![]() “It’s been a mystery why there hasn’t been much carbonate seen from orbit,” Bristow said. But for two decades now, orbiting spacecraft have not found those deposits yet, only much lesser amounts than anticipated. So with all that liquid water, there should be carbonate deposits left behind. On Earth, carbon dioxide combines with positively charged ions such as magnesium and ferrous iron to form carbonate minerals. Scientists had thought they would find more carbonates on Mars than they have. There is evidence, from isotopic ratios, that the Martian atmosphere was indeed denser back then, but theoretical models suggest that it still would have been difficult for that atmosphere to allow liquid water on the surface for long periods of time (in millions of years). Two primary factors can affect how much surface there may have been on Mars – the amount of energy coming from the younger Sun at the time, and the thickness of the atmosphere. “It would be really hard to get liquid water even if there were a hundred times more carbon dioxide in the atmosphere than what the mineral evidence in the rock tells us.” “We’ve been particularly struck with the absence of carbonate minerals in sedimentary rock the rover has examined,” said Thomas Bristow of NASA’s Ames Research Center, Moffett Field, California. Image Credit: Goddard Space Flight Center Accumulated evidence has shown that Mars used to be much wetter, but just how water was able to remain liquid isn’t known yet. Illustration depicting how early Mars, with lakes, rivers and maybe oceans, changed to the dry, cold world we see today. But, those same rocks also showed no evidence for carbonate minerals, meaning that the atmosphere was lacking in carbon at the time. #ANCIENT SPACE PARADOX SERIES#Gale crater itself was once filled with a lake or series of lakes. The rover has found that the bedrock it has been studying used to be on a lake bottom. New findings from Curiosity however have thrown a wrench into that idea. Mars’ atmosphere is still mostly carbon dioxide today, but it is much, much thinner. One of the leading theories has been that Mars had a much thicker atmosphere of carbon dioxide than it does now, which would have acted like a greenhouse. How can these two scenarios be reconciled? But all over the planet there are ancient riverbeds, ancient lakebeds (Curiosity is in one right now) and the possible shorelines of an ancient northern ocean (another topic of much debate). The problem is rooted in the fact that at this time in Mars’ early history, about 3.5 billion years ago, the Sun was about one-third less hot than it is today with Mars farther from the Sun than Earth, this would have made it difficult for Mars’ surface to remain warm enough for liquid water. #ANCIENT SPACE PARADOX HOW TO#These two lines of evidence seem to contradict each other, so how to resolve this puzzle? Curiosity has revealed a paradox of sorts – it has found abundant evidence for ancient lakes in now-dry Gale crater, but at the same time has not found evidence for a previous thicker atmosphere with more carbon dioxide, which normally would be needed for water to remain liquid on the surface. There have been apparent conflicting lines of evidence, and now findings from the Curiosity rover have only added to the mystery. Most scientists now generally agree on this, but as to how much water there was, how long it lasted and how warm the environment was, is another question. The subject of water on Mars is one of the most highly debated in planetary science various missions have provided ample evidence that the planet used to be a lot wetter than it is now, with rivers, lakes and maybe even oceans. Drilled samples here and elsewhere provided evidence that this region used to be at the bottom of a lake, but also that there are little or no carbonate mineral deposits, which should have been produced if the carbon dioxide atmosphere was thicker and warmer billions of years ago. View from Curiosity of the Yellowknife Bay rock formation. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |