Opportunity: 8 years on Mars

NASA’s Opportunity rover landed on the Red Planet on 25 January 2004. Designed to work for at least 90 days, it is still going! In 8 years, it has found indications suggesting the presence of liquid water in Mars’ past.

 

Opportunity rover on Mars (illustration for the rover, real photographic data from the rover for Mars' surface). Credit: NASA/JPL

The rover Opportunity arrived on the surface of Mars on 25 January 2004 at 05:05 Universal Time, 21 days after its twin Spirit. It used a landing technique that was based on inflatable balloons. The video below summarises its journey, from its blast-off on 7 June 2003 to its landing on the fourth planet.



Eagle Crater: a superb golf stroke!
Whereas Spirit landed in the immense, 166 km diameter Gusev crater which proved to be dotted with rocks of volcanic origin, Opportunity set up home in a small crater 22 m in diameter and 3 m deep. With the first images and analyses, scientists very quickly realised that rocks exposed on the edge of the crater showed that this so-called Meridiani Planum region could, in the past (here we are talking about a hundred million or even 2 to 3 billion years), have housed liquid water or have even been the bottom of an ocean.

Opportunity took this photograph as it was leaving Eagle crater. We would point out its transportation platform in the middle of the photograph. Credit: NASA/JPL

The crater was dubbed Eagle Crater, not only in tribute to the Eagle Lunar Module used during the Apollo 11 mission (the first men on the Moon in 1969), but also in reference to a golfing term. An Eagle means that a player has reached a hole in two strokes below par (the number of strokes theoretically required to reach it). And on a par 3, this leads to “a hole in one”, a magical gesture that all golfers dream of achieving and that Opportunity had achieved on the scientific front: sent to find geological proof of Mars’ “wet past”, it found the most convincing indications first go!

Opportunity bogged down in sand! Despite having 6 drive wheels, there was a very real risk of the rover remaining a prisoner in this trap. However, its “pilots” cleverly and patiently got it out of this tricky situation. Credit: NASA

Some luck, but above all a great deal of perseverance
How lucky you might think... However, Opportunity’s undeniable success after 8 years spent on the Red Planet (record activity for a probe, whether stationary or mobile, on Mars) also owes a great deal to the perseverance of all those who worked on the manufacture of this machine and its twin Spirit (who stopped transmitting on 22 March 2010) as well as to the determination of the scientific managers led by Steve Squyres, who is, moreover, an ardent promoter of the need to send men there in the future.

This is a panoramic view of Victoria crater (800 m in diameter) that Opportunity rover explored from 2006 to 2008. Credit: NASA/JPL

In fact, NASA’s Mars Exploration Rover programme had, even before its double blast-off (Spirit and Opportunity lifted off on two separate rockets), come up against some serious snags. For instance, the inflatable balloons provided for cushioning the landing on the ground tore during testing. Although this innovative technique had been successfully tested with the Mars Pathfinder mission in 1997, the weights involved were not the same: 264 kg for the Pathfinder lander and 533 kg for that of Spirit and Opportunity (the rovers each weighed 185 kg). And that’s not all. A few months prior to the blast-offs, the parachutes were not ready. During testing, those planned did not withstand the impact as they were released! Furthermore, the total budget for the mission exceeded that forecast, but NASA agreed to the additional necessary funds. We do not suppose that this choice is questioned now!

In 2005, Opportunity examined its carrier spaceship’s heat shield (left-hand photograph) (said spaceship having crashed as planned on to Mars’ surface during the landing) and discovered this strange rock dubbed “Heat Shield Rock” (right-hand photograph). It turned out to be the first meteorite to be identified on a planet other than Earth! Credit: NASA/JPL/Enjoy Space

And lastly, although the rovers’ reliable performance, particularly that of Opportunity, should be highlighted, a remarkable achievement on the part of their designers and manufacturers, tribute should also be paid on this eighth anniversary to the “pilots”, technicians, engineers and scientists who have continuously had to make choices so as to reach the research objectives whilst making the right decisions as regards the directions to take (a delicate balance between risk and prudence in order to examine that which ought to be examined). And there have been no lack of obstacles such as the time Opportunity became bogged down in sand, which required the development of manoeuvres to free the rover calmly without falling into the trap of trying to go too quickly. NASA’s video below was made to celebrate the rover’s eight years on Mars.



Winter quarters for Opportunity
Eight years after its arrival, Opportunity continues to send back relevant and even spectacular analyses. This was, for instance, the case recently with the discovery of a vein of gypsum that was formed in the past when liquid water was in contact with volcanic rocks. According to Steve Squyres, “it’s the kind of thing that makes geologists jump out of their chairs” (see this article).

The edge of Endeavour crater that took Opportunity 3 months to reach. The rover has currently travelled a total of 34 km on Mars. Credit: NASA/JPL

But over the eight years, the valiant rover’s solar array has become more and more covered with Martian dust, which has diminished its efficiency. And, unless a small storm were miraculously to clean the photovoltaic cells by blowing the dust off (which has already happened!), Opportunity has this time to take special precautions in order to survive its fifth Martian winter (the seasons on this planet are twice as long as those on Earth), despite being in the southern hemisphere and relatively close to the equator. Its “pilots” have, therefore, parked it on a gentle, north-facing slope in order to optimise the angle with which the panels receive the rays of the Sun which will be low on the horizon. The site has been dubbed Greeley Haven in tribute to Ronald Greeley (1939-2011), a planetologist from Arizona State University (a university that takes an active part in the mission with NASA’s JPL).

This photograph was taken from Greeley Haven where Opportunity is to spend the winter season whilst continuing to carry out scientific tasks. Credit: NASA/JPL

This does not mean that all science will cease. Without moving, the rover will study the area around it on the edge of the 22 km diameter Endeavour crater (an objective which required a long journey that began half way through 2008). Furthermore, by transmitting radio signals with its high-gain antenna received by radio telescopes on Earth, scientists hope to track the minute “imperfections” as Mars rotates on its axis. Said imperfections will reveal the planet’s internal structure, thus enabling us to get a better understanding of Mars.
It is worthy of note that as of August 2012, Opportunity will no longer be the only rover in action on Mars. It is to be joined by the impressive MSL-Curiosity which is carrying two French instruments (see the EnjoySpaceTV video below).



And, as of 11 February 2012, the Cité de l’espace in Toulouse, France, will be opening a brand new exhibition devoted to the exploration of Mars, notably with full-size models of three types of rovers that have travelled on this planet: the Mars Pathfinder’s small Sojourner, Opportunity (or Spirit, the two being identical) and obviously Curiosity which is as big as an urban car.



Many other discoveries, experiments and surprises await you. In short, you will have the impression that you have visited the Red Planet!

Published on 25 January 2012