*4.2.2 The robotic geologists*

The Spirit and Opportunity rovers were designed with these questions on mind, considering the rovers as geologists *roving* on the Martian surface, and equipped with a portable laboratory to perform *in situ* analysis of the samples. A 360° panoramic camera (Pancam) and an IR thermal emission spectrometer (Mini-TES) were placed on the rover mast at 1.5 m above the ground. These allowed the optical characterization of the terrain (the geologist eyes) plus a first IR analysis on the potentially interesting targets. In addition, the rovers were equipped with an articulated robotic arm with several tools: a Microscopic Imager (MI) to take closeup images of the samples (the geologist magnifier); the Rock Abrasion Tool (RAT) to allow access to the interior of the rocks (the geologist hammer); and a series of instruments constituting the geologist portable laboratory—the Alpha Particle X-Ray Spectrometer (APXS), the Mossbauer Spectrometer (MS), and a Magnet array for direct analysis of the samples (another Magnet array was placed on the rover chassis to passively analyze the powder depositing on them). The rovers were also equipped with navigation (NavCams) and Hazard Avoidance (HazCams) cameras to facilitate a safe roving capability of these robotic geologists.

### *4.2.3 A journey through the Martian geology*

The MER rovers landed on Mars at the beginning of 2004, during the last days of the southern summer. The soft landings were achieved by means of airbags, with which the rovers bounced very long distances along the Martian surface for a period of time much longer than expected. Spirit landed on January 4, 2004 in the Gusev crater (14.572° S, 175.478° E). Three weeks later, on January 25, Opportunity landed inside a 20-m diameter crater in Terra Meridiani (1.946° S and 354.473° E) in the opposite side of the planet.

MER rovers' journey on the Martian surface is one of the greatest successes among all the planetary exploration missions. From an engineering perspective, the results are impressive: rovers were designed for a 90-sol nominal mission and to rove up to 600 m. However, both rovers operated successfully for years (Spirit

**99**

*Evolution of the Scientific Instrumentation for* In Situ *Mars Exploration*

lasted for 6 years and 2 months, or 1892 sols; and Opportunity worked for 14 years and 42 days, or 5111 sols). During this time, they managed to travel 7.73 km in the case of Spirit, and a stounding distance of 45.16 km in the case of Opportunity. This longevity and traveling capacity allowed the generation of tens of GB of data that were downloaded to Earth. This enormous data volume allowed an unprecedented identification and consolidation of scientific advances to date, contributing greatly

First Opportunity success was its initial lucky-shot, landing inside the Eagle crater,

where it performed analysis for 2 months. It detected hematite, which was a clear indicator of a past presence of water in the area, as it is formed in water environments. However, it was also deduced that the water presence was salty and with low pH (so not optimal for life thriving due to the water acidity), with this area probably being a coast region with tidal waters [26]. Later in December 2011, Opportunity also detected other evidences of liquid water in the Martian past. In the Endeavor crater, the instruments detected veins of gypsum (calcium sulfate) inside some rocks. This hydrated mineral was probably formed by water flowing through cracks in the rocks, where the calcium was left behind [27]. Before that, in October 2005, while analyzing the Comanche outcrop by MS, APXS and Mini-TES, the Spirit rover identified rocks formed by key chemical elements such as magnesium and iron carbonates, in proportions up to 10 times higher than the previous analysis on Mars [28]. This discovery was evidence that the Martian past had warmer and wetter areas, with a thick atmosphere and with neutral pH values that are required for the formation of these carbonates. These conditions would potentially favor the existence of some kinds of microscopic life compared to any of the previous analysis performed on the Martian surface.

One of the Spirit wheels was damaged long after the nominal mission had passed, which was in itself a stroke of luck. In March 2007, the stuck wheel uncovered a whitish area below the soil regolith, which, after analysis, revealed as an area composed by silica with 90% concentration. This kind of crystals, with this purity, can only be found (on Earth) in areas bathed by thermal waters, or water vapor currents where the water or vapor get in contact with volcanic rocks. These places in Earth are thriving with bacteria and microorganisms due to the optimal conditions

The Spirit mission looked terribly bad when it was trapped in sand without any possibility of moving from that position. However, during the maneuvers to try to be released, the wheels uncovered sulfates (among other things) under the regolith in the Troy location. These sulfates seemed to have been in contact with water only 1 million years ago (a very short time by geological standards), suggesting the pos-

In May 2007, Spirit observed the ancient remains of a volcanic eruption in Home Plate. The remains suggested that the explosion might have been caused by a waterlava interaction [30], as suggested by the "bomb sag" structures found in the lower

sibility of the existence of an active water cycle on the planet.

*4.2.3.4 Stable water bodies and volcanic activity*

*DOI: http://dx.doi.org/10.5772/intechopen.93377*

*4.2.3.1 A dense atmosphere and fresh water*

*4.2.3.2 Thermal waters*

set by the hot and wet ambient [29].

*4.2.3.3 An active water cycle*

to the knowledge of Mars and its geological history.

#### *Evolution of the Scientific Instrumentation for* In Situ *Mars Exploration DOI: http://dx.doi.org/10.5772/intechopen.93377*

lasted for 6 years and 2 months, or 1892 sols; and Opportunity worked for 14 years and 42 days, or 5111 sols). During this time, they managed to travel 7.73 km in the case of Spirit, and a stounding distance of 45.16 km in the case of Opportunity. This longevity and traveling capacity allowed the generation of tens of GB of data that were downloaded to Earth. This enormous data volume allowed an unprecedented identification and consolidation of scientific advances to date, contributing greatly to the knowledge of Mars and its geological history.
