are, so we’re entertaining multiple hypotheses and gathering more data to figure it out.”
Despite being in service for a little over 14 years, and suffering its share of setbacks, Opportunity is once again in a position to reveal things about Mars’ past and how it evolved to become what it is today. Never let it be said that an old rover can’t reveal new secrets! If there’s one thing Opportunity has proven during its long history of service on Mars, it is that the underdog can make some of the greatest contributions.
On August 5th, 2012, after spending over 8 months in space, NASA’s Curiosity rover landed on Mars. As part of the NASA Mars Science Laboratory (MSL) mission, and the latest in a series of rovers deployed to the Martian surface, Curiosity had some rather ambitious research goals. In addition to investigating Mars’ climate and geology, the rover was also tasked with revealing more about Mars’ past and determining if it ever supported microbial life.
And recently, the Curiosity rover hit another major milestone in its exploration of the Red Planet. As of January 26th, 2018 the rover has spent a total of 2,000 days on Mars, which works out to 5 years, 5 months and 21 days – or 1947 Martian days (sols). That’s especially impressive when you consider that the mission was only meant to last 687 days (668 sols), or just little under 2 years.
In all that time, the Curiosity rover has accomplished some major feats and has the scars to prove it! Some of it’s wheels have become teared, holed and cracked and its drill has been pushed almost to the point of breaking. And yet, Curiosity is still hard at work pushing itself up a mountain – both literally and figuratively! The rover has also managed to exceed everyone’s expectations.
As Ashwin Vasavada, the MSL Project Scientist, told Universe Today via email:
“In terms of challenges, the first 2000 days of Curiosity’s mission went better than I could have hoped. For much of the time, the rover remained as capable as the day it landed. We had a scare in the first year when a memory fault triggered additional problems and nearly resulted in the loss of the mission. We famously wore down our wheels pretty early, as well, but since then we’ve kept that under control. In the last year, we’ve had a major problem with our drill. That’s the only major issue currently, but we believe we’ll be back to drilling in a month or so. If that works out, we’ll amazingly be back to having all systems ready for science!”
As of the penning of this article, the rover is climbing Mount Sharp in order to collect further samples from Mars’ past. Also known as Aeolis Mons, this mountain resides in the center of the Gale Crater where Curiosity landed in 2012 and has been central to Curiosity’s mission. Standing 5,500 meters (18,000 ft) above the valley floor, Mount Sharp is believed to have formed from sediment that was slowly deposited by flowing water over billions of years.
This is all in keeping with current theories about how Mars once had a denser atmosphere and was able to sustain liquid water on its surface. But between 4.2 and 3.7 billion years ago, this atmosphere was slowly stripped away by solar wind, thus turning Mars into the cold and desiccated place that we know today. As a result, the study of Mount Sharp was always expected to reveal a great deal about Mars’ geological evolution.
In it’s first year, Curiosity achieved a major milestone when the rover obtained drill samples from low-lying areas that indicated that lakes and streams existed in the Gale Crater between 3.3 to 3.8 billion years ago. In addition, the rover has also obtained ample evidence that the crater once had all the chemical elements and even a chemical source of energy needed for microbial life to exist.
“NASA’s charge to our mission was to determine whether Mars ever had conditions suitable for life,” said Vasavada. “Success was not a foregone conclusion. Would we arrive safely? Would the scientific instruments work? Would the area we chose for the landing site hold the clues we were looking for? For me, meeting each of these objectives are the highlights of the mission. I’ll never forget witnessing the launch, or nervously waiting for a safe touchdown. Discovering an ancient, freshwater lake environment at Gale crater was profound scientifically, but also was the moment that I knew that our team had delivered what we promised to NASA.”
Basically, by scaling Mount Sharp and examining the layers that were deposited over the course of billions of years, Curiosity is able to examine a living geological record of how the planet has evolved since then. Essentially, the lower layers of the mountain are believed to have been deposited 3.5 billion years ago when the Gale Crater was still a lakebed, as evidenced by the fact that they are rich in clay minerals.
