Curiosity is over its first decade on Mars

Curiosity is over its first decade on Mars

To the south of the Mars equator is a crater 150 km wide, which we call Gail. It's supposed to be a shock crater formed between 3.5 and 3.8 billion years ago, then covered with sediment, which was subsequently washed away by the Martian wind. According to our current knowledge, this site was weathered by Martian weather for thousands of millions of years, up to 6 August 2012.

Curiosity is a so-called flagship, which is part of a small circle that includes the most expensive, ambitious and strategic missions of NASA. To give due weight to this definition, the James Webb Space Telescope, the Kassini probe, and the Perseverance Marshoe also belong to the same family.

The mission was conceived in 2003 as Mars Science Laboratory, when it appeared in the 10-year review of the National Research Council of the United States, a document in which the National Research Council of the United States proposed a focus on space exploration beyond the Earth's orbit over the next 10 years.

It was said that by the end of 2004, NASA had already had eight different proposals for the construction, launch and operation of the Martian Science Laboratory, which will be launched seven years later, on 26 November 2011, from Cape Canaveral.

In the more than 3,500 days of being on the Martian surface of Curiosity, 13 scientific instruments have produced a great deal of scientific data. What are the main purposes for which the sailor was sent to Mars? In two words:

Study of the climate and evolution of the Martian atmosphere, in particular the cycles of water and carbon dioxide, study of the chemical, isotopic and mineralogenic composition of the Red Planet To assess whether the conditions necessary for the development of microbial life, as we understand it, were in Gail's crater.

It would not be possible to report all the scientific discoveries that had been made through Curiosity, so let us confine ourselves to the most important of them. First of all, Mars Science Laboratory has shown that Gail's crater contained liquid water and that it contained organic building blocks necessary to develop and sustain a possible microbial life that, however, was never found.

With regard to the Martian atmosphere, the merit of the Muriosity Martial is that we now know that in a few billion years it has become thinner, starting with the highest layers, and this process has also affected the availability of liquid water on the surface of the Red Planet.

One of the most interesting discoveries, however, is that there is a seasonal cycle of methane. Although many have rushed to attribute the cause of microbial life to this phenomenon, the reality is probably much less poetic.

Curiosity was not the first Mars marcher to be sent to Mars, nor is it the longest to live; this record is owned by Opportunity with its 5352 Martian days; however, it still represents a major breakthrough in research on the Red Planet and the solar system as a whole.

With a weight of about 900 kilos and the size of the car, Curiosity is facing severe Martian conditions even better than its predecessors Spirit and Opportunity, thanks, of course, to the radioisotope thermoelectric generator RTG, which provides electricity to the system regardless of the influence of sunlight.

In RTG, the Zeebec effect is used to convert the heat released by the break-up of the radioactive isotope into electrical energy, allowing the janitor to operate even under extreme conditions, for example during long-term Martian sandstorms, which proved fatal for Opportunity.

One of the most revolutionary aspects of the Curiosity mission was undoubtedly the method used to place the rover on the Martian surface; entering the atmosphere of Mars has always been and will be one of the greatest obstacles to the exploration of this planet because of its extremely thin yet existing atmosphere.

This depression is reflected in the failure of the atmosphere itself to adequately slow down the fall masses, especially the size of the self-propelled laboratory. If for Spirit and Opportunity, in addition to the heat shield, there were enough parachutes and airbags, then Curiosity had to resort to parachutes and retrorockets.

But how could we keep the fragile instruments on board in the event of a soul landing until the moment of contact? The solution was developed by the legendary Jet Propulsion Laboratory and was named Skycrane.

It has many advantages, but it is very complex. In two words, the shell containing Curiosity slowed down with eight retrorackets until it was about eight metres above the Martian soil, and the cable dropped the rover to contact the surface, then the sensor signaled the disconnect from the celestial crane, which was then removed to fall at a safe distance.

Its use has significantly improved the accuracy of the landing, the ellipse of which has reduced its uncertainty to 20 x 7 km in total. By comparison, we recall that Spirit and Opportunity had to be content with an ellipse of 150 km x 20 km in size. This incredible step forward has led to the development of a fully autonomous system. This was because the distance to Earth did not allow real-time manoeuvres that could only be performed with data from a large number of sensors.

In the early stages of entry into the atmosphere, when the janitor was still protected by an aerosol shell, the control system continuously adjusted the descent trajectory to correctly point the centre of gravity of the entire capsule.

This method, already used for re-entrys during Apollo flights, has not yet been used in the interplanetary mission; it uses the discrepancy between the centre of gravity of the capsule and its symmetry axis; this results in a force that, if properly oriented by the steering devices, minimizes the deviation from the optimal trajectory.

A fully similar system was also used in 2021 for the landing of the Perseverance rover. At that time, technological advances further reduced the landing ellipse to 7.7 x 6.6 km.

Of course, these ten years on the Red Planet have not been without their shortcomings.

The Opportunity record is still 45 kilometers away, but wheels seem to be the main threat to the long-term continuation of Courisity.

For the moment, it is not possible to say how much longer Curiosity will be able to continue its activities; undoubtedly, its contribution to our knowledge of Mars and planetary research has already far exceeded even the most optimistic expectations.

NASA has already taken precautions to preserve its precious wheels, hoping to delay as much as possible the date of decommissioning of this self-propelled laboratory, which basically includes a thorough assessment of the daily rover route in order to avoid a particularly cross-sectional area. Only time will show how much longer Curiosity remains to live, but one thing can be said for sure: despite the age difference, his name will remain forever tied to the name of the Gale crater.