Special Guests:
This week’s guest is Abigail “Astronaut Abby” Harrison. Abigail is the founder of The Mars Generation nonprofit. Currently a sophomore at Wellesley College in Massachusetts majoring in Astrobiology and Russian. Harrison is positioned to enter a PhD program upon graduation and continue her pursuit of becoming a scientist, astronaut and member of the first human crew to land on Mars in the 2030’s. Hundreds of thousands of supporters from around the world follow her journey to becoming an astronaut via the blog Harrison authors at AstronautAbby.org.
The Mars Generation is a 510c3 nonprofit in the United States. The organization is volunteer-driven with a board of directors that includes astronauts, engineers, scientists and professionals from the nonprofit and business communities. With a reach of more than 10 million people in the organization’s first year of operation and more than 650 students from around the world participating in its Student Space Ambassador Leadership Program, over 600 donors, 350 members and several space industry sponsors in place, the organization continues to grow and offer programs to excite and educate students and adults about the importance of human space exploration and STEM education.
We use a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
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We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page<
NASA’s Opportunity rover scans around and across to vast Endeavour crater on Dec. 19, 2016, as she climbs steep slopes on the way to reach a water carved gully along the eroded craters western rim. Note rover wheel tracks at center. This navcam camera photo mosaic was assembled from raw images taken on Sol 4587 (19 Dec. 2016) and colorized. Credit: NASA/JPL/Cornell/Ken Kremer/kenkremer.com/Marco Di Lorenzo
NASA’s Opportunity rover scans around and across to vast Endeavour crater on Dec. 19, 2016, as she climbs steep slopes on the way to reach a water carved gully along the eroded craters western rim. Note rover wheel tracks at center. This navcam camera photo mosaic was assembled from raw images taken on Sol 4587 (19 Dec. 2016) and colorized. Credit: NASA/JPL/Cornell/Ken Kremer/kenkremer.com/Marco Di Lorenzo
On the brink of 4600 Sols of a profoundly impactful life, NASA’s long lived Opportunity rover celebrates the Christmas/New Year’s holiday season on Mars marching relentlessly towards an ancient water carved gully along the eroded rim of vast Endeavour crater – the next science target on her heroic journey traversing across never before seen Red Planet terrains.
“Opportunity is continuing its great 21st century natural history expedition on Mars, exploring the complex geology and record of past climate here on the rim of the 22-km Endeavour impact crater,” writes Larry Crumpler, a science team member from the New Mexico Museum of Natural History & Science, in a mission update.
Indeed, New Years Day 2017 equates to 4600 Sols, or Martian Days – of boundless exploration and epic discovery by the longest living Martian rover ever dispatched by humanity to survey the most Earth-like planet in our solar system.
One can easily imagine our beloved Princess Leia gazing quite proudly upon the feistiness and resourcefulness of this never-give-up Martian Princess rover – climbing steeply uphill no less – nearly 13 YEARS into her 3 MONTH mission!!
“Not a boring flat terrain, but heroically rugged terrain,” says Crumpler.
“Hopefully the brakes are good! For a rover that originally landed 12 years ago on what amounts to a flat parking lot, the current terrain is about as different and rugged as any mountain goat rover could handle.”
Indeed she is 51 times beyond her “warrantied” life expectancy of merely 90 Sols roving the surface of the 4th rock from the Sun during her latest extended mission. (And this time round, the clueless Washington bean counters did not even dare threaten to shut her down – lest they suffer the wrath of a light saber or sister Curiosity’s laser canon !!).
Check out the glorious view from Opportunity’s current Martian holiday season exploits in our newest photo mosaics created by the imaging team of Ken Kremer and Marco Di Lorenzo.
“Opportunity has begun the ascent of the steep slopes here in the inner wall of Endeavour impact crater after completion of a survey of outcrops close to the crater floor. The goal now is to climb back to the rim where the terrain is less hazardous, drive south quickly about 1 km south, and arrive at the next major mission target on the rim before the next Martian winter,” Crumpler elaborated.
On Christmas Day 2016, NASA’s Opportunity rover scans around vast Endeavour crater as she ascends steep rocky slopes on the way to reach a water carved gully along the eroded craters western rim. This navcam camera photo mosaic was assembled from raw images taken on Sol 4593 (25 Dec. 2016) and colorized. Credit: NASA/JPL/Cornell/Ken Kremer/kenkremer.com/Marco Di Lorenzo
After surviving the scorching ‘6 minutes of Terror’ plummet through the thin Martian atmosphere, Opportunity bounced to an airbag cushioned landing on the plains of Meridiani Planum on January 24, 2004 – nearly 13 years ago!
Opportunity was launched on a Delta II rocket from Cape Canaveral Air Force Station in Florida on July 7, 2003.
NASA’s Opportunity rover scans ahead to Spirit Mound and vast Endeavour crater as she celebrates 4500 sols on the Red Planet after descending down Marathon Valley. This navcam camera photo mosaic was assembled from raw images taken on Sol 4500 (20 Sept 2016) and colorized. Credit: NASA/JPL/Cornell/ Ken Kremer/kenkremer.com/Marco Di Lorenzo
The newest 2 year extended mission phase just began on Oct. 1, 2016 as the six wheeled robot was stationed at the western rim of Endeavour crater at the bottom of Marathon Valley at a spot called “Bitterroot Valley” and completing investigation of nearby “Spirit Mound.”
She is now ascending back up to the top of the crater rim for the southward trek to ‘the gully’ in 2017.
“Opportunity is making progress towards the next science objective of the extended mission,” researchers leading the Mars Exploration Rover (MER) Opportunity mission wrote in a status update.
“The rover is headed toward an ancient water-carved gully about a kilometer south of the rover’s current location on the rim of Endeavour Crater.”
Endeavour crater spans some 22 kilometers (14 miles) in diameter.
Opportunity has been exploring Endeavour since arriving at the humongous crater in 2011. Endeavour crater was formed when it was carved out of the Red Planet by a huge meteor impact billions of years ago.
“Endeavour crater dates from the earliest Martian geologic history, a time when water was abundant and erosion was relatively rapid and somewhat Earth-like,” Crumpler explains.
“So in addition to exploring the geology of a large crater, a type of feature that no one has ever explored in its preserved state, the mission seeks to take a close look at the evidence in the rocks for the past environment. Thus we are trying to stick to the crater rim where the oldest rocks are.”
But the crater slopes ahead are steep! As much as 20 degrees and more – and thus potentially dangerous! So the team is commanding Opportunity to proceed ahead with caution to “the gully” which is the primary target of her latest extended mission.
The rover has even done “quite a bit of exploratory driving in an effort to attain a good vantage point for finding a path through a troubling area of boulder patch and steep slopes ahead. The concern was whether the available routes to avoid the boulders were all too steep to traverse, in which case we would have to forgo the current ‘Extended Mission 10’ (EM10) route and backtrack to find a different route to our main objective, the ‘gully.’”
“The slopes here exceed 20 degrees and the surface consists of flat outcrops of impact breccias covered with tiny rocks that act like ball bearings,” Crumpler writes. “Anyone who has attempted to walk on a 20 degree slope with a covering of fine pebbles on hard outcrop can attest to the difficulty. Opportunity has been operating at these extreme slope for several months. But going down hill is one thing, And going back up hill is another entirely.”
NASA’s Opportunity rover discovers a beautiful Martian dust devil moving across the floor of Endeavour crater as wheel tracks show robots path today exploring the steepest ever slopes of the 13 year long mission, in search of water altered minerals at Knudsen Ridge inside Marathon Valley on 1 April 2016. This navcam camera photo mosaic was assembled from raw images taken on Sol 4332 (1 April 2016) and colorized. Credit: NASA/JPL/Cornell/ Ken Kremer/kenkremer.com/Marco Di Lorenzo
As of today, Sol 4598, Dec. 29, 2016, Opportunity has taken over 215,900 images and traversed over 27.12 miles (43.65 kilometers) – more than a marathon.
See our updated route map below.
The rover surpassed the 27 mile mark milestone early last month on November 6 (Sol 4546).
The power output from solar array energy production is currently 414 watt-hours, before heading into another southern hemisphere Martian winter in 2017.
