On June 10, 2018, the people of Earth received their last transmission from the Opportunity rover of Mars.
Now, 248 days later, scientists and engineers at NASA's Jet Propulsion Lab have had to make a hard decision: They have declared the rover dead. The mission is over.
The cause of Opportunity's demise was an immense Martian dust storm. The atmosphere of Mars is thin (surface pressure there is about 0.6% of Earth's sea level), but it has an effect; winds can pick up dust and whip it around. This fine-grained stuff (mostly eroded basalt and red rust — literally, iron oxide) can stay in the air a long time, darkening the surface.
These global storms happen every few years. The last intense one was in 2007, which the rover was able to survive. This most recent one started locally on one small area of Mars on May 30 of 2018, but grew and grew and GREW and within three weeks had gone global. The surface got so dark that only 0.002% of the light from the Sun got through: a drop by a factor of 60,000.
Opportunity got its power through solar panels, so the problem here is obvious (Curiosity, on the other side of the planet, missed the worst of the storm, but also didn't run on solar; its advanced instruments needed a lot more power, so it used electricity generated by the decay of radioactive isotopes). Also, in this case, the problem was fatal. Without enough juice to power its instruments, it put itself into sleep mode. The storm cleared in September, but by then it was too late. The continuous bitter cold for weeks drained the battery and made it impossible for the rover to wake itself back up (the specifics of this aren't known entirely, though there are ideas). Mission team members on Earth tried many times over the past months — over 800 times! — to communicate with Opportunity, but (despite some false alarms) were never able to get it to respond.
It's always sad when a mission comes to an end, especially one that lasted so long, did so much, and, to be honest, was so easy to anthropomorphize. But let's take a look at what Opportunity accomplished, shall we?
No; there is too much. Let's sum up.
Among Opportunity's successes:
- Opportunity landed in a crater as planned, and immediately found hematite, which forms in standing (though acidic) water.
- It later found rocks with different compositions that indicated they formed when Mars was warmer and wetter, and the water wasn't nearly as acidic.
- It found gypsum, formed from flowing water through cracks in rocks.
- It studied so many craters up close that scientists could get an idea of how they formed and changed (eroded) over time.
- Opportunity studied the Martian atmosphere, too, so that scientists can understand it better in prelude to sending humans there. It also looked at sand dunes, which, coupled with knowledge of the air and wind, allowed scientists to better understand the nature of the sand that covers Mars. It also saw clouds, many times.
- Speaking of weather, Opportunity got images of many dust devils, tornado-like vortices of swirling air. Some of these on Mars grow huge; one was over 20 kilometers high!
I could go on and on. If you want more, NASA provides.
Incidentally, while doing all this, Opportunity managed to drive farther than any other rover on Mars — a total of over 45 km — and lasted for 5,250 days (14+ years). Mind you, the initial mission was for 90 days, so Opportunity lived for 58 times that long. Imagine buying a car with a 100,000-mile guarantee and having it go for nearly 6 million miles.
That's a bargain. But then, that's what NASA and JPL do. Create missions that pay off far, far more than the investment.
Perhaps that's the true legacy Opportunity, and indeed any given space mission, leaves behind. The science we learn may be incremental or may be a leap ahead, but in a decade, five decades, a century, will those achievements be remembered? Or will our descendants remember them not for the science specifically, but as all having their place in the timeline of exploration, fitting into and playing their part in the adventure that takes us into the future and out into the solar system?
Remember, we send these rovers, these landers, these machines to Mars as an extension of ourselves. We remain on Earth, and that's a good thing! The expertise, the experience, the desire, the hope, the passion: These all are here, in us, in our teams, in our desire to explore the Universe around us. Opportunity joins the Viking landers, Sojourner, Phoenix, and her own sister Spirit as Mars surface missions that have gone quiet … but InSight and Curiosity live on. We as a species are still just getting started with Mars.
This won't even stop when a human bootprint is placed in the Martian dust. Even then, that will still be just one small step. The goal of the Mars exploration program is to see if there was ever or if there is still life on Mars.
Eventually, because of this exploration, there certainly will be.