It was just a few months after NASA's Opportunity Rover moved on March 2004, it showed a geological curiosity: small…
It was just a few months after NASA’s Opportunity Rover moved on March 2004, it showed a geological curiosity: small iron-rich spheres scattered across the stone surface near the robotic landing site. Snack-loving researchers working on the mission dubbed these objects “blueberries”, but the features were easier to name than understanding. Their recipes are still something of a puzzle.
Trying to sort out the origins of these blueberries has always been with and studied similar spherical formations here on earth. New research takes inspiration from these terrestrial analogues to offer a new perception of chemistry that may have whipped up these marian blueberries. In turn, this research contributes to revealing what old Mars might have looked like.
Blueberries are tantalizing for more than just their whimsical names; they also constituted some of the earliest evidence we had that Mars was once incredibly wet. “No matter what the exact chemistry of this kernel would begin, we tell [that] a lot of fluid water moved through these stones over time,” Briony Horgan, a planet scientist at Purdue University, Indiana, told Space.com. [1
0 Amazing Mars Discoveries by Rovers Spirit & Opportunity]
And if researchers can analyze exactly how the blueberries formed, it can help us understand what Mars was like when the features were formed – and what kind of life could theoretically have been under these circumstances, Horgan said.
So the team behind the new research traveled to two different terrestrial destinations in search of rock formations similar to martian blueberries: Utah and Mongolia. These formations are not identical to Mars, which is about one-tenth of Earth’s equivalents. Our planet’s formations are also less organized than the Mars versions. “They are all blobbed together, they are different sizes,” Horgan says about the terrestrial features.
But it is much easier to get to Utah and Mongolia than to Mars, so researchers use these features despite the incomprehensible comparison. The researchers found that the formations seemed to have been built around nuclei of a mineral called kalcite, with iron-rich material in the outer shell only. “That moment [of discovery] was very exciting”, geo-chemical co-author Hidekazu Yoshida from Nagoya University and Hitoshi Hasegawa from Kochi University in Japan wrote in an email to Space.com.
Based on these observations in the field and chemical modeling, researchers suggested that floods of iron, gently acidic water were washed over the original calcite structures. Unlike terrestrial versions, martian blueberries seem to be made of hematite all the way, no longer a calcite heart. But it can point to a long period of floods that ate through all the calcite, the researchers said.
The great details about chemical reactions that may or may not have taken place during the early March have greater consequences. First of all, these details are relevant to the researchers’ natural interests in all the water flowing through rocks to form blueberries. “Water chemistry tells about the environment,” said Horgan.
The second potential implication would relate to another long-standing debate about Mars – what happened to its once thick atmosphere. The authors of the new study argued that this atmosphere could have penetrated carbonate ions locked in calcite precursors to blueberries.
But it would not solve the atmospheric mystery, Steve Ruff, a planet geologist at Arizona State University who works on the Opportunity Mission, told Space.com. “My sense of what we know about the area hematite that we can map from orbit is not a big area,” which covers less than 1 percent of the Mars area, he said. There is just not enough blueberries to pack a lot of atmosphere. [Latest Mars Rover Photos from Opportunity & Spirit]
He also said that he also worries that the Earth’s formations are not as great for them on Mars for researchers to learn about blueberries. But Ruff did not let go of the new paper. “I am fascinated by this idea,” he said. “The formation of these little concrete things on earth and really on Mars has always been a bit of a mystery, and there are several ideas on how to form these things.”
Martian blueberries are small enough that in order to truly solve their mystery, scientists will need more sophisticated tools than currently on the red planet. NASA’s next robber, Mars 2020 Rover, will have instruments with sufficient resolution to handle these issues. But the rover is slated to visit a site called Jezero Crater, far away from the plain where Opportunity discovered blueberries.
“Going back to places on Mars with NASA is not something people want to do. They want to go to new places,” said Ruff. Nevertheless, he said he did not give hope that the new robber could solve the blueberry mystery. “Maybe we’re lucky to see something like this with the 2020 rover.”
The new paper is a new reminder of the great time scales – and the possible complexity dare brings – involved in marcheology, Horgan said. “Time can play a very important role in the minerals we see,” said Horgan. “We should be careful. There could have been several things that happened to these stones.”
The research is described in a paper published today (December 5) in the journal Science Advances.