Meanwhile Opportunity’s younger sister rover Curiosity traverses and drills into the lower sedimentary layers at the base of Mount Sharp.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
13 Year Traverse Map for NASA’s Opportunity rover from 2004 to 2016. This map shows the entire 43 kilometer (27 mi) path the rover has driven on the Red Planet during nearly 13 years and more than a marathon runners distance for some 4600 Sols, or Martian days, since landing inside Eagle Crater on Jan 24, 2004 – to current location at the western rim of Endeavour Crater. After descending down Marathon Valley and after studying Spirit Mound, the rover is now ascending back uphill on the way to a Martian water carved gully. Rover surpassed Marathon distance on Sol 3968 after reaching 11th Martian anniversary on Sol 3911. Opportunity discovered clay minerals at Esperance – indicative of a habitable zone – and searched for more at Marathon Valley. Credit: NASA/JPL/Cornell/ASU/Marco Di Lorenzo/Ken Kremer/kenkremer.com
Artist concept of the Mars Ice Home. Credit: NASA.
At first glance, a new concept for a NASA habitat on Mars looks like a cross between Mark Watney’s inflatable potato farm from “The Martian” and the home of Luke’s Uncle Owen on Tatooine from “Star Wars.”
The key to the new design relies on something that may or may not be abundant on Mars: underground water or ice.
The “Mars Ice Home” is a large inflatable dome that is surrounded by a shell of water ice. NASA said the design is just one of many potential concepts for creating a sustainable home for future Martian explorers. The idea came from a team at NASA’s Langley Research Center that started with the concept of using resources on Mars to help build a habitat that could effectively protect humans from the elements on the Red Planet’s surface, including high-energy radiation.
The Mars Ice Home concept. Credit: Clouds Architecture Office, NASA Langley Research Center, Space Exploration Architecture.
Langley senior systems engineer Kevin Vipavetz who facilitated the design session said the team assessed “many crazy, out of the box ideas and finally converged on the current Ice Home design, which provides a sound engineering solution,” he said.
The advantages of the Mars Ice Home is that the shell is lightweight and can be transported and deployed with simple robotics, then filled with water before the crew arrives. The ice will protect astronauts from radiation and will provide a safe place to call home, NASA says. But the structure also serves as a storage tank for water, to be used either by the explorers or it could potentially be converted to rocket fuel for the proposed Mars Ascent Vehicle. Then the structure could be refilled for the next crew.
A cutaway of the interior of the Mars Ice Home concept. Credit: NASA Langley/Clouds AO/SEArch.
Other concepts had astronauts living in caves, or underground, or in dark, heavily shielded habitats. The team said the Ice Home concept balances the need to provide protection from radiation, without the drawbacks of an underground habitat. The design maximizes the thickness of ice above the crew quarters to reduce radiation exposure while also still allowing light to pass through ice and surrounding materials.
Team members of the Ice Home Feasibility Study discuss past and present technology development efforts in inflatable structures at NASA’s Langley Research Center. Credits: Courtesy of Kevin Kempton/NASA.
“All of the materials we’ve selected are translucent, so some outside daylight can pass through and make it feel like you’re in a home and not a cave,” said Kevin Kempton, also part of the Langley team.
One key constraint is the amount of water that can be reasonably extracted from Mars. Experts who develop systems for extracting resources on Mars indicated that it would be possible to fill the habitat at a rate of one cubic meter, or 35.3 cubic feet, per day. This rate would allow the Ice Home design to be completely filled in 400 days, so the habitat would need to be constructed robotically well before the crew arrives. The design could be scaled up if water could be extracted at higher rates.
The team wanted to also include large areas for workspace so the crew didn’t have to wear a pressure suit to do maintenance tasks such as working on robotic equipment. To manage temperatures inside the Ice Home, a layer of carbon dioxide gas — also available on Mars — would be used as in insulation between the living space and the thick shielding layer of ice.
“The materials that make up the Ice Home will have to withstand many years of use in the harsh Martian environment, including ultraviolet radiation, charged-particle radiation, possibly some atomic oxygen, perchlorates, as well as dust storms – although not as fierce as in the movie ‘The Martian’,” said Langley researcher Sheila Ann Thibeault.
So if you’ve been to Yellowstone National Park, you’ve seen one of the most amazing features of the natural world – geysers. In today’s episode, we’re going to talk about geysers on Earth, and where they might be in the solar system.
We usually record Astronomy Cast as a live Google+ Hangout on Air every Friday at 1:30 pm Pacific / 4:30 pm Eastern. You can watch here on Universe Today or from the Astronomy Cast Google+ page.
Geoglogic Ages of Mars – From Wet and Wild to Desolate Desert
Today, Mars is a desolate wasteland, with dusty red rocks and sand stretching out to the horizon. But billions of years ago, it was a vastly different world. It was blue, with oceans, rivers, lakes, and maybe life? Let’s tell the story of geology on Mars, and we got from that world to the one we see today.
We usually record Astronomy Cast as a live Google+ Hangout on Air every Friday at 1:30 pm Pacific / 4:30 pm Eastern. You can watch here on Universe Today or from the Astronomy Cast Google+ page.
Artist's impression of geysers at the Martian south polar icecap as southern spring begins. Credit: NASA/JPL-Caltech/Arizona State University/Ron Miller
For years, scientists have understood that in Mars’ polar regions, frozen carbon dioxide (aka. dry ice) covers much of the surface during the winter. During the spring, this ice sublimates in places, causing the ice to crack and jets of CO² to spew forth. This leads to the formation of dark fans and features known as “spiders”, both of which are unique to Mars’ southern polar region.
For the past decade, researchers have failed to see these features changing from year-to-year, where repeated thaws have led to their growth. However, using data from the Mars Reconnaissance Orbiter‘s (MRO) HiRISE camera, a research team from the University of Colorado, Boulder and the Planetary Science Institute in Arizona have managed to catch sight of the cumulative growth of a spider for the first time from one spring to the next.
Spiders are so-named because of their appearance, where multiple channels converge on a central pit. Dark fans, on the other hand, are low-albedo patches that are darker than the surrounding ice sheet. For some time, astronomers have been observed these features in the southern polar region of Mars, and multiple theories were advanced as to their origin.
HiRISE images of the Martian landscape, showing outgassing and the formation of dark fans and “spiders”. Credit: NASA/JPL
In 2007, Hugh Kieffer of the Space Science Institute in Boulder, Colorado theorized that the dark fans and spiders were linked, and that both features were the result of spring thaws. In short, during Mars’ spring season – when the southern polar region is exposed to more sunlight – the Sun’s rays penetrates the ice sheets and warm the ground underneath.
This causes gas flows to form beneath the ice that build up pressure, eventually causing the ice to crack and triggering geysers. These geysers deposit mineral dust and sand across the surface downwind from the eruption, while the cracks in the ice grow and become visible from orbit. While this explanation has been widely-accepted, scientists have been unable to observe this process in action.
By using data from the MRO’s High Resolution Imaging Science Experiment (HiRISE), the research team was able to spot a small-channeled troughs in the southern region which persisted and grew over a three year period. In addition to closely resembling spidery terrain, it was in proximity to dark fan sites. From this, they determined that they were witnessing a spider that was in the process of formation.
As Dr. Ganna Portyankina – a researcher from the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder, and the lead author on the team’s research paper – explained to Universe Today via email,
“We have observed different changes in the surface caused by CO² jets before. However, they all were either seasonal changes in surface albedo, like dark fans, or they were only short-lived and were gone the next year, like furrows. This time, the troughs have stayed over several years and they develop dendritic-type of extension – right the way we expect the large spiders to develop.”
Spiders trace a delicate pattern on top of the residual polar cap, after the seasonal carbon-dioxide ice slab has disappeared. Next spring, these will likely mark the sites of vents when the CO2 icecap returns. This MOC image is about 2 miles wide. Credit: NASA/JPL/MSSS
Furrows that were similar to the spidery terrain have been spotted at Mars’ north pole in the past, which coincided with a Martian spring. On these occasions, scientists using data from HiRISE instrument reported seeing small furrows on sand dunes, where eruptions had deposited dark fans. However, in what is typical of northern furrows, these were non-persisting annual occurrences, disappearing when summer winds deposited sand in them.
In contrast, the troughs Dr. Portyankina and her team observed in the southern polar region were persistent over a three-year period. During this time, these features extended and developed new “tributaries”, forming a dendritic pattern that resembled a Martian spider. From this, they concluded that the previously-observed northern furrows have the same cause – i.e. sublimation causing outgassing.
