My batteries are low and it’s getting dark: Opportunity by Luke B Richardson

Opportunity lasted fifty-six and a bit times longer than it was supposed to. It had a broken wheel, it’s instruments had run out of the radioactive power that made them function, and the memory in its computer had lost the ability to write anything down. It had also found Mars’ first meteorite, provided some of the first compelling evidence for water once existing on Mars, and even took pictures of its moons. The little rover, which only stands as high as your waist and as wide as a patio table, had achieved beyond it’s designer’s wildest dreams.

Opportunity and Spirit were twin rovers. Spirit was to be launched first, and was very much the “Lead” rover, with Opportunity being a nice bonus if both succeeded. Less than half of the probes sent to the surface of Mars had survived, so the two rovers were insurance. Both were named by nine-year-old Sophie Collis, who had won an essay competition, then packed onto two separate rockets and launched at a cost of $830 million for the pair.

Spirit and Opportunity were expected to last 90 sols, which aren’t quite the same as days on Earth. The Martian day is 24 hours and 37 minutes long, meaning for every 39 Mars days, 40 Earth days pass. Curiosity lasted for 5111 Sols, or 5243 Earth days. The rovers are agonisingly slow, averaging 0.022 mph. This is because of the great distance between the rovers, even radio signals take about half an hour to be transmitted. The rovers drive themselves, stopping every 10 seconds for 20 seconds to scan for obstacles. Even at this glacial speed, Opportunity has moved 28.06 miles on Mars, an all-time record.

Opportunity’s crowning achievement was the discovery of solid evidence for water on Mars. On sol 23, while digging its first hole, it found small shiny, spherical stones, known as spherules. Analysis of these revealed them to be lumps of Haematite, an Iron based ore that only readily forms in bodies of water. Nasa later judged that the rocks the rover was driving on were sedimentary, and formed by waves lapping at the shore of an incredibly ancient sea. While Opportunity found no direct evidence of life once existing on the red planet, all life as we know it requires liquid water, questioning the possibility. Sedimentary rock takes millions of years to form, meaning this ocean existed for a long time. Long enough, perhaps, for life.

The computers on the rover were outdated when they launched, using a processor from 1990 that was hardened to resist radiation. The memory capability of the rover was insufficient, thousands of times smaller than today’s average laptops. Around Sol 3730, the miniscule 256 Megabyte memory developed “Amnesia”, scrambling any data that was stored there beyond use. This meant the rover had to store everything in the even smaller 128 megabytes of ram, and everything written in ram is lost when it turns off. The rover relied on this memory for the rest of the mission, with much data lost to power outages.

As Mars gets very cold; around -125 ℃, the batteries stop working as the plastic of its circuit-boards shrinks and cracks. To stop this, some parts of the rover must be heated when the temperature gets this low. These heaters use a lot of power, so are only used when absolutely needed. This was fine when the rover had lots of sun for power, but when hibernating to survive the dust storms it had no access to light leaving the rover powerless. The only way to turn off the heater entirely was to turn the whole computer system off, leaving the rover unaccessible for communication.

Around sol 5105, the largest dust storm ever seen started to blot out the sun. By sol 5111, the whole planet was engulfed, and no power came to the panels. If the heater was not broken, the rover could’ve waited in the storm sipping power while still being able to communicate. As it was, all that could be done was to turn the rover off, and hope the sun became bright enough to reactivate the rover. The solar panels were too covered in dust as this energy never came. NASA declared opportunity lost on 13/02/2019, 16 years after launch and fourteen years, nine months and twenty-one days after its mission was planned to end.