On the 24th of January 2004, the Opportunity rover touched down on the surface of Mars. Opportunity was one of two rovers tasked with finding ancient evidence of water on the Martian surface, and after travelling 45km over the incredible Martian landscape, it did exactly that … but it didn’t stop there.

Despite a life expectancy of just 90 days, Opportunity ended up working on Mars for an incredible 14 years before succumbing to an enormous dust storm in 2018. And although Opportunity’s time has come to an end, its incredible scientific discoveries live on in NASA’s Curiosity rover.

Curiosity arrives on Mars

After a six-month journey through space, Curiosity finally made Mars its home when it touched down on the 6th of August 2012. Armed with an array of advanced tools, Curiosity looked to make new discoveries about the Martian climate and the geological processes that shaped Mars over its lifetime. One of the most interesting goals was to find out if the conditions on Mars were once suitable for microbial life to exist.

Since arriving on Mars, Curiosity’s main focus has been on Gale crater, which had been an area of high interest for scientists. Almost right away, Curiosity found strong evidence that this crater was once filled with water. Gale crater is an enormous 3.5 billion year old impact crater, making it a great location to study the Martian landscape.

In the past, rivers of liquid water would have flown into the crater carrying sand, silt and gravel along with it but, over time, these layers would build up and compress into rock – leaving a snapshot in time for Curiosity to discover.

In order to further examine these ancient formations, Curiosity drilled into the lake bed and discovered several types of organic compounds. These are chemical compounds that contain carbon (one of the most common elements found in life on Earth). The drill on Curiosity can cut into boulders and capture a sample of the powder to be analyzed by its onboard instruments. One of these uses an x-ray to scan the powder and analyze which minerals are present in the sample. The fact that it found carbon in some of these samples is a great clue that Mars used to be a very habital place for life.

Looking for life on Mars

Although there is a lot of carbon in our solar system that doesn’t originate from life, this was a good sign that microbial life could have existed on Mars billions of years ago.

Curiosity continues to travel around Gale crater, discovering interesting formations and analyzing rock samples. So far, Curiosity has travelled 22km across the Martian surface – but it hasn’t all been smooth sailing.

Over the last 7 years, the rough Martian terrain has caused a significant amount of damage to Curiosity’s wheels. This is just one of the many problems that threaten Curiosity on the Martian surface. In order to reduce wear, the engineers that control the rover have started to re-route Curiosity on its journey to avoid the harshest of terrain. Engineers even created a kind of “traction control” software which can adjust the speed of each wheel depending on what type of terrain it’s trying to go over. At lot of the lessons learned with Curiosity’s wheels have been carried into the design of Perseverance, which has been on Mars since 2021. It’s wheels are slightly larger and contain more treads than Curiosity.

Communicating with Curiosity

Curiosity remains in close communication with Earth via the Deep Space Network, which consists of antenna complexes at three locations around the world. The rover uses a steerable high-gain antenna which can be pointed directly towards Earth.

The data rates when talking directly to Earth are slow, so Curiosity often sends its data through the Mars Reconnaissance Orbiter. This orbiter passes over the rover for around 8 minutes each day and in that short period of time, Curiosity can send around 30 megabytes of data up to the orbiter which can then pass it onto Earth.

This is because if Curiosity was to send the same amount of data directly to Earth, it would take 20 hours. Communicating directly with Earth also uses a lot of power from the spacecrafts batteries, so sending information can only be done for a few hours each day.

Curiosity is powered by a radioactive thermoelectric generator. This works by converting heat from radioactive isotopes into electricity and this electricity charges two lithium-ion batteries allowing Curiosity to carry out high power tasks each day. This is a common power source for space probes. The two Voyager space probes that launched in the late 70’s were powered by RTG’s and they still work to this day. The advantage is how long they last for, but over time, their power output decreases drastically. And so, the actual power output of Curiosity’s RTG will be less than what it was back in 2012.

Curiosity’s power

The RTG is expected to fully power Curiosity until at least 2026, but after that, the power output will be very low and the amount of movement and science it can perform each day will be limited. 

At this point, engineers will start to shut down the various instruments that draw the most power from Curiosity and although Curiosity will continue to limp on, it’s entirely possible that mechanical failure or the Martian weather might stop Curiosity’s exploration before its power runs out.

A Martian dust storm, much like the one which silenced Opportunity may also be the end of Curiosity’s mission. Dust storms on Mars form clouds which can reach up to 100km above the surface of the planet. The dust particles which circulate during these storms are small and slightly electrostatic, so they can often stick to the rovers surfaces and interfere with electrical components.

Mars rovers are becoming more complex, more intelligent and more useful, and while Curiosity may have many years left to roam, it’s electrical power weakens each day and the threat of dust storms could easily be the end for Curiosity. Over time, engineers will slowly start shutting off instruments to preserve power until Curiosity sends its last bit of data and disappears silently into the Martian landscape. Either way, we can appreciate the enormous amount of information that Curiosity has collected on Mars and the incredible journey it’s been on to get there.