However, they also concluded that the northern furrows do not develop over time because of the high-mobility of dune material in the northern polar region. The difference, it seems, comes down to the presence of erosive sand material in the north and south, which creates (or starts) the erosive process that leads to the formation of spider-like troughs – which both kick-stars the process but can also erase it.
“Many locations in the south polar regions with seasonal dark fans show no visible sand deposits,” said Dr. Portyankina. “Dark fans in those locations might be only a mix of regolith and dust, or even just dust on its own – as it is really everywhere on Mars… [T]hose locations that have sand will experience higher erosion simply because there is granular material in the gas flow. Basically, it is old simple sandblasting. This means, it must be easier and faster to carve spiders in those locations.”
Images of dark spots (left) and fans (right) observed on top of the Martian south polar cap taken in southern spring. Credit: NASA/JPL/MSSS
In other words, where sand exists beneath the ice sheet, the ground beneath that is likely to be rockier (i.e. harder)> The formation of spider terrain may thereofre require that the ground beneath the ice be soft enough to be carved, but not so loose that it will refill the channels during a single seasonal cycle. In short, the formation of spidery terrain appears to be dependent upon the difference in surface composition between the poles.
In addition, from the many year’s of HiRISE data that has been accumulated, Dr. Portyankina and her team were also able to gauge the current rate of erosion in Mars’ southern polar region. Ultimately, they estimated that smaller spider-like furrows would require a thousand Martian years (about 1,900 Earth years) in order to become a full-scale spider.
This study is certainly significant, since understanding how seasonal changes and present-day erosion lead to the creation of new topographical features is important when it comes to understanding the processes that shape Mars’ polar regions. As we get closer and closer to the day when crewed missions and even settlement become a reality, knowing how these processes shape the planet will be fundamental to making a go of things on Mars.
This self-portrait of NASA's Curiosity Mars rover shows the vehicle at the "Big Sky" site. Credit: NASA/JPL-Caltech/MSSS
Following is the final excerpt from my new book, “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos.” The book is an inside look at several current NASA robotic missions, and this excerpt is part 3 of 3 posted here on Universe Today, of Chapter 2, “Roving Mars with Curiosity.” You can read Part 1 here, and Part 2 here. The book is available in print or e-book (Kindle or Nook) Amazon and Barnes & Noble.
How to Drive a Mars Rover
How does Curiosity know where and how to drive across Mars’ surface? You might envision engineers at JPL using joysticks, similar to those used for remote control toys or video games. But unlike RC driving or gaming, the Mars rover drivers don’t have immediate visual inputs or a video screen to see where the rover is going. And just like at the landing, there is always a time delay of when a command is sent to the rover and when it is received on Mars.
“It’s not driving in a real-time interactive sense because of the time lag,” explained John Michael Morookian, who leads the team of rover drivers.
The actual job title of Morookian and his team are ‘Rover Planners,’ which precisely describes what they do. Instead of ‘driving’ the rovers per se; they plan out the route in advance, program specialized software, and upload the instructions to Curiosity.
“We use images taken by the rover of its surroundings,” said Morookian. “We have a set of stereo images from four black-and-white Navigation Cameras, along with images from the Hazcams (hazard avoidance cameras), supported by high-resolution color images from the MastCam that give us details about the nature of the terrain ahead and clues about types of rocks and minerals at the site. This helps identify structures that look interesting to the scientists.”
Using all available data, they can create a three-dimensional visualization of the terrain with specialized software called the Rover Sequencing and Visualization Program (RSVP).
“This is basically a Mars simulator and we put a simulated Curiosity in a panorama of the scene to visualize how the rover could traverse on its path,” Morookian explained. “We can also put on stereo glasses, which allow our eyes to see the scene in three dimensions as if we were there with the rover.
In virtual reality, the rover drivers can manipulate the scene and the rover to test every possibility of which routes are the best and what areas to avoid. There, they can make all the mistakes (get stuck in a dune, tip the rover, crash into a big rock, drive off a precipice) and perfect the driving sequence while the real rover remains safe on Mars.
“The scientists also review the images for features that are interesting and consult with the Rover Planners to help define a path. Then we compose the detailed commands that are necessary to get Curiosity from Point A to Point B along that path,” Morookian said. “”We can also incorporate the commands needed to give the rover direction to make contact with the site using its robotic arm.”
When Curiosity’s Navigation Cameras (Navcams) take black-and-white images and send them back to Earth each day, rover planners combine them with other rover data to create 3D terrain models. By adding a computerized 3D rover model to the terrain model, rover planners can understand better the rover’s position, as well as distances to, and scale of, features in the landscape. Credit: NASA/JPL-Caltech.
So, every night the rover is commanded to shut down for eight hours to recharge its batteries with the nuclear generator. But first Curiosity sends data to Earth, including pictures of the terrain and any science information. On Earth, the Rover Planners take that data, do their planning work, complete the software programing and beam the information back to Mars. Then Curiosity wakes up, downloads the instructions and sets to work. And the cycle repeats.
Curiosity also has an AutoNav feature which allows the rover to traverse areas the team hasn’t seen yet in images. So, it could go over the hill and down the other side to uncharted territory, with the AutoNav sensing potential hazards.
“We don’t use it too often because it is computationally expensive, meaning it takes much longer for the rover to operate in that mode,” Morookian said. “We often find it’s a better trade to just come in the next day, look at the images and drive as far as we can see.”
A view of the Space Flight Operations Facility at the Jet Propulsion Laboratory, where all the data going both to and from all planetary missions is sent and received via the Deep Space Network. Credit: Nancy Atkinson.
As Morookian showed me the various rooms used by rover planning teams at JPL, he explained how they need to operate over a number of different timescales.
“We not only have the daily route planning,” he said, “but also do long-range strategic planning using orbital imagery from the HiRISE camera on the Mars Reconnaissance Orbiter and choose paths based on features seen from orbit. Our team works strategically, looking many months out to define the best paths.”
Another process called Supra-Tactical looks out to just the next week. This involves science planners managing and refining the types of activities the rover will be doing in the short term. Also, since no one on the team lives on Mars Time anymore, on Fridays the Rover Planners work out the plans for several days.
“Since we don’t work weekends, Friday plans contain multiple sols of activities,” Morookian said. “Two parallel teams decide which days the rover will drive and which days it will do other activities, such as work with the robotic arm or other instruments.”
The data that comes down from the rover over the weekend is monitored, however, and if there is a problem, a team is called in to do a more detailed assessment. Morookian indicated they’ve had to engage the emergency weekend team several times, but so far there have been no serious problems. “It does keep us on our toes, however,” he said.
The rover features a number of reactive safety checks on the amount of overall tilt of the rover deck and the articulation of the suspension system of the wheels, so if the rover is going over an object that is too large, it will automatically stop.
Curiosity wasn’t built for speed. It was designed to travel up to 660 feet (200 meters) in a day, but it rarely travels that far in a Sol. By early 2016 the rover had driven a total of about 7.5 miles (12 km) across Mars’ surface.
This image shows a close-up of track marks left by the Curiosity rover. Holes in the rover’s wheels, seen here in this view, leave imprints in the tracks that can be used to help the rover drive more accurately. The imprint is Morse code for ‘JPL,’ and aids in tracking how far the rover has traveled. Credit: NASA/JPL-Caltech.
There are several ways to determine how far Curiosity has traveled, but the most accurate measurement is called ‘Visual Odometry.’ Curiosity has specialized holes in its wheels in the shape of Morse code letters, spelling out ‘JPL’ – a nod to the home of the rover’s science and engineering teams – across the Martian soil.
“Visual odometry works by comparing the most recent pair of stereo images collected roughly every meter over the drive,” said Morookian. “Individual features in the scene are matched and tracked to provide a measure of how the camera (and thus the rover) has translated and rotated in 3 dimensional space between the two images and it tells us in a very real sense how far Curiosity has gone.”
Careful inspection of the rover tracks can reveal the type of traction the wheels have and if they have slipped, for instance due to high slopes or sandy ground.
Unfortunately, Curiosity now has new holes in its wheels that aren’t supposed to be there.
Rover Problems
Morookian and Project Scientist Ashwin Vasavada both expressed relief and satisfaction that overall — this far into the mission — Curiosity is a fairly healthy rover. The entire science payload is currently operating at nearly full capability. But the engineering team keeps an eye on a few issues.
