As reported over the weekend, the Opportunity rover has discovered a new type of small spherical formation on the Martian surface that — while at first glance seemed to be more of the same hematite 'blueberries' that the rover has been seeing all along — are proving to be something of a mystery to mission scientists. At the same time, new research here on Earth has given fresh importance to these 'blueberries', suggesting that they may be a sign that both liquid water and life did exist on the red planet.
When Opportunity landed on Mars in January of 2004, the rover found an abundance of these spherules resting on the surface. They were nicknamed 'blueberries' by NASA scientists because of the bright blue color of their hematite shells. Hematite typically forms under watery conditions, so these 'blueberries' were listed as evidence of past liquid water on Mars' surface. However, scientists eventually concluded that they were more likely caused by volcanic activity or by meteoroid impacts. Adding to this, a recent study called into question a watery past for Mars by showing that large clay deposits found on Mars may be the result of volcanic activity, rather than deposition by water.
However, according to this latest research, we cannot rule out a watery origin for these 'blueberries', and they may even be proof that there was life on Mars at one time. Scientists from the University of Western Australia and University of Nebraska used high resolution NanoSIMS (Nanoscale Secondary Ion Mass Spectrometry) to examine the biosignature of similar iron-oxide spheroids here on Earth, called Moqui marbles. Found on beaches and in deserts such as Utah's Jurassic Navajo Sandstone, Moqui marbles show clear evidence that microbial life, such as the iron-oxidizing Gallionella, plays an important part in their formation and therefore it is possible that the 'blueberries' may have also been formed by similar microbes on Mars.
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If this is recorded as evidence for life on Mars, it will not be the first.
Results from the Viking 1 mission — which showed the presence of organic compounds that were dismissed by subsequent tests — were re-examined in recent years and scientists concluded that Viking 1's initial findings were a definitive sign of life. In 2008, the Phoenix lander mission discovered perchlorate in the Martian soil, which was first thought to have given a false-positive in Viking's test. However, upon further study, the scientists concluded that organic compounds may have been present in the soil tested, because the Viking samples showed the presence of chloromethane and dichloromethane when they were heated — the exact chemicals that they would expect to see if perchlorate had broken down any organics in the soil.
Further evidence has been added due to detecting trace amounts of methane and formaldehyde in the Martian atmosphere, both of which point to the possibility that large colonies of microorganisms currently live on the planet.
When the Spirit rover accidentally uncovered rich silica deposits below the surface, which typically form when hot spring water or steam contacts volcanic rocks, this was added to the list, as scientists consider it evidence of a past environment that was favourable to microbial life, and the discovery of geysers near the southern polar region have been taken as possible evidence of photosynthetic microorganisms.
Over the next 5 years, the Mars Curiosity rover will take on the next phases of this search, and will hopefully send back new data that not only supports and confirms the findings of past missions, but also will provide its own evidence for life on the red planet.