Spirit, one of NASA’s Mars Exploration Rovers has finally transmitted its last data back to Earth. We look back upon the career of this valiant space explorer.
Our neighbouring planet Mars came closer to Earth than it has for thousands of years, in August 2003. NASA had decided in 2000 that they should take advantage of this unusually close proximity to this still mysterious planet by launching two rovers to its rusty surface. The design process of such promising investigative vehicles, was a long one, looking at various aspects of previous successful other-planetary spacecraft. Elements such as six wheels and a special suspension for rough terrain, airbag shell for a cushioned landing, solar panels, rechargeable batteries, and a special heater for protecting the power source thorough the harsh Martian winter. Each of the rovers ended up weighing 174 kilograms and being 1.6m long and 1.5 meters tall. The final concept reminds me of Johnny Five from the 1986 movie Short Circuit, or even Disney and Pixar’s Wall.e animation from 2008. What do you think?
The naming of these amazing feats of engineering, fell to the ten thousand students who submitted essays with name suggestions. The names Spirit and Opportunity were chosen from among these entries, although they were also officially known and MER-A (Mars Exploration Rover – A) and MER-B (Mars Exploration Rover – B).
On 10 June 2003, NASA launched Spirit, one of the most successful planetary rovers of our age, from Cape Canaveral Air Force Station in Florida. After several delays, its twin, Opportunity, was also launched, on 7 July 2003. Their mission was multi-pronged, but the main objective was to investigate whether certain parts of the red planet may have previously experienced environments wet enough to support life of some kind.
The journey from blue planet to red planet was a harrowing one, as these spacecraft were exposed to the most intense solar flare on record. Mission controllers were concerned about the effects these high energy particle blasts may have had on the computer memory, despite being tightly ensconced like a Russian nesting doll, inside the landing spacecraft and a protective heat shield and attached to the Cruise Stage. In reaction an emergency reboot of the rovers’ computers was conducted mid flight. This process was not designed to be conducted at this stage of the journey, but for possible use on the Martian surface and thankfully it seemed to do the trick as both lander’s reached Mars orbit successfully.
After this eventful journey, Spirit landed on the surface of Mars, at Gusev Crater, on 4 January 2004. This site was chosen because evaluation from orbit suggested that it may have experienced a wet environment at some point in its history. Spirit, continuing its apparent taste for adventure, did not land smoothly. It bounced 28 times before coming to rest nearly 300 m from its initial contact landing site.
Now in spite of the research that went into choosing a landing site, Spirit’s initial exploration of its surrounding area was not a promising as that of Opportunity’s chosen site.
The initial photos sent by Spirit, stretched out across a plain, pockmarked with impact craters and rocks. This was the start of Spirit’s first mission. The little rover had problems getting going. As the parachute used to slow its descent had become trapped under the main ramp and if Spirit had gone down the ramp as planned, the wheels would have become tangled in the material. The only way out was to turn and go down a side ramp, finally rolling onto the surface on 15 January 2004. The next day the rover took our first microscopic image of the soil on another planet using its robotic arm. Scientists chose a rock in proximity, which they named “Adirondack” to be the first thoroughly examined using Spirit’s extensive tools, however after reaching the rock on 20 January, Spirit stopped communication on 21 January for 2 days! What little data being received made no sense to the controllers back in NASA. On 23 January, scientists discovered a glitch involving the computer’s flash memory, causing it to reboot repeatedly. After some re-gigging of its programming, Spirit finished its study of “Adirondack” showing us our first look at the inside of a Martian rock on 6 February, and then proceeded on its Martian travels.
By April 2004 both rovers had completed their initial three month missions studying many rock and soil samples and continuing to send us amazing images of the surface of the Red Planet. Opportunity was the more successful of the two, by finding rock evidence of a salty body of water once present on this cold dry planet.
Both rovers entered their extended mission in April 2004, with Spirit being directed towards the Columbia Hills, it was hoped they were had been present in a wetter time of the area’s history and still bore evidence of vanished oceans. Spirit continued to stop periodically to take more samples and images. In early August, and discovering exposed bedrock for the first time.
In the middle of September 2004, both rovers stopped moving, and powered down. Mars was passing behind the Sun and our communications with the intrepid adventurers would have become unreliable. Two weeks later they resumed full operations, and NASA approved a second extended mission. Spirit and Opportunity had already far exceeded their expected mission lifespan of 90 days. In spite of this Spirit’s life has never been without upheaval for long.
The years moved on, Spirit continued to search the barren planet for signs of moisture, grinding samples of rock and soil for study. Our plucky rover had many new exciting and troubling experiences. In March 2005, a series of dust whirlwinds cleaned off the rover’s solar panels increasing their efficiency by 30% and improving the rover’s possible lifespan. After driving 3.6 km (six times the goal set for such vehicles) in its continued investigation of the Columbia Hills, Spirit was finding more and more evidence of how water exposure had altered the landscape. Along this treacherous trail, the right front wheel of Spirit, began experiencing extra friction in March 2006. NASA compensated by driving the rover in reverse and allowing the wonky wheel to drag behind. In the April following, Spirit stopped driving for eight months due to the onset of the Martian winter and low power levels, however it continued to send images of the area to help us understand how the landscape changed during this time.
Approaching the third anniversary of their landing in early 2007, both rovers received an upgrade to their software which allowed the rovers to decide themselves when to take an image or extend its arm to examine rocks. The extra autonomy of the robots made life easier for the controllers on Earth. (I have visions of the rover from the movie “Planet 51” scuttling across the desert randomly picking up rocks, scanning them and storing them for later).
As June approached, the rovers encountered a very stormy period…literally. Huge Martian dust storms clouded the area and blocked out the vital power from the Sun. As a result these intrepid vehicles entered a hibernation state, using only the battery power necessary to protect their hardware.
In December of 2007, Spirit hit the jackpot, thanks to the wonky broken wheel. The wheel scraped off the top layer of Martian soil, exposing a patch which got scientists extremely excited. This area was similar to regions on Earth where water or steam was in contact with volcanic rocks. On Earth these areas are perfect breeding grounds for bacteria and other microbial life.
And so Spirit’s life continued, through 2008, samples, images, investigations, duststorms, power downs, and on and on. Never let it be said that the life of a rover is a simple one. And the real “piece de resistance” was yet to come.
On 1 May 2009 Spirit got stuck. The wheels became imbedded in soft soil, and after months of attempts to extricate it, including the failure of yet another right side wheel, the “rover” was finally declared a stationary research platform on 26 January 2010. This allowed the vehicle to continue its mission in some form, but in March of that year, Spirit stopped communicating, and it was thought that it had entered its hibernation period for the Martian winter. This however turned out to be the last communication from our little friend. It’s thought that energy levels dropped so low that the internal clock stopped. Controllers at the JPL (Jet Propulsion Lab) continued to attempt to establish contact with Spirit, and the decision was made to cease such attempts on 25 May 2011.
Opportunity continues on its journey of Mars and these 2 rovers are undeniably the most successful in our history. What we have learned from them is amazing. All that knowledge and experience has been put forward into the design and prep of a new Mars rover named “Curiosity”, due for launch in November 2011.
I know I will continue to hold a special place in my heart for Spirit, who was amply named and its “spirit” continued to endure through many trials and tribulations of its life, and it succeeded in tantalising us with hints at possible life, previously found on our rusty neighbour. Keep an eye out for details on Curiosity’s journey due to begin later this year.
(Article by Tracy McConnell)