“Around sol 400, we realized the wheels were wearing faster than we expected,” Vasavada said.
The team operating the Curiosity Mars rover uses the Mars Hand Lens Imager (MAHLI) camera on the rover’s arm to check the condition of the wheels at routine intervals. This image of Curiosity’s left-middle and left-rear wheels is part of an inspection set taken on April 18, 2016, during the 1,315th sol of the rover’s work on Mars. Credit: NASA/JPL-Caltech/MSSS.
And the wear didn’t consist of just little holes; the team started to see punctures and nasty tears. Engineers realized the holes were being created by the hard, jagged rocks the rover was driving over during that time.
“We weren’t fully expecting the kind of ‘pointy’ rocks that were doing damage,” Vasavada said. “We also did some testing and saw how one wheel could push another wheel into a rock, making the damage worse. We now drive more carefully and don’t drive as long as we have in the past. We’ve been able to level off the damage to a more acceptable rate.”
Early in the mission, Curiosity’s computer went into ‘safe mode’ several times, as Curiosity’s software recognized a problem, and the response was to disallow further activity and phone home.
Specialized fault protection software runs throughout the modules and instruments, and when a problem occurs, the rover stops and sends data called ‘event records’ to Earth. The records include various categories of urgency, and in early 2015, the rover sent a message that essentially said, “This is very, very bad.” The drill on the rover’s arm had experienced a fluctuation in an electrical current – like a short circuit.
“Curiosity’s software has the ability to detect shorts, like the ground fault circuit interrupter you have in your bathroom,” Morookian explained, “except this one tells you ‘this is very, very bad’ instead of just giving you a yellow light.”
Since the team can’t go to Mars and repair a problem, everything is fixed either by sending software updates to the rover or by changing operational procedures.
Curiosity’s drill in the turret of tools at the end of the robotic arm positioned in contact with the rock surface for the first drilling of the mission on the 170th sol of Curiosity’s work on Mars (Jan. 27, 2013) in Yellowknife Bay. The picture was taken by the front Hazard-Avoidance Camera (Hazcam). Image credit: NASA/JPL-Caltech.
“We are just more careful now with how we use the drill,” Vasavada said, “and don’t drill with full force at the beginning, but slowly ramp up. It’s sort of like how we drive now, more gingerly but it still gets the job done. It hasn’t been a huge impact as of yet.”
A lighter touch on the drill also was necessary for the softer mudstones and sandstones the rover encountered. Morookian said there was concern the layered rocks might not hold up under the assault of the standard drilling protocol, and so they adjusted the technique to use the lowest ‘settings’ that still allows the drill to make sufficient progress into the rock.
But opportunities to use the drill are increasing as Curiosity begins its traverse up the mountain. The rover is traveling through what Vasavada calls a “target rich, very interesting area,” as the science team works to tie together the geological context of everything they are seeing in the images.
Finding Balance on Mars
While the diversion at Yellowknife Bay allowed the team to make some major discoveries, they felt pressure to get to Mt. Sharp, so “drove like hell for a year,” Vasavada said.
Now on the mountain, there is still the pressure to make the most of the mission, with the goal of making it through at least four different rock units – or layers — on Mt. Sharp. Each layer could be like a chapter in the book of Mars’ history.
A portion of a panorama from Curiosity’s Mastcam shows the rugged surface of ‘Naukluft Plateau’ plus part of the rim of Gale Crater, taken on April 4, 2016 or Sol 1301. Credit: NASA/JPL-Caltech/MSSS
“Exploring Mt. Sharp is fascinating,” Vasavada said, “and we’re trying to maintain a mix between really great discoveries, which – you hate to say — slows us down, and getting higher on the mountain. Looking closely at a rock in front of you means you’ll never be able to go over and look at that other interesting rock over there.”
Vasavada and Morookian both said it’s a challenge to preserve that balance every day — to find what’s called the ‘knee in the curve’ or ‘sweet spot’ of the perfect optimization between driving and stopping for science.
Then there’s the balance between stopping to do a full observation with all the instruments and doing ‘flyby science’ where less intense observations are made.
“We take the observations we can, and generate all the hypotheses we can in real time,” Vasavada said. “Even if we’re left with 100 open questions, we know we can answer the questions later as long as we know we’ve taken enough data.”
Curiosity’s primary target is not the summit, but instead a region about 1,330 feet (400 meters) up where geologists expect to find the boundary between rocks that saw a lot of water in their history, and those that didn’t. That boundary will provide insight into Mars’ transition from a wet planet to dry, filling in a key gap in the understanding of the planet’s history.
he Curiosity rover recorded this view of the Sun setting at the close of the mission’s 956th sol (April 15, 2015), from the rover’s location in Gale Crater. This was the first sunset observed in color by Curiosity. The image comes from the left-eye camera of the rover’s Mast Camera (Mastcam). Credit: NASA/JPL-Caltech/MSSS/Texas A&M University.
No one really knows how long Curiosity will last, or if it will surprise everyone like its predecessors Spirit and Opportunity. Having made it past the ‘prime mission’ of one year on Mars (two Earth years), and now in the extended mission, the one big variable is the RTG power source. While the available power will start to steadily decrease, both Vasavada and Morookian don’t expect that to be in an issue for at least four more Earth years, and with the right “nurturing,” power could last for a dozen years or more.
But they also know there’s no way to predict how long Curiosity will go, or what unexpected event might end the mission.
The Beast
Does Curiosity have a personality like the previous Mars rovers?
“Actually no, we don’t seem to anthropomorphize this rover like people did with Spirit and Opportunity,” Vasavada said. “We haven’t bonded emotionally with it. Sociologists have actually been studying this.” He shook his head with an amused smile.
Vasavada indicated it might have something to do with Curiosity’s size.
“I think of it as a giant beast,” he said straight-faced. “But not in a mean way at all.”
Curiosity appears to be photobombing Mount Sharp in this selfie image, a mosaic created from several MAHLI images. Credit: NASA/JPL-Caltech/MSSS/Edited by Jason Major.
What has come to come to characterize this mission, Vasavada said, is the complexity of it, in every dimension: the human component of getting 500 people to work and cooperate together while optimizing everyone’s talents; keeping the rover safe and healthy; and keeping ten instruments going every day, which are sometimes doing completely unrelated science tasks.
“Every day is our own little ‘seven minutes of terror,’ where so many things have to go right every single day,” Vasavada said. “There are a million potential issues and interactions, and you have to constantly be thinking about all the ways things can go wrong, because there are a million ways you can mess up. It’s an intricate dance, but fortunately we have a great team.”
Then he added with a smile, “This mission is exciting though, even if it’s a beast.”
“Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” is published by Page Street Publishing, a subsidiary of Macmillan.
Author Nancy Atkinson at JPL with a model of the Curiosity Rover.
Curiosity's view of Mount Sharp, taken with the MastCam on Sept. 9th, 2015. Credit: NASA/JPL-Caltech/MSSS
Following is Part 2 of an excerpt from my new book, “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos.” The book is an inside look at several current NASA robotic missions, and this excerpt is part 2 of 3 which will be posted here on Universe Today, of Chapter 2, “Roving Mars with Curiosity.” You can read Part 1 here. The book is available in print or e-book (Kindle or Nook) Amazon and Barnes & Noble.
Living on Mars Time
The landing occurred at 10:30 pm in California. The MSL team had little time to celebrate, transitioning immediately to mission operations and planning the rover’s first day of activity. The team’s first planning meeting started at 1 o’clock in the morning, ending about 8 a.m. They had been up all night, putting in a nearly 40-hour day.
This was a rough beginning of the mission for the scientists and engineers who needed to live on ‘Mars Time.’
A day on Mars day is 40 minutes longer than Earth’s day, and for the first 90 Mars days – called sols — of the mission, the entire team worked in shifts around the clock to constantly monitor the newly landed rover. To operate on the same daily schedule as the rover meant a perpetually shifting sleep/wake cycle where the MSL team would alter their schedules 40 minutes every day to stay in sync with the day and night schedules on Mars. If team members came into work at 9:00 a.m., the next day, they’d come in at 9:40 a.m., and the next day at 10:20 a.m., and so on.
Those who have lived through Mars Time say their bodies continually feel jet-lagged. Some people slept at JPL so as not to disrupt their family’s schedule, some wore two watches so they would know what time it was on two planets.
