Rough Roving: Curiosity's Wheels Show Damage
Curiosity’s dusty wheels. Dents are evident on the inner edge of the wheel’s skin and scratches cover the outer edge.
Mars rover Curiosity. Credit: Ian O'Neill/Dis
When Discovery News Met Mars Rover 'Curiosity'
April 4, 2011 --
I've fallen in love with a robot. But this wouldn't be the first time. When NASA's lunchbox-sized Sojourner rover made its first, timid steps on Martian soil in 1997, I was in love. When NASA's twin rovers Spirit and Opportunity bounced across the Red Planet's terrain and sent that heart-stopping signal that they were "OK" in 2004, I was in love. Most recently, with the help of social media and my addiction to Twitter, I was besotted with the Mars Phoenix lander when it touched red dirt in 2008. But today, I met NASA's biggest wheeled robot yet: the Mars Science Laboratory, or simply, "Curiosity." And yes, even before she's left the clean room where she was assembled, I'm in love with that six-wheeled, laser-toting, nuclear-powered machine. In a special media event held at NASA's Jet Propulsion Laboratory (JPL) near Pasadena, Calif., on April 4, I had the exciting opportunity to see Curiosity with my own eyes before she's shipped to Cape Canaveral, Fla., for launch later this year. Here are a few photos from this memorable event.
Me in my bunny suit, hood and mask, all preca
Keeping it Clean
On arriving at JPL, I collected my visitor's badge and was escorted to the Spacecraft Assembly Facility with freelance photographer Joseph Linaschke who was covering the event for BoingBoing. Renowned Peter Theisinger, Project Manager of the Mars Science Laboratory, was there to meet us in the gallery overlooking the "clean room" where Curiosity awaited below. Theisinger enlightened us on a few of the finer points of the mission while we watched an animated movie of the reentry, descent and landing of this ingenious robot. After being escorted downstairs, we went into a small changing room where all of us media folks had to change into our "bunny suits" before entering the clean room. One of the guys helping us to "suit up," obviously used to visitors getting excited about dressing up, pointed to a mirror and said, "You can get a photo there if you like?" Why not?
Very excited to be there. Credit: Ian O'Neill
There She Is
The first thing that struck me about the rover was her size. I often hear scientists comparing Curiosity to the size of a Mini Cooper car, but that didn't prepare me for what I saw. Hoisted atop a metal frame, with all six wheels off the ground, I was amazed by the suite of experimental equipment that had been packed on board. Gold cables snaked over the rover, the prominent mast with cameras attached towered above, the robotic arm and various experiments jutted out of Curiosity's body. If you compare the completed rover with previous artist's impressions, you'd notice a big difference. This is one tough-looking robot. A special thanks to Joseph Linaschke for taking my picture!
The suite of cameras on Curiosity's mast, inc
Curiosity Has a Face
One instrument that has been receiving a lot of attention is the ChemCam, a suite of remote sensing instruments. The large circle shown in the "head" of Curiosity (pictured here) is the first "laser-induced breakdown spectroscopy system" to be used on Mars. For an explanation for how this worked, I asked rover support engineer Matt Horner. "The ChemCam, the large window up there [on the mast], has a laser that can actually vaporize the surface of a rock and look at the light reflected to tell us what that rock is made of," Horner told me. "It has a range of up to 30 feet." Horner also described how the invisible infrared laser made sparks on the surface of sample targets they fired the laser at during tests, which I thought sounded like fun.
Photo. One of Curiosity's wheels. Credit: Ian
If you thought the rims on your car are impressive, take a look at Curiosity's bling. Constructed from aircraft-grade aluminum, the rover sports six of these durable, lightweight, 20 inch (50 centimeter) wheels. They are twice the diameter of Spirit and Opportunity's wheels and will help Curiosity roll over obstacles up to 30" (75 cm) high.
Bill Nye interviews Emily Lakdawalla in front
Although it was hard to know who was who in the clean room, I bumped into Emily Lakdawalla, Planetary Society blogger who was in a similar state of excitement as I was. Planetary Society Executive Director Bill Nye (The Science Guy) was also there quizzing mission scientists.
The aeroshell that will house Curiosity. Cred
To protect it in space during transit to Mars and entry through the Martian atmosphere, Curiosity will be encased inside an Apollo-sized capsule consisting of an aeroshell and heat shield. The back shell was on display in the clean room and Jennifer Knight, cruise stage and aeroshell integration lead, was there to answer questions. "It's very similar in structure [to the Mars Exploration Rovers' (MER) aeroshell]," Knight told me. "It's a honeycombe composite structure. The white that you see here is a thermal protection material, the same material we used on MER and very similar to space shuttle tiles to protect it as it enters the atmosphere." The aeroshell is approximately 15 feet (4.6 meters) in diameter, double the size of ones used to deliver Spirit and Opportunity to Mars.
The "sky crane" descent stage. Credit: Ian O'
The Sky Crane
To ensure a gentle touchdown on the Martian surface, Curiosity will use a rocket-powered "sky crane" to control the final stage of descent. After the back shell has been ejected, the sky crane will lower the rover via a system of cables and then fire up the rockets. Once the rover touches down, the sky crane will release Curiosity and then fly away. But what happens to the sky crane assembly then? "The descent stage has to fly away and maintain a certain distance from the rover so when it does crash on the ground, it's not going to cause damage [to the rover] by anything that's kicked up," said Mark Yerdon, descent stage integration lead. "It's controlled in the sense that it's controlled to fly away, to throttle up and move away from the rover. But it's not going to make a nice soft touchdown, like a helicopter." Basically, after delivering Curiosity, the only thing the sky crane has to do is to ditch, at a safe distance, into the Martian dirt.