The upper layers, meanwhile, are believed to have been deposited over the ensuing millions of years, during which time the lake in the Gale Crater appears to have grown, shrunk, disappeared and then reappeared. Basically, by scaling the mountain and obtaining samples, Curiosity will be able to illustrate how Mars underwent the transition from being a warmer, wetter place to a frozen and dry one.
As Vasavada explained, this exploration is also key to answering a number of foundational questions about the search for life beyond Earth:
“Curiosity established that Mars was once a suitable home for life; it had liquid water, key chemical building blocks, and energy sources required by life in the lake and groundwater environment within Gale crater. Curiosity also has detected organic molecules in ancient rocks, in spite of all the degradation that could have occurred in three billion years. While Curiosity cannot detect life itself, knowing that Mars can preserve organic molecules bodes well for missions that will explore ancient rocks, looking for signs of past life.”
At this juncture, its not clear how much longer Curiosity will last. Considering that it has already lasted over twice as long as originally intended, it is possible the rover will remain in operation for years to come. However, unlike the Opportunity rover – who’s mission was intended to last for 90 days, but has remained in operation for 5121 days (4984 sols) – Curiosity has a shelf life.
Whereas Opportunity is powered by solar cells, Curiosity is dependent on its Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). Eventually, this slow-fission reactor will exhaust its supply of nuclear fuel and the rover will be forced to come to a halt. And considering how the rover has been put through its paces in the past 5 years, there’s also the chance that it will suffer a mechanical failure.
But in the meantime, there’s plenty of work to be done and lots of opportunities for vital research. As Vasavada put it:
“Curiosity won’t last forever, but in the years we have left, I hope we can complete our traverse through the lowermost strata on Mount Sharp. We’re well over halfway through. There are changes in the composition of the rocks ahead that might tell us how the climate of Mars changed over time, perhaps ending the era of habitability. Every day on Mars still counts, perhaps even more than before. Now every new discovery adds a piece to a puzzle that’s more than halfway done; it reveals more given all the other pieces already around it.”
And be sure to check out this retrospective of the Curiosity rover’s mission, courtesy of NASA:
The Curiosity Rover has made some incredible discoveries during the five years it has been operating on the surface of Mars. And in the course of conducting its research, the rover has also accrued some serious mileage. However, it certainly came as a surprise when during a routine examinations in 2013, members of the Curiosity science team noted that its wheels had suffered rips in their treads (followed by breaks reported in 2017).
Looking to the future, researchers at NASA’s Glenn Research Center hope to equip next-generation rovers with a new wheel. It is based on the “Spring Tire“, which NASA developed with Goodyear back in the mid-2000s. However, rather than using coiled steel wires woven into a mesh pattern (which was part of the original design) a team of NASA scientists has created a more durable and flexible version which could revolution space exploration.
When it comes right down to it, the Moon, Mars, and other bodies in the Solar System have harsh, punishing terrain. In the case of the Moon, the main issue is the regolith (aka. Moon dust) which covers the majority of its surface. This fine dust is essentially jagged bits of lunar rock which play havoc with engines and machine components. On Mars, the situation is slightly different, with regolith and sharp rocks covering most of the terrain.
In 2013, after just a year on the surface, the Curiosity rover’s wheels began to show signs of wear and tear due it traversing unexpectedly harsh terrain. This led many to worry that the rover might not be able to complete its mission. It also led many at NASA’s Glenn Research Center to reconsider a design they had been working on almost a decade prior, which was intended for renewed missions to the Moon.
For NASA Glenn, tire development has been a focus of research for about a decade now. In this respect, they are returning to a time-honored tradition of NASA engineers and scientists, which began back in the Apollo era. At the time, both the American and Russian space programs were evaluating multiple tires designs for use on the lunar surface. Overall, three major designs were proposed.
First, you had the wheels specially designed for Lunokhod rover, a Russian vehicle whose name literally translates to “Moon Walker”. The wheel design for this rover consisted of eight rigid-rim, wire-mesh tires that were connected to their axles by bicycle-type spokes. Metal cleats were also mounted on the outside of the tire to ensure better traction in the lunar dust.
