To celebrate the third “landiversary” of the Curiosity rover touching down on Mars, a team of engineers and scientists associated with NASA’s Mars rover Curiosity participated in a Reddit AMA (“Ask Me Anything”) thread on Aug. 5. Registered users were allowed to submit questions to the team about the Mars mission.

NASA’s Jet Propulsion Laboratory in Pasadena, Calif., a division of the California Institute of Technology, built the rover and manages the project for NASA’s Science Mission Directorate in Washington. The JPL is home to the Spacecraft Assembly Facility, a Class 10,000 ISO 7 cleanroom with horizontal airflow and return.

I submitted a question and was thrilled to see an answer pop up within a few minutes:

CE: Hi! Congratulations on the success your mission has had thus far. Curiosity was built in the JPL cleanroom, correct? What was that like? What lessons have you taken from this experience to improve aerospace cleanrooms in the future?

Curiosity Mars Rover: Yes, Curiosity was built in the JPL cleanroom. This is necessary to ensure the vehicle stays as clean as possible – even small amount of dust and dirt can interfere with the systems. You have to wear a special white gown, booties, and cap to contain all of your human filthiness. Then you pass through an air shower and airlock when entering the room. Everything worked as expected and the cleanroom worked great. One of the biggest challenges was accommodating the size of MSL with all of its stages. The assembly team had to choreograph the motion of the individual stages very carefully.

Other Reddit users asked insightful questions that were answered by the Curiosity team. Here are some of the things we learned from the NASA team’s AMA session:

• Their most surprising discovery, which they uncovered during the first drill hole on Mars, is that that Yellowknife Bay was once a habitable environment.
• Most of the rover’s computer software is written in C programming language. 
• Their biggest challenge thus far? “We’ve had a few, actually!” said Kim Lichtenberg, Mission Operations Engineer and SAM Instrument Engineer. “On sol 199 [a “sol” is a Martian solar day; a little under 25 hours], part of our flash memory failed on the A-side computer in a section of memory that prevented the rover from shutting down. When the rover is ‘awake’, it is actually power-negative — it needs to ‘sleep’ in order to recharge the batteries. So we get the downlink from sol 199, and we see the rover is in serious trouble — if it doesn’t go to sleep soon, it is going to run out of power and we’ll lose the spacecraft. So we made the decision to switch to the B-side computer on the rover — not knowing if the same malfunction was happening on the B-side — because it was the only thing we could do that would allow us to regain control of the spacecraft. It worked, and we were able to configure the A-side computer so that it could function as our back-up computer! We’ve also had a few electrical issues with our drill which we’ve been able to figure out workarounds for, and the terrain in Gale crater hasn’t been as gentle on our wheels as we’d like. As for challenges we have not yet overcome, we always have it in the back of our heads that anything can happen on the rover at any time, and we have to be prepared for it!”
• They wish they had installed a higher-mounted camera on Curiosity, to see farther and over low-lying features. Also, some kind of ground penetrating radar (GPR) to see bedrock layers underneath us. GPR will be on the future Mars2020 rover.
• “The long-term science goal [for Curiosity] is to traverse up the side of Mt. Sharp to study the changing layers that we see in the mountain. As we ascend, it’s like a time capsule, as subsequent layers reflect different time periods of Mars’ history,” said Michael Mischna, Science Operations Working Group chair (coordinator of daily science activities) and an atmospheric scientist. “We’re at the base of the mountain right now, studying the earliest, oldest time in Mars’ history. Curiosity has been designed to last much longer than its one-Mars-year nominal mission, and all signs so far point to a long life for the rover.”
• Curiosity used a skycrane system to land rather than the airbag landings of previous rovers. The reason — Curiosity was too heavy for an airbag landing and the bags would “stroke out.”
• In response to a Reddit user who asked if Curiosity has implanted living microbes onto the surface of Mars that remained on the rover since its launch from Earth: “We have gone to great lengths to sterilize, as best we can, the entire rover to avoid cross-contamination with the Martian environment. After all, if/when we discover life on Mars, we’d like to be absolutely certain it’s native to Mars and not something we brought ourselves,” said Mischna. “Inevitably, though, there are probably some extremely robust microbes that have survived the sterilization process and trip to Mars — same as with every robotic explorer. But we’ve not ‘implanted’ microbes (intentionally or unintentionally) onto the surface.”
• Raw images from Mars can be viewed here: http://mars.jpl.nasa.gov/msl/multimedia/raw/
• Curiosity’s Radiation Assessment Detector (RAD) is the first instrument to measure the radiation during our trip to Mars from inside the spacecraft. This will help NASA figure out the type of shielding future missions will need. NASA hopes to send a manned mission to Mars in the late 2030s.
• Given the choice of sending one bus-sized rover or 100 duck-sized rovers on the next Mars mission, the team would rather send 100 duck-sized rovers to cover more ground. 
• The rover has already survived longer than its nominal mission of one Mars year, and has traveled over 11 km (almost 7 miles) on the surface. The biggest problem to date is wear-and-tear on the wheels — the Martian surface lacks lacking the smoothing influence of water, and rocks and soil tend to be very sharp and angular, which wears out the wheels further. All of this falls within NASA’s expectations, but sooner or later the wheels will be unusable.
• There is a prototype Mars helicopter under development at the JPL; although Curiosity doesn’t use it, it’s possible that a future mission will. Click here for video: https://www.youtube.com/watch?v=vpBsFzjyRO8 
• According to Lichtenberg, Curiosity’s prime mission was one Mars year, equal to about two Earth years. “The team is always keeping track of what we call ‘consumables’ — resources on the rover that once they’re gone, they’re gone!” she says. “We use those sparingly so we can keep the rover going as long as possible and get the most science out of the mission! We also have to be aware of how our human crew is doing — at this point it’s kind of a like a marathon instead of a sprint, so we’re continuously making small tweaks to how we operate the rover so that it’s less taxing on the operations team.”
• It’s a “long shot,” but some day we might find life deeper on Mars. According to Deputy Project Scientist Joy Crisp, “The environment on the surface of Mars today is quite harsh for life as we know it, but if life exists on Mars, it would be protected from radiation at depth and liquid water could be stable there too.”
• No, Curiosity has never jumped a crater X-Games style.