Mars rover Curiosity. Credit: Ian O'Neill/Dis
The Ideal Mission
After visiting Curiosity, I wasn't only wowed by the technology and the groundbreaking science this robot will do on the Martian surface. I was also humbled by the strong personal connection between the rover and everyone that has worked on her. Also, confidence in this mission is high, especially when following in the footsteps of the awesome Mars Expedition Rovers, one of which is still trundling across the Martian surface 7 years on. So, ideally, how is Curiosity expected to perform? Will she exceed our wildest expectations like her predecessors? Matt Horner told me that so long as everything goes to plan, he'll be happy. His ideal mission would be "a nice successful landing, everything waking up nicely and then completing our primary mission 687 day mission that we spec'd out, hopefully finding some pretty interesting things along the way." I'll be following the progress of Curiosity very closely, and will look forward to launch around Thanksgiving later this year. Special thank you to Guy Webster for inviting Discovery News to JPL.
If, like me, you spend time obsessively perusing the thousands of incredible raw images flooding from NASA’s Mars rover Curiosity every day (or sol), you may have noticed that the car-sized robot is picking up obvious signs of wear and tear. Dust is an inevitable part of rolling in the Martian dirt, but Curiosity’s 20 inch (50 centimeter) wheels have picked up more than just dust, they have some pretty gnarly dents and scratches, too.
Having only traveled less than a kilometer from its landing site, 281 sols into its several-mile, two year primary mission (a mission that will be extended assuming full health of the rover is maintained), could these early signs of wheel damage be a problem for the longevity of Curiosity’s Mars roving?
Pushing this concern for Curiosity’s mobility to one side for now, I pondered the tough engineering tests these wheels would have been subjected to during rover construction. But surprises do happen, after all, especially when exploring a brand new region on an alien world. Could the material inside Gale Crater be harsher than predicted?
Take, for example, Curiosity’s rocket-powered landing on the Martian surface on Aug. 5, 2012. On viewing the stunning high-resolution photos from the robot’s MastCam, I noticed small rocks littered the deck of the rover. Indeed, during landing, mission managers suspected an errant piece of gravel was the likely culprit that damaged one of Curiosity’s wind sensors.
During one of the press conferences that followed, I asked the rover team about the rocks that littered the rover’s deck. Although they quickly ruled out any complications with the debris being there, they did admit that the debris was “unexpected.” The gravel could have been of a lower density than predicted, causing it to be kicked off the surface higher than expected, one of the first of many surprises that have excited the world in the first few sols of this historic mission.
So in the spirit of Martian surprises, could this rover wheel wear and tear be an unexpected side effect of rolling such a massive robot across jagged bedrock? Fortunately, there’s good news.
Detail of the inner edge of Curiosity’s front left wheel (contrast enhanced) — dents and possible punctures are evident.
“The wear in the wheels is expected,” Matt Heverly, lead rover driver for the MSL mission at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., told Discovery News via email. “The ‘skin’ of the wheel is only 0.75mm thick and we expect dents, dings, and even a few holes due to the wheels interacting with the rocks.”
Curiosity’s wheels are constructed from tough aircraft-grade aluminum, but they will certainly bear the brunt of rock attrition as the mission progresses.
Back on Earth, JPL scientists carry out test runs on Curiosity’s skinny “twin” rover. The “Scarecrow,” as its lovingly called, carries the same weight that Curiosity carries on Mars. Keep in mind that Mars gravity is roughly one-third of that on Earth, so the Scarecrow looks very spidery and small compared to its Martian sibling.
“We have the same wheels on our Scarecrow test rover, which weighs the same on Earth as Curiosity weighs on Mars,” Heverly added. “We have driven Scarecrow about 12 kilometers (7.5 miles) in the Marsyard over rocks and slopes much harsher than we expect for Curiosity.
“There are some dents and holes in these wheels, but the rover is still performing well.”
As seen in the inset image above, a closeup section of the inner edge of Curiosity’s front left wheel not only has obvious denting, there may also be the beginnings of punctures in the aluminum skin. It may seem alarming, but it is an expected consequence of roving on Mars.
“We will continue to characterize the wheels both on Mars and in the Marsyard, but we don’t expect the wear to impact our ability to get to Mt. Sharp,” said Heverly.
The top photograph was captured by Curiosity’s Mars Hand Lens Imager (MAHLI), a camera mounted on its robotic arm, on sol 275 of the mission to Gale Crater. Periodically, MSL rover drivers command the camera to survey the rover’s undercarriage and wheels to look for damage. The famous “self portraits” are used for the same reason — to make sure the rover is fully intact and to monitor dust build-up.
So, when looking closely at the wonderful array of imagery being beamed back from Mars, keep in mind that Curiosity’s big wheels were designed to dominate Mars, but don’t be surprised if they pick up some battle scars on the way.
Special thanks to JPL’s Guy Webster and Whitney Clavin
Image credits: NASA/JPL-Caltech