Rovers are the most important component of the present-day Mars exploration missions. Over the past two decades, we have seen tremendous growth in size and capability of these six-wheeled robotic emissaries which has enabled us to reveal some of the ground-breaking information about the geological conditions (present and past) of the Red Planet. It is because of their ability to move which has allowed scientists to collect samples and investigate at multiple locations before announcing that Mars was habitable in the past than it is today.
The first rover to Mars was named after early women’s rights activist Sojourner Truth as Sojourner. It was the first probe that touched the Martian surface with NASA’s Pathfinder mission on July 4, 1997, after the Viking landers of 1976. It landed on large, ancient flood plains called Ares Vallis so that it could easily analyze the rock samples around.
In comparison to its successors, Sojourner was ‘tiny’. According to NASA, it belonged to a class of rovers called “microrovers” which is roughly of the dimension of your cabinet drawer (66 cm long, 48 cm wide and 30 cm tall). It roved on six 13 cm wheels, each one of which was capable of moving independently. This means that if one of the six wheels, got struck in the soft-sand of Mars, the others can still work to power the robot forward. Its top speed, as reported by NASA was 0.024 kilometers per hour.
Rover was installed with the necessary hardware to conduct scientific experiments along with front and rear cameras. It analyzed the rocks of Ares Vallis, which were given nicknames like Scooby-Doo and Barnacle Bill. It was through these investigations that NASA suggested that Mars (Ares Vallis) was extremely water-rich in history. It is also interesting to note that Sojourner which was designed to operate for just a week ended up being operational for twelve weeks (3 months), covering a distance of 100 m from Pathfinder and sending back over 550 images from the Red Planet.
NASA believes that Pathfinder must have stopped working because of its battery getting overloaded by repeated charging and discharging. We lost communication with Pathfinder on September 27, 1997.
Spirit and Opportunity
The next rovers that landed on the Martian surface were the golf-cart-size twins called Spirit and Opportunity which landed a few weeks apart in January 2004 at two different locations to search for traces of water on the Red Planet. These rovers were solar powered and were over three times the height of Sojourner and weighed about 180 kg.
Spirit landed at a place which was suspected of being a lake in the past called Gusev Crater. Rover collected and analyzed enough samples of rocks to provide enough shreds of evidence to prove that they were formed because of interaction with water. It was the first rover to record the formation of Martian dust devils in 2005.
While the landing of its twin was not as smooth as it had. Opportunity landed in an unplanned manner inside a crater which was later named as Eagle Crater. It came across the plains, meteorites and sand dunes as it investigated the surroundings. It sent back the photos of small iron-rich pebbles which were later nicknamed as “blueberries’ as they were thought to suggest the watery past of the Red Planet. However, scientists are yet to justify the presence of these rocks there. Together, these two siblings have added a completely new dimension to our understanding of Mars. The place we thought to be dead planet has now been transformed into a planet with a rich interesting and complex geological history where life also might have survived. Alike its predecessor, these twins also survived for more time than what they were designed for.
On May 30, 2018, a global Martian dust storm began and continued for over four months. Dust of this storm must have obscured the solar panel causing Opportunity to lose its contact from the Earth. NASA made several attempts since May 2018 to contact Opportunity, until finally on February 13, 2019, NASA stopped trying to contact the robot and this mission was declared complete. During this period of fifteen years, Opportunity drove more than 45 km on Martian surface (most distance covered by any vehicle on the Martian surface till date).
The most recent rover that landed on the Martian soil was on August 6, 2012, and was called Curiosity. This is an SUV-size machine that weighs about 1-ton is the largest vehicle to reach the Martian surface. The landing of this rover required an elaborate sky-crane mechanism to lower the rover down on the ground which was followed by an infamous “seven minutes of terror” (during this duration of time, engineers lost contact with the robot). This is the first rover that is powered by a nuclear radioisotope thermoelectric generator and not by the Sun. It produces electricity from the heat which is generated by the radioactive decay of Plutonium-238. It has been designed to travel a distance of 200 m per day.
The main scientific goal of this rover is to determine the habitability of life on the Martian surface. The machine is configured with a wide range of instruments, including multiple cameras and spectrometers that have been installed to analyze the composition of rocks. A laser has also been installed in this rover to vaporize the big chunks of rocks into smaller ones so that they can be analyzed by the spectrometers. This rover is a darling of media that has a special inclination for snapping selfies. In 2018, organic materials (building blocks of life) have been discovered in 3.5 billion-year-old Martian rocks by Curiosity.
This rover has been exploring Martian surface for over six years now, and nobody knows till when this would survive. The nuclear battery that has been installed in the rover could keep going for another six years, or perhaps longer.
We are still not done with sending rovers to the Martian surface. NASA plans to launch the Mars2020 rover (a near twin to Curiosity), that would move around and analyze an area called Jezero Crater and collect samples which could be brought back to Earth.
The same year Mars2020 is scheduled to land on Mars, the European Space Agency intends to land its own vehicle called the ExoMars 2020 rover. This rover is named after the famous British scientist Rosalind Franklin. It would be carrying a drill that can penetrate up to 2 m below the Martian surface to search for information about the potential signatures of life.