About 350 scientists from around the world were involved with MSL and many of them stayed at JPL for the first 90 sols of the mission, living on Mars Time.
But it took less than 60 Earth days for the team to announce Curiosity’s first big discovery.
Water, Water …
A 16-ft. (5 m) high sand dune on Mars called Namib Dune is part of the dark-sand ‘Bagnold Dunes’ field along the northwestern flank of Mount Sharp. Images taken from orbit indicate that dunes in the Bagnold field move as much as about 3 feet (1 m) per Earth year. This image is part of a 360 degree panorama taken by the Curiosity rover on Dec. 18, 2015 or the 1,197th Martian day, or sol, of the rover’s work on Mars. Credit: NASA/JPL-Caltech/MSSS.
Ashwin Vasavada grew up in California and has fond childhood memories of visiting state and national parks in the southwest United States with his family, playing among sand dunes and hiking in the mountains. He’s now able to do both on another planet, vicariously through Curiosity. The day I visited Vasavada at his office at JPL in early 2016, the rover was navigating through a field of giant sand dunes at the base of Mount Sharp, with some dunes towering 30 feet (9 meters) above the rover.
“It’s just fascinating to see dunes close up on another planet,” Vasavada said. “And the closer we get to the mountain, the more fantastic the geology gets. So much has gone on there, and we have so little understanding of it … as of yet.”
At the time we talked, Curiosity was approaching four Earth years on Mars. The rover is now studying those enticing sedimentary layers on Mt. Sharp in closer detail. But first, it needed to navigate through the “Bagnold Dunes” which form a barrier along the northwestern flank of the mountain. Here, Curiosity is doing what Vasavada calls “flyby science,” stopping briefly to sample and study the sand grains of the dunes while moving through the area as quickly as possible.
Now working as the lead Project Scientist for the mission, Vasavada plays an even larger role in coordinating the mission.
“It’s a constant balance of doing things quickly, carefully and efficiently, as well as using the instruments to their fullest,” he said.
Since the successful August 2012 landing, Curiosity has sent back tens of thousands of images from Mars – from expansive panoramas to extreme close-ups of rocks and sand grains, all of which are helping to tell the story of Mars’ past.
‘Selfies’ taken by the Curiosity rover are actually a mosaic created from numerous images taken with the Mars Hand Lens Imager (MAHLI), located on the end of the rover’s robotic arm. However, the arm is not shown in the selfies, because with the wrist motions and turret rotations used in pointing the camera for the component images, the arm was positioned out of the shot in the frames or portions of frames used in this mosaic. However, the shadow of the arm is visible on the ground. This low-angle selfie shows the vehicle at the site from which it reached down to drill into a rock target called “Buckskin” on lower Mount Sharp. Credit: NASA/JPL-Caltech/MSSS.
The images the public seems to love the most are the ‘selfies,’ the photos the rover takes of itself sitting on Mars. The selfies aren’t just a single image like the ones we take with our cell phones, but a mosaic created from dozens of separate images taken with the Mars Hand Lens Imager (MAHLI) camera at the end of the rover’s robotic arm. Other fan favorites are the pictures Curiosity takes of the magnificent Martian landscape, like a tourist documenting its journey.
Vasavada has a unique personal favorite.
“For me, the most meaningful picture from Curiosity really isn’t that great of an image,” he said, “but it was one of our first discoveries so it has an emotional tie to it.”
Within the first 50 sols, Curiosity took pictures of what geologists call conglomerates: a rock made of pebbles cemented together. But these were no ordinary pebbles — they were pebbles worn by flowing water. Serendipitously, the rover had found an ancient streambed where water once flowed vigorously. From the size of pebbles, the science team could interpret the water was moving about 3 feet (1 meter) per second, with a depth somewhere between a few inches to several feet. This geological feature on Mars is exposed bedrock made up of smaller fragments cemented together, or what geologists call a sedimentary conglomerate, and is evidence for an ancient, flowing stream. Some of embedded and loose gravel are round in shape, leading the Curiosity science team to conclude it were transported by a vigorous flow of water. Curiosity’s 100-millimeter Mastcam telephoto lens on its 39th sol of the mission (Sept. 14, 2012). Credit: NASA/JPL-Caltech/MSSS
“When you see this picture, and whether you are a gardener or geologist, you know what this means,” Vasasvada said excitedly. “At Home Depot, the rounded rock for landscaping are called river pebbles! It was mind-blowing to me to think that the rover was driving through a streambed. That picture really brought home there was actually water flowing here long ago, probably ankle to hip deep.”
Vasavada looked down. “It still gives me the shivers, just thinking about it,” he said, with his passion for exploration and discovery visibly evident.
From that early discovery, Curiosity continued to find more water-related evidence. The team took a calculated gamble and instead of driving straight towards Mt. Sharp, took a slight detour to the east to an area dubbed ‘Yellowknife Bay.’
“Yellowknife Bay was something we saw with the orbiters,” Vasavada explained, “and there appeared to be a debris fan fed by a river—evidence for flowing water in the ancient past.”
This map shows the route driven by NASA’s Curiosity Mars rover from the location where it landed in August 2012 to its location in September 2016 at “Murray Buttes,” and the path planned for reaching destinations at “Hematite Unit” and “Clay Unit” on lower Mount Sharp. Credits: NASA/JPL-Caltech/Univ. of Arizona
Here, Curiosity fulfilled ones of its main goals: determining whether Gale Crater ever was habitable for simple life forms. The answer was a resounding yes. The rover sampled two stone slabs with the drill, feeding half-baby-aspirin-sized portions to SAM, the onboard lab. SAM identified traces of elements like carbon, hydrogen, nitrogen, oxygen, and more —the basic building blocks of life. It also found sulfur compounds in different chemical forms, a possible energy source for microbes.
Data gathered by Curiosity’s other instruments constructed a portrait detailing how this site was once a muddy lakebed with mild – not acidic – water. Add in the essential elemental ingredients for life, and long ago, Yellowknife Bay would have been the perfect spot for living organisms to hang out. While this finding doesn’t necessarily mean there is past or present life on Mars, it shows the raw ingredients existed for life to get started there at one time, in a benign environment.
“Finding the habitable environment in Yellowknife Bay was wonderful because it really showed the capability our mission has to measure so many different things,” Vasavada said. “A wonderful picture came together of streams that flowed into a lake environment. This was exactly what we were sent there to find, but we didn’t think we’d find it that early in the mission.”
Still, this lakebed could have been created by a one-time event over just hundreds of years. The ‘jackpot’ would be to find evidence of long-term water and warmth.
That discovery took a little longer. But personally, it means more to Vasavada.
Mars’ climate was one of Vasavada’s early interests in his career and he spent years creating models, trying to understand Mars’ ancient history.
“I grew up with pictures of Mars from the Viking mission,” he said, “and thinking of it as a barren place with jagged volcanic rock and a bunch of sand. Then I had done all this theoretical work about Mars climate, that rivers and oceans perhaps once existed on Mars, but we had no real evidence.”
That’s why the discovery made by Curiosity in late 2015 is so exciting to Vasavada and his team.
“We didn’t just see the rounded pebbles and remnants of the muddy lake bottom at Yellowknife Bay, but all along the route,” Vasavada said. “We saw river pebbles first, then tilted sandstones where the river emptied into lakes. Then as we got to Mt. Sharp, we saw huge expanses of rock made of the silt that settled out from the lakes.”
The explanation that best fits the “morphology” in this region — that is, the configuration and evolution of rocks and land forms – is rivers formed deltas as they emptied into a lake. This likely occurred 3.8 to 3.3 billion years ago. And the rivers delivered sediment that slowly built up the lower layers of Mt. Sharp.
Curiosity picture showing the layers and color variations on Mount Sharp, Mars. Credit: NASA/JPL
“My gosh, we were seeing this full system now,” Vasavada explained, “showing how the entire lower few hundred meters of Mount Sharp were likely laid down by these river and lake sediments. That means this event didn’t take hundreds or thousands of years; it required millions of years for lakes and rivers to be present to slowly build up, millimeter by millimeter, the bottom of the mountain.”
For that, Mars also needed a thicker atmosphere than it has now, and a greenhouse gas composition that Vasavada said they haven’t quite figured out yet.
