The 6th of August 2012 is a date to be remembered in NASA’s history. On this day, it’s most successful Mars rover, Curiosity, landed on the Martian soil with the distinction of being the most precise landing in the history of Martian exploration. Curiosity is more than just a rover; it is a mobile laboratory that has uncovered a lot of previously unknown facts about the red planet. Having known that the Martian environment was, at one time, well suited to support microbial life, Curiosity is now busy searching for traces of microbial life on the planet.
Curiosity’s stint at uncovering the secrets of Mars was initially planned for 23 months. Owing to its success, it is now extended indefinitely. In its four years of crawling on the Martian soil at a speed of 5 cm per second, it has covered a distance of about 14.6 kilometres. It has hiked up Aeolis Mons aka Mount Sharp, a 5.5 kilometre high mountain in the Gale crater, walked on the plains of Aeolis Palus, a plain in the crater, and has studied the Martian climate and geology. The data collected by Curiosity would be used for planning a manned mission to Mars in mid 2030s.
“Curiosity is the largest and most complex of the rovers launched by NASA. Its mission was to determine whether the red planet ever was, or is, habitable to microbial life. Curiosity’s primary scientific goal was to explore and quantitatively assess a local region on Mars’ surface as a potential habitat for Mars life. As part of this, it is exploring biological potential, geology and geochemistry, the role of water, and hazards to life in the region around its landing site. The rover for this exploration carries ten scientific instruments. In its first year on Mars, Curiosity found evidence of a once-habitable environment at the site of an ancient lake”, explains Dr. Gajanana Birur, a Principal Engineer in the Mechanical Engineering Division at NASA’s Jet Propulsion Laboratory.
Curiosity was launched on November 26, 2011, from the Cape Canaveral Air Force Station, Florida, USA. After travelling a distance of 570 million kilometres in cold, void space for eight months, it entered the Martian orbit to land. The launch of the biggest ever rover to Mars has its set of challenges. “The biggest challenge faced during the eight-month cruise is the last part of the journey - Entry, Descent, and soft Landing (EDL). An aeroshell, carrying the rover inside its womb, enters the Martian environment and this phase lasts for six minutes. A unique technique, called the actively pumped fluid loop technology, is used to keep Curiosity and its spacecraft at safe temperatures where two independent active fluid loops removed waste heat from the rover. Along with this active fluid loop, traditional spacecraft thermal control techniques such as insulation blankets, temperature sensors, heaters, white painted radiators etc. were also used”, explains Dr. Birur who specializes in the areas of advanced spacecraft thermal control technologies and the design, build and testing of planetary spacecraft missions. .
Landing on Mars is another daunting challenge, and just one in two such landings are successful. The recent incident of the European Space Agency’s “Schiaparelli” lander crash-landing on October 19, 2016, on the Martian surface is an example of how a small miscalculation in the height can spell doom. “One of the biggest challenges of the mission was that the rover inside the entry body had to reduce its speed from about 13,000 miles per hour to two miles per hour at the touchdown on the Mars surface in six minutes. A specialized landing sequence, which employed a giant parachute, a rocket-controlled descent vehicle and an apparatus called a "sky crane" that lowered the rover on a tether for landing, was devised because other landing techniques used during previous rover missions could not safely accommodate the much larger and heavier rover. Also, a supersonic parachute had to be designed and tested for the first time for this landing sequence. This technology was specially developed for the Mars Science Laboratory (MSL) mission”, explains Dr. Birur.
Choosing the best landing site in an unknown terrain is another crucial aspect for a smooth landing. Even with the best of the technologies, landing on an uneven, rocky terrain could result in a crash. “It was well known that the selecting the landing site for Curiosity would profoundly influence the nature and quality of the scientific return from the mission, as well as the pace and strategy for surface operations. Three criteria were used for the selection - evidence suggestive of a past or present habitable environment, ability of the mission to meet or exceed all engineering and safety constraints, and the acceptable operational performance”, articulates Dr. Birur. In fact, the NASA appointed Landing Site Steering committee had come up with four final landing sites of which the final site, Gale Crater, was selected in July 2011.
But what makes the rover so heavy? Curiosity has seventeen cameras on-board - eight for hazard detection, four for navigation, two for multiple spectra images, one for chemical analysis, and two for helping the movement of the robotic arm and the base. It also has a cleaning system that removes the dust from surface to be analysed, sample acquisition and preparation tools, tools to scoop soil, drill into rocks and sort samples by particle size and deliver them to the on-board lab.
Curiosity also works like a lab technician, quite literally! Its high-resolution cameras search for interesting features on surrounding rocks and if it finds one, the ChemCam vaporizes a small part to study its composition. If the composition is intriguing, Curiosity uses its robotic arm to look up the rock with a microscope and an X-ray spectrometer. It then drills the rocks to collect powdered samples that is analysed by other instruments on-board. Finally, once the results are obtained, it sends the data to its controllers at NASA. Curiosity is the only rover till date that has the ability to drill holes.
Curiosity has quenched some of our curiosity about the red planet. It has ascertained the absence of atmospheric methane, analysed some of the meteorites on Mars and confirmed that the Martian atmosphere was thicker in its past, similar to that of the Earth today. Scientists believed that Mars is too cold for liquid water to exist, but the recent analysis of the Martian soil by Curiosity points out that liquid brine may exist. Powered by the treasure trove of such data, scientists around the world have pursued further research to uncover more facts about the red planet. The next big task for Curiosity is to explore the foothills of Mt. Sharp for biosignatures. An undeterred explorer, Curiosity moves on despite its punctured titanium tyres, a fact revealed by its recent selfie!
Mars is currently at the centre stage of planetary exploration by world’s major space agencies with Russia, Europe, Japan, China and India joining the race. Its Earth-like features of an atmosphere that can ward off harmful radiations, a comparable gravitational force, presence of water, polar ice caps, volcanoes, canyons, seasonal weather and a hospitable temperature ranging between 70OC and -200OC makes the planet boom with life, someday. Until then, two rovers - Spirit and Curiosity roam about freely in the company of 14 orbiters orbiting the planet, including ISRO’s Mangalyaan.
NASA has planned a Mars Mission in 2020. “The primary objectives of this mission is to search for the habitability on Mars and biosignatures”, shares Dr. Birur. “Such missions will help us reach new heights and reveal the unknown, so that what we do and learn will benefit humankind”, he signs off.