Then there was NASA’s concept for a Modularized Equipment Transporter (MET), which was developed with the support of Goodyear. This unpowered cart came with two nitrogen-filled, smooth rubber tires to make it easier to pull the cart through lunar soil and over rocks. And then there was the design for the Lunar Roving Vehicle (LRV), which was the last NASA vehicle to visit the Moon.
This crewed vehicle, which Apollo astronauts used to drive around on the challenging lunar surface, relied on four large, flexible wire-mesh wheels with stiff inner frames. During the mid-2000s, when NASA began planning on mounting new missions to the Moon (and future missions to Mars), they began reevaluating the LRV tire and incorporating new materials and technologies into the design.
The fruit of this renewed research was the Spring Tire, which was the work of mechanical research engineer Vivake Asnani, who worked closely with Goodyear to develop it. The design called for an airless, compliant tire made up of hundreds of coiled steel wires, which were then woven into a flexible mesh. This not only ensured light weight, but also gave the tires the ability to support high loads while conforming to the terrain.
To see how the Spring Tire would fare on Mars, engineers at NASA’s Glenn Research Center began testing them in the Slope lab, where they ran them through an obstacle course that simulated the Martian environment. While the tires performed generally well in simulated sand, they experienced problems when the wire mesh deformed after passing over jagged rocks.
To address this, Colin Creager and Santo Padua (a NASA engineer and materials scientist, respectively) discussed possible alternatives. In time, they agreed the steel wires should be replaced with nickel titanium, a shape memory alloy that is capable of retaining its shape under tough conditions. As Padua explained in a NASA Glenn video segment, the inspiration to use this alloy was very serendipitous:
“I just happened to be over in the building here, where the Slope lab is. And I was over here for a different meeting for the work that I do in shape memory alloys, and I happen to run into Colin in the hall. And I was like ‘what are you doing back and why aren’t you over in the impact lab?’ – because I knew him as a student. He said, ‘well, I’ve graduated, and I’ve been working out here full-time for awhile… I work in Slope.”
Despite working at JPL for ten years, Padua had not seen the Slope lab before and accepted an invitation to see what they were working on. After entering the lab and looking at the Spring Tires they were testing, Padua asked if they were experiencing problems with deformation. When Creager admitted that they were, Padua proposed a solution which just happened to be his field of expertise.
“I had never even heard of the term shape memory alloys before, but I knew [Padua] was a materials science engineer,” said Creager. “And so, since then we’ve been collaborating on these tires using his materials expertise, especially in shape memory alloys, to come up with this new tire that we think is really going to revolutionize planetary rover tires and potentially even tires for Earth too.”
The key to shape memory alloys is their atomic structure, which is assembled in such a way that the material “remember” its original shape and is able to return to it after being subjected to deformation and strain. After building the shape memory alloy tire, the Glenn engineers sent it to the Jet Propulsion Laboratory, where it was tested in the Mars Life Test Facility.
Overall, the tires not only performed well in simulated Martian sand, but were able to withstand going over punishing rocky outcroppings without difficulty. Even after the tires were deformed all the way down to their axles, they were able to retain their original shape. They also managed to do this while carrying a significant payload, which is another prerequisite when developing tires for exploration vehicles and rovers.
The priorities for the Mars Spring Tire (MST) are to offer greater durability, better traction in soft sand, and lighter weight. As NASA indicates on the MST website (part of the Glenn Research Center’s website), there are three major benefits to developing high performing compliant tires like the Spring Wheel:
“First, they would allow rovers to explore greater regions of the surface than currently possible. Secondly, because they conform to the terrain and do not sink as much as rigid wheels, they can carry heavier payloads for the same given mass and volume. Lastly, because the compliant tires can absorb energy from impacts at moderate to high speeds, they can be used on crewed exploration vehicles which are expected to move at speeds significantly higher than the current Mars rovers.”
The first available opportunity to test these tires out is just a few years away, when NASA’s Mars 2020 Rover will be sent to the surface of the Red Planet. Once there, the rover will pick up where Curiosity and other rovers have left off, searching for signs of life in Mars’ harsh environment. The rover is also tasked with preparing samples that will eventually be returned to Earth by a crewed mission, which is expected to take place sometime in the 2030s.