This is an article by JansenP for the Young Astronomers
Artist's concept of a rover working on Mars. Credit: NASA
Apart from the Earth, Mars is the most explored planet in our Solar System. Since the 1960’s, dozens of spacecraft have been sent to orbit and, in some cases, land on our planetary neighbour.
Mars does not seem an interesting place at first glance: the low temperature and pressure have given the planet a very hostile environment. However, some pictures, taken by spacecraft orbiting Mars and telescopes on Earth, suggest that the early Mars was wetter and more “hospitable” than it is today. So, did Mars once have water flowing on its surface; and if so, how long ago?
To answer these questions, NASA sent two robotic rovers to the red planet– named Spirit and Opportunity – to study two different areas of the Martian surface and look for any evidence that there was once liquid water on Mars.
Getting to Mars
Spirit and Opportunity were launched separately in June 2003 and arrived at the red planet in January 2004. Nevertheless, this long trip was not the worst part: the biggest preoccupation of the mission scientists was landing the robots on Mars safely. In the video below you can see how difficult – and terrific – this task was.
Credit: NASA
Robotic geologists
As we already said, this mission has as main objective finding signs of past water on Mars. To do so, the robots are loaded with instruments to grab and analyze rocks.
Artist's rendering of one of the rovers using the RAT on Mars. Credit: NASA
Both rovers have a robotic arm with a drill – called a Rock Abrasion Tool (RAT) – that can bore into a rock and, through a camera mounted at the same arm, the scientists can check out the rock’s inner composition. This is needed because the huge amount of solar radiation striking the surface of the planet and the Martian dust have given to rocks a kind of “rind” that covers the minerals that scientists want to study.
The robots are also equipped with nine cameras – from a microscopic imager to a high-resolution panoramic camera –, spectrometers (tools to identify the composition of a body measuring its light spectrum) and a lot more. Even the rovers’ wheels in addition to allowing mobility, are used to dig shallow trenches to evaluate soil properties.
Another interesting feature of Spirit and Opportunity is that they are autonomous, this means, they can move and control themselves. For example, when the scientists look at a rock in the landscape, they can tell the rover to “go check out that rock,” and it will drive over to that rock and examine it. This allows the rovers to be much more useful as the time lag for radio signals to travel between Earth and Mars (which varies between 3 to 30 minutes roughly) is too great for the rovers to be directly radio controlled.
Finding the traces of water
Two months after land on Mars, Opportunity found, in a thin rocks outcrop in Eagle Crater, rocks rich in sulfate-salts, evidence that salt water flowed once over them. Preliminary interpretations point to a past environment that implies this crater could have been hospitable to life and could have preserved fossil evidence of it, though these rovers are not equipped to detect life or to be fossil hunters, such duties will be carried out by future, perhaps manned missions.
This is an image of a meteorite that Opportunity found and examined in September 2010. Credit: NASAJPL
Spirit, during its primary mission (which in this case meant, the first 90 days), explored a plain strewn with volcanic rocks and pot-marked with impact craters. It found indications that small amounts of water may have found their way into cracks in the rocks and may have affected some of the rocks’ surfaces.
Unfortunately, since 2009, Spirit has been stuck in a sand dune and probably will never free itself. As Spirit’s instruments were, and are in very good health, NASA decided to turn the robot into a “Martian observatory”: to look at the stars, clouds and to study the weather and landscape of Mars.
Opportunity continues working hard. It is now located at Santa Maria Crater. There, the rover found other interesting minerals that can only form in presence of water for a long period. The next big objective for Opportunity is to head for the Endeavour Crater and to analyse the minerals present on its rim.
As of January, both rovers have completed 7 years of work on Mars – a much longer time than was expected of either them, let alone both. The primary mission was expected to be last three months after the spacecrafts’ landing, i.e. until April 2004. As the vehicles were still doing well, NASA decided to extend the mission.
So, even as you read this the Mars Exploration Rovers still looking for water on Mars and changing the way we look at the Red planet.
You can see the latest news about the twin robots at the mission’s official website.