Curiosity rover marks fifth year on Mars

By Bryan Dyne
9 August 2017

Since its remarkable and complex landing on the Martian surface on August 6, 2012, the Curiosity rover has proven to be the most fruitful astrobiological study of the red planet to date. For the past five years, Curiosity has provided a deluge of scientific data on the planet’s geological history, organic compounds, atmospheric conditions, radiation levels, liquid water and past and present potential for human habitability and alien life.

Curiosity's self-portrait at Rocknest, the site of the mission's first sampling of Martian soil. Credit: NASA/JPL-Caltech/Malin Space Science Systems

Curiosity has so far lived more than twice its original specifications. When it first landed on Mars via sky-crane, it was only slated for a two-year mission to land in Gale Crater and explore the slopes of Aeolis Mons (Mount Sharp). The mission was extended indefinitely in December 2012 and has allowed Curiosity to return 427,000 images to Earth, traverse a total of 19 kilometers and climb more than 180 meters while deepening our knowledge of the 4.5 billion year history of the red planet.

The rover’s major achievement is showing that the conditions of early Mars may have been able to sustain terrestrial-like life. It is now thought that a primordial Martian ocean covered the planet’s northern hemisphere and reached depths of 1.6 kilometers. Moreover, this ocean likely lasted for around 900 million years. While Curiosity’s scientific instruments aren’t equipped to actually find the remnants of life from early Mars, they do provide evidence for a primordial ocean, and further evidence of various organic compounds from that period strongly suggest that, at the very least, Mars once had a rich reservoir of the diverse set of chemical environments needed for Earth-like life.

The rover began its journey at the Bradbury landing site and is currently exploring the Vera Rubin Ridge. Credit: NASA/JPL-Caltech/Univ. of Arizona

Gale Crater and Mount Sharp themselves were chosen because of their likely connection to this ancient ocean. The Gale impact crater contains a large central peak, Mount Sharp, much larger than typical central peaks found in large craters. Based on data Curiosity has gathered, there is every possibility that, in early Martian history, Gale Crater would have been known as Gale Lake. The liquid would have likely been some combination of water and sulfuric acid, and infused with the carbon-based compounds Curiosity has discovered in the rocks and dirt during its journey. It would have also flowed through the ancient streambed studied by the rover.

Another significant result from Curiosity is a 10-fold spike in methane in the air around the rover, first detected in 2014. It immediately drew interest because the creation of the gas was localized, indicating that Mars is a chemically active planet, most likely some underground interaction between rocks and liquid water. A different (though less likely) scenario is that the pocket of methane was released by some sort of organic process, such as the waste product of Martian microbes. Moreover, why was the process so short-lived? And will Curiosity detect it happening again?

Curiosity's view of Mount Sharp as it studied the different epochs of Martian geology revealed in the layers of rock and sediment in the buttes of Logan Pass. Credit: NASA/JPL-Caltech/MSSS

Curiosity was the first Mars explorer to fly with a radiation detector “inside” the spacecraft, to monitor the types and levels of radiation during the flight to Mars and during Martian explorations that might be experienced in future human explorations. The information already returned is influencing design concepts for future manned missions to the Moon, Mars, and beyond.

Curiosity is currently investigating how exactly such a large central peak formed in the midst of the ancient Gale Lake. Sediment found in the older layers of Mount Sharp indicate that it may be the result of a series of ancient rivers which carried silt and sand into the lake, depositing material about the original central peak that slowly built up over time and was then shaped by the Martian atmosphere. As Curiosity travels up Mount Sharp, its main task will be to search for further clues to clarify this hypothesis as well as to better understand the geological history of Mars as a whole.

Curiosity, the blue feature at the center of this image, was at the northwestern flank of Mount Sharp when it was viewed by NASA's Mars Reconnaissance Orbiter. Credit: NASA/JPL-Caltech/Univ. of Arizona

Curiosity’s fifth anniversary falls near another auspicious date in the history of Martian exploration, 20 years since the Mars Pathfinder mission landed in 1997. It consisted of a base station and the first Martian rover, Sojourner. Both were essentially designed as a proof of concept, that a lander and rover could in fact be safely placed on Mars. As such they were only designed to last one month and one week respectively. They both ended up collecting data for nearly three months, returning more than 17,000 images, 8.5 million measurements of Mars’s atmospheric pressure, temperature and wind speed and 16 chemical analyses of Martian geology.

The success of Pathfinder and Sojourner led directly to the development of two further missions, Europe’s Mars Express and NASA’s Mars Exploration Rover program. While the lander of Mars Express, the Beagle 2, failed to deploy properly, the orbiter has remained in operation since it arrived at Mars in 2003. It both collects scientific data and acts as a relay between Earth and all of the ground-based Martian explorers, including Curiosity.

NASA’s Mars Exploration Rovers, better known as Spirit and Opportunity, are some of the most successful planetary exploration missions to date. Both landed in January 2004 and have enhanced and entranced our view of Mars ever since. They provided the first high-resolution color photos of the Martian surface, revealing a world very alien although at the same time very similar to our own. Mars is a dry, cold, arid place, hostile to all known life. At the same time, it has dunes, storms, ice caps, mountains and dried-up streams, rivers and lake beds. There are even quite spectacular sunsets, the shades of blue seen on Mars beautifully contrasting with the reds and yellows found on Earth.

A contrasting image of a sunset on Earth (left) and Mars (right), the blue hues on the red planet likely caused by the unique scattering properties of Martian dust. Credit: NASA/JPL-Caltech/MSSS/Damia Bouic

Each rover was designed to last only 92 days and both have far outlived their original specifications. Spirit functioned until 2010, and Opportunity continues to collect data to this day, having worked on Mars for more than 13 years.

Curiosity follows in this tradition. It stands alongside Spirit and Opportunity as well as the Hubble Space Telescope, the Cassini Saturn orbiter, and the New Horizons Pluto explorer as a testament to the power of science, planning and the ability of the human race to understand the reality in which it lives.

The last decades have vastly enlarged the scope of potential explorations possible in the Solar System, and these missions are only a small part of what could have been accomplished within this timespan. They provide a glimpse of the enlarged compass of exploration and investigation possible when the fetters of the profit system are overthrown.

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