But then, somehow dramatic climate change caused the water to disappear and winds in the crater carved the mountain to its current shape.
The rover had landed in exactly the right place, because here in one area was a record of much of Mars’ environmental history, including evidence of a major shift in the planet’s climate, when the water that once covered Gale Crater with sediment dried up.
“This all is a significant driver now for what we need to explain about Mars’ early climate,” Vasavada said. “You don’t get millions of years of climate change from a single event like a meteor hit. This discovery has broad implications for the entire planet, not just Gale Crater.”
Other Discoveries
• Silica: The rover made a completely unanticipated discovery of high-content silica rocks as it approached Mt. Sharp. “This means that the rest of the normal elements that form rocks were stripped away, or that a lot of extra silica was added somehow,” Vasavada said, “both of which are very interesting, and very different from rocks we had seen before. It’s such a multifaceted and curious discovery, we’re going to take a while figuring it out.”
• Methane on Mars: Methane is usually a sign of activity involving organic matter — even, potentially, of life. On Earth, about 90 percent of atmospheric methane is produced from the breakdown of organic matter. On Mars, methane has been detected by other missions and telescopes over the years, but it was tenuous – the readings seemed to come and go, and are hard to verify. In 2014, the Tunable Laser Spectrometer within the SAM instrument observed a ten-fold increase in methane over a two-month period. What caused the brief and sudden increase? Curiosity will continue to monitor readings of methane, and hopefully provide an answer to the decades-long debate.
• Radiation Risks for Human Explorers: Both during her trip to Mars and on the surface, Curiosity measured the high-energy radiation from the Sun and space that poses a risk astronauts. NASA will use data from the Radiation Assessment Detector (RAD) instrument Curiosity’s data to design future missions to be safe for human explorers.
Tomorrow: The conclusion of this chapter, including ‘How To Drive a Mars Rover, and ‘The Beast.’ Part 1 is available here.
“Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” is published by Page Street Publishing, a subsidiary of Macmillan.
This self-portrait of NASA's Curiosity Mars rover shows the vehicle at the "Big Sky" site. Credit: NASA/JPL-Caltech/MSSS
Following is an excerpt from my new book, “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos,” which will be released tomorrow, Dec. 20, 2016. The book is an inside look at several current NASA robotic missions, and this excerpt is part 1 of 3 which will be posted here on Universe Today, of Chapter 2, “Roving Mars with Curiosity.” The book is available for order on Amazon and Barnes & Noble.
Seven Minutes of Terror
It takes approximately seven minutes for a moderate-sized spacecraft – such as a rover or a robotic lander — to descend through the atmosphere of Mars and reach the planet’s surface. During those short minutes, the spacecraft has to decelerate from its blazing incoming speed of about 13,000 mph (20,900 kph) to touch down at just 2 mph (3 kph) or less.
This requires a Rube Goldberg-like series of events to take place in perfect sequence, with precise choreography and timing. And it all needs to happen automatically via computer, with no input from anyone on Earth. There is no way to guide the spacecraft remotely from our planet, about 150 million miles (250 million km) away. At that distance, the radio signal delay time from Earth to Mars takes over 13 minutes. Therefore, by the time the seven-minute descent is finished, all those events have happened – or not happened – and no one on Earth knows which. Either your spacecraft sits magnificently on the surface of Mars or lies in a crashed heap.
A depiction of the numerous events required for the Curiosity rover to land successfully on Mars. Credit: NASA/JPL.
That’s why scientists and engineers from the missions to Mars call it “Seven Minutes of Terror.”
And with the Mars Science Laboratory (MSL) mission, which launched from Earth in November of 2011, the fear and trepidation about what is officially called the ‘Entry, Descent and Landing’ (EDL) increased exponentially. MSL features a 1-ton (900 kg), 6-wheeled rover named Curiosity, and this rover was going to use a brand new, untried landing system.
To date, all Mars landers and rovers have used — in order — a rocket-guided entry, a heat shield to protect and slow the vehicle, then a parachute, followed by thrusters to slow the vehicle even more. Curiosity would use this sequence as well. However, a final, crucial component encompassed one of the most complex landing devices ever flown.
Artists concept of the moment the Curiosity rover touches down on the Martian surface, suspended on a bridle beneath the spacecraft’s descent stage. Credit: NASA/JPL-Caltech
Dubbed the “Sky Crane,” a hovering rocket stage would lower the rover on 66 ft. (20 meter) cables of Vectran rope like a rappelling mountaineer, with the rover soft-landing directly on its wheels. This all needed to be completed in a matter of seconds, and when the on-board computer sensed touchdown, pyrotechnics would sever the ropes, and the hovering descent stage would zoom away at full throttle to crash-land far from Curiosity.
Complicating matters even further, this rover was going to attempt the most precise off-world landing ever, setting down inside a crater next to a mountain the height of Mount Rainier.
A major part of the uncertainty was that engineers could never test the entire landing system all together, in sequence. And nothing could simulate the brutal atmospheric conditions and lighter gravity present on Mars except being on Mars itself. Since the real landing would be the first time the full-up Sky Crane would be used, there were questions: What if the cables didn’t separate? What if the descent stage kept descending right on top of the rover?
If the Sky Crane didn’t work, it would be game-over for a mission that had already overcome so much: technical problems, delays, cost overruns, and the wrath of critics who said this $2.5 billion Mars rover was bleeding money away from the rest of NASA’s planetary exploration program.
Mosaic of the Valles Marineris hemisphere of Mars, similar to what one would see from orbital distance of 2500 km. Credit: NASA/JPL-Caltech
Missions to Mars
With its red glow in the nighttime sky, Mars has beckoned skywatchers for centuries. As the closest planet to Earth that offers any potential for future human missions or colonization, it has been of great interest in the age of space exploration. To date, over 40 robotic missions have been launched to the Red Planet … or more precisely, 40-plus missions have been attempted.
Including all US, European, Soviet/Russian and Japanese efforts, more than half of Mars missions have failed, either because of a launch disaster, a malfunction en route to Mars, a botched attempt to slip into orbit, or a catastrophic landing. While recent missions have had greater success than our first pioneering attempts to explore Mars in situ (on location) space scientists and engineers are only partially kidding when they talk about things like a ‘Great Galactic Ghoul’ or the ‘Mars Curse’ messing up the missions.
View of Mars from Viking 2 lander, September 1976. (NASA/JPL-Caltech)
But there have been wonderful successes, too. Early missions in the 1960’s and 70’s such as Mariner orbiters and Viking landers showed us a strikingly beautiful, although barren and rocky world, thereby dashing any hopes of ‘little green men’ as our planetary neighbors. But later missions revealed a dichotomy: magnificent desolation combined with tantalizing hints of past — or perhaps even present day – water and global activity.
Today, Mars’ surface is cold and dry, and its whisper-thin atmosphere doesn’t shield the planet from bombardment of radiation from the Sun. But indications are the conditions on Mars weren’t always this way. Visible from orbit are channels and intricate valley systems that appear to have been carved by flowing water.
For decades, planetary scientists have debated whether these features formed during brief, wet periods caused by cataclysmic events such as a massive asteroid strike or sudden climate calamity, or if they formed over millions of years when Mars may have been continuously warm and wet. Much of the evidence so far is ambiguous; these features could have formed either way. But billions of years ago, if there were rivers and oceans, just like on Earth, life might have taken hold.
Three Generations of Mars Rovers in the ‘Mars Yard’ at the Jet Propulsion Laboratory. The Mars Pathfinder Project (front) landed the first Mars rover – Sojourner – in 1997. The Mars Exploration Rover Project (left) landed Spirit and Opportunity on Mars in 2004. The Mars Science Laboratory Curiosity rover landed on Mars in August 2012. Credit: NASA/JPL-Caltech.
The Rovers
The Curiosity rover is the fourth mobile spacecraft NASA has sent to Mars’ surface. The first was a 23-pound (10.6 kg) rover named Sojourner that landed on a rock-covered Martian plain on July 4, 1997. About the size of a microwave oven, the 2-foot- (65 cm) long Sojourner never traversed more than 40 feet away from its lander and base station. The rover and lander together constituted the Pathfinder mission, which was expected to last about a week. Instead, it lasted nearly three months and the duo returned 2.6 gigabits of data, snapping more than 16,500 images from the lander and 550 images from the rover, as well as taking chemical measurements of rocks and soil and studying Mars’ atmosphere and weather. It identified traces of a warmer, wetter past for Mars.
