Even after the landing of NASA's rover Curiosity, predecessor Opportunity still remains active. After many years of active service, the car recently discovered something very curious. A group of protruding rocks near the western rim of Endeavor Crater revealed a dense group of spheres the size of tiny marbles that puzzles experts.
The NASA scientists who guided the Opportunity first thought of so-called Martian blueberries. Discovered as early as 2004 at the rover's landing site, these iron-rich spheres were thought to form billions of years ago when the Red Planet was still warm enough to allow liquid water on its surface.
In some places, minerals seeped with the water and accumulated as the water evaporated, leaving the hard remains. Wind erosion eventually exposed the hard spheres. Similar spheres are known from terrestrial desert regions, such as in sandstone in the southwest of the US. According to some scientists these may contain traces of microbial life on Mars. The globules on earth contain more organic molecules in the paved outside than in the softer inside. This could also be the case on Mars, according to some geologists.
Mysterious, unknown species
However, further investigation with Opportunity's X-ray spectrometer came as a surprise. The globules turned out to be something completely different from the previously found 'blueberries'. For example, these spheres of about 3 mm in diameter contain much less iron. They are also much closer together than the previously found spheres and are also more fragile: brittle on the outside and soft on the inside. These 'blueberries' differ from the globules found earlier in four different ways: composition, distribution, structure and concentration. In short, yet another geological puzzle that could potentially provide a crucial clue to the existence of life on Mars.
The now-aged Opportunity is still functioning well and the team of accompanying NASA researchers will spend the coming weeks further investigating this puzzling phenomenon.