The Curiosity Rover

If you’re in the Boston area, you may (or may not) know that the Museum of Science has been on a bit of a Mars kick recently. With new discoveries pouring in from our Martian spacecraft and humanity finally putting itself on the road to Mars with Project Artemis, Mars is big news these days. And one of our Martian explorers is celebrating a birthday this week, so let’s hop on the Mars train!

Landing the Big One

Happy birthday Curiosity! Eleven (Earth) years ago the Mars Science Laboratory, also known by its much cuter name, Curiosity, successfully landed on Mars after a roughly 8.5 month trip from Earth. And let me tell ya, nailing that landing was a feat.

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Landing on Mars is tricky, to put it mildly. The planet has an atmosphere, so you can’t just use the kinds of methods you might use to land on the Moon, where there is no air. But there’s not much atmosphere, so you can’t really use it to properly slow your spacecraft down for landing the way you would on Earth. It’s an annoying in-between.

Prior to Curiosity, all of our Martian spacecraft had used a highly amusing and undignified method of getting to the surface—they bounced (no really, click that link, jump to the 50 second mark, and have a good giggle). After using a heat shield and parachute to slow themselves down as much as possible, the landing craft deployed a whole bunch of airbags around itself, cut the parachute line, and then literally bounced around on the surface until coming to a stop, at which point the airbags deflated and the landing module unfolded itself, revealing the lander or rover safe inside and ready to go.

That was not going to fly (or, well, land) for the massive Curiosity, the largest, heaviest thing we had ever landed on Mars at that point. To put it into perspective, the Spirit and Opportunity rovers, which were the largest rovers we’d landed prior to Curiosity, were just over 400 lbs. Curiosity is nearly 2,000 lbs. That mass would have burst the airbags, so engineers came up with the super complex but also amazing idea of the skycrane. 

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Essentially after doing the usual heat shield and parachute, Curiosity was carried down to a height of 25 feet above the surface by a rocket-powered platform, which then lowered the lander the final distance. This process not only allowed for the greater mass of the rover, but it also resulted in a much more precise landing (it turns out it’s hard to control your precise landing site when you bounce to the surface). It was also had so many things that could go wrong, many of which had never been tried before. The whole landing process took seven minutes, leading NASA to nickname it the “Seven Minutes of Terror”.

Needless to say at this point, eleven years later, Curiosity’s landing went absolutely perfectly, and it put its wheels down in the red dust of Gale Crater at 1:17 AM Eastern time on August 6, 2012 (if you look up the official date of the landing it will say August 5, because that’s the day it was in Mission Control when the landing occurred) and sent its first images back to the planet it left behind. It was an intense time in Mission Control.

Gale Crater

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So why, out of all of Mars, did we choose to send what was then the biggest and most technologically advanced Mars rover to Gale Crater? For the highs and the lows! Gale is a large crater, nearly 100 miles across, with an enormous central peak. This mountain is officially named Aeolus Mons, but literally everyone calls it Mount Sharp instead, and it’s taller than Mount Rainier on Earth. Its sides have all kinds of interesting layers and materials on them. How’s that for a high? 

On the other hand, Gale formed somewhere around 3.5-3.8 billion years ago during the wet period of Mars’ history. Since this crater formed at low elevation (so there’s your low), water from elsewhere drained into it, creating a lake and bringing materials from elsewhere to the bottom of the crater. 

So Gale gives us a spot with a watery past and a whole bunch of different interesting terrains, geological (or, as my coworker Becca will insist since we’re talking about Mars instead of Earth, areological) histories, and varying compositions. What more could a rover want?

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The Rover

Curiosity is different from anything we landed on Mars before it, and served as a blueprint for its younger sibling Perseverance. For one thing, this baby is large.

 We’ve already mentioned how heavy it is, but the rover is nearly 10 feet long, over twice the size of Spirit and Opportunity, and its upper mast is over seven feet above the ground. It comes equipped with spectrometers, microscopes, radiation detectors, and a drill. It even has a high-powered laser it uses to shoot rocks (for science)!

The rover has an incredible array of cameras that allow it to not only take breathtaking images of Mars, but also allow the rover to take selfies. This allows the engineers to visually assess the rover’s condition and immediate surroundings. Also, you know, it’s cute. 

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Curiosity is also our first nuclear-powered rover. Solar panels are much cheaper, but there’s a major downside to solar-powered Mars rovers: dust. We’ve seen the entire planet become engulfed in dust storms in the past. And these storms can last for months. This, alas, is what finally did in our intrepid and long-lived rover Opportunity. After fourteen years on the surface Opportunity found itself in the path of a long-lived storm that cut off the sunlight it needed to survive and it went to sleep for the last time, which I will never not be sad about. Curiosity, on the other hand, weathered the same storm without a problem, because it carries its own power source within it.

Of course, it hasn’t all been smooth sailing.  Mars has teeth in the form of rough terrain and sharp rocks. Early in the mission it was assumed the rover could handle the terrain. By 2014 images of the holes ripped into Curiosity’s wheels by Martian rocks had proven that they are not, in fact, all-terrain approved. Its younger sibling Perseverance was able to benefit from this knowledge and has thicker wheels. 

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Curiosity was also very nearly lost to us for good six months after touchdown when its primary computer decided to throw a tantrum and just…stop doing things. It came within an hour of turning off the radio and turning Curiosity into an expensive Martian lawn ornament before NASA could convince it to shut down and let the backup computer take over.

So what do you do with a rover whose computer has proven rebellious? Why give it the ability to make its own decision, naturally! Over time Curiosity’s software has been updated to provide it greater autonomy. This past spring it received an upgrade that allows it to select its own path to a destination. This not only allows Curiosity to get places faster, it can also select a path that will best reduce the wear on its poor wheels.

Not only is Curiosity better at driving itself than the average self-driving car here on Earth, it also can select its own science targets. On the plus side this means it doesn’t have to wait for the long lag times between communications with Earth to choose an interesting rock and perform a science operation on it. On the other hand, Curiosity can now choose on its own when to fire its powerful rock-vaporizing laser, which I’m pretty sure every sci-fi movie ever has told me is a bad precedent.

11 Years on Mars

After its landing, Curiosity never really got the attention of its ancestors or descendant. A lot of its Martian tenure overlapped with the epic marathon of Opportunity’s existence, as we waited to see just how long and how far the little rover that was only meant to last three months could go. Then a lot of Mars-related attention got taken up by Perseverance: bigger, more advanced, and with a cute helicopter sidekick.

But Curiosity has been trucking along through Gale Crater and up the slopes of Mount Sharp for eleven years now! 

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 It has proven that Gale Crater once had the right conditions to support life as we know it! It has inspected the sites of lakes and found evidence of streams high on the slopes of the mountain! It has puzzled scientists by repeatedly detecting methane probably seeping from an unknown source underground! It has made over a decade of Martian weather measurements, including those taken during the dust storm that killed Opportunity! It discovered organic molecules in drill samples in the rocks of Gale! It even played the first song ever played on another planet, as it sang “Happy Birthday” to itself to mark its first Earth year on Mars! And it’s done all of this on some screwed up wheels!

Nobody knows how long Curiosity will last. The mission has been extended indefinitely and the nuclear power source has an expected minimum lifetime of 14 years, but could go well beyond that, especially if the rover stops using some of its instruments as its power sources run low. That said, power might not be what gets it in the end. Mars, as we’ve seen, is a rough place. The simple wear and tear of over a decade in such a harsh environment could ultimately take its toll on any one of a number of critical components. But for now Curiosity is still going strong with no end in sight.

Did I mention it takes really incredible pictures?