When you want to find out something, but can’t get to where the action is taking place, what’s the next best thing? You would probably entrust others with the task, asking them to report the findings to you. What if the place we want to study is way beyond anywhere human eyes have reached? We would probably have to employ rovers to get there and relay what it finds back to us.
The Spirit and Opportunity were twins rovers built as part of NASA’s Mars Exploration Program. Also known as the Mars Exploration Rover 2 (MER 2, became MER-A), the Spirit rover was about the size of a golf cart and weighed nearly 185 kg.
Spirit goes first
Spirit and Opportunity were launched within a month of each other in 2003 and sent to opposite sides of Mars, in order to study the history of climate and water at those sites.
Spirit made its way first, launched on June 10, 2003 from Cape Canaveral, Florida. After initially being sent to an intermediary parking orbit round Earth, the spacecraft was thrust into a heliocentric orbit on a trajectory to intercept Mars. A number of course corrections later, Spirit approached Mars for landing.
Bounce, roll and stop
The lander, which was still inside a protective aeroshell, separated from the cruise stage only about 15 minutes before entering the martian atmosphere. A parachute was deployed at an altitude of 6 to 7.5 km and four massive airbags were inflated, but as these alone would not suffice to reduce velocity (atmosphere on Mars is less than 1% the density of Earth’s), retrorockets were fired.
On January 4 2004, the entire package hit the Martian surface at a velocity of 14m/s. It bounced 28 times before rolling to a stop bout 250 m from the point of first impact. The landing happened inside the Gusev crater, about 13.4 km away from the planned target.
Blessing in disguise
Even though Spirit’s original mission was scheduled to last only 90 Martian days – until about April 4, 2004 – mission planners were able to repeatedly extend the mission. One of the reasons for this was the passing of dust devils (strong, well-formed, short-lived whirlwinds) that swept dust from the top of the petal solar panels of Spirit, thereby increasing the power coming into the rover.
Even when Spirit faced stumbling blocks, it turned out to be to its advantage. For when its front wheel stopped working, it turned out to be a blessing in disguise as the non-functional wheel then scraped soil as the rover moved. This exposed bright silica-rich dust, an indicator of contact between soil and water.
Throughout its operating time on Mars, Spirit was able to discover a surprising variety of bedrock, churn up soil that contained more sulphur and a trace of water, unearth a patch of almost pure silica and find evidence of an ancient explosion. This, apart from the fact that the mast-mounted cameras provided never-before-seen images of our neighbouring planet and captured many movies of dust devils in action, helping us better understand wind effects on the Martian surface.
Loses contact
On May 1, 2009, Spirit got stuck in soft soil and after several attempts to get it moving failed, the mission was changed to a stationary science platform in January 2010. But after March 22, 2010, mission controllers were unable to regain contact with the rover.
Recovery efforts were officially concluded on May 25, 2011. The excessive cold is seen as the likely reason for loss of contact, as it would have made the rovers several heaters incapable of performing their duty. By the time it lost contact, Spirit had operated for six years, two months and 19 days, travelling 7.73 km across the Martian plains and collecting a treasure trove of data.
Picture Credit : Google
