Saturday, February 17 marked the 5000th local day (sol) of operations for NASA's Mars Opportunity rover, which was originally designed to last for just 90 sols after its January 2004 landing date, but has instead continued to set milestones like completing a marathon-length tour of its surroundings and taking huge composite photos of its new world's surface.
An artist's conception of Opportunity on Mars. Photo: AP
A Martian "sol" lasts about 40 minutes longer than an Earth day, and a Martian year lasts nearly two Earth years. Opportunity's Sol 1 was landing day, Jan. 25, 2004 (that's in Universal Time; it was Jan. 24 in California). The prime mission was planned to last 90 sols. NASA did not expect the rover to survive through a Martian winter. Sol 5,000 will begin early Friday, Universal Time, with the 4,999th dawn a few hours later. Opportunity has worked actively right through the lowest-energy months of its eighth Martian winter.
According to JPL, Opportunity has now taken over 225,000 photos, including a recent selfie NASA posted on Friday.
Teen Life: Now 14-year-old Opportunity celebrates 5,000 sols on Mars with first full #selfie.
— Spirit and Oppy (@MarsRovers) February 17, 2018
While its twin rover, Spirit, sent its last transmission in 2010 after getting stuck in sand and losing power, Opportunity has been able to continuously recharge thanks to Marian winds which clear dust from its solar panels. It has at times experienced significant downtime like 19 weeks stuck in a single spot, Space.com reported, or another occasion it got stuck in a sand dune.
Opportunity's NASA controllers have to periodically re-orient the rover to get better exposure to sunlight.
Per NASA, Spirit and Opportunity's onboard instruments included four spectrometers and rock abrasion tools, which helped provide huge amounts of information about the composition of Mars' surface and its weather patterns:
With data from the rovers, mission scientists have reconstructed an ancient past when Mars was awash in water. Spirit and Opportunity each found evidence for past wet conditions that possibly could have supported microbial life. Opportunity's study of "Eagle" and "Endurance" craters revealed evidence for past inter-dune playa lakes that evaporated to form sulfate-rich sands. The sands were reworked by water and wind, solidified into rock, and soaked by groundwater.
While Spirit's initial travels in Gusev Crater revealed a more basaltic setting, after reaching the "Columbia Hills" the rover found a variety of rocks indicating that early Mars was characterised by impacts, explosive volcanism, and subsurface water. Unusual-looking bright patches of soil turned out to be extremely salty and affected by past water. At "Home Plate," a circular feature in the "Inner Basin" of the "Columbia Hills," Spirit discovered finely layered rocks that are as geologically compelling as those found by Opportunity.
Both models were major improvements on their predecessors, Popular Science noted. In 1997, NASA's Pathfinder mission arrived on Mars, but its Sojourner rover broke down after just three months and carried a relative dearth of useful scientific tools. The United Kingdom's Beagle 2 lander was lost in 2003 upon arrival, likely after failing to fully deploy solar arrays that blocked its transmitters.
The most recent NASA craft to roam the Red Planet, the Curiosity rover, uses a small radioisotope thermoelectric generator as its power source and has currently spent just over 1960 sols on Mars.