Sojourner – NASA’s 1st Mars Rover. Rover takes an Alpha Proton X-ray Spectrometer (APXS) measurement of Yogi rock after Red Planet landing on July 4, 1997 landing. Credit: NASA
The mission took place when the Internet was just gaining popularity, and NASA decided to post pictures from the rover online as soon as they were beamed to Earth. This ended up being one of the biggest events in the young Internet’s history, with NASA’s website (and mirror sites set up for the high demand) receiving over 430 million hits in the first 20 days after landing.
Pathfinder, too, utilized an unusual landing system. Instead of using thrusters to touch down on the surface, engineers concocted a system of giant airbags to surround and protect the spacecraft. After using the conventional system of a rocket-guided entry, heat shield, parachutes and thrusters, the airbags inflated and the cocooned lander was dropped from 100 feet (30 m) above the ground. Bouncing several times across Mars’ surface times like a giant beach ball, Pathfinder eventually came to a stop, the airbags deflated and the lander opened up to allow the rover to emerge.
While that may sound like a crazy landing strategy, it worked so well that NASA decided to use larger versions of the airbags for the next rover mission: two identical rovers named Spirit and Opportunity. The Mars Exploration Rovers (MER) are about the size of a riding lawn mower, at 5.2 feet (1.6 meters) long, weighing about 400 lbs (185 kilograms). Spirit landed successfully near Mars’ equator on January 4, 2004, and three weeks later Opportunity bounced down on the other side of the planet. The goal of MER was to find evidence of past water on Mars, and both rovers hit the jackpot. Among many findings, Opportunity found ancient rock outcrops that were formed in flowing water and Spirit found unusual cauliflower-shaped silica rocks that scientists are still studying, but they may provide clues to potential ancient Martian life.
A self-portrait of the Opportunity rover shortly after dust cleared its solar panels in March 2014. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.Incredibly, at this writing (2016) the Opportunity rover is still operating, driving more than a marathon (26 miles/42 km) and it continues to explore Mars at a large crater named Endeavour. Spirit, however, succumbed to a loss of power during the cold Martian winter in 2010 after getting stuck in a sandtrap. The two rovers far outlived their projected 90-day lifetime.
Somehow, the rovers each developed a distinct ‘personality’ – or, perhaps a better way to phrase it is that people assigned personalities to the robots. Spirit was a problem child and drama queen but had to struggle for every discovery; Opportunity, a privileged younger sister, and star performer, as new findings seemed to come easy for her. Spirit and Opportunity weren’t designed to be adorable, but the charming rovers captured the imaginations of children and seasoned space veterans alike. MER project manager John Callas once called the twin rovers “the cutest darn things out in the Solar System.” As the long-lived, plucky rovers overcame hazards and perils, they sent postcards from Mars every day. And Earthlings loved them for it.
Curiosity
While it’s long been on our space to-do list, we haven’t quite yet figured out how to send humans to Mars. We need bigger and more advanced rockets and spacecraft, better technology for things like life support and growing our own food, and we really don’t have the ability to land the very large payloads needed to create a human settlement on Mars.
But in the meantime – while we try to figure all that out — we have sent the robotic equivalent of a human geologist to the Red Planet. The car-sized Curiosity rover is armed with an array of seventeen cameras, a drill, a scoop, a hand lens, and even a laser. These tools resemble equipment geologists use to study rocks and minerals on Earth. Additionally, this rover mimics human activity by mountain climbing, eating (figuratively speaking), flexing its (robotic) arm, and taking selfies.
Artist concept of the Curiosity rover, with the various science instruments labeled. Credit: NASA/JPL.
This roving robotic geologist is also a mobile chemistry lab. A total of ten instruments on the rover help search for organic carbon that might indicate the raw material required by life, and “sniff” the Martian air, trying to smell if gasses like methane — which could be a sign of life — are present. Curiosity’s robotic arm carries a Swiss Army knife of gadgets: a magnifying lens-like camera, a spectrometer to measure chemical elements, and a drill to bore inside rocks and feed samples to the laboratories named SAM (Sample Analysis at Mars) and) and CheMin (Chemistry and Mineralogy). The ChemCam laser can vaporize rock from up to 23 feet (7 meters) away, and identify the minerals from the spectrum of light emitted from the blasted rock. A weather station and radiation monitor round out the devices on board.
With these cameras and instruments, the rover becomes the eyes and hands for an international team of about 500 earthbound scientists.
While the previous Mars rovers used solar arrays to gather sunlight for power, Curiosity uses an RTG like New Horizons. The electricity generated from the RTG repeatedly powers rechargeable lithium-ion batteries, and the RTG’s heat is also piped into the rover chassis to keep the interior electronics warm.
With Curiosity’s size and weight, the airbag landing system used by the previous rovers was out of the question. As NASA engineer Rob Manning explained, “You can’t bounce something that big.” The Sky Crane is an audacious solution.
Curiosity’s mission: figure out how Mars evolved over billions of years and determine if it once was — or even now is — capable of supporting microbial life.
Curiosity’s target for exploration: a 3.4 mile (5.5 km) -high Mars mountain scientists call Mt. Sharp (formally known as Aeolis Mons) that sits in the middle of Gale Crater, a 96-mile (155-km) diameter impact basin.
Gale was chosen from 60 candidate sites. Data from orbiting spacecraft determined the mountain has dozens of layers of sedimentary rock, perhaps built over millions of years. These layers could tell the story of Mars’ geologic and climate history. Additionally, both the mountain and the crater appear to have channels and other features that look like they were carved by flowing water.
The plan: MSL would land in a lower, flatter part of the crater and carefully work its way upward towards the mountain, studying each layer, essentially taking a tour of the epochs of Mars’ geologic history.
The hardest part would be getting there. And the MSL team only had one chance to get it right.
Landing Night
Curiosity’s landing on August 5, 2012 was one of the most anticipated space exploration events in recent history. Millions of people watched events unfold online and on TV, with social media feeds buzzing with updates. NASA TV’s feed from JPL’s mission control was broadcast live on the screens in New York’s Time Square and at venues around the world hosting ‘landing parties.’
But the epicenter of action was at JPL, where hundreds of engineers, scientists and NASA officials gathered at JPL’s Space Flight Operations Facility. The EDL team – all wearing matching light blue polo shirts — monitored computer consoles at mission control.
Two members of the team stood out: EDL team lead Adam Steltzner — who wears his hair in an Elvis-like pompadour — paced back and forth between the rows of consoles. Flight Director Bobak Ferdowski sported and an elaborate stars and stripes Mohawk. Obviously, in the twenty-first century, exotic hairdos have replaced the 1960’s black glasses and pocket protectors for NASA engineers.
MSL project scientist Ashwin Vasavada with a full scale model of the Curiosity rover. Credit: NASA/JPL.
At the time of the landing, Ashwin Vasavada was one of the longest serving scientists on the mission team, having joined MSL as the Deputy Project Scientist in 2004 when the rover was under construction. Back then, a big part of Vasavada’s job was working with the instrument teams to finalize the objectives of their instruments, and supervise technical teams to help develop the instruments and integrate them with the rover.
Each of the ten selected instruments brought a team of scientists, so with engineers, additional staff and students, there were hundreds of people getting the rover ready for launch. Vasavada helped coordinate every decision and modification that might affect the eventual science done on Mars. During the landing, however, all he could do was watch.
“I was in the room next door to the control room that was being shown on TV,” Vasavada said. “For the landing there was nothing I could do except realize the past eight years of my life and my entire future was all riding on that seven minutes of EDL.”
Plus, the fact that no would know the real fate of the rover until 13 minutes after the fact due to the radio delay time led to a feeling of helplessness for everyone at JPL.
“Although I was sitting in a chair,” Vasavada added, “I think I was mentally curled up in the fetal position.”
As Curiosity sped closer to Mars, three other veteran spacecraft already orbiting the planet moved into position to be able to keep an eye on the newcomer MSL as it transmitted information on its status. At first, MSL communicated directly to the Deep Space Network (DSN) antennas on Earth.
