Wednesday was a bittersweet day for NASA and JPL as they said goodbye to the second of the rover twins exploring the Red Planet.
Launched in 2003, Opportunity landed shortly after its twin counterpart, Spirit, in 2004.
Though the mission is considered a success, it was declared complete this afternoon after NASA/JPL team members failed to receive a response from Opportunity after having sent the final recovery commands.
Initially slated to run for only 90 days, the total mission lasted a surprising 14 ½ years. At the onset, the mission was racked with issues beginning with a massive solar storm that threatened to irreparably damage the rovers. In order to save functionality, JPL ordered Spirit and Opportunity to completely shut down onboard computers in order to save them.
Once safely on the surface of Mars, mission specialists noticed that the heater on Opportunity’s robotic arm was stuck in the ON position.
This meant that precious battery power was being wasted. JPL then sent commands to the rover instructing it to go into deep sleep mode on a nightly basis. With a battery life consisting of 5000 charge/discharge cycles, it would now operate at a continued 80% capacity for the remainder of its mission.
Because this deep sleep mode could not be initiated prior to the historic dust storm that encircled the planet in June 2018, mission specialists believe this is the main reason for its failure to respond to recovery commands: the battery has likely been completely drained.
Another issue Opportunity encountered during the mission was that of the failure of the flash memory. When this stopped working, Opportunity could no longer save data collected in a given day, prior to shut down at night. This meant that the team back on Earth had to work quickly to download all the data collected each day to prevent an irretrievable loss of valuable information.
Despite these issues, Opportunity spent nearly two decades on Mars, producing some important scientific discoveries.
Akin to a forensic scientist, the rover was a robotic field geologist that used it rock sampling ability to determine information about Mars’ past. While today Mars is a cold, dry, and desolate place, it wasn’t always so. The Red Planet used to be quite the opposite: a hot and steamy place with violent meteor impacts and volcanic explosions. This was proven by Opportunity when it found evidence of past hydrothermal activity.
This evidence shows that Mars may once have been an extremely habitable place for hearty microorganisms.
The first mission given to Opportunity lasted for 9 years and hit geologic pay-dirt from the beginning. Starting at Little Eagle Crater, the rover made the journey to Endurance Crater, and then Victoria Crater.
This mission took 4 ½ years to complete. Younger rocks in these areas showed that liquid water had once existed below the surface. Though to say liquid water gives the wrong impression.
It was discovered that the liquid was in the form of sulfuric acid when the rover determined that the rocks in the area were composed of sulfate sandstone, which is largely made up of sulfur and evaporated salt water.
Once this part of the mission was complete, JPL set its sights on Endeavor Crater. Because of topographical issues, the route to Endeavor was not a direct one, making the journey take years. Once Opportunity was on the rim of the newest target, it saw evidence of drinkable water.
This was determined by studying rocks that predated the creation of the crater, itself, that were composed of clay minerals that are typically formed near neutral Ph (drinkable) water.
Chief Administrator Jim Bridenstine, joked that he takes full responsibility for the end of the rover mission since the massive dust storm and ensuing radio silence occurred shortly after he took on this new position with NASA.
But NASA promises we will see much more science to come with the launch of the Mars 2020 rover in July of next year. It is the legacy of Spirit and Opportunity that helped with the development of this newest mobile science station.
Mars 2020 will be equipped with better wheels, have the ability to talk to the orbiters, and the ability to do things faster with the help of auto-navigation that will allow the rover to navigate more complex terrain.
Slated to land in Jezero Crater in Columbia Hills, the rover will be looking for evidence of past life. Jezero Crater is known to have once had standing water within it and the team hopes to find out if life ever existed there. Additionally, JPL is hoping to find out why Mars’ climate changed and where all the life (if ever any existed) went.
Another cool mission we can look forward to is that of a sample return mission. This will allow samples collected on the Red Planet to be brought back to Earth for more detailed study about Mars’ past climate and habitability.
In talking of plans to eventually send humans to Mars, Bridenstine stresses the importance of figuring out how to safeguard our men and women against the deadly solar flares that affected Spirit and Opportunity en route, given that these flares are a regular occurrence. He reinforced the importance of working with international partners in order to get to Mars safely to work alongside the robots and rovers that will already be there.
He further stated that the main goal is to discover life on another world, especially given that the Curiosity rover found complex organic compounds on the Red Planet not too long ago. Though, Bridenstine admits these compounds do not guarantee that life ever existed on Mars.
As for the rovers, themselves, there are no plans to ever retrieve them. Mars is their permanent home and they sit where they worked as a testament to human ingenuity and the drive to learn and explore.