Curiosity recently rolled into a region filled with boxwork formations. These hardened ridges are believed to have been created by underground water billions of years ago. Stretching for miles on this part of Mount Sharp, a 3-mile-tall (5-kilometer-tall) mountain, the formations might reveal whether microbial life could have survived in the Martian subsurface eons ago, extending the period of habitability farther into when the planet was drying out.
Carrying out this detective work involves a lot of energy. Besides driving and extending a robotic arm to study rocks and cliffsides, Curiosity has a radio, cameras, and 10 science instruments that all need power. So do the multiple heaters that keep electronics, mechanical parts, and instruments operating at their best. Past missions like the Spirit and Opportunity rovers and the InSight lander relied on solar panels to recharge their batteries, but that technology always runs the risk of not receiving enough sunlight to provide power.
Instead, Curiosity and its younger sibling Perseverance each use their MMRTG nuclear power source, which relies on decaying plutonium pellets to create energy and recharge the rover's batteries. Providing ample power for the rovers' many science instruments, MMRTGs are known for their longevity (the twin Voyager spacecraft have relied on RTGs since 1977). But as the plutonium decays over time, it takes longer to recharge Curiosity's batteries, leaving less energy for science each day.
The team carefully manages the rover's daily power budget, factoring in every device that draws on the batteries. While these components were all tested extensively before launch, they are part of complex systems that reveal their quirks only after years in the extreme Martian environment. Dust, radiation, and sharp temperature swings bring out edge cases that engineers couldn't have expected.
"We were more like cautious parents earlier in the mission," said Reidar Larsen of NASA's Jet Propulsion Laboratory in Southern California, which built and operates the rover. Larsen led a group of engineers who developed the new capabilities. "It's as if our teenage rover is maturing, and we're trusting it to take on more responsibility. As a kid, you might do one thing at a time, but as you become an adult, you learn to multitask."
For example, Curiosity's radio regularly sends data and images to a passing orbiter, which relays them to Earth. Could the rover talk to an orbiter while driving, moving its robotic arm, or snapping images? Consolidating tasks could shorten each day's plan, requiring less time with heaters on and instruments in a ready-to-use state, reducing the energy used. Testing showed Curiosity safely could, and all of these have now been successfully demonstrated on Mars. Another trick involves letting Curiosity decide to nap if it finishes its tasks early. Engineers always pad their estimates for how long a day's activity will take just in case hiccups arise. Now, if Curiosity completes those activities ahead of the time allotted, it will go to sleep early.
By letting the rover manage when it naps, there is less recharging to do before the next day's plan. Even actions that trim just 10 or 20 minutes from a single activity add up over the long haul, maximizing the life of the MMRTG for more science and exploration down the road.
JPL also developed an algorithm to reduce wear on Curiosity's rock-battered wheels. And while engineers closely monitor any new damage, they aren't worried: After 22 miles (35 kilometers) and extensive research, it's clear that, despite some punctures, the wheels have years' worth of travel in them. (And in a worst-case scenario, Curiosity could remove the damaged part of the wheel's "tread" and still drive on the remaining part.)
Together, these measures are doing their job to keep Curiosity as busy as ever.
Related Links
Curiosity Mars Rover
Mars News and Information at MarsDaily.com
Lunar Dreams and more
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