To make telemetry from the spacecraft as streamlined as possible during EDL, Curiosity sent out 128 simple but distinct tones indicating when steps in the landing process were activated. Allen Chen, an engineer in the control room announced each as they came: one sound indicated the spacecraft entered Mars’ atmosphere; another signaled the thrusters fired, guiding the spacecraft towards Gale Crater. Tentative clapping and smiles came from the team at Mission Control at the early tones, with emotions increasing as the spacecraft moved closer and closer to the surface.
Partway through the descent, MSL went below the Martian horizon, putting it out of communication with Earth. But the three orbiters — Mars Odyssey, Mars Reconnaissance Orbiter and Mars Express — were ready to capture, record and relay data to the DSN.
Scenes from landing night for the Curiosity rover at JPL’s Space Flight Operations Facility. Credit: NASA/JPL.
Seamlessly, the tones kept coming to Earth as each step of the landing continued flawlessly. The parachute deployed. The heat shield dropped away. A tone signaled the descent stage carrying the rover let go of the parachute, another indicated powered flight and descent toward the surface. Another tone meant the Sky Crane began lowering the rover to the surface.
A tone arrived, indicating Curiosity’s wheels touched the surface, but even that didn’t mean success. The team had to make sure the Sky Crane flyaway maneuver worked.
Then, came the tone they were waiting for: “Touchdown confirmed,” cheered Chen. “We’re safe on Mars!”
Pandemonium and joy erupted in JPL’s mission control, at the landing party sites, and on social media. It seemed the world celebrated together at that moment. Cost overruns, delays, all the negative things ever said about the MSL mission seemed to vanish with the triumph of landing.
“Welcome to Mars!” the Director of the Jet Propulsion Laboratory, Charles Elachi said at a press conference following the dramatic touchdown, “Tonight we landed, tomorrow we start exploring Mars. Our Curiosity has no limits.”
Curiosity’s Twitter feed announced its arrival on Mars on August 5, 2012. Credit: Twitter.
“The seven minutes actually went really fast,” said Vasavada. “It was over before we knew it. Then everybody was jumping up and down, even though most of us were still processing that it went so successfully.”
That the landing went so well — indeed perfectly — may have actually shocked some of the team at JPL. While they had rehearsed Curiosity’s landing several times, remarkably, they were never able to land the vehicle in their simulations.
“We tried to rehearse it very accurately,” Vasavada said, “so that everything was in synch — both the telemetry that we had simulated that would be coming from the spacecraft, along with real-time animations that had been created. It was a pretty complex thing, but it never actually worked. So the real, actual landing was the first time everything worked right.”
Curiosity was programmed to immediately take pictures of its surroundings. Within two minutes of the landing, the first images were beamed to Earth and popped up on the viewing screens at JPL.
“We had timed the orbiters to fly over during the landing, but didn’t know for sure if their relay link would last long enough to get the initial pictures down,” Vasavada said. “Those first pictures were fairly ratty because the protective covers were still on the cameras and the thrusters had kicked up a lot of dust on the covers. We couldn’t really see it very well but we still jumped up and down nevertheless because these were pictures from Mars.”
Amazingly, one of the first pictures showed exactly what the rover had been sent to study.
“We had landed with the cameras basically facing directly at Mt. Sharp,” Vasavada said, shaking his head. “In the HazCam (hazard camera) image, right between the wheels, we had this gorgeous shot. There was the mountain. It was like a preview of the whole mission, right in front of us.”
An image captured by the Curiosity rover shortly after it landed on the Red Planet on August 5, 2015, showing the rover’s main science target, Mount Sharp. The rover’s shadow can be seen in the foreground and the dark band beyond are dunes. Credit; NASA/JPL-Caltech.
Tomorrow: Part 2 of “Roving Mars With Curiosity,” with ‘Living on Mars Time’ and ‘Discoveries’
“Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” is published by Page Street Publishing, a subsidiary of Macmillan.
What is the gravity on Mars? NASA's Hubble Space Telescope took this close-up of the red planet Mars
The planet Mars has few things in common. Both planets have roughly the same amount of land surface area, sustained polar caps, and both have a similar tilt in their rotational axes, affording each of them strong seasonal variability. Additionally, both planets present strong evidence of having undergone climate change in the past. In Mars’ case, this evidence points towards it once having a viable atmosphere and liquid water on its surface.
At the same time, our two planets are really quite different, and in a number of very important ways. One of these is the fact that gravity on Mars is just a fraction of what it is here on Earth. Understanding the effect this will likely have on human beings is of extreme importance when it comes time to send crewed missions to Mars, not to mention potential colonists.
Mars Compared to Earth:
The differences between Mars and Earth are all crucial for the existence of life as we know it. For instance, atmospheric pressure on Mars is a tiny fraction of what it is here on Earth – averaging 7.5 millibars on Mars to just over 1000 here on Earth. The average surface temperature is also lower on Mars, ranking in at a frigid -63 °C compared to Earth’s balmy 14 °C.
Artist rendition of the interior of Mars. Image credit: NASA/JPL-Caltech
And while the length of a Martian day is roughly the same as it is here on Earth (24 hours 37 minutes), the length of a Martian year is significantly longer (687 days). On top that, the gravity on Mars’ surface is much lower than it is here on Earth – 62% lower to be precise. At just 0.376 of the Earth standard (or 0.376 g), a person who weighs 100 kg on Earth would weigh only 38 kg on Mars.
This difference in surface gravity is due to a number of factors – mass, density, and radius being the foremost. Even though Mars has almost the same land surface area as Earth, it has only half the diameter and less density than Earth – possessing roughly 15% of Earth’s volume and 11% of its mass.
Calculating Martian Gravity:
Scientists have calculated Mars’ gravity based on Newton’s Theory of Universal Gravitation, which states that the gravitational force exerted by an object is proportional to its mass. When applied to a spherical body like a planet with a given mass, the surface gravity will be approximately inversely proportional to the square of its radius. When applied to a spherical body with a given average density, it will be approximately proportional to its radius.
The Mars Gravity Model 2011 (MGM2011), showing variations of gravity accelerations over Mars’s surface. Credit: geodesy.curtin.edu.au
These proportionalities can be expressed by the formula g = m/r2, where g is the surface gravity of Mars (expressed as a multiple of the Earth’s, which is 9.8 m/s²), m is its mass – expressed as a multiple of the Earth’s mass (5.976·1024 kg) – and r its radius, expressed as a multiple of the Earth’s (mean) radius (6,371 km).
For instance, Mars has a mass of 6.4171 x 1023 kg, which is 0.107 times the mass of Earth. It also has a mean radius of 3,389.5 km, which works out to 0.532 Earth radii. The surface gravity of Mars can therefore be expressed mathematically as: 0.107/0.532², from which we get the value of 0.376. Based on the Earth’s own surface gravity, this works out to an acceleration of 3.711 meters per second squared.
Implications:
At present, it is unknown what effects long-term exposure to this amount of gravity will have on the human body. However, ongoing research into the effects of microgravity on astronauts has shown that it has a detrimental effect on health – which includes loss of muscle mass, bone density, organ function, and even eyesight.
Understanding Mars’ gravity and its affect on terrestrial beings is an important first step if we want to send astronauts, explorers, and even settlers there someday. Basically, the effects of long-term exposure to gravity that is just over one-third the Earth normal will be a key aspect of any plans for upcoming manned missions or colonization efforts.
Artist’s concept of a Martian astronaut standing outside the Mars One habitat. Credit: Bryan Versteeg/Mars One
For example, crowd-sourced projects like Mars One make allowances for the likelihood of muscle deterioration and osteoporosis for their participants. Citing a recent study of International Space Station (ISS) astronauts, they acknowledge that mission durations ranging from 4-6 months show a maximum loss of 30% muscle performance and maximum loss of 15% muscle mass.
Their proposed mission calls for many months in space to get to Mars, and for those volunteering to spend the rest of their lives living on the Martian surface. Naturally, they also claim that their astronauts will be “well prepared with a scientifically valid countermeasures program that will keep them healthy, not only for the mission to Mars, but also as they become adjusted to life under gravity on the Mars surface.” What these measures are remains to be seen.
Learning more about Martian gravity and how terrestrial organisms fare under it could be a boon for space exploration and missions to other planets as well. And as more information is produced by the many robotic lander and orbiter missions on Mars, as well as planned manned missions, we can expect to get a clearer picture of what Martian gravity is like up close.
As we get closer to NASA’s proposed manned mission to Mars, which is currently scheduled to take place in 2030, we can certainly expect that more research efforts will be attempted.
