As seems to happen with any Mars rover or lander mission, there are unexpected surprises waiting to be found. The Curiosity rover mission has been no exception so far; some interesting things have been seen in the landscape near the rover's landing spot which indicate that this area has a long and varied geological history.
Evidence for a now long-dry stream which once ran through this spot, bedrock slabs that appear to have once been drenched in water and calcium-rich veins and pits in the rocks which also point to past water activity are all part of the story being told here.
There is another odd feature in this area which hasn't been explained yet, but may also be water-related. As Curiosity moved into the Yellowknife Bay region, a large shallow bay-like depression near the landing site, images sent back to Earth showed that the rocks were often covered by little nodules that kind of looked like bubbles - tiny cone-like protuberances with a pit or hole on top.
What they are is still speculative, but theories range from fossilized mud bubbles or other gas vents to eroded concretions or maybe even something completely new. They've been dubbed "bubbles" in various discussion forums, etc. but what actually are they?
The bedrock in this area is a type of mudstone or siltstone, thought to have been laid down in water a long time ago. These features do resemble mud bubbles seen in rocks on Earth, where gas bubbles have formed on mudflats that later became fossilized. Could the same thing have happened here?
There are other rounded little nodules on these rocks which resemble the concretions, the famous "blueberry" spherules, seen elsewhere on Mars by the Opportunity rover. Could the "bubbles" just be oddly eroded concretions or places where some of these have broken off from the rock?
They also bear a resemblance to other little gas domes formed in connection with microbial mats. Such an interpretation would of course be the most controversial...
A better understanding of the origin of these features will have to wait until they can, hopefully, be studied